Patent Application
20140305031
This application includes an electronic sequence listing in a file named “445642-Sequence.txt”, created on Apr. 23, 2014 and containing 8,705 bytes, which is hereby incorporated by reference in its entirety for all purposes.
The present invention relates to the production of oils, soaps and fuels made from microorganisms. In particular, the disclosure relates oil-bearing microalgae, methods of cultivating them for the production of useful compounds, including lipids, fatty acid esters, and alkanes, and the chemical modification of such useful compounds for the production of soaps, chemicals and fuels.
Increased demand for energy by the global economy has placed increasing pressure on the cost of fossil fuels. This, along with increasing interest in reducing air pollution, has spurred the development of domestic energy supplies and triggered the development of non-petroleum fuels for internal combustion engines. For compression ignition (diesel) engines, it has been shown that the simple alcohol esters of fatty acids (biodiesel) are acceptable as an alternative diesel fuel. Biodiesel has a higher oxygen content than diesel derived from fossil fuels, and therefore reduces emissions of particulate matter, hydrocarbons, and carbon monoxide, while also reducing sulfur emissions due to a low sulfur content (Sheehan, J., et al., Life Cycle Inventory of Biodiesel and Petroleum Diesel for Use in an Urban Bus, National Renewable Energy Laboratory, Report NREL/SR-580-24089, Golden, Colo. (1998); Graboski, M. S., and R. L. McCormick, Prog. Energy Combust. Sci., 24:125-164 (1998)).
Initial efforts at the production, testing, and use of biodiesel employed refined edible vegetable oils (expelled or recovered by solvent extraction of oilseeds) and animal fats (e.g., beef tallow) as feedstocks for fuel synthesis (see, e.g., Krawczyk, T., INFORM, 7: 800-815 (1996); and Peterson, C. L., et al., Applied Engineering in Agriculture, 13: 71-79 (1997). Further refinement of the methods has enabled production of fatty acid methyl esters (FAME) from cheaper, less highly refined lipid feedstocks such as spent restaurant grease and soybean soapstock (see, e.g., Mittelbach, M., and P. Tritthart, J. Am. Oil Chem. Soc., 65(7):1185-1187 (1988); Graboski, M. S., et al., The Effect of Biodiesel Composition on Engine Emissions from a DDC Series 60 Diesel Engine, Final Report to USDOE/National Renewable Energy Laboratory, Contract No. ACG-8-17106-02 (2000).
For decades, photoautotrophic growth of algae has been proposed as an attractive method of manufacturing biodiesel from algae; see A Look Back at the U.S. Department of Energy's Aquatic Species Program: Biodiesel from Algae, NREL/TP-580-24190, John Sheehan, Terri Dunahay, John Benemann and Paul Roessler (1998). Many researchers believe that because sunlight is a “free” resource, photoautotrophic growth of algae is the most desirable method of culturing microalgae as a feedstock for biofuel production (see, for example Chisti, Biotechnol Adv. 2007 May-June; 25(3):294-306: “heterotrophic production is not as efficient as using photosynthetic microalgae . . . because the renewable organic carbon sources required for growing heterotrophic microorganisms are produced ultimately by photosynthesis, usually in crop plants”). Other research has not only assumed that photoautotrophic growth is the best way to grow microalgae for biofuels, but also that there is no need to transesterify any material from microalgal biomass before introduction into a diesel engine (see Screagg et al., Enzyme and Microbial Technology, Vol. 33:7, 2003, Pages 884-889).
Photosynthetic growth methods have been the focus of considerable research over the past several decades, spurred in part by the U.S. Department of Energy's Office of Fuels Development, which funded a program to develop renewable transportation fuels from algae during the period spanning 1978 to 1996. The principal production design was centered around a series of shallow outdoor sunlight-driven ponds designed as “raceways” in which algae, water and nutrients were circulated around a circular pond in proximity to a source of waste CO2 (e.g., a fossil fuel powered electricity generating plant).
Transesterification of extracted/refined plant oils is conventionally performed by reacting a triacylglycerol (“TAG”) with a lower-alkyl alcohol (e.g., methanol) in the presence of a catalyst (e.g., a strong acid or strong base) to yield fatty acid alkyl esters (e.g., fatty acid methyl esters or “FAME”) and glycerol.
As described above, traditional biodiesel production has relied on extracted and/or refined oils (expelled or recovered by solvent extraction of oilseeds) as a feedstock for the transesterification process. Oil sources, including soy, palm, coconut, and canola, are commonly used, and extraction is performed by drying the plant material and pretreating the material (e.g., by flaking) to facilitate penetration of the plant structure by a solvent, such as hexane. Extraction of these oils for use as a starting material contributes significantly to the cost of traditional biodiesel production.
Similar to the solvent extraction processes utilized to extract oils from dried plant materials, solvent extraction of oils from microbial biomass is carried out in the presence of an organic solvent. Solvent extraction in this context requires the use of a solvent that is essentially immiscible in water, such as hexane, to produce a solvent phase, in which the oil is soluble, and an aqueous phase, which retains the largely non-lipid portion of the biomass. Unfortunately, in an industrial scale production, the volume of volatile, potentially carcinogenic, and flammable organic solvent that must be used for efficient extraction creates hazardous operating conditions having both environmental and worker safety aspects. Moreover, the solvent extraction process generates a substantial solvent waste stream that requires proper disposal, thereby increasing overall production costs.
Alternatively, “solventless” extraction processes have been reported; these employ an aqueous solvent comprising no more than about 5% organic solvent for extracting lipids from microorganisms for use as a feedstock in a transesterification process for the production of biodiesel. Briefly, the “solventless” extraction process includes contacting a lysed cell mixture with an aqueous solvent containing no more than about 5% organic solvent (e.g., hexane) to produce a phase separated mixture. The mixture comprises a heavier aqueous layer and a lighter layer comprising emulsified lipids. The extraction process is repeatedly performed on the lighter lipid layer until a non-emulsified lipid layer is obtained. Unfortunately, the repeated isolation and washing of the lipid layer makes the “solventless” process particularly laborious.
There remains a need for cheaper, more efficient methods for extracting valuable biomolecules derived from lipids produced by microorganisms and for converting them into valuable fuels and other chemicals. The present invention meets this need.
Additionally, PCT Pub. No. 2008/151149 describes methods and materials for cultivating microalgae for the production of oil and particularly exemplifies the production of diesel fuel from oil produced by the microalgae Chlorella protothecoides. There remains a need for improved methods for producing oil in microalgae, particularly for methods that produce oils with shorter chain length and a higher degree of saturation and without pigments, with greater yield and efficiency. The present invention meets this need.
In a first aspect, the present invention relates to the discovery that direct chemical modification of lipid-containing microbial biomass can dramatically increase the efficiency and decrease the cost of obtaining valuable materials derived from those lipids. Thus, in a first embodiment, then invention provides a method of chemically modifying lipid-containing microbial biomass including the steps of culturing a population of microbes, harvesting microbial biomass that contains at least 5% lipid by dry cell weight (DCW), and subjecting the biomass to a chemical reaction that covalently modifies at least 1% of the lipid. In some embodiments, the method further includes separating the covalently modified lipid from other components of the biomass.
In various embodiments, the ratio of the covalently modified lipid to the biomass from which it is separated is between 10% lipid and 90% biomass and 90% biomass and 10% lipid by dry weight. In some embodiments, the step of separating the lipid from other components of the biomass includes a phase separation step in which the covalently modified lipids form a lighter non-aqueous phase and components of the biomass form one or more heavier phases. In some embodiments, the biomass is subjected to the chemical reaction without a step of prior enrichment that increases the ratio of the lipids to the non-lipid material by more than 50% by weight. In other embodiments, the biomass is subjected to the chemical reaction with a step of prior enrichment that increases the ratio of the lipids to the dry weight of the microbes. In some embodiments, the harvested biomass is not subjected to any treatment other than the removal of water and/or lysis of the cells before the chemical reaction. In some embodiments, the biomass subjected to the chemical reaction contains components other than water in the same relative proportions as the cell culture. In some embodiments, the lipid content of the biomass is less than 90% of the biomass subjected to the chemical reaction.
In one embodiment, chemical modification of the lipid-containing microbial biomass comprises transesterifying the biomass to generate a lipophilic phase containing fatty acid alkyl esters and a hydrophilic phase containing cell material and glycerol. In some embodiments, the method further comprises removing water from the biomass prior to subjecting the biomass to the transesterifying chemical reaction. In other embodiments, the method further comprises removing water from the biomass after the disrupting of the biomass. In some embodiments, removing water from the biomass is performed using a method selected from the group consisting of lyophilization, drum drying, and oven drying the biomass.
In some embodiments, in which the chemical modification of the lipid-containing microbial biomass comprises transesterifying the biomass, the method further comprises disrupting the biomass prior to transesterifying the biomass. In some embodiments, water is removed from the biomass prior to the disrupting of the biomass. In some embodiments, disrupting the biomass comprises heating the biomass to generate a lysate. In other embodiments, disrupting the biomass comprises contacting the biomass with an acid or base sufficient to generate a lysate. In still other embodiments, disrupting the biomass comprises contacting the biomass with one or more enzymes to generate a lysate. In some embodiments, the biomass is contacted with at least one protease and at least one polysaccharide-degrading enzyme. In some embodiments, disrupting the biomass comprises mechanically lysing the population of microbes to generate a lysate. In other embodiments, disrupting the biomass comprises subjecting the biomass to osmotic shock to generate a lysate. In still other embodiments, disrupting the biomass comprises infecting the population of microbes with a lytic virus to generate a lysate. In other embodiments, disrupting the biomass comprises inducing the expression of a lytic gene within the population of microbes to promote autolysis and generation of a lysate.
In some embodiments of the chemical modification method in which the chemical reaction comprises transesterification, the fatty acid alkyl esters are fatty acid methyl esters or fatty acid ethyl esters. In some embodiments, transesterifying the biomass comprises contacting the biomass with an alcohol and a base. In some embodiments, the alcohol is selected from methanol, ethanol, propanol, isopropanol, and mixtures thereof. In some embodiments, the base is selected from NaOH, KOH, and mixtures thereof. In one embodiment, the alcohol is methanol and the base is NaOH. In some embodiments, transesterifying the biomass comprises contacting the biomass with an alcohol and a lipase. In some embodiments, the lipase is expressed from an exogenous lipase gene within the population of microbes. In some embodiments, expression of the exogenous lipase gene is induced by contacting the biomass with a stimulus to activate an inducible promoter controlling expression of the exogenous lipase gene.
In various embodiments, the amount of calcium and magnesium, combined, by weight in the lipophilic phase is no greater than 5 parts per million. In some embodiments, the amount of phosphorous in the lipophilic phase is no greater than 0.001%, by mass. In some embodiments, the amount of sulfur in the lipophilic phase is no greater than 15 parts per million. In some embodiments, the amount of potassium and sodium, combined, by weight in the lipophilic phase is no greater than 5 parts per million. In some embodiments, the total carotenoid content of the lipophilic phase is no greater than 100 micrograms of carotenoid per gram. In some embodiments, the total chlorophyll content in the lipophilic phase is no greater than 0.1 mg/kg.
In some embodiments, subjecting the biomass to a chemical reaction includes contacting the biomass with an enzyme to catalyze the chemical reaction. In some embodiments, the enzyme is a lipase. In one embodiment, the method further comprises separating a lipophilic phase containing the covalently modified lipids from hydrophilic cell material of the biomass.
In some embodiments, the microbes are a species of the genus Chlorella, and in various embodiments, the species is selected from the group consisting of Chlorella fusca, Chlorella protothecoides, Chlorella pyrenoidosa, Chlorella kessleri, Chlorella vulgaris, Chlorella saccharophila, Chlorella sorokiniana and Chlorella ellipsoidea. In one embodiment, the species is Chlorella protothecoides. In some embodiments, the microbes is a species of the genus Prototheca, or the species is selected from the group consisting of Prototheca wickerhamii, Prototheca stagnora, Prototheca portoricensis, Prototheca moriformis, and Prototheca zopfii. In some embodiments, the microbial biomass comprises a mixture of biomass from two distinct strains or species of microbes that have been separately cultured. In one embodiment, at least two of the distinct strains or species of microbes have different glycerolipid profiles. In some embodiments, the species has a high degree of taxonomic similarity to members of the Prototheca genus, such as at least 95% nucleotide identity at the 23S rRNA level, as disclosed in the examples. In some embodiments the cell is a strain of the species Prototheca moriformis, Prototheca krugani, Prototheca stagnora or Prototheca zopfii, and in other embodiment the cell has a 23S rRNA sequence with at least 70, 75, 80, 85 or 95% nucleotide identity to one or more of SEQ ID NOs: 3-11.
In various embodiments of the present invention, the harvested biomass comprises a lipid content of at least 5%, at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, or at least 90% by DCW. In some embodiments, at least 20% of the lipid is C18. In some embodiments, at least 30% of the lipid is C18. In some embodiments, at least 40% of the lipid is C18. In some embodiments, at least 50% of the lipid is C18. In some embodiments, at least 50% of the lipid is C16 or longer chain lengths.
In some embodiments of the present invention, the population of microbes expresses an exogenous sucrose utilization gene. In some embodiments, the gene is a sucrose invertase. In some embodiments, the population of microbes expresses an exogenous lipid pathway enzyme. In some embodiments, the lipid pathway enzyme comprises an acyl-ACP thioesterase. In some embodiments, the population of microbes further expresses an exogenous “naturally co-expressed” acyl carrier protein that is co-expressed with the acyl-ACP thioesterase. In some embodiments, the lipid pathway enzyme has a specificity for acting on a substrate having a specified number of carbon atoms in a chain.
In some embodiments, chemical modification of the lipid-containing microbial biomass comprises hydrogenating the biomass to saturate at least a subset of unsaturated bonds in the lipid. In some embodiments, chemical modification of the lipid-containing microbial biomass comprises interesterifying the biomass to generate a mixture of glycerolipids having a modified arrangement of fatty acid constituents relative to the glycerolipids in the harvested biomass. In some embodiments, chemical modification of the lipid-containing microbial biomass comprises hydroxylating the biomass to generate hydroxylated lipids. In some embodiments, at least a portion of the hydroxylated lipids are esterified to generate estolides. In some embodiments, chemical modification of the lipid-containing microbial biomass comprises hydrolyzing the biomass to generate free fatty acids from the lipid. In some embodiments, the free fatty acids are subjected to further chemical modification. In one embodiment, chemical modification of the lipid-containing microbial biomass comprises deoxygenation at elevated temperature in the presence of hydrogen and a catalyst, isomerization in the presence of hydrogen and a catalyst, and removal of gases and naphtha compounds.
In another embodiment, chemical modification of the lipid-containing microbial biomass comprises saponifying the biomass to generate fatty acid salts from the lipid. In one embodiment, the biomass is derived from a microalgae of the genus Prototheca. In some embodiments, saponifying the biomass comprises contacting the biomass with a base sufficient to convert at least a portion of the glycerolipid and/or fatty acid ester components of the lipid to fatty acid salts. In some embodiments, the base is an alkali metal hydroxide, such as NaOH or KOH. In some embodiments, the method further comprises contacting the biomass with a salt to precipitate the fatty acid salts from solution. In some embodiments, the salt comprises a water-soluble alkali metal halide, such as NaCl or KCl.
In some embodiments, two distinct strains or species of microbes are separately cultured, and biomass from both cultures is mixed prior to subjecting the biomass to a chemical reaction that modifies at least 1% of the lipid. In some embodiments, at least two of the distinct strains of microbes have different glycerolipid profiles.
In one aspect, the present invention is directed to a saponification method for making a soap. In some embodiments, the method includes culturing a population of microbes, harvesting microbial biomass that contains at least 5% lipid by DCW, including glycerolipids or fatty acid esters, and subjecting the biomass to an alkaline hydrolysis reaction to produce a soap from the chemical conversion of at least a portion of the glycerolipids or fatty acid esters to fatty acid salts. In some embodiments, the alkaline hydrolysis reaction includes contacting the biomass with a base and optionally heating the biomass. In some embodiments, the base is an alkali metal hydroxide such as NaOH or KOH. In some embodiments, less than 100% of the glycerolipids and fatty acid esters in the biomass are converted to fatty acid salts. In some embodiments, less than 1% of the glycerolipids and fatty acid esters in the biomass are converted to fatty acid salts.
In some embodiments of the saponification method, the method further comprises substantially separating the fatty acid salts from other components of the biomass. Some methods of the invention further comprise boiling the separated fatty acid salts in water and re-precipitating the fatty acid salts by introducing a salt into the aqueous solution to produce a purified soap. In some embodiments, the salt is a water-soluble alkali metal halide, such as NaCl or KCl.
Some saponification methods of the invention further comprise combining the purified soap or saponified oil composition with one or more additives selected from the group consisting of essential oils, fragrance oils, flavor oils, botanicals, extracts, CO2 extracts, clays, colorants, titanium dioxide, micas, tinting herbs, glitters, exfoliants, fruit seeds, fibers, grain powders, nut meals, seed meals, oil beads, wax beads, herbs, hydrosols, vitamins, milk powders, preservatives, antioxidants, tocopherols, salts, sugars, vegetable oils, waxes, glycerin, sea vegetables, nutritive oils, moisturizing oils, vegetable butters, propylene glycol, parabens, honey, bees wax, aloe, polysorbate, cornstarch, cocoa powder, coral powder, humectants, gums, emulsifying agents, and thickeners. In one embodiment, the mixture is packaged as a cosmetics product. In another embodiment, the cosmetic product comprises a facial cleanser.
In some embodiments of the saponification method, the ratio of fatty acid salts to the biomass from which they are separated is between 10% fatty acid salts to 90% biomass and 90% fatty acid salts to 10% biomass by dry weight. In some methods, the biomass is subjected to the alkaline hydrolysis reaction without a step of prior enrichment that increases a ratio of lipid to non-lipid material in the biomass by more than 50% by weight. In some methods, the harvested biomass is not subjected to treatments other than lysis before the alkaline hydrolysis reaction. In other methods, the biomass is subjected to the alkaline hydrolysis reaction with a step of prior enrichment that increases the ratio of lipid to non-lipid material in the biomass as compared to the ratio at harvesting. In some embodiments, the biomass subjected to the alkaline hydrolysis reaction contains components other than water in the same relative proportions as the biomass at harvesting. In some embodiments, lipid comprises no more than 90% of the biomass subjected to the alkaline hydrolysis reaction.
In some embodiments of the saponification method, the harvested biomass comprises a lipid content of at least 5%, at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, or at least 90% by DCW. In some embodiments, the lipid comprises at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, or at least 95% saturated fatty acid constituents.
In some embodiments, the saponification method further comprises disrupting the biomass prior to subjecting the biomass to the alkaline hydrolysis reaction. In some embodiments, disrupting the biomass comprises mechanically lysing the population of microbes to generate a lysate. In some embodiments, the oil is extracted from the biomass before saponification. In some embodiments, the extracted oil is substantially free of color or pigments.
In another aspect, the present invention is directed to a composition comprising a lighter phase containing fatty acid alkyl esters, and at least one heavier phase containing microbial biomass.
In various embodiments of the composition, at least 20% of the fatty acid alkyl esters are C18. In some embodiments, at least 30% of the fatty acid alkyl esters are C18. In some embodiments, at least 40% of the fatty acid alkyl esters are C18. In some embodiments, at least 50% of the fatty acid alkyl esters are C18. In some embodiments, at least 50% of the fatty acid alkyl esters are C16 or longer chain lengths. In some embodiments, at least 10% of the fatty acid alkyl esters are C14 or shorter chain lengths. In some embodiments., at least 20% of the fatty acid alkyl esters are C14 or shorter chain lengths.
In another aspect, the present invention is directed to a composition comprising a lighter phase containing completely saturated lipids and at least one heavier phase containing microbial biomass. In another aspect, the present invention is directed to a composition comprising a lighter phase containing lipids and at least one heavier phase containing microbial biomass from more than one species or strain. In another aspect, the present invention is directed to a composition comprising a lighter phase containing hydroxylated lipids, and at least one heavier phase containing microbial biomass. In another aspect, the present invention is directed to a composition comprising a lighter phase containing free fatty acids and at least one heavier phase containing microbial biomass.
In another aspect, the present invention is directed to a composition comprising saponified oil derived from the alkaline hydrolysis of biomass produced by culturing a population of microbes. In some embodiments, the composition further comprises at least one and optionally more than one oil selected from the group of oils consisting of soy, rapeseed, canola, palm, palm kernel, coconut, corn, waste vegetable, Chinese tallow, olive, sunflower, cotton seed, chicken fat, beef tallow, porcine tallow, microalgae, macroalgae, Cuphea, flax, peanut, choice white grease, lard, Camelina sativa, mustard seed cashew nut, oats, lupine, kenaf, calendula, hemp, coffee, linseed (flax), hazelnut, euphorbia, pumpkin seed, coriander, camellia, sesame, safflower, rice, tung oil tree, cocoa, copra, pium poppy, castor beans, pecan, jojoba, jatropha, macadamia, Brazil nuts, avocado, a fossil oil or a distillate fraction thereof.
In various embodiments, the saponified oil composition can be a solid (including a powder), or a liquid. In some embodiments, the composition further comprises carotenoids derived from the biomass, and/or unsaponified glycerolipids derived from the biomass, and/or polysaccharides derived from the biomass. In some embodiments, the saponified oil comprises at least 50% of the composition's total mass. In some embodiments, the saponified oil comprises at least 75% of the composition's total mass. In other embodiments, the saponified oil comprises less than 50% of the composition's total mass. In other embodiments, the saponified oil comprises less than 25% of the composition's total mass. In some embodiments, components derived from the biomass constitute at least 50% of the composition's total mass. In some embodiments, components derived from the biomass constitute no more than 50% of the composition's total mass.
In another aspect, the present invention is directed to a kit comprising a saponified oil composition as described herein and an oral supplement. In some embodiments, the oral supplement comprises a vitamin or an herb.
In other embodiments the triglyceride oil composition is blended with at least one other composition selected from the group consisting of soy, rapeseed, canola, palm, palm kernel, coconut, corn, waste vegetable, Chinese tallow, olive, sunflower, cotton seed, chicken fat, beef tallow, porcine tallow, microalgae, macroalgae, Cuphea, flax, peanut, choice white grease, lard, Camelina sativa, mustard seed cashew nut, oats, lupine, kenaf, calendula, hemp, coffee, linseed (flax), hazelnut, euphorbia, pumpkin seed, coriander, camellia, sesame, safflower, rice, tung tree, cocoa, copra, pium poppy, castor beans, pecan, jojoba, jatropha, macadamia, Brazil nuts, avocado, petroleum, or a distillate fraction of any of the preceding oils.
Methods of the invention also include processing the aforementioned oils of by performing one or more chemical reactions from the list consisting of transesterification, hydrogenation, hydrocracking, deoxygenation, isomerization, interesterification, hydroxylation, hydrolysis to yield free fatty acids, and saponification. The invention also includes hydrocarbon fuels made from hydrogenation and isomerization of the aforementioned oils and fatty acid alkyl esters made from transesterification of the aforementioned oils. In some embodiments the hydrocarbon fuel is made from triglyceride isolated from cells of the genus Prototheca wherein the ASTM D86 T10-T90 distillation range is at least 25° C. In other embodiments the fatty acid alkyl ester fuel is made from triglyceride isolated from cells of the genus Prototheca, wherein the composition has an ASTM D6751 A1 cold soak time of less than 120 seconds.
The invention also includes methods of manufacturing a chemical comprising performing one or more chemical reactions from the list consisting of transesterification, hydrogenation, hydrocracking, deoxygenation, isomerization, interesterification, hydroxylation, hydrolysis, and saponification on a triglyceride oil, wherein the oil has a lipid profile of at least 4% C8-C14 and one or more of the following attributes: 0.1-0.4 micrograms/ml total carotenoids; less than 0.02 milligrams of chlorophyll per kilogram of oil; 0.10-0.60 milligrams of gamma tocopherol per 100 grams of oil; 0.1-0.5 milligrams of total tocotrienols per gram of oil, 1-8 mg per 100 grams of oil of campesterol, and 10-60 mg per 100 grams of oil of stigmasterol.
In some methods the hydrolysis reaction is selected from the group consisting of saponification, acid hydrolysis, alkaline hydrolysis, enzymatic hydrolysis, catalytic hydrolysis, and hot-compressed water hydrolysis, including a catalytic hydrolysis reaction wherein the oil is split into glycerol and fatty acids. In further methods the fatty acids undergo an amination reaction to produce fatty nitrogen compounds or an ozonolysis reaction to produce mono- and dibasic-acids. In some embodiments the oil undergoes a triglyceride splitting method selected from the group consisting of enzymatic splitting and pressure splitting. In some methods a condensation reaction follows the hydrolysis reaction. Other methods include performing a hydroprocessing reaction on the oil, optionally wherein the product of the hydroprocessing reaction undergoes a deoxygenation reaction or a condensation reaction prior to or simultaneous with the hydroprocessing reaction. Some methods additionally include a gas removal reaction. Additional methods include processing the aforementioned oils by performing a deoxygenation reaction selected from the group consisting of: a hydrogenolysis reaction, hydrogenation, a consecutive hydrogenation-hydrogenolysis reaction, a consecutive hydrogenolysis-hydrogenation reaction, and a combined hydrogenation-hydrogenolysis reaction. In some methods a condensation reaction follows the deoxygenation reaction. Other methods include performing an esterification reaction on the aforementioned oils, optionally an interestification reaction or a transesterification reaction. Other methods include performing a hydroxylation reaction on the aforementioned oils, optionally wherein a condensation reaction follows the hydroxylation reaction.
The present invention arises from the discovery that Prototheca and certain related microorganisms have unexpectedly advantageous properties for the production of oils, fuels and other hydrocarbon or lipid compositions economically and in large quantities. The oils produced by these microorganisms and the oil-bearing biomass itself can be used in the transportation fuel, petrochemical, and/or food and cosmetic industries, among other applications. Transesterification of lipids or the lipid-bearing biomass yields long-chain fatty acid esters useful as biodiesel. Other enzymatic and chemical processes can be tailored to yield fatty acids, aldehydes, alcohols, alkanes and alkenes. In some applications, renewable diesel, jet fuel, or other hydrocarbon compounds are produced. In other applications, the lipid or the lipid-bearing biomass is saponified to produce soaps.
This detailed description of the invention is divided into sections for the convenience of the reader. Section I provides definitions of terms used herein. Section II provides a general description of chemical modifications of lipids and lipid-bearing microorganisms. Section III provides microorganisms and a description of culture conditions useful in the methods of the invention. Section IV provides a description of transesterification of lipids and lipid-bearing microorganisms. Section V provides a description of producing fuels and oleochemicals with microbial oils. Section VI provides a description of other methods of chemical modification of lipid-bearing microorganisms. Section VII describes saponified compositions. Section VIII discloses examples and embodiments of the invention. The detailed description of the invention is followed by examples that illustrate the various aspects and embodiments of the invention.
Unless defined otherwise, all technical and scientific terms used herein have the meaning commonly understood by a person skilled in the art to which this invention belongs. The following references provide one of skill with a general definition of many of the terms used in this invention: Singleton et al., Dictionary of Microbiology and Molecular Biology (2nd ed. 1994); The Cambridge Dictionary of Science and Technology (Walker ed., 1988); The Glossary of Genetics, 5th Ed., R. Rieger et al. (eds.), Springer Verlag (1991); and Hale & Marham, The Harper Collins Dictionary of Biology (1991). As used herein, the following terms have the meanings ascribed to them unless specified otherwise.
“Active in microalgae,” with reference to a nucleic acid, refers to a nucleic acid that is functional in microalgae. For example, a promoter that has been used to drive an antibiotic resistance gene to impart antibiotic resistance to a transgenic microalgae is active in microalgae. Examples of promoters active in microalgae include promoters endogenous to certain algae species and promoters found in plant viruses.
“Acyl carrier protein” or “ACP” is a protein that binds a growing acyl chain during fatty acid synthesis as a thiol ester at the distal thiol of the 4′-phosphopantetheine moiety and comprises a component of the fatty acid synthase complex. The phrase “naturally co-expressed” with reference to an acyl carrier protein in conjunction with a fatty acyl-ACP thioesterase means that the ACP and the thioesterase are co-expressed naturally (in nature) in a tissue or organism from which they are derived, e.g., because the genes encoding the two enzymes are under the control of a common regulatory sequence or because they are expressed in response to the same stimulus.
“Acyl-CoA molecule” or “acyl-CoA” is a molecule comprising an acyl moiety covalently attached to coenzyme A through a thiol ester linkage at the distal thiol of the 4′-phosphopantetheine moiety of coenzyme A.
“Area percent” refers to the area of peaks observed using FAME GC/FID detection methods in which every fatty acid in the sample is converted to a fatty acid methyl ester (FAME) prior to detection. For example, a separate peak is observed for a fatty acid of 14 carbon atoms with no unsaturation (C14:0) compared to any other fatty acid such as C14:1. The peak area for each class of FAME is directly proportional to its percent composition in the mixture and is calculated based on the sum of all peaks present in the sample (i.e., [area under specific peak/total area of all measured peaks]×100). When referring to lipid profiles of oil and cells of the invention, “at least 20% C16” means that at least 20% of the total fatty acids in the cell or in the extracted glycerolipid composition have a chain length that includes 16 carbon atoms.
“Axenic” means a culture of an organism that is free from contamination by other living organisms.
“Biodiesel” refers to a fatty acid ester produced from the transesterification of lipid. The ester can be a methyl ester, ethyl ester, or other ester depending on the components of the transesterification reaction.
“Biomass” refers to material produced by growth and/or propagation of cells. Biomass may contain cells and/or intracellular contents as well as extracellular material. Extracellular material includes, but is not limited to, compounds secreted by a cell.
“Bioreactor” means an enclosure or partial enclosure in which cells, e.g., microorganisms, are cultured, optionally in suspension.
“Catalyst” refers to an agent, such as a molecule or macromolecular complex, capable of facilitating or promoting a chemical reaction of a reactant to a product without becoming a part of the product. A catalyst thus increases the rate of a reaction, after which, the catalyst may act on another reactant to form the product. A catalyst generally lowers the overall activation energy required for the reaction such that the reaction proceeds more quickly or at a lower temperature and/or a reaction equilibrium may be more quickly attained. Examples of catalysts include enzymes, which are biological catalysts, and heat, which is a non-biological catalyst.
“Cellulosic material” means the products of digestion of cellulose, such as glucose, xylose, arabinose, disaccharides, oligosaccharides, lignin, furfurals and other molecules.
“Co-culture”, and variants thereof such as “co-cultivate”, refer to the presence of two or more types of cells in the same bioreactor. The two or more types of cells may both be microorganisms, such as microalgae, or may be a microalgal cell cultured with a different cell type. The culture conditions may be those that foster growth and/or propagation of the two or more cell types or those that facilitate growth and/or propagation of one cell type, or a subset of the cell types, of the two or more cell types while maintaining cellular growth for the remainder.
“Cofactor” is used herein to refer to any molecule, other than the substrate, that is required for an enzyme to carry out its enzymatic activity.
“Complementary DNA” (“cDNA”) is a DNA copy of an mRNA, which can be obtained, for example, by reverse transcription of messenger RNA (mRNA) or amplification (e.g., via polymerase chain reaction (“PCR”)).
“Cultivated” and variants thereof refer to the intentional fostering of growth (increases in cell size, cellular contents, and/or cellular activity) and/or propagation (increases in cell numbers via mitosis) of one or more cells by use of appropriate culture conditions. The combination of both growth and propagation may be termed proliferation. The one or more cells may be those of a microorganism, such as microalgae. Examples of appropriate conditions include the use of a defined medium (with known characteristics such as pH, ionic strength, and carbon source), specified temperature, oxygen tension, and carbon dioxide levels in a bioreactor. The term does not refer to the growth or propagation of microorganisms in nature or otherwise without direct human intervention, such as natural growth of an organism that ultimately becomes fossilized to produce geological crude oil.
“Delipidated meal” and “delipidated microbial biomass” is microbial biomass after oil (including lipids) has been extracted or isolated from it, either through the use of mechanical (i.e., exerted by an expeller press) or solvent extracted or both. Delipidated meal has a reduced amount of oil/lipids as compared to before the extraction or isolation of oil/lipids from the microbial biomass but may contain some residual oil/lipid.
“Exogenous gene” refers to a nucleic acid transformed (introduced) into a cell. A transformed cell may be referred to as a recombinant cell, into which additional exogenous gene(s) may be introduced. The exogenous gene may be from a different species (and so heterologous) or from the same species (and so homologous) relative to the cell being transformed. In the case of a homologous gene, the introduced gene occupies a different location in the genome of the cell relative to the endogenous copy of the gene or is under different regulatory controls of the endogenous gene it replaces or both. The exogenous gene may be present in more than one copy in the cell. The exogenous gene may be maintained in a cell as an insertion into the genome or as an episomal molecule.
“Exogenously provided” describes a molecule provided to the culture media of a cell culture.
“Expeller pressing” is a mechanical method for extracting oil from raw materials such as soybeans and rapeseed. An expeller press is a screw type machine, which presses material through a caged barrel-like cavity. Raw materials enter one side of the press and spent cake exits the other side while oil seeps out between the bars in the cage and is collected. The machine uses friction and continuous pressure from the screw drives to move and compress the raw material. The oil seeps through small openings that do not allow solids to pass through. As the raw material is pressed, friction typically causes it to heat up.
“Extracted” refers to oil or lipid separated from aqueous biomass with or without the use of solvents.
“Fatty acyl-ACP thioesterase” is an enzyme that catalyzes the cleavage of a fatty acid from an acyl carrier protein (ACP) during lipid synthesis.
“Fixed carbon source” means molecule(s) containing carbon, typically organic molecules, that are present at ambient temperature and pressure in solid or liquid form.
“Fungus,” as used herein, means heterotrophic organisms characterized by a chitinous cell wall from the kingdom of fungi.
“Glycerolipid profile” or “lipid profile” refers to the distribution of different carbon chain lengths and saturation levels of glycerolipids in a particular sample of biomass. For example, a sample could contain glycerolipids in which approximately 60% of the glycerolipid is C18:1, 20% is C18:0, 15% is C16:0, and 5% is C14:0. Where a carbon length is referenced without regard to saturation, as in “C18”, such reference can include any amount of saturation; for example, microbial biomass that contains 20% lipid as C18 can include C18:0, C18:1, C18:2, etc., in equal or varying amounts, the sum of which constitute 20% of the microbial biomass.
“Homogenate” means biomass that has been physically disrupted.
“Hydrocarbon” is (a) a molecule containing only hydrogen and carbon atoms wherein the carbon atoms are covalently linked to form a linear, branched, cyclic, or partially cyclic backbone to which the hydrogen atoms are attached. The molecular structure of hydrocarbon compounds varies from the simplest, in the form of methane (CH4), which is a constituent of natural gas, to the very heavy and very complex, such as some molecules such as asphaltenes found in crude oil, petroleum, and bitumens. Hydrocarbons may be in gaseous, liquid, or solid form, or any combination of these forms, and may have one or more double or triple bonds between adjacent carbon atoms in the backbone. Accordingly, the term includes linear, branched, cyclic, or partially cyclic alkanes, alkenes, lipids, and paraffin. Examples include propane, butane, pentane, hexane, octane, and squalene.
“Hydrogen:carbon ratio” is the ratio of hydrogen atoms to carbon atoms in a molecule on an atom-to-atom basis. The ratio may be used to refer to the number of carbon and hydrogen atoms in a hydrocarbon molecule. For example, the hydrocarbon with the highest ratio is methane CH4 (4:1).
“Hydrophobic fraction” refers to the portion, or fraction, of a material that is more soluble in a hydrophobic phase than in an aqueous phase. A hydrophobic fraction is substantially immiscible with water and usually non-polar.
“Increased lipid yield” refers to an increase in the lipid productivity of a microbial culture, which can be achieved by, for example, increasing dry weight of cells per liter of culture, increasing the percentage of cells that constitute lipid, or increasing the overall amount of lipid per liter of culture volume per unit time.
“Inducible promoter” is a promoter that mediates transcription of an operably linked gene in response to a particular stimulus.
“In operable linkage” refers to a functional linkage between two nucleic acid sequences, such as a control sequence (typically a promoter) and the linked sequence. A promoter is in operable linkage with an exogenous gene if it can mediate transcription of the gene.
“In situ” means “in place” or “in its original position”. For example, a culture may contain a first microorganism, such as a microalgae, secreting a catalyst and a second microorganism secreting a substrate, wherein the first and second microorganisms produce the components necessary for a particular chemical reaction to occur in situ in the co-culture without requiring further separation or processing of the materials.
“Lipase” is an enzyme that catalyzes the hydrolysis of ester bonds in lipid substrates. Lipases catalyze the hydrolysis of lipids into glycerols and fatty acids, and can function to catalyze the transesterification of TAGs to fatty acid alkyl esters.
“Lipids” are a class of molecules that are soluble in nonpolar solvents (such as ether and chloroform) and are relatively or completely insoluble in water. Lipid molecules have these properties, because they consist largely of long hydrocarbon tails which are hydrophobic in nature. Examples of lipids include fatty acids (saturated and unsaturated); glycerides or glycerolipids (such as monoglycerides, diglycerides, triglycerides or neutral fats, and phosphoglycerides or glycerophospholipids); nonglycerides (sphingolipids, sterol lipids including cholesterol and steroid hormones, prenol lipids including terpenoids, fatty alcohols, waxes, and polyketides); and complex lipid derivatives (sugar-linked lipids, or glycolipids, and protein-linked lipids). “Fats” are a subgroup of lipids called “triacylglycerides.”
A “lipid pathway enzyme” is an enzyme involved in lipid metabolism, i.e., either lipid synthesis, modification, or degradation, and includes, without limitation, lipases, fatty acyl-ACP thioesterases, and acyl carrier proteins.
A “limiting concentration of a nutrient” is a nutrient concentration in a culture that limits the propagation of a cultured organism. A “non-limiting concentration of a nutrient” is a nutrient concentration that can support maximal propagation during a given culture period. Thus, the number of cells produced during a given culture period is lower in the presence of a limiting concentration of a nutrient than when the nutrient is non-limiting. A nutrient is said to be “in excess” in a culture when the nutrient is present at a concentration greater than that which supports maximal propagation.
“Lysate” refers to a solution containing the contents of lysed cells.
“Lysing” refers to disrupting the cellular membrane and optionally cell wall of a cell sufficient to release at least some intracellular contents.
“Lysis” refers to the breakage of the plasma membrane and optionally the cell wall of a biological organism sufficient to release at least some intracellular contents, often by mechanical, viral or osmotic mechanisms that compromise its integrity.
“Microalgae” is a eukarytotic microbial organism that contains a chloroplast or plastid, and optionally that is capable of performing photosynthesis, or a prokaryotic microbial organism capable of performing photosynthesis. Microalgae include obligate photoautotrophs, which cannot metabolize a fixed carbon source as energy, as well as heterotrophs, which can live solely off of a fixed carbon source. Microalgae include unicellular organisms that separate from sister cells shortly after cell division, such as Chlamydomonas, as well as microbes such as, for example, Volvox, which is a simple multicellular photosynthetic microbe of two distinct cell types. Microalgae include cells such as Chlorella, Dunaliella, and Prototheca. Microalgae also include other microbial photosynthetic organisms that exhibit cell-cell adhesion, such as Agmenellum, Anabaena, and Pyrobotrys. Microalgae also include obligate heterotrophic microorganisms that have lost the ability to perform photosynthesis, such as certain dinoflagellate algae species and species of the genus Prototheca.
“Microorganism” and “microbe” are used interchangeably herein to refer to microscopic unicellular organisms.
“Oleaginous yeast,” as used herein, means yeast that can accumulate more than 10% of DCW as lipid. Oleaginous yeast includes yeasts such as Yarrowia lipolytica, as well as engineered strains of yeast such as Saccharomyces cerevisiae that have been engineered to accumulate more than 10% of the DCW as lipid.
“Osmotic shock” refers to the rupture of bacterial, algal, or other cells in a solution following a sudden reduction in osmotic pressure. Osmotic shock is sometimes induced to release cellular components into a solution.
“Photobioreactor” refers to a container, at least part of which is at least partially transparent or partially open, thereby allowing light to pass through, in which one or more microalgae cells are cultured. Photobioreactors may be closed, as in the instance of a polyethylene bag or Erlenmeyer flask, or may be open to the environment, as in the instance of an outdoor pond.
A “polysaccharide-degrading enzyme” refers to an enzyme capable of catalyzing the hydrolysis, or depolymerization, of any polysaccharide. For example, cellulases are polysaccharide degrading enzymes that catalyze the hydrolysis of cellulose.
“Polysaccharides” (or “glycans”) are carbohydrates made up of monosaccharides joined together by glycosidic linkages. Cellulose is an example of a polysaccharide that makes up certain plant cell walls. Cellulose can be depolymerized by enzymes to yield monosaccharides such as xylose and glucose, as well as larger disaccharides and oligosaccharides.
“Recombinant,” when used with reference, e.g., to a cell, or nucleic acid, protein, or vector, indicates that the cell, nucleic acid, protein, or vector, has been modified by the introduction of a heterologous nucleic acid or protein or the alteration of a native (naturally occurring) nucleic acid or protein, or that the cell is derived from a cell so modified. Thus, e.g., recombinant cells express non-native genes, genes not found in the native (non-recombinant) form of the cell, or express native genes differently than does the non-recombinant cell, i.e., the native gene is over-expressed, under-expressed or not expressed at all, relative to gene expression in the non-recombinant cell. “Recombinant nucleic acid” refers to a nucleic acid, typically formed in vitro by the manipulation of nucleic acid, e.g., using polymerases and endonucleases, in a form not found in nature (and can include purified preparations of naturally occurring nucleic acids). Thus, an isolated nucleic acid, in a linear form, or an expression vector formed in vitro by ligating DNA molecules that are not normally joined (for example to place two different nucleic acids in operable linkage with one another), are recombinant. Once a recombinant nucleic acid is introduced into a host cell or organism, it may replicate non-recombinantly, i.e., using the in vivo cellular machinery of the host cell; however, such nucleic acids, produced recombinantly and subsequently replicated non-recombinantly, are still considered recombinant. Similarly, a “recombinant protein” is a protein made using recombinant techniques, i.e., through the expression of a recombinant nucleic acid.
“Renewable diesel” is a mixture of alkanes (such as C10:0, C12:0, C14:0, C16:0 and C18:0) produced through hydrogenation and deoxygenation of lipids.
“Saponified oil” refers to the carboxylic acid salts and associated compounds that are created during saponification of fatty acid esters from microbial sources. Fatty acid esters can be derived from the triacylgylcerols (TAGs) produced by microorganisms. Compounds associated with oils from microbial sources include carotenoids, tocopherols, tocotrienols, and other compounds of biological origin.
“Sonication” refers to a process of disrupting biologic materials, such as a cell, by use of sound wave energy.
“Stover” refers to the dried stalks and leaves of a crop remaining after a grain has been harvested.
A “sucrose utilization gene” is a gene that, when expressed, aids the ability of a cell to utilize sucrose as an energy source. Proteins encoded by a sucrose utilization gene are referred to herein as “sucrose utilization enzymes” and include sucrose transporters, sucrose invertases, and hexokinases such as glucokinases and fructokinases.
Certain microorganisms can be used to produce lipids in large quantities for use in the transportation fuel and petrochemical industries, among other applications. The present invention provides methods that significantly decrease the cost and increase the efficiency of obtaining lipids and valuable lipid-derived compounds form microorganisms. Suitable microorganisms for use in the methods of the invention include microalgae, oleaginous yeast, fungi, bacteria, and cyanobacteria. Microalgae for use in the invention are the lipid-producing microalgae from the genera Chlorella and Prototheca. The present invention also provides methods for the production, isolation, and chemical modification of lipids, particularly microalgal lipids, to produce valuable fuels and other chemicals. The present invention also provides methods for the in situ transesterification of triacylglycerols (TAGs) to fatty acid alkyl esters, which are useful as biodiesel fuels and/or for other applications, hydroprocessing of TAGs to create renewable diesel, as well as other methods for chemical modification of the lipids in microbial biomass.
The present invention also provides methods of making fatty acid alkyl esters (e.g., fatty acid methyl esters (FAME)) by culturing a population of microbes that generate at least 5% of their DCW as lipid, such as triglycerides. In this method, the microbial biomass is harvested from the culture and optionally dried to remove water. Transesterification is then accomplished by the addition of a lower-alkyl alcohol and a catalyst (e.g., NaOH) to generate a lipophilic phase containing the fatty acid alkyl esters and a hydrophilic phase containing hydrophilic cell material. The lipophilic phase can be readily separated from the hydrophilic phase.
The direct transesterification of the biomass, without an intervening separation process step in which the lipophilic components are extracted from the biomass prior to transesterification, permits production of biodiesel at greatly reduced costs, as compared to methods which employ traditional extraction and refining steps prior to transesterification.
The methods of the present invention provide further advantages in the generation of biodiesel via the in situ transesterification of glycerolipids to fatty acid alkyl esters. In particular, the microbes of the present invention can be cultured under conditions which permit modulation of the glycerolipid content of the cells. Surprisingly, it has been discovered that a greater proportion of total glycerolipids can be converted to fatty acid alkyl esters in cells which comprise increasingly higher oil:non-oil ratios as a function of DCW. Moreover, these higher oil:non-oil ratios also lead to another unexpected advantage: fatty acid alkyl esters generated from cells that comprise increasingly higher oil:non-oil ratios have a lower concentration of heteroatoms than those produced from cells with lower oil:non-oil ratios. The methods provided contrast markedly with current dogma in the field, namely that photoautotrophic growth of microalgae is the best method of microalgae cultivation for biofuel production (see for example, Rodolfi, et al., Biotechnology & Bioengineering 102(1):100-112 (2008) for discussion on screening microalgal strains for their biomass productivity and lipid content for growth in an outdoor photobioreactor). It was also discovered that the higher the oil content of the biomass, the higher quality of the resulting product after direct chemical modification. The present invention provides heterotrophic methods of culturing microbes (e.g., microalgae) to achieve higher oil content for direct chemical modification for the production of higher quality chemical products.
The present invention also provides other methods of chemically modifying lipid-containing microbial biomass, including without limitation, hydrogenation, interesterification, hydroxylation, hydrolysis, and saponification. These methods can be used with the various microorganisms and culturing conditions set forth herein to produce a wide variety of chemical products for a multitude of applications.
The present invention also provides useful compositions, including: a composition comprising a lighter phase containing fatty acid alkyl esters and at least one heavier phase containing microbial biomass; a composition comprising a lighter phase containing completely saturated lipids and at least one heavier phase containing microbial biomass; a composition comprising a lighter phase containing lipids and at least one heavier phase containing microbial biomass from more than one species or strain; a composition comprising a lighter phase containing hydroxylated lipids and at least one heavier phase containing microbial biomass; and a composition comprising a lighter phase containing free fatty acids and at least one heavier phase containing microbial biomass. The present invention also provides compositions comprising saponified oil derived from the alkaline hydrolysis of biomass produced by culturing a population of microorganisms.
Microorganisms useful in the invention produce lipids suitable for chemical modification for biodiesel production and for production of fatty acid esters for other purposes such as industrial chemical feedstocks and edible oils, as well as the production of other chemical entities. Suitable lipids for biodiesel and chemicals production include TAGs containing fatty acid molecules. In some embodiments, suitable fatty acids contain at least 8, at least 10, at least 12, at least 14, at least 16, at least 18, at least 20, at least 22, at least 24, at least 26, at least 28, at least 30, at least 32, or at least 34 carbon atoms or more. Preferred fatty acids for biodiesel generally contain 16 and 18 carbon atoms. In certain embodiments, the above fatty acids are saturated (with no carbon-carbon double or triple bonds); mono unsaturated (single double bond); polyunsaturated (two or more double bonds); are linear (not cyclic); and/or have little or no branching in their structures.
In some embodiments, culturing microorganisms useful in the in situ transesterification and modification methods of the present invention yields a biomass that, when dry, comprises an oil content of at least 5%, at least 10%, at least 15%, at least 20%, or at least 25%. In other embodiments, the dried biomass comprises an oil content of at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, or at least 90%. “Dry” or “dried,” as used in this context, refers to the absence of substantially all water. Biomass can also be chemically modified without being dried; for example, biomass includes a centrifuged cell paste.
In some embodiments, culturing microorganisms useful in the in situ transesterification and other chemical modification methods of the invention yields a biomass in which at least 10% of the lipid is C18, at least 15% of the lipid is C18, at least 20% of the lipid is C18, or at least 25% of the lipid is C18. In other embodiments, the biomass comprises a lipid constituent which is at least 30% C18, at least 35% C18, at least 40% C18, at least 45% C18, or at least 50% C18. In still other embodiments, the biomass can comprise a lipid component that is at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, or at least 50% C14 and/or C16, or longer chain lengths. Alternatively, the biomass can comprise a lipid component that is at least 10% or at least 20% C14, or shorter chain lengths.
A preferred microorganism useful to produce lipids for use in the invention are microalgae in the genus Prototheca. For the convenience of the reader, this section is subdivided into subsections. Subsection 1 describes Prototheca species and strains and how to identify new Prototheca species and strains related microalgae by genomic DNA comparison. Subsection 2 describes bioreactors useful for cultivation. Subsection 3 describes media for cultivation. Subsection 4 describes oil/lipid production in accordance with illustrative cultivation methods of the invention.
A. Prototheca Species and Strains
Prototheca is a remarkable microorganism for use in the production of lipid, because it can produce high levels of lipid, particularly lipid suitable for fuel production. The lipid produced by Prototheca has hydrocarbon chains of shorter chain length and a higher degree of saturation than that produced by other microalgae. Chain length and saturated lipid produced by Prototheca species is suitable for saponification and other chemical modifications used to produced chemicals and fuels. Moreover, Prototheca lipid is generally free of pigment (low to undetectable levels of chlorophyll and certain carotenoids) and in any event contains much less pigment than lipid from other microalgae. Illustrative Prototheca strains for use in the methods of the invention include Prototheca wickerhamii, Prototheca stagnora (including UTEX 327), Prototheca portoricensis, Prototheca moriformis (including UTEX strains 1441, 1435), and Prototheca zopfii. Species of the genus Prototheca are obligate heterotrophs.
Species of Prototheca for use in the invention can be identified by amplification of certain target regions of the genome. For example, identification of a specific Prototheca species or strain can be achieved through amplification and sequencing of nuclear and/or chloroplast DNA using primers and methodology using any region of the genome, for example using the methods described in Wu et al., Bot. Bull. Acad. Sin. (2001) 42:115-121 Identification of Chlorella spp. isolates using ribosomal DNA sequences. Well established methods of phylogenetic analysis, such as amplification and sequencing of ribosomal internal transcribed spacer (ITS1 and ITS2 rDNA), 23S rRNA, 18S rRNA, and other conserved genomic regions can be used by those skilled in the art to identify species of not only Prototheca, but other hydrocarbon and lipid producing organisms with similar lipid profiles and production capability. For examples of methods of identification and classification of algae also see for example Genetics, 2005 August; 170(4):1601-10 and RNA, 2005 April; 11(4):361-4.
Thus, genomic DNA comparison can be used to identify suitable species of microalgae to be used in the present invention. Regions of conserved genomic DNA, such as but not limited to DNA encoding for 23S rRNA, can be amplified from microalgal species and compared to consensus sequences in order to screen for microalgal species that are taxonomically related to the preferred microalgae used in the present invention. Examples of such DNA sequence comparison for species within the Prototheca genus are shown below. Genomic DNA comparison can also be useful to identify microalgal species that have been misidentified in a strain collection. Often a strain collection will identify species of microalgae based on phenotypic and morphological characteristics. The use of these characteristics may lead to miscategorization of the species or the genus of a microalgae. The use of genomic DNA comparison can be a better method of categorizing microalgae species based on their phylogenetic relationship.
Microalgae for use in the present invention typically have genomic DNA sequences encoding for 23S rRNA that have at least 99%, least 95%, at least 90%, or at least 85% nucleotide identity to at least one of the sequences listed in SEQ ID NOs: 3-11.
For sequence comparison to determine percent nucleotide or amino acid identity, typically one sequence acts as a reference sequence, to which test sequences are compared. When using a sequence comparison algorithm, test and reference sequences are input into a computer, subsequence coordinates are designated, if necessary, and sequence algorithm program parameters are designated. The sequence comparison algorithm then calculates the percent sequence identity for the test sequence(s) relative to the reference sequence, based on the designated program parameters.
Optimal alignment of sequences for comparison can be conducted, e.g., by the local homology algorithm of Smith & Waterman, Adv. Appl. Math. 2:482 (1981), by the homology alignment algorithm of Needleman & Wunsch, J. Mol. Biol. 48:443 (1970), by the search for similarity method of Pearson & Lipman, Proc. Nat'l. Acad. Sci. USA 85:2444 (1988), by computerized implementations of these algorithms (GAP, BESTFIT, FASTA, and TFASTA in the Wisconsin Genetics Software Package, Genetics Computer Group, 575 Science Dr., Madison, Wis.), or by visual inspection (see generally Ausubel et al., supra).
Another example algorithm that is suitable for determining percent sequence identity and sequence similarity is the BLAST algorithm, which is described in Altschul et al., J. Mol. Biol. 215:403-410 (1990). Software for performing BLAST analyses is publicly available through the National Center for Biotechnology Information (at the web address www.ncbi.nlm.nih.gov). This algorithm involves first identifying high scoring sequence pairs (HSPs) by identifying short words of length W in the query sequence, which either match or satisfy some positive-valued threshold score T when aligned with a word of the same length in a database sequence. T is referred to as the neighborhood word score threshold (Altschul et al., supra.). These initial neighborhood word hits act as seeds for initiating searches to find longer HSPs containing them. The word hits are then extended in both directions along each sequence for as far as the cumulative alignment score can be increased. Cumulative scores are calculated using, for nucleotide sequences, the parameters M (reward score for a pair of matching residues; always >0) and N (penalty score for mismatching residues; always <0). For amino acid sequences, a scoring matrix is used to calculate the cumulative score. Extension of the word hits in each direction are halted when: the cumulative alignment score falls off by the quantity X from its maximum achieved value; the cumulative score goes to zero or below due to the accumulation of one or more negative-scoring residue alignments; or the end of either sequence is reached. For identifying whether a nucleic acid or polypeptide is within the scope of the invention, the default parameters of the BLAST programs are suitable. The BLASTN program (for nucleotide sequences) uses as defaults a word length (W) of 11, an expectation (E) of 10, M=5, N=−4, and a comparison of both strands. For amino acid sequences, the BLASTP program uses as defaults a word length (W) of 3, an expectation (E) of 10, and the BLOSUM62 scoring matrix. The TBLATN program (using protein sequence for nucleotide sequence) uses as defaults a word length (W) of 3, an expectation (E) of 10, and a BLOSUM 62 scoring matrix. (see Henikoff & Henikoff, Proc. Natl. Acad. Sci. USA 89:10915 (1989)).
In addition to calculating percent sequence identity, the BLAST algorithm also performs a statistical analysis of the similarity between two sequences (see, e.g., Karlin & Altschul, Proc. Nat'l. Acad. Sci. USA 90:5873-5787 (1993)). One measure of similarity provided by the BLAST algorithm is the smallest sum probability (P(N)), which provides an indication of the probability by which a match between two nucleotide or amino acid sequences would occur by chance. For example, a nucleic acid is considered similar to a reference sequence if the smallest sum probability in a comparison of the test nucleic acid to the reference nucleic acid is less than about 0.1, more preferably less than about 0.01, and most preferably less than about 0.001.
Other considerations affecting the selection of microorganisms for use in the invention include, in addition to production of suitable lipids or hydrocarbons for production of oils, fuels, and oleochemicals: (1) high lipid content as a percentage of cell weight; (2) ease of growth; and (3) ease of biomass processing. In particular embodiments, microorganism yields cells that are at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, or at least 70% or more lipid. Preferred organisms grow heterotrophically (on sugars in the absence of light).
B. Bioreactor
Microorganisms are cultured both for purposes of conducting genetic manipulations and for production of hydrocarbons (e.g., lipids, fatty acids, aldehydes, alcohols, and alkanes). The former type of culture is conducted on a small scale and initially, at least, under conditions in which the starting microorganism can grow. Culture for purposes of hydrocarbon production is usually conducted on a large scale (e.g., 10,000 L, 40,000 L, 100,000 L or larger bioreactors) in a bioreactor. Prototheca are typically cultured in the methods of the invention in liquid media within a bioreactor. Typically, the bioreactor does not allow light to enter.
The bioreactor or fermentor is used to culture microalgal cells through the various phases of their physiological cycle. Bioreactors offer many advantages for use in heterotrophic growth and propagation methods. To produce biomass for use in food, microalgae are preferably fermented in large quantities in liquid, such as in suspension cultures as an example. Bioreactors such as steel fermentors can accommodate very large culture volumes (40,000 liter and greater capacity bioreactors are used in various embodiments of the invention). Bioreactors also typically allow for the control of culture conditions such as temperature, pH, oxygen tension, and carbon dioxide levels. For example, bioreactors are typically configurable, for example, using ports attached to tubing, to allow gaseous components, like oxygen or nitrogen, to be bubbled through a liquid culture. Other culture parameters, such as the pH of the culture media, the identity and concentration of trace elements, and other media constituents can also be more readily manipulated using a bioreactor.
Bioreactors can be configured to flow culture media though the bioreactor throughout the time period during which the microalgae reproduce and increase in number. In some embodiments, for example, media can be infused into the bioreactor after inoculation but before the cells reach a desired density. In other instances, a bioreactor is filled with culture media at the beginning of a culture, and no more culture media is infused after the culture is inoculated. In other words, the microalgal biomass is cultured in an aqueous medium for a period of time during which the microalgae reproduce and increase in number; however, quantities of aqueous culture medium are not flowed through the bioreactor throughout the time period. Thus in some embodiments, aqueous culture medium is not flowed through the bioreactor after inoculation.
Bioreactors equipped with devices such as spinning blades and impellers, rocking mechanisms, stir bars, means for pressurized gas infusion can be used to subject microalgal cultures to mixing. Mixing may be continuous or intermittent. For example, in some embodiments, a turbulent flow regime of gas entry and media entry is not maintained for reproduction of microalgae until a desired increase in number of said microalgae has been achieved.
Bioreactor ports can be used to introduce, or extract, gases, solids, semisolids, and liquids, into the bioreactor chamber containing the microalgae. While many bioreactors have more than one port (for example, one for media entry, and another for sampling), it is not necessary that only one substance enter or leave a port. For example, a port can be used to flow culture media into the bioreactor and later used for sampling, gas entry, gas exit, or other purposes. Preferably, a sampling port can be used repeatedly without altering compromising the axenic nature of the culture. A sampling port can be configured with a valve or other device that allows the flow of sample to be stopped and started or to provide a means of continuous sampling. Bioreactors typically have at least one port that allows inoculation of a culture, and such a port can also be used for other purposes such as media or gas entry.
Bioreactors ports allow the gas content of the culture of microalgae to be manipulated. To illustrate, part of the volume of a bioreactor can be gas rather than liquid, and the gas inlets of the bioreactor to allow pumping of gases into the bioreactor. Gases that can be beneficially pumped into a bioreactor include air, air/CO2 mixtures, noble gases, such as argon, and other gases. Bioreactors are typically equipped to enable the user to control the rate of entry of a gas into the bioreactor. As noted above, increasing gas flow into a bioreactor can be used to increase mixing of the culture.
Increased gas flow affects the turbidity of the culture as well. Turbulence can be achieved by placing a gas entry port below the level of the aqueous culture media so that gas entering the bioreactor bubbles to the surface of the culture. One or more gas exit ports allow gas to escape, thereby preventing pressure buildup in the bioreactor. Preferably a gas exit port leads to a “one-way” valve that prevents contaminating microorganisms from entering the bioreactor.
C. Media
Microalgal culture media typically contains components such as a fixed nitrogen source, a fixed carbon source, trace elements, optionally a buffer for pH maintenance, and phosphate (typically provided as a phosphate salt). Other components can include salts such as sodium chloride, particularly for seawater microalgae. Nitrogen sources include organic and inorganic nitrogen sources, including, for example, without limitation, molecular nitrogen, nitrate, nitrate salts, ammonia (pure or in salt form, such as, (NH4)2SO4 and NH4OH), protein, soybean meal, cornsteep liquor, and yeast extract. Examples of trace elements include zinc, boron, cobalt, copper, manganese, and molybdenum in, for example, the respective forms of ZnCl2, H3BO3, CoCl2.6H2O, CuCl2.2H2O, MnCl2.4H2O and (NH4)6Mo7O24.4H2O.
Microorganisms useful in accordance with the methods of the present invention are found in various locations and environments throughout the world. As a consequence of their isolation from other species and their resulting evolutionary divergence, the particular growth medium for optimal growth and generation of lipid and/or hydrocarbon constituents can be difficult to predict. In some cases, certain strains of microorganisms may be unable to grow on a particular growth medium because of the presence of some inhibitory component or the absence of some essential nutritional requirement required by the particular strain of microorganism.
Solid and liquid growth media are generally available from a wide variety of sources, and instructions for the preparation of particular media that is suitable for a wide variety of strains of microorganisms can be found, for example, online at http://www.utex.org/, a site maintained by the University of Texas at Austin, 1 University Station A6700, Austin, Tex., 78712-0183, for its culture collection of algae (UTEX). For example, various fresh water and salt water media include those described in PCT Pub. No. 2008/151149, incorporated herein by reference.
In a particular example, Proteose Medium is suitable for axenic cultures, and a 1 L volume of the medium (pH ˜6.8) can be prepared by addition of 1 g of proteose peptone to 1 liter of Bristol Medium. Bristol medium comprises 2.94 mM NaNO3, 0.17 mM CaCl2.2H2O, 0.3 mM MgSO4.7H2O, 0.43 mM, 1.29 mM KH2PO4, and 1.43 mM NaCl in an aqueous solution. For 1.5% agar medium, 15 g of agar can be added to 1 L of the solution. The solution is covered and autoclaved, and then stored at a refrigerated temperature prior to use. Another example is the Prototheca isolation medium (PIM), which comprises 10 g/L potassium hydrogen phthalate (KHP), 0.9 g/L sodium hydroxide, 0.1 g/L magnesium sulfate, 0.2 g/L potassium hydrogen phosphate, 0.3 g/L ammonium chloride, 10 g/L glucose 0.001 g/L thiamine hydrochloride, 20 g/L agar, 0.25 g/L 5-fluorocytosine, at a pH in the range of 5.0 to 5.2 (see Pore, 1973, App. Microbiology, 26: 648-649). Other suitable media for use with the methods of the invention can be readily identified by consulting the URL identified above, or by consulting other organizations that maintain cultures of microorganisms, such as SAG, CCAP, or CCALA. SAG refers to the Culture Collection of Algae at the University of Göttingen (Göttingen, Germany), CCAP refers to the culture collection of algae and protozoa managed by the Scottish Association for Marine Science (Scotland, United Kingdom), and CCALA refers to the culture collection of algal laboratory at the Institute of Botany (T{hacek over (r)}ebo{hacek over (n)}, Czech Republic). Additionally, U.S. Pat. No. 5,900,370 describes media formulations and conditions suitable for heterotrophic fermentation of Prototheca species.
For oil production, selection of a fixed carbon source is important, as the cost of the fixed carbon source must be sufficiently low to make oil production economical. Thus, while suitable carbon sources include, for example, acetate, floridoside, fructose, galactose, glucuronic acid, glucose, glycerol, lactose, mannose, N-acetylglucosamine, rhamnose, sucrose, and/or xylose, selection of feedstocks containing those compounds is an important aspect of the methods of the invention. Suitable feedstocks useful in accordance with the methods of the invention include, for example, black liquor, corn starch, depolymerized cellulosic material, milk whey, molasses, potato, sorghum, sucrose, sugar beet, sugar cane, rice, and wheat. Carbon sources can also be provided as a mixture, such as a mixture of sucrose and depolymerized sugar beet pulp. The one or more carbon source(s) can be supplied at a concentration of at least about 50 μM, at least about 100 μM, at least about 500 μM, at least about 5 mM, at least about 50 mM, and at least about 500 mM, of one or more exogenously provided fixed carbon source(s). Carbon sources of particular interest for purposes of the present invention include cellulose (in a depolymerized form), glycerol, sucrose, and sorghum, each of which is discussed in more detail below.
In accordance with the present invention, microorganisms can be cultured using depolymerized cellulosic biomass as a feedstock. Cellulosic biomass (e.g., stover, such as corn stover) is inexpensive and readily available; however, attempts to use this material as a feedstock for yeast have failed. In particular, such feedstocks have been found to be inhibitory to yeast growth, and yeast cannot use the 5-carbon sugars produced from cellulosic materials (e.g., xylose from hemi-cellulose). By contrast, microalgae can grow on processed cellulosic material. Cellulosic materials generally include about 40-60% cellulose; about 20-40% hemicellulose; and 10-30% lignin.
Suitable cellulosic materials include residues from herbaceous and woody energy crops, as well as agricultural crops, i.e., the plant parts, primarily stalks and leaves, not removed from the fields with the primary food or fiber product. Examples include agricultural wastes such as sugarcane bagasse, rice hulls, corn fiber (including stalks, leaves, husks, and cobs), wheat straw, rice straw, sugar beet pulp, citrus pulp, citrus peels; forestry wastes such as hardwood and softwood thinnings, and hardwood and softwood residues from timber operations; wood wastes such as saw mill wastes (wood chips, sawdust) and pulp mill waste; urban wastes such as paper fractions of municipal solid waste, urban wood waste and urban green waste such as municipal grass clippings; and wood construction waste. Additional cellulosics include dedicated cellulosic crops such as switchgrass, hybrid poplar wood, and miscanthus, fiber cane, and fiber sorghum. Five-carbon sugars that are produced from such materials include xylose.
In another embodiment of the methods of the invention, the carbon source is glycerol, including acidulated and non-acidulated glycerol byproduct from biodiesel transesterification. In one embodiment, the carbon source includes glycerol and at least one other carbone source. In some cases, all of the glycerol and the at least one other fixed carbon source are provided to the microorganism at the beginning of the fermentation. In some cases, the glycerol and the at least one other fixed carbon source are provided to the microorganism simultaneously at a predetermined ratio. In some cases, the glycerol and the at least one other fixed carbon source are fed to the microbes at a predetermined rate over the course of fermentation.
Some microalgae undergo cell division faster in the presence of glycerol than in the presence of glucose (see PCT Pub. No. 2008/151149). In these instances, two-stage growth processes in which cells are first fed glycerol to rapidly increase cell density, and are then fed glucose to accumulate lipids can improve the efficiency with which lipids are produced. The use of the glycerol byproduct of the transesterification process provides significant economic advantages when put back into the production process. Other feeding methods are provided as well, such as mixtures of glycerol and glucose. Feeding such mixtures also captures the same economic benefits. In addition, the invention provides methods of feeding alternative sugars to microalgae such as sucrose in various combinations with glycerol.
In another embodiment of the methods of the invention, the carbon source is sucrose, including a complex feedstock containing sucrose, such as thick cane juice from sugar cane processing. In one embodiment, the culture medium further includes at least one sucrose utilization enzyme. In some cases, the culture medium includes a sucrose invertase. In one embodiment, the sucrose invertase enzyme is a secrectable sucrose invertase enzyme encoded by an exogenous sucrose invertase gene expressed by the population of microorganisms.
Complex feedstocks containing sucrose include waste molasses from sugar cane processing; the use of this low-value waste product of sugar cane processing can provide significant cost savings in the production of hydrocarbons and other oils. Another complex feedstock containing sucrose that is useful in the methods of the invention is sorghum, including sorghum syrup and pure sorghum. Sorghum syrup is produced from the juice of sweet sorghum cane. Its sugar profile consists of mainly glucose (dextrose), fructose and sucrose.
D. Oil Production
For the production of oil in accordance with the methods of the invention, it is preferable to culture cells in the dark, as is the case, for example, when using extremely large (40,000 liter and higher) fermentors that do not allow light to strike the culture. Microalgae, including Prototheca species are grown and propagated for the production of oil in a medium containing a fixed carbon source and in the absence of light; such growth is known as heterotrophic growth.
As an example, an inoculum of lipid-producing microalgal cells are introduced into the medium; there is a lag period (lag phase) before the cells begin to propagate. Following the lag period, the propagation rate increases steadily and enters the log, or exponential, phase. The exponential phase is in turn followed by a slowing of propagation due to decreases in nutrients such as nitrogen, increases in toxic substances, and quorum sensing mechanisms. After this slowing, propagation stops, and the cells enter a stationary phase or steady growth state, depending on the particular environment provided to the cells. For obtaining lipid rich biomass, the culture is typically harvested well after then end of the exponential phase, which may be terminated early by allowing nitrogen or another key nutrient (other than carbon) to become depleted, forcing the cells to convert the carbon sources, present in excess, to lipid. Culture condition parameters can be manipulated to optimize total oil production, the combination of lipid species produced, and/or production of a specific oil.
As discussed above, a bioreactor or fermentor is used to allow cells to undergo the various phases of their growth cycle. As an example, an inoculum of lipid-producing cells can be introduced into a medium followed by a lag period (lag phase) before the cells begin growth. Following the lag period, the growth rate increases steadily and enters the log, or exponential, phase. The exponential phase is in turn followed by a slowing of growth due to decreases in nutrients and/or increases in toxic substances. After this slowing, growth stops, and the cells enter a stationary phase or steady state, depending on the particular environment provided to the cells. Lipid production by cells disclosed herein can occur during the log phase or thereafter, including the stationary phase wherein nutrients are supplied, or still available, to allow the continuation of lipid production in the absence of cell division.
Preferably, microorganisms grown using conditions described herein and known in the art comprise at least about 20% by weight of lipid, preferably at least about 40% by weight, more preferably at least about 50% by weight, and most preferably at least about 60% by weight. Process conditions can be adjusted to increase the yield of lipids suitable for a particular use and/or to reduce production cost. For example, in certain embodiments, a microalgae is cultured in the presence of a limiting concentration of one or more nutrients, such as, for example, nitrogen, phosphorous, or sulfur, while providing an excess of fixed carbon energy such as glucose. Nitrogen limitation tends to increase microbial lipid yield over microbial lipid yield in a culture in which nitrogen is provided in excess. In particular embodiments, the increase in lipid yield is at least about: 10%, 50%, 100%, 200%, or 500%. The microbe can be cultured in the presence of a limiting amount of a nutrient for a portion of the total culture period or for the entire period. In particular embodiments, the nutrient concentration is cycled between a limiting concentration and a non-limiting concentration at least twice during the total culture period. Lipid content of cells can be increased by continuing the culture for increased periods of time while providing an excess of carbon, but limiting or no nitrogen.
Microalgal biomass with a high percentage of oil/lipid accumulation by dry weight has been generated using a variety of different methods of culture known in the art. Microalgal biomass with a higher percentage of accumulated oil/lipid is useful in accordance with the present invention. Li et al. describe Chlorella vulgaris cultures with up to 56.6% lipid by DCW in stationary cultures grown under autotrophic conditions (i.e., photosynthetic growth conditions) using high iron concentrations (Li et al., Bioresource Technology 99(11):4717-22 (2008)). Rodolfi et al. describe Nanochloropsis sp. and Chaetoceros calcitrans cultures with 60% lipid DCW and 39.8% lipid DCW, respectively, grown in a photobioreactor under nitrogen starvation conditions (Rodolfi et al., Biotechnology & Bioengineering 102(1):100-112 (2008)). Solovchenko et al. describe Parietochloris incise cultures with approximately 30% lipid accumulation (DCW) when grown phototrophically and under low nitrogen conditions (Solovchenko et al., Journal of Applied Phcology 20:245-251 (2008)). Chlorella protothecoides can produce up to 55% lipid (DCW) grown under certain heterotrophic conditions with nitrogen starvation (Miao and Wu, Bioresource Technology 97:841-846 (2006)). Other Chlorella species including Chlorella emersonii, Chlorella sorokiniana, and Chlorella minutissima have been described to have accumulated up to 63% oil (DCW) when grown in stirred tank bioreactors under low-nitrogen media conditions (Illman et al., Enzyme and Microbial Technology 27:631-635 (2000)). Still higher percent lipid accumulation by DCW has been reported, including 70% lipid (DCW) accumulation in Dumaliella tertiolecta cultures grown in increased NaCl conditions (Takagi et al., Journal of Bioscience and Bioengineering 101(3): 223-226 (2006)) and 75% lipid accumulation in Botryococcus braunii cultures (Banerjee et al., Critical Reviews in Biotechnology 22(3): 245-279 (2002)). These and similar methods can be used for photosynthetic and heterotrophic growth of microalgae to produce oil.
In another embodiment, lipid yield is increased by culturing a lipid-producing microbe (e.g., microalgae) in the presence of one or more cofactor(s) for a lipid pathway enzyme (e.g., a fatty acid synthetic enzyme). Generally, the concentration of the cofactor(s) is sufficient to increase microbial lipid (e.g., fatty acid) yield over microbial lipid yield in the absence of the cofactor(s). In a particular embodiment, the cofactor(s) are provided to the culture by including in the culture a microbe (e.g., microalgae) containing an exogenous gene encoding the cofactor(s). Alternatively, cofactor(s) may be provided to a culture by including a microbe (e.g., microalgae) containing an exogenous gene that encodes a protein that participates in the synthesis of the cofactor. In certain embodiments, suitable cofactors include any vitamin required by a lipid pathway enzyme, such as, for example: biotin, pantothenate. Genes encoding cofactors suitable for use in the invention or that participate in the synthesis of such cofactors are well known and can be introduced into microbes (e.g., microalgae), using contructs and techniques such as those described above.
The specific examples of bioreactors, culture conditions, and heterotrophic growth and propagation methods described herein can be combined in any suitable manner to improve efficiencies of microbial growth and lipid and/or protein production.
Microalgal biomass with a high percentage of oil/lipid accumulation by dry weight has been generated using different methods of culture, which are known in the art (see PCT Pub. No. 2008/151149). Microalgal biomass generated by the culture methods described herein and useful in accordance with the present invention comprises at least 10% microalgal oil by dry weight. In some embodiments, the microalgal biomass comprises at least 25%, at least 50%, at least 55%, or at least 60% microalgal oil by dry weight. In some embodiments, the microalgal biomass contains from 10-90% microalgal oil, from 25-75% microalgal oil, from 40-75% microalgal oil, or from 50-70% microalgal oil by dry weight.
The microalgal oil of the biomass described herein, or extracted from the biomass for use in the methods and compositions of the present invention can comprise glycerolipids with one or more distinct fatty acid ester side chains. Glycerolipids are comprised of a glycerol molecule esterified to one, two or three fatty acid molecules, which can be of varying lengths and have varying degrees of saturation. The length and saturation characteristics of the fatty acid molecules (and the microalgal oils) can be manipulated to modify the properties or proportions of the fatty acid molecules in the microalgal oils of the present invention via culture conditions. Thus, specific blends of algal oil can be prepared either within a single species of algae by mixing together the biomass or algal oil from two or more species of microalgae, or by blending algal oil of the invention with oils from other sources such as soy, rapeseed, canola, palm, palm kernel, coconut, corn, waste vegetable, Chinese tallow, olive, sunflower, cottonseed, chicken fat, beef tallow, porcine tallow, microalgae, macroalgae, microbes, Cuphea, flax, peanut, choice white grease, lard, Camelina sativa, mustard seed, cashew nut, oats, lupine, kenaf, calendula, help, coffee, linseed (flax), hazelnut, euphorbia, pumpkin seed, coriander, camellia, sesame, safflower, rice, tung tree, cocoa, copra, pium poppy, castor beans, pecan, jojoba, macadamia, Brazil nuts, avocado, petroleum, or a distillate fraction of any of the preceding oils.
The oil composition, i.e., the properties and proportions of the fatty acid constituents of the glycerolipids, can also be manipulated by combining biomass or oil from at least two distinct species of microalgae. In some embodiments, at least two of the distinct species of microalgae have different glycerolipid profiles. The distinct species of microalgae can be cultured together or separately as described herein, preferably under heterotrophic conditions, to generate the respective oils. Different species of microalgae can contain different percentages of distinct fatty acid constituents in the cell's glycerolipids.
Generally, Prototheca strains have very little or no fatty acids with the chain length C8-C14. For example, Prototheca moriformis (UTEX 1435), Prototheca krugani (UTEX 329), Prototheca stagnora (UTEX 1442) and Prototheca zopfii (UTEX 1438) contains no (or undectable amounts) C8 fatty acids, between 0-0.01% C10 fatty acids, between 0.03-2.1% C12 fatty acids and between 1.0-1.7% C14 fatty acids. Prototheca strains have a lipid profile of at least 20% C16 fatty acids, at least 50% C18:1 fatty acids and at least 8% C18:2 fatty acids. As a non-limiting example, strains and species of Prototheca have a lipid profile of: C14:0 fatty acid, 1.3±0.6%; C16:0 fatty acid, 23±4%; C16:1, 1.0±0.5%; C18:0 fatty acid, 3.5±1.5%; C18:1 fatty acid 62±5%; C18:2 fatty acid, 8.5±1.0%; and each other fatty acid, ≦1.0%.
Microalgal oil can also include other constituents produced by the microalgae, or incorporated into the microalgal oil from the culture medium. These other constituents can be present in varying amount depending on the culture conditions used to culture the microalgae, the species of microalgae, the extraction method used to recover microalgal oil from the biomass and other factors that may affect microalgal oil composition. Non-limiting examples of such constituents include carotenoids, present from 0.1-0.4 micrograms/ml, chlorophyll present from 0-0.02 milligrams/kilogram of oil, gamma tocopherol present from 0.4-0.6 milligrams/100 grams of oil, and total tocotrienols present from 0.2-0.5 milligrams/gram of oil.
The other constituents can include, without limitation, phospholipids, tocopherols, tocotrienols, carotenoids (e.g., alpha-carotene, beta-carotene, lycopene, etc.), xanthophylls (e.g., lutein, zeaxanthin, alpha-cryptoxanthin and beta-crytoxanthin), and various organic or inorganic compounds.
In some cases, the oil extracted from Prototheca species comprises no more than 0.02 mg/kg chlorophyll. In some cases, the oil extracted from Prototheca species comprises no more than 0.4 mcg/ml total carotenoids. In some cases the Prototheca oil comprises between 0.40-0.60 milligrams of gamma tocopherol per 100 grams of oil. In other cases, the Prototheca oil comprises between 0.2-0.5 milligrams of total tocotrienols per gram of oil.
In situ transesterification of TAGs to fatty acid alkyl esters in accordance with the methods of the present invention can be performed on biomass generated from the microbial cultures described above. In some embodiments, the biomass may comprise biomass combined from two or more cultures of distinct strains or species of microorganisms.
In some methods of the invention, the microbial biomass is first harvested from the culture medium and dried, and then subjected to an optional biomass disruption process prior to transesterification. In other methods of the invention, the microbial biomass is subjected to a biomass disruption process prior to drying and transesterification. In some methods, harvesting the biomass comprises separating the cellular components of the biomass from the water and cell culture media by, for example, passing the contents of the cell culture bioreactor through a screen or similar filtering apparatus. In some embodiments, harvesting the biomass comprises processing the cellular components of the cell culture into a paste or low moisture-content composition.
A. Drying Methods
Drying the biomass generated from the cultured microorganisms described herein removes water that would otherwise be available as a substrate during the transesterification reaction, described in greater detail below, leading to the formation of free fatty acids, rather than the desired fatty acid alkyl esters. The extent to which biomass used in the in situ transesterification methods of the present invention must be dried depends on the alcohol:biomass ratio used in the transesterification process, the cost of the alcohol, and the cost or other volume constraints placed on the size of the reaction vessel in which the transesterification is to be performed. As will be appreciated, these factors, balanced against the costs of drying the biomass, determine an “acceptable dryness” for the biomass.
In some embodiments, the biomass can be dried using a drum dryer in which the biomass is rotated in a drum and dried with the application of air, which may be heated to expedite the drying process. In other embodiments, an oven or spray dryer can be used to facilitate drying of the biomass. Alternatively, the biomass may be dried via a lyophilization process. The lyophilization process may summarily be described as a “freeze-drying” process, in which the biomass is frozen in a freeze-drying chamber. The application of a vacuum to the freeze-drying chamber results in sublimation (primary drying) and desorption (secondary drying) of the water from the biomass, resulting in a product suitable for further processing as described below. In still other embodiments a combination of the foregoing may be utilized to appropriately dry the biomass for further processing in accordance with the methods described herein.
B. Biomass Disruption Methods
In some embodiments it may be desirable to disrupt the biomass prior to in situ transesterification to make the intracellular contents of the microorganisms more readily accessible to the alcohol and catalyst transesterification reagents. This can help to facilitate the conversion of TAGs to fatty acid alkyl esters or other molecules in accordance with the methods of the invention.
In some methods of the invention, disruption of the biomass can be accomplished prior to subjecting the biomass to one or more of the drying processes described above. In other methods, disruption of the biomass can follow such a drying process. In some methods, water is removed from the biomass prior to or after disruption of the biomass, with or without subjecting the biomass to a drying process. Following growth, the microorganisms are optionally isolated by centrifuging the culture medium to generate a concentrated microbial biomass. Disruption of the biomass can be accomplished by lysing the microbial cells to produce a lysate. Cell lysis can be achieved by any convenient means including heat-induced lysis, addition of a base, addition of an acid, via the use of enzymes such as proteases or polysaccharide degradation enzymes such as amylases, via the use of ultrasound, mechanical lysis, via the use of osmotic shock, infection with a lytic virus, and/or expression of one or more lytic genes. Lysis is performed to release intracellular molecules which have been produced by the microorganism. Each of these methods for lysing a microorganism can be used as a single method or in combination.
The extent of cell disruption can be observed by microscopic analysis. Using one or more of the methods described herein, typically more than 70% cell breakage is observed. Preferably, cell breakage is more than 80%, more preferably more than 90% and most preferably about 100%.
In particular embodiments, the microorganism is lysed after growth, for example to increase the exposure of cellular lipid to a catalyst for transesterification such as a lipase or a chemical catalyst, expressed as described below. The timing of lipase expression (e.g., via an inducible promoter), cell lysis, and the adjustment of transesterification reaction conditions (e.g., removal of water, addition of alcohol, etc.) can be adjusted to optimize the yield of fatty acid esters from lipase-mediated transesterification.
In one embodiment of the present invention, the process of lysing a microorganism comprises heating a cellular suspension containing the microorganisms. In this embodiment, the culture medium containing the microorganisms (or a suspension of microorganisms isolated from the culture medium) is heated until the microorganisms, i.e., the cell walls and membranes of microorganisms, degrade or breakdown. Typically, temperatures applied are at least 50° C. Higher temperatures, such as, at least 60° C., at least 70° C., at least 80° C., at least 90° C., at least 100° C., at least 110° C., at least 120° C., at least 130° C. or higher are used for more efficient cell lysis. Lysing cells by heat treatment can be performed by boiling the microorganism. Alternatively, heat treatment (without boiling) can be performed in an autoclave. The heat treated lysate may be cooled for further treatment. Cell disruption can also be performed by steam treatment, i.e., through addition of pressurized steam. Steam treatment of microalgae for cell disruption is described, for example, in U.S. Pat. No. 6,750,048. In some embodiments steam treatment may be achieved by sparging steam into the fermentor and maintaining the broth at a desired temperature for less than about 90 minutes, preferably less than about 60 minutes, and more preferably less than about 30 minutes.
In another embodiment of the present invention, the process of lysing a microorganism comprises adding a base to a cellular suspension containing the microorganism. The base should be strong enough to hydrolyze at least a portion of the proteinaceous compounds of the microorganisms used. Bases which are useful for solubilizing proteins are known in the art of chemistry. Exemplary bases which are useful in these methods include, but are not limited to, hydroxides, carbonates and bicarbonates of lithium, sodium, potassium, calcium, and mixtures thereof. A preferred base is KOH. In another embodiment of the present invention, the process of lysing a microorganism comprises adding an acid to a cellular suspension containing the microorganism.
In another embodiment of the present invention, the process of lysing a microorganism comprises lysing the microorganism with an enzyme. Enzymes for lysing a microorganism include proteases and polysaccharide-degrading enzymes such as hemicellulase, pectinase, cellulase, and driselase. A polysaccharide-degrading enzyme, optionally from Chlorella or a Chlorella virus, is preferred. A preferred pair of enzymes for lysing oil bearing biomass are alcalase and mannaway (Novozymes).
In another embodiment of the present invention, the process of lysing a microorganism is performed using ultrasound, i.e., sonication. Cells can also by lysed with high frequency sound. The sound can be produced electronically and transported through a metallic tip to an appropriately concentrated cellular suspension. This sonication (or ultrasonication) disrupts cellular integrity based on the creation of cavities in the cell suspension.
In another embodiment of the present invention, the process of lysing a microorganism is performed by mechanical means. Cells can be lysed mechanically and optionally homogenized to facilitate lipid transesterification. For example, a pressure disrupter can be used to pump a cell containing slurry through a restricted orifice valve. High pressure (up to 1500 bar) is applied, followed by an instant expansion through an exiting nozzle. Cell disruption is accomplished by three different mechanisms: impingement on the valve, high liquid shear in the orifice, and sudden pressure drop upon discharge, causing an explosion of the cell. The method releases intracellular molecules. Alternatively, a ball mill can be used. In a ball mill, cells are agitated in suspension with small abrasive particles, such as beads. Cells break because of shear forces, grinding between beads, and collisions with beads. The beads disrupt the cells to release cellular contents. Cells can also be disrupted by shear forces, such as with the use of blending (e.g., with a high speed or Waring blender), the french press, or even centrifugation in case of weak cell walls.
In another embodiment of the present invention, the process of lysing a microorganism is performed by applying an osmotic shock.
In another embodiment of the present invention, the process of lysing a microorganism is performed by steam treatment, i.e., through addition of pressurized steam. Steam treatment of microalgae for cell disruption is described, for example, in U.S. Pat. No. 6,750,048.
In another embodiment of the present invention, the process of lysing a microorganism comprises infection of the microorganism with a lytic virus. A wide variety of viruses are known to lyse microorganisms suitable for use in the methods of the present invention, and the selection and use of a particular lytic virus for a particular microorganism is within the level of skill in the art. For example, paramecium bursaria chlorella virus (PBCV-1) is the prototype of a group (family Phycodnaviridae, genus Chlorovirus) of large, icosahedral, plaque-forming, double-stranded DNA viruses that replicate in, and lyse, certain unicellular, eukaryotic chlorella-like green algae. Accordingly, any susceptible microalgae, such as C. protothecoides, can be lysed by infecting the culture with a suitable chlorella virus. Methods of infecting species of Chlorella with a chlorella virus are known. See for example Adv. Virus Res. 2006; 66:293-336; Virology, 1999 Apr. 25; 257(1):15-23; Virology, 2004 Jan. 5; 318(1):214-23; Nucleic Acids Symp. Ser. 2000; (44):161-2; J. Virol. 2006 March; 80(5):2437-44; and Annu. Rev. Microbiol. 1999; 53:447-94.
In another embodiment of the present invention, the process of lysing a microorganism comprises autolysis. In this embodiment, a microorganism useful in the methods of the invention is genetically engineered to produce a lytic gene that will lyse the microorganism. This lytic gene can be expressed using an inducible promoter, so that the cells can first be grown to a desirable density in a culture medium and then harvested, followed by induction of the promoter to express the lytic gene to lyse the cells. In one embodiment, the lytic gene encodes a polysaccharide-degrading enzyme. In certain other embodiments, the lytic gene is a gene from a lytic virus. Thus, for example, a lytic gene from a Chlorella virus can be expressed in a Chlorella such as C. protothecoides.
Expression of lytic genes is preferably done using an inducible promoter, such as a promoter active in microalgae that is induced by a stimulus such as the presence of a small molecule, light, heat, and other stimuli. Lytic genes from chlorella viruses are known. For example, see Virology 260, 308-315 (1999); FEMS Microbiology Letters 180 (1999) 45-53; Virology 263, 376-387 (1999); and Virology 230, 361-368 (1997).
In another embodiment, lysis can be performed using an expeller press. In this process, biomass is forced through a screw-type device at high pressure, lysing the cells and causing the intracellular lipid to be released and separated from the protein and fiber (and other components) in the cells.
In particular embodiments, the microoganisms are lysed after growth, for example to increase the exposure of cellular lipid to a catalyst for transesterification such as a lipase, discussed below, or a chemical catalyst. The timing of lipase expression (e.g., via an inducible promoter), cell lysis, and the modification of transesterification reaction conditions (e.g., removal of water, addition of alcohol, etc.) can be adjusted to optimize the yield of fatty acid esters from lipase-mediated transesterification.
C. Transesterification
Lipids produced by microorganisms as described above are subjected to a process of transesterification in accordance with the methods of the invention to generate a lipophilic phase containing fatty acid alkyl esters and a hydrophilic phase comprising cell material and glycerol. In some methods of the invention, the lipophilic phase is then separated from the hydrophilic cell material.
1. General Chemical Process
Animal and plant oils are typically made of triacylglycerols (TAGs), which are esters of free fatty acids with the trihydric alcohol, glycerol. In transesterification, the glycerol in a TAG is replaced with a lower alkyl alcohol such as methanol, ethanol or isopropanol. A typical reaction scheme is as follows:
In this scheme, the alcohol is deprotonated with a base to make it a stronger nucleophile. Commonly, ethanol or methanol is used in vast excess (up to 50-fold). Normally, this reaction will proceed either exceedingly slowly or not at all. Heat, as well as an acid or base, can be used to help speed the reaction. The acid or base is not consumed by the transesterification reaction; thus, they are not reactants but catalysts. Almost all biodiesel has traditionally been produced using the base-catalyzed technique, as it requires only low temperatures and pressures and produces over 98% conversion yield (provided the starting oil is low in moisture and free fatty acids).
A special case of transesterification is glycerolysis or the use of glycerol(glycerin) to break chemical bonds. The glycerolysis reaction is usually catalyzed by the addition of an acid or a base. Glycerolysis can be performed on simple esters, fats, free fatty acids or TAGs, wherein the methyl esters react with excess glycerol to form mono- and/or diglycerides, producing methanol as a by-product. Mono- and diglycerides are useful as emulsifiers and are commonly added to food products.
2. Using Recombinant Lipases for Transesterification
Transesterification has also been carried out experimentally using an enzyme, such as a lipase, instead of a base. Lipase-catalyzed transesterification can be carried out, for example, at a temperature between the room temperature and 80° C., and a molar ratio of the TAG to the lower alcohol of greater than 1:1, preferably about 3:1. Lipases suitable for use in transesterification in accordance with the methods of the present invention include, but are not limited to, those listed in Table 1. Other examples of lipases useful for transesterification are found in, e.g. U.S. Pat. Nos. 4,798,793; 4,940,845 5,156,963; 5,342,768; 5,776,741 and WO89/01032, each of which is incorporated herein by reference. Such lipases include, but are not limited to, lipases produced by microorganisms of Rhizopus, Aspergillus, Candida, Mucor, Pseudomonas, Rhizomucor, Candida, and Humicola and pancreas lipase.
Aspergillus niger lipase ABG73614, Candida antarctica lipase B
Candida lipolytica lipase (Lipase L; Amano Pharmaceutical Co., Ltd.),
Candida rugosa lipase (e.g., Lipase-OF; Meito Sangyo Co., Ltd.), Mucor
miehei lipase (Lipozyme IM 20), Pseudomonas fluorescens lipase
Rhizomucor miehei lipase B34959, Rhizopus oryzae lipase (Lipase F)
Thermomyces lanuginosa lipase CAB58509, Lipase P (Nagase ChemteX
One challenge to using a lipase for the production of fatty acid esters suitable for biodiesel is that the price of lipase is much higher than the price of sodium hydroxide (NaOH) used by the strong base process. This challenge has been addressed by using an immobilized lipase, which can be recycled. However, the activity of the immobilized lipase must be maintained after being recycled for a minimum number of cycles to allow a lipase-based process to compete with the strong base process in terms of the production cost. Immobilized lipases are subject to poisoning by the lower alcohols typically used in transesterification. U.S. Pat. No. 6,398,707 (issued Jun. 4, 2002 to Wu et al.), incorporated herein by reference, describes methods for enhancing the activity of immobilized lipases and regenerating immobilized lipases having reduced activity. Some suitable methods include immersing an immobilized lipase in an alcohol having a carbon atom number not less than 3 for a period of time, preferably from 0.5-48 hours, and more preferably from 0.5-1.5 hours. Some suitable methods also include washing a deactivated immobilized lipase with an alcohol having a carbon atom number not less than 3 and then immersing the deactivated immobilized lipase in a vegetable oil for 0.5-48 hours.
In particular embodiments, a recombinant lipase is expressed in the same microorganisms that produce the lipid on which the lipase acts. Suitable recombinant lipases include those listed above in Table 1 and/or those described under the GenBank Accession numbers listed above in Table 1, or a polypeptide that has at least 70% amino acid identity with one of the lipases listed above in Table 1 and that exhibits lipase activity. In additional embodiments, the enzymatic activity is present in a sequence that has at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or at least about 99% identity with one of the above described sequences, all of which are hereby incorporated by reference. DNA encoding the lipase and selectable marker is preferably codon-optimized cDNA. Methods of recoding genes for expression in microalgae are described in U.S. Pat. No. 7,135,290.
An exemplary vector design for expression of a lipase gene in a microorganism such as a microalgae contains a gene encoding a lipase in operable linkage with a promoter active in microalgae. Alternatively, if the vector does not contain a promoter in operable linkage with the lipase gene, the lipase gene can be transformed into the cells such that it becomes operably linked to an endogenous promoter at the point of vector integration. The promoterless method of transformation has been demonstrated in microalgae (see, for example, Plant Journal 14:4, (1998), pp. 441-447). The vector can also contain a second gene that encodes a protein that imparts resistance to an antibiotic or herbicide, i.e., a selectable marker. Optionally, one or both gene(s) is/are followed by a 3′ untranslated sequence containing a polyadenylation signal. Expression cassettes encoding the two genes can be physically linked in the vector or on separate vectors. Co-transformation of microalgae can also be used, in which distinct vector molecules are simultaneously used to transform cells (see, for example, Protist 2004 December; 155(4):381-93). The transformed cells can be optionally selected based upon the ability to grow in the presence of the antibiotic or other selectable marker under conditions in which cells lacking the resistance cassette would not grow.
DNA encoding the lipase and selectable marker can be codon-optimized cDNA. Methods of recoding genes for expression in microalgae are described in U.S. Pat. No. 7,135,290. Additional information is available at the web address www.kazusa.or.jp/codon.
Many promoters are active in microalgae, including promoters that are endogenous to the algae being transformed, as well as promoters that are not endogenous to the algae being transformed (i.e., promoters from other algae, promoters from higher plants, and promoters from plant viruses or algae viruses). Exogenous and/or endogenous promoters that are active in microalgae, and antibiotic resistance genes functional in microalgae are known in the art. The promoter used to express an exogenous gene can be the promoter naturally linked to that gene or can be a heterologous gene. Some promoters are active in more than one species of microalgae. Other promoters are species-specific. Preferred promoters include promoters such as RBCS2 from Chlamydomonas reinhardtii and viral promoters, such as cauliflower mosaic virus (CMV) and chlorella virus, which have been shown to be active in multiple species of microalgae (see, for example, Plant Cell Rep. 2005 March; 23(10-11):727-35; J. Microbiol. 2005 August; 43(4):361-5; Mar Biotechnol (NY). 2002 January; 4(1):63-73).
Promoters, cDNAs, and 3′UTRs, as well as other elements of the vectors, can be generated through cloning techniques using fragments isolated from native sources (see, for example, Molecular Cloning: A Laboratory Manual, Sambrook et al. (3d edition, 2001, Cold Spring Harbor Press; and U.S. Pat. No. 4,683,202). Alternatively, elements can be generated synthetically using known methods (see, for example, Gene 1995 Oct. 16; 164(1):49-53).
Cells can be transformed by any suitable technique including, e.g., biolistics, electroporation, glass bead transformation and silicon carbide whisker transformation.
In particular embodiments, the lipase is expressed in an inducible and/or targeted manner. The use of an inducible promoter to express a lipase gene permits production of the lipase after growth of the microorganism when conditions have been adjusted, if necessary, to enhance transesterification, for example, after disruption of the cells, reduction of the water content of the reaction mixture, and/or addition sufficient alcohol to drive conversion of TAGs to fatty acid esters. Inducible promoters useful in the invention include those that mediate transcription of an operably linked gene in response to a stimulus, such as an exogenously provided small molecule, temperature (heat or cold), light, etc. Suitable promoters can activate transcription of an essentially silent gene or upregulate, preferably substantially, transcription of an operably linked gene that is transcribed at a low level. In the latter case, the level of transcription of the lipase preferably does not significantly interfere with the growth of the microorganism in which it is expressed.
It can be advantageous, in particular embodiments, to target expression of the lipase to one or more cellular compartments, where it is sequestered from the majority of cellular lipids until initiation of the transesterification reaction.
Microbial oil can be isolated from microbial biomass (as described, for example, for various strains of Chlorella and Prototheca in the examples below) and chemically treated to produce a variety of useful fuels and other chemicals.
The common international standard for biodiesel is EN 14214. ASTM D6751 is the most common biodiesel standard referenced in the United States and Canada. Germany uses DIN EN 14214 and the UK requires compliance with BS EN 14214. Basic industrial tests to determine whether the products conform to these standards typically include gas chromatography, HPLC, and others. Biodiesel meeting the quality standards is very non-toxic, with a toxicity rating (LD50) of greater than 50 mL/kg.
Although biodiesel that meets the ASTM standards has to be non-toxic, there can be contaminants which tend to crystallize and/or precipitate and fall out of solution as sediment. Sediment formation is particularly a problem when biodiesel is used at lower temperatures. The sediment or precipitates may cause problems such as decreasing fuel flow, clogging fuel lines, clogging filters, etc. Processes are well-known in the art that specifically deal with the removal of these contaminants and sediments in biodiesel in order to produce a higher quality product. Examples for such processes include, but are not limited to, pretreatment of the oil to remove contaminants such as phospholipids and free fatty acids (e.g., degumming, caustic refining and silica adsorbant filtration) and cold filtration. Cold filtration is a process that was developed specifically to remove any particulates and sediments that are present in the biodiesel after production. This process cools the biodiesel and filters out any sediments or precipitates that might form when the fuel is used at a lower temperature. Such a process is well known in the art and is described in US Patent Application Publication No. 2007-0175091. Suitable methods may include cooling the biodiesel to a temperature of less than about 38° C. so that the impurities and contaminants precipitate out as particulates in the biodiesel liquid. Diatomaceous earth or other filtering material may then added to the cooled biodiesel to form a slurry, which may then filtered through a pressure leaf or other type of filter to remove the particulates. The filtered biodiesel may then be run through a polish filter to remove any remaining sediments and diatomaceous earth, so as to produce the final biodiesel product.
Subsequent processes may also be used if the biodiesel will be used in particularly cold temperatures. Such processes include winterization and fractionation. Both processes are designed to improve the cold flow and winter performance of the fuel by lowering the cloud point (the temperature at which the biodiesel starts to crystallize). There are several approaches to winterizing biodiesel. One approach is to blend the biodiesel with petroleum diesel. Another approach is to use additives that can lower the cloud point of biodiesel. Another approach is to remove saturated methyl esters indiscriminately by mixing in additives and allowing for the crystallization of saturates and then filtering out the crystals. Fractionation selectively separates methyl esters into individual components or fractions, allowing for the removal or inclusion of specific methyl esters. Fractionation methods include urea fractionation, solvent fractionation and thermal distillation.
Another valuable fuel provided by the methods of the present invention is renewable diesel, which comprises alkanes, such as C16:0 and C18:0 and thus, are distinguishable from biodiesel. High quality renewable diesel conforms to the ASTM D975 standard. The lipids produced by the methods of the present invention can serve as feedstock to produce renewable diesel. Thus, in another aspect of the present invention, a method for producing renewable diesel is provided. Renewable diesel can be produced by at least three processes: hydrothermal processing (hydrotreating); hydroprocessing; and indirect liquefaction. These processes yield non-ester distillates. During these processes, triacylglycerides produced and isolated as described herein, are converted to alkanes.
In one embodiment, the method for producing renewable diesel comprises (a) cultivating a lipid-containing microorganism using methods disclosed herein (b) lysing the microorganism to produce a lysate, (c) isolating lipid from the lysed microorganism, and (d) deoxygenating and hydrotreating the lipid to produce an alkane, whereby renewable diesel is produced. Lipids suitable for manufacturing renewable diesel can be obtained via extraction from microbial biomass using an organic solvent such as hexane, or via other methods, such as those described in U.S. Pat. No. 5,928,696. Some suitable methods may include mechanical pressing and centrifuging.
In some methods, the microbial lipid is first cracked in conjunction with hydrotreating to reduce carbon chain length and saturate double bonds, respectively. The material is then isomerized, also in conjunction with hydrotreating. The naptha fraction can then be removed through distillation, followed by additional distillation to vaporize and distill components desired in the diesel fuel to meet a D975 standard while leaving components that are heavier than desired for meeting a D 975 standard. Hydrotreating, hydrocracking, deoxygenation and isomerization methods of chemically modifying oils, including triglyceride oils, are well known in the art. See for example European patent applications EP1741768 (A1); EP1741767 (A1); EP1682466 (A1); EP1640437 (A1); EP1681337 (A1); EP1795576 (A1); and U.S. Pat. Nos. 7,238,277; 6,630,066; 6,596,155; 6,977,322; 7,041,866; 6,217,746; 5,885,440; 6,881,873.
In one embodiment of the method for producing renewable diesel, treating the lipid to produce an alkane is performed by hydrotreating of the lipid composition. In hydrothermal processing, typically, biomass is reacted in water at an elevated temperature and pressure to form oils and residual solids. Conversion temperatures are typically 300° to 660° F., with pressure sufficient to keep the water primarily as a liquid, 100 to 170 standard atmosphere (atm). Reaction times are on the order of 15 to 30 minutes. After the reaction is completed, the organics are separated from the water. Thereby a distillate suitable for diesel is produced.
A renewable diesel, also known as “green diesel,” can also be produced from fatty acids by traditional hydroprocessing technology. The triglyceride-containing oils can be hydroprocessed either as co-feed with petroleum or as a dedicated feed. The product is a diesel fuel that conforms with the ASTM D975 specification. Thus, in another embodiment of the method for producing renewable diesel, treating the lipid composition to produce an alkane is performed by hydroprocessing of the lipid composition.
In some methods of making renewable diesel, the first step of treating a triglyceride is hydroprocessing to saturate double bonds, followed by deoxygenation at elevated temperature in the presence of hydrogen and a catalyst. In some methods, hydrogenation and deoxygenation occur in the same reaction. In other methods deoxygenation occurs before hydrogenation. Isomerization is then optionally performed, also in the presence of hydrogen and a catalyst. Naphtha components are preferably removed through distillation. For examples, see U.S. Pat. No. 5,475,160 (hydrogenation of triglycerides); U.S. Pat. No. 5,091,116 (deoxygenation, hydrogenation and gas removal); U.S. Pat. No. 6,391,815 (hydrogenation); and U.S. Pat. No. 5,888,947 (isomerization).
One suitable method for the hydrogenation of triglycerides includes preparing an aqueous solution of copper, zinc, magnesium and lanthanum salts and another solution of alkali metal or preferably, ammonium carbonate. The two solutions may be heated to a temperature of about 20° C. to about 85° C. and metered together into a precipitation container at rates such that the pH in the precipitation container is maintained between 5.5 and 7.5 in order to form a catalyst. Additional water may be used either initially in the precipitation container or added concurrently with the salt solution and precipitation solution. The resulting precipitate may then be thoroughly washed, dried, calcined at about 300° C. and activated in hydrogen at temperatures ranging from about 100° C. to about 400° C. One or more triglycerides may then be contacted and reacted with hydrogen in the presence of the above-described catalyst in a reactor. The reactor may be a trickle bed reactor, fixed bed gas-solid reactor, packed bubble column reactor, continuously stirred tank reactor, a slurry phase reactor, or any other suitable reactor type known in the art. The process may be carried out either batchwise or in continuous fashion. Reaction temperatures are typically in the range of from about 170° C. to about 250° C. while reaction pressures are typically in the range of from about 300 psig to about 2000 psig. Moreover, the molar ratio of hydrogen to triglyceride in the process of the present invention is typically in the range of from about 20:1 to about 700:1. The process is typically carried out at a weight hourly space velocity (WHSV) in the range of from about 0.1 hr−1 to about 5 hr−1. One skilled in the art will recognize that the time period required for reaction will vary according to the temperature used, the molar ratio of hydrogen to triglyceride, and the partial pressure of hydrogen. The products produced by the such hydrogenation processes include fatty alcohols, glycerol, traces of paraffins and unreacted triglycerides. These products are typically separated by conventional means such as, for example, distillation, extraction, filtration, crystallization, and the like.
Petroleum refiners use hydroprocessing to remove impurities by treating feeds with hydrogen. Hydroprocessing conversion temperatures are typically 300° to 700° F. Pressures are typically 40 to 100 atm. The reaction times are typically on the order of 10 to 60 minutes. Solid catalysts are employed to increase certain reaction rates, improve selectivity for certain products, and optimize hydrogen consumption.
Suitable methods for the deoxygenation of an oil includes heating an oil to a temperature in the range of from about 350° F. to about 550° F. and continuously contacting the heated oil with nitrogen under at least pressure ranging from about atmospeheric to above for at least about 5 minutes.
Suitable methods for isomerization includes using alkali isomerization and other oil isomerization known in the art.
Hydrotreating and hydroprocessing ultimately lead to a reduction in the molecular weight of the feed. In the case of triglyceride-containing oils, the triglyceride molecule is reduced to four hydrocarbon molecules under hydroprocessing conditions: a propane molecule and three heavier hydrocarbon molecules, typically in the C8 to C18 range.
Thus, in one embodiment, the product of the one or more chemical reaction(s) is a straight chain alkane mixture that comprises ASTM D975 renewable diesel. Production of hydrocarbons by microorganisms is reviewed by Metzger et al. Appl Microbiol Biotechnol (2005) 66: 486-496 and A Look Back at the U.S. Department of Energy's Aquatic Species Program: Biodiesel from Algae, NREL/TP-580-24190, John Sheehan, Terri Dunahay, John Benemann and Paul Roessler (1998).
A traditional ultra-low sulfur diesel can be produced from any form of biomass by a two-step process. First, the biomass is converted to a syngas, a gaseous mixture rich in hydrogen and carbon monoxide. Then, the syngas is catalytically converted to liquids. Typically, the production of liquids is accomplished using Fischer-Tropsch (FT) synthesis. This technology applies to coal, natural gas, and heavy oils. Thus, in yet another preferred embodiment of the method for producing renewable diesel, treating the lipid composition to produce an alkane is performed by indirect liquefaction of the lipid composition.
The present invention also provides methods to produce jet fuel. Jet fuel is clear to straw colored. The most common fuel is an unleaded/paraffin oil-based fuel classified as Aeroplane A-1, which is produced to an internationally standardized set of specifications. Jet fuel is a mixture of a large number of different hydrocarbons, possibly as many as a thousand or more. The range of their sizes (molecular weights or carbon numbers) is restricted by the requirements for the product, for example, freezing point or smoke point. Kerosone-type Aeroplane fuel (including Jet A and Jet A-1) has a carbon number distribution between about 8 and 16 carbon numbers. Wide-cut or naphta-type Aeroplane fuel (including Jet B) typically has a carbon number distribution between about 5 and 15 carbons.
Both Aeroplanes (Jet A and Jet B) may contain a number of additives. Useful additives include, but are not limited to, antioxidants, antistatic agents, corrosion inhibitors, and fuel system icing inhibitor (FSII) agents. Antioxidants prevent gumming and usually, are based on alkylated phenols, for example, AO-30, A0-31, or AO-37. Antistatic agents dissipate static electricity and prevent sparking. Stadis 450 with dinonylnaphthylsulfonic acid (DINNSA) as the active ingredient, is an example. Corrosion inhibitors, e.g., DCI-4A is used for civilian and military fuels and DCI-6A is used for military fuels. FSII agents, include, e.g., Di-EGME.
In one embodiment of the invention, a jet fuel is produced by blending algal fuels with existing jet fuel. The lipids produced by the methods of the present invention can serve as feedstock to produce jet fuel. Thus, in another aspect of the present invention, a method for producing jet fuel is provided. Herewith two methods for producing jet fuel from the lipids produced by the methods of the present invention are provided: fluid catalytic cracking (FCC); and hydrodeoxygenation (HDO).
Fluid Catalytic Cracking (FCC) is one method which is used to produce olefins, especially propylene from heavy crude fractions. The lipids produced by the method of the present invention can be converted to olefins. The process involves flowing the lipids produced through an FCC zone and collecting a product stream comprised of olefins, which is useful as a jet fuel. The lipids produced are contacted with a cracking catalyst at cracking conditions to provide a product stream comprising olefins and hydrocarbons useful as jet fuel.
In one embodiment, the method for producing jet fuel comprises (a) cultivating a lipid-containing microorganism using methods disclosed herein, (b) lysing the lipid-containing microorganism to produce a lysate, (c) isolating lipid from the lysate, and (d) treating the lipid composition, whereby jet fuel is produced. In one embodiment of the method for producing a jet fuel, the lipid composition can be flowed through a fluid catalytic cracking zone, which, in one embodiment, may comprise contacting the lipid composition with a cracking catalyst at cracking conditions to provide a product stream comprising C2-C5 olefins.
In certain embodiments of this method, it may be desirable to remove any contaminants that may be present in the lipid composition. Thus, prior to flowing the lipid composition through a fluid catalytic cracking zone, the lipid composition is pretreated. Pretreatment may involve contacting the lipid composition with an ion-exchange resin. The ion exchange resin is an acidic ion exchange resin, such as Amberlyst™-15 and can be used as a bed in a reactor through which the lipid composition is flowed, either upflow or downflow. Other pretreatments may include mild acid washes by contacting the lipid composition with an acid, such as sulfuric, acetic, nitric, or hydrochloric acid. Contacting is done with a dilute acid solution usually at ambient temperature and atmospheric pressure.
The lipid composition, optionally pretreated, is flowed to an FCC zone where the hydrocarbonaceous components are cracked to olefins. Catalytic cracking is accomplished by contacting the lipid composition in a reaction zone with a catalyst composed of finely divided particulate material. The reaction is catalytic cracking, as opposed to hydrocracking, and is carried out in the absence of added hydrogen or the consumption of hydrogen. As the cracking reaction proceeds, substantial amounts of coke are deposited on the catalyst. The catalyst is regenerated at high temperatures by burning coke from the catalyst in a regeneration zone. Coke-containing catalyst, referred to herein as “coked catalyst”, is continually transported from the reaction zone to the regeneration zone to be regenerated and replaced by essentially coke-free regenerated catalyst from the regeneration zone. Fluidization of the catalyst particles by various gaseous streams allows the transport of catalyst between the reaction zone and regeneration zone. Methods for cracking hydrocarbons, such as those of the lipid composition described herein, in a fluidized stream of catalyst, transporting catalyst between reaction and regeneration zones, and combusting coke in the regenerator are well known by those skilled in the art of FCC processes. Exemplary FCC applications and catalysts useful for cracking the lipid composition to produce C2-C5 olefins are described in U.S. Pat. Nos. 6,538,169, 7,288,685, which are incorporated in their entirety by reference.
Suitable FCC catalysts generally comprise at least two components that may or may not be on the same matrix. In some embodiments, both two components may be circulated throughout the entire reaction vessel. The first component generally includes any of the well-known catalysts that are used in the art of fluidized catalytic cracking, such as an active amorphous clay-type catalyst and/or a high activity, crystalline molecular sieve. Molecular sieve catalysts may be preferred over amorphous catalysts because of their much-improved selectivity to desired products. IN some preferred embodiments, zeolites may be used as the molecular sieve in the FCC processes. Preferably, the first catalyst component comprises a large pore zeolite, such as an Y-type zeolite, an active alumina material, a binder material, comprising either silica or alumina and an inert filler such as kaolin.
In one embodiment, cracking the lipid composition of the present invention, takes place in the riser section or, alternatively, the lift section, of the FCC zone. The lipid composition is introduced into the riser by a nozzle resulting in the rapid vaporization of the lipid composition. Before contacting the catalyst, the lipid composition will ordinarily have a temperature of about 149° C. to about 316° C. (300° F. to 600° F.). The catalyst is flowed from a blending vessel to the riser where it contacts the lipid composition for a time of abort 2 seconds or less.
The blended catalyst and reacted lipid composition vapors are then discharged from the top of the riser through an outlet and separated into a cracked product vapor stream including olefins and a collection of catalyst particles covered with substantial quantities of coke and generally referred to as “coked catalyst.” In an effort to minimize the contact time of the lipid composition and the catalyst which may promote further conversion of desired products to undesirable other products, any arrangement of separators such as a swirl arm arrangement can be used to remove coked catalyst from the product stream quickly. The separator, e.g. swirl arm separator, is located in an upper portion of a chamber with a stripping zone situated in the lower portion of the chamber. Catalyst separated by the swirl arm arrangement drops down into the stripping zone. The cracked product vapor stream comprising cracked hydrocarbons including light olefins and some catalyst exit the chamber via a conduit which is in communication with cyclones. The cyclones remove remaining catalyst particles from the product vapor stream to reduce particle concentrations to very low levels. The product vapor stream then exits the top of the separating vessel. Catalyst separated by the cyclones is returned to the separating vessel and then to the stripping zone. The stripping zone removes adsorbed hydrocarbons from the surface of the catalyst by counter-current contact with steam.
Low hydrocarbon partial pressure operates to favor the production of light olefins. Accordingly, the riser pressure is set at about 172 to 241 kPa (25 to 35 psia) with a hydrocarbon partial pressure of about 35 to 172 kPa (5 to 25 psia), with a preferred hydrocarbon partial pressure of about 69 to 138 kPa (10 to 20 psia). This relatively low partial pressure for hydrocarbon is achieved by using steam as a diluent to the extent that the diluent is 10 to 55 wt-% of lipid composition and preferably about 15 wt-% of lipid composition. Other diluents such as dry gas can be used to reach equivalent hydrocarbon partial pressures.
The temperature of the cracked stream at the riser outlet will be about 510° C. to 621° C. (950° F. to 1150° F.). However, riser outlet temperatures above 566° C. (1050° F.) make more dry gas and more olefins. Whereas, riser outlet temperatures below 566° C. (1050° F.) make less ethylene and propylene. Accordingly, it is preferred to run the FCC process at a preferred temperature of about 566° C. to about 630° C., preferred pressure of about 138 kPa to about 240 kPa (20 to 35 psia). Another condition for the process is the catalyst to lipid composition ratio which can vary from about 5 to about 20 and preferably from about 10 to about 15.
In one embodiment of the method for producing a jet fuel, the lipid composition is introduced into the lift section of an FCC reactor. The temperature in the lift section will be very hot and range from about 700° C. (1292° F.) to about 760° C. (1400° F.) with a catalyst to lipid composition ratio of about 100 to about 150. It is anticipated that introducing the lipid composition into the lift section will produce considerable amounts of propylene and ethylene.
In another embodiment of the method for producing a jet fuel using the lipid composition or the lipids produced as described herein, the structure of the lipid composition or the lipids is broken by a process referred to as hydrodeoxygenation (HDO). HDO means removal of oxygen by means of hydrogen, that is, oxygen is removed while breaking the structure of the material. Olefinic double bonds are hydrogenated and any sulphur and nitrogen compounds are removed. Sulphur removal is called hydrodesulphurization (HDS). Pretreatment and purity of the raw materials (lipid composition or the lipids) contribute to the service life of the catalyst.
Generally in the HDO/HDS step, hydrogen is mixed with the feed stock (lipid composition or the lipids) and then the mixture is passed through a catalyst bed as a co-current flow, either as a single phase or a two phase feed stock. After the HDO/MDS step, the product fraction is separated and passed to a separate isomerization reactor. An isomerization reactor for biological starting material is described in the literature (FI 100 248) as a co-current reactor.
The process for producing a fuel by hydrogenating a hydrocarbon feed, e.g., the lipid composition or the lipids herein, can also be performed by passing the lipid composition or the lipids as a co-current flow with hydrogen gas through a first hydrogenation zone, and thereafter the hydrocarbon effluent is further hydrogenated in a second hydrogenation zone by passing hydrogen gas to the second hydrogenation zone as a counter-current flow relative to the hydrocarbon effluent. Exemplary HDO applications and catalysts useful for cracking the lipid composition to produce C2-C5 olefins are described in U.S. Pat. No. 7,232,935, which is incorporated in its entirety by reference.
Typically, in the hydrodeoxygenation step, the structure of the biological component, such as the lipid composition or lipids herein, is decomposed, oxygen, nitrogen, phosphorus and sulphur compounds, and light hydrocarbons as gas are removed, and the olefinic bonds are hydrogenated. In the second step of the process, i.e. in the so-called isomerization step, isomerization is carried out for branching the hydrocarbon chain and improving the performance of the paraffin at low temperatures.
In the first step, i.e. HDO step, of the cracking process, hydrogen gas and the lipid composition or lipids herein which are to be hydrogenated are passed to a HDO catalyst bed system either as co-current or counter-current flows, said catalyst bed system comprising one or more catalyst bed(s), preferably 1-3 catalyst beds. The HDO step is typically operated in a co-current manner. In case of a HDO catalyst bed system comprising two or more catalyst beds, one or more of the beds may be operated using the counter-current flow principle. In the HDO step, the pressure varies between 20 and 150 bar, preferably between 50 and 100 bar, and the temperature varies between 200 and 500° C., preferably in the range of 300-400° C. In the HDO step, known hydrogenation catalysts containing metals from Group VII and/or VIB of the Periodic System may be used. Preferably, the hydrogenation catalysts are supported Pd, Pt, Ni, NiMo or a CoMo catalysts, the support being alumina and/or silica. Typically, NiMo/Al2O3 and CoMo/Al2O3 catalysts are used.
Prior to the HDO step, the lipid composition or lipids herein may optionally be treated by prehydrogenation under milder conditions thus avoiding side reactions of the double bonds. Such prehydrogenation is carried out in the presence of a prehydrogenation catalyst at temperatures of 50 400° C. and at hydrogen pressures of 1 200 bar, preferably at a temperature between 150 and 250° C. and at a hydrogen pressure between 10 and 100 bar. The catalyst may contain metals from Group VIII and/or VIB of the Periodic System. Preferably, the prehydrogenation catalyst is a supported Pd, Pt, Ni, NiMo or a CoMo catalyst, the support being alumina and/or silica.
A gaseous stream from the HDO step containing hydrogen is cooled and then carbon monoxide, carbon dioxide, nitrogen, phosphorus and sulphur compounds, gaseous light hydrocarbons and other impurities are removed therefrom. After compressing, the purified hydrogen or recycled hydrogen is returned back to the first catalyst bed and/or between the catalyst beds to make up for the withdrawn gas stream. Water is removed from the condensed liquid. The liquid is passed to the first catalyst bed or between the catalyst beds.
After the HDO step, the product is subjected to an isomerization step. It is substantial for the process that the impurities are removed as completely as possible before the hydrocarbons are contacted with the isomerization catalyst. The isomerization step comprises an optional stripping step, wherein the reaction product from the HDO step may be purified by stripping with water vapour or a suitable gas such as light hydrocarbon, nitrogen or hydrogen. The optional stripping step is carried out in counter-current manner in a unit upstream of the isomerization catalyst, wherein the gas and liquid are contacted with each other, or before the actual isomerization reactor in a separate stripping unit utilizing counter-current principle.
After the stripping step the hydrogen gas and the hydrogenated lipid composition or lipids herein, and optionally an n-paraffin mixture, are passed to a reactive isomerization unit comprising one or several catalyst bed(s). The catalyst beds of the isomerization step may operate either in co-current or counter-current manner.
It is important for the process that the counter-current flow principle is applied in the isomerization step. In the isomerization step this is done by carrying out either the optional stripping step or the isomerization reaction step or both in counter-current manner. In the isomerization step, the pressure varies in the range of 20 150 bar, preferably in the range of 20 100 bar, the temperature being between 200 and 500° C., preferably between 300 and 400° C. In the isomerization step, isomerization catalysts known in the art may be used. Suitable isomerization catalysts contain molecular sieve and/or a metal from Group VII and/or a carrier. Preferably, the isomerization catalyst contains SAPO-11 or SAPO41 or ZSM-22 or ZSM-23 or ferrierite and Pt, Pd or Ni and Al2O3 or SiO2. Typical isomerization catalysts are, for example, Pt/SAPO-11/Al2O3, Pt/ZSM-22/Al2O3, Pt/ZSM-23/Al2O3 and Pt/SAPO-11/SiO2. The isomerization step and the HDO step may be carried out in the same pressure vessel or in separate pressure vessels. Optional prehydrogenation may be carried out in a separate pressure vessel or in the same pressure vessel as the HDO and isomerization steps.
Thus, in one embodiment, the product of the one or more chemical reactions is a straight chain alkane mixture that comprises ASTM D1655 jet fuel. In some embodiments, the composition conforming to the specification of ASTM 1655 jet fuel has a sulfur content that is less than 10 ppm. In other embodiments, the composition conforming to the specification of ASTM 1655 jet fuel has a T10 value of the distillation curve of less than 205° C. In another embodiment, the composition conforming to the specification of ASTM 1655 jet fuel has a final boiling point (FBP) of less than 300° C. In another embodiment, the composition conforming to the specification of ASTM 1655 jet fuel has a flash point of at least 38° C. In another embodiment, the composition conforming to the specification of ASTM 1655 jet fuel has a density between 775K/M3 and 840K/M3. In yet another embodiment, the composition conforming to the specification of ASTM 1655 jet fuel has a freezing point that is below −47° C. In another embodiment, the composition conforming to the specification of ASTM 1655 jet fuel has a net Heat of Combustion that is at least 42.8 MJ/K. In another embodiment, the composition conforming to the specification of ASTM 1655 jet fuel has a hydrogen content that is at least 13.4 mass %. In another embodiment, the composition conforming to the specification of ASTM 1655 jet fuel has a thermal stability, as tested by quantitative gravimetric JFTOT at 260° C., that is below 3 mm of Hg. In another embodiment, the composition conforming to the specification of ASTM 1655 jet fuel has an existent gum that is below 7 mg/dl.
Thus, the present invention discloses a variety of methods in which chemical modification of microalgal lipid is undertaken to yield products useful in a variety of industrial and other applications. Examples of processes for modifying oil produced by the methods disclosed herein include, but are not limited to, hydrolysis of the oil, hydroprocessing of the oil, and esterification of the oil. The modification of the microalgal oil produces basic oleochemicals that can be further modified to selected derivative oleochemicals for a desired function. In a manner similar to that described above with reference to the fuel producing processes—these chemical modifications can also be performed on oils generated from the microbial cultures described herein. Examples of basic oleochemicals include, but are not limited to, soaps, fatty acids, fatty acid methyl esters, and glycerol. Examples of derivative oleochemicals include, but are not limited to, fatty nitriles, esters, dimer acids, quats, surfactants, fatty alkanolamides, fatty alcohol sulfates, resins, emulsifiers, fatty alcohols, olefins, and higher alkanes.
Hydrolysis of the fatty acid constituents from the glycerolipids produced by the methods of the invention yields free fatty acids that can be derivatized to produce other useful chemicals. Hydrolysis occurs in the presence of water and a catalyst which may be either an acid or a base. The liberated free fatty acids can be derivatized to yield a variety of products, as reported in the following: U.S. Pat. No. 5,304,664 (Highly sulfated fatty acids); U.S. Pat. No. 7,262,158 (Cleansing compositions); U.S. Pat. No. 7,115,173 (Fabric softener compositions); U.S. Pat. No. 6,342,208 (Emulsions for treating skin); U.S. Pat. No. 7,264,886 (Water repellant compositions); U.S. Pat. No. 6,924,333 (Paint additives); U.S. Pat. No. 6,596,768 (Lipid-enriched ruminant feedstock); and U.S. Pat. No. 6,380,410 (Surfactants for detergents and cleaners).
With regard to hydrolysis, in one embodiment of the invention, a triglyceride oil is optionally first hydrolyzed in a liquid medium such as water or sodium hydroxide so as to obtain glycerol and soaps. There are various suitable triglyceride hydrolysis methods, including, but not limited to, saponification, acid hydrolysis, alkaline hydrolysis, enzymatic hydrolysis (referred herein as splitting), and hydrolysis using hot-compressed water. One skilled in the art will recognize that a triglyceride oil need not be hydrolyzed in order to produce an oleochemical; rather, the oil may be converted directly to the desired oleochemical by other known process. For example, the triglyceride oil may be directly converted to a methyl ester fatty acid through esterification.
In some embodiments, catalytic hydrolysis of the oil produced by methods disclosed herein occurs by splitting the oil into glycerol and fatty acids. As discussed above, the fatty acids may then be further processed through several other modifications to obtained derivative oleochemicals. For example, in one embodiment the fatty acids may undergo an amination reaction to produce fatty nitrogen compounds. In another embodiment, the fatty acids may undergo ozonolysis to produce mono- and dibasic-acids.
In other embodiments hydrolysis may occur via the, splitting of oils produced herein to create oleochemicals. In some preferred embodiments of the invention, a triglyceride oil may be split before other processes is performed. One skilled in the art will recognize that there are many suitable triglyceride splitting methods, including, but not limited to, enzymatic splitting and pressure splitting.
Generally, enzymatic oil splitting methods use enzymes, lipases, as biocatalysts acting on a water/oil mixture. Enzymatic splitting then slpits the oil or fat, respectively, is into glycerol and free fatty acids. The glycerol may then migrates into the water phase whereas the organic phase enriches with free fatty acids.
The enzymatic splitting reactions generally take place at the phase boundary between organic and aqueous phase, where the enzyme is present only at the phase boundary. Triglycerides that meet the phase boundary then contribute to or participate in the splitting reaction. As the reaction proceeds, the occupation density or concentration of fatty acids still chemically bonded as glycerides, in comparison to free fatty acids, decreases at the phase boundary so that the reaction is slowed down. In certain embodiments, enzymatic splitting may occur at room temperature. One of ordinary skill in the art would know the suitable conditions for splitting oil into the desired fatty acids.
By way of example, the reaction speed can be accelerated by increasing the interface boundary surface. Once the reaction is complete, free fatty acids are then separated from the organic phase freed from enzyme, and the residue which still contains fatty acids chemically bonded as glycerides is fed back or recycled and mixed with fresh oil or fat to be subjected to splitting. In this manner, recycled glycerides are then subjected to a further enzymatic splitting process. In some embodiments, the free fatty acids are extracted from an oil or fat partially split in such a manner. In that way, if the chemically bound fatty acids (triglycerides) are returned or fed back into the splitting process, the enzyme consumption can be drastically reduced.
The splitting degree is determined as the ratio of the measured acid value divided by the theoretically possible acid value which can be computed for a given oil or fat. Preferably, the acid value is measured by means of titration according to standard common methods. Alternatively, the density of the aqueous glycerol phase can be taken as a measure for the splitting degree.
In one embodiment, the splitting process as described herein is also suitable for splitting the mono-, di- and triglyceride that are contained in the so-called soap-stock from the alkali refining processes of the produced oils. In this manner, the soap-stock can be quantitatively converted without prior saponification of the neutral oils into the fatty acids. For this purpose, the fatty acids being chemically bonded in the soaps are released, preferably before splitting, through an addition of acid. In certain embodiments, a buffer solution is used in addition to water and enzyme for the splitting process.
In one embodiment, oils produced in accordance with the methods of the invention can also be subjected to saponification as a method of hydrolysis Animal and plant oils are typically made of triacylglycerols (TAGs), which are esters of fatty acids with the trihydric alcohol, glycerol. In an alkaline hydrolysis reaction, the glycerol in a TAG is removed, leaving three carboxylic acid anions that can associate with alkali metal cations such as sodium or potassium to produce fatty acid salts. In this scheme, the carboxylic acid constituents are cleaved from the glycerol moiety and replaced with hydroxyl groups. The quantity of base (e.g., KOH) that is used in the reaction is determined by the desired degree of saponification. If the objective is, for example, to produce a soap product that comprises some of the oils originally present in the TAG composition, an amount of base insufficient to convert all of the TAGs to fatty acid salts is introduced into the reaction mixture. Normally, this reaction is performed in an aqueous solution and proceeds slowly, but may be expedited by the addition of heat. Precipitation of the fatty acid salts can be facilitated by addition of salts, such as water-soluble alkali metal halides (e.g., NaCl or KCl), to the reaction mixture. Preferably, the base is an alkali metal hydroxide, such as NaOH or KOH. Alternatively, other bases, such as alkanolamines, including for example triethanolamine and aminomethylpropanol, can be used in the reaction scheme. In some cases, these alternatives may be preferred to produce a clear soap product.
In some methods, the first step of chemical modification may be hydroprocessing to saturate double bonds, followed by deoxygenation at elevated temperature in the presence of hydrogen and a catalyst. In other methods, hydrogenation and deoxygenation may occur in the same reaction. In still other methods deoxygenation occurs before hydrogenation. Isomerization may then be optionally performed, also in the presence of hydrogen and a catalyst. Finally, gases and naphtha components can be removed if desired. For example, see U.S. Pat. No. 5,475,160 (hydrogenation of triglycerides); U.S. Pat. No. 5,091,116 (deoxygenation, hydrogenation and gas removal); U.S. Pat. No. 6,391,815 (hydrogenation); and U.S. Pat. No. 5,888,947 (isomerization).
In some embodiments of the invention, the triglyceride oils are partially or completely deoxygenated. The deoxygenation reactions form desired products, including, but not limited to, fatty acids, fatty alcohols, polyols, ketones, and aldehydes. In general, without being limited by any particular theory, the deoxygenation reactions involve a combination of various different reaction pathways, including without limitation: hydrogenolysis, hydrogenation, consecutive hydrogenation-hydrogenolysis, consecutive hydrogenolysis-hydrogenation, and combined hydrogenation-hydrogenolysis reactions, resulting in at least the partial removal of oxygen from the fatty acid or fatty acid ester to produce reaction products, such as fatty alcohols, that can be easily converted to the desired chemicals by further processing. For example, in one embodiment, a fatty alcohol may be converted to olefins through FCC reaction or to higher alkanes through a condensation reaction.
One such chemical modification is hydrogenation, which is the addition of hydrogen to double bonds in the fatty acid constituents of glycerolipids or of free fatty acids. The hydrogenation process permits the transformation of liquid oils into semi-solid or solid fats, which may be more suitable for specific applications.
Hydrogenation of oil produced by the methods described herein can be performed in conjunction with one or more of the methods and/or materials provided herein, as reported in the following: U.S. Pat. No. 7,288,278 (Food additives or medicaments); U.S. Pat. No. 5,346,724 (Lubrication products); U.S. Pat. No. 5,475,160 (Fatty alcohols); U.S. Pat. No. 5,091,116 (Edible oils); U.S. Pat. No. 6,808,737 (Structural fats for margarine and spreads); U.S. Pat. No. 5,298,637 (Reduced-calorie fat substitutes); U.S. Pat. No. 6,391,815 (Hydrogenation catalyst and sulfur adsorbent); U.S. Pat. No. 5,233,099 and U.S. Pat. No. 5,233,100 (Fatty alcohols); U.S. Pat. No. 4,584,139 (Hydrogenation catalysts); U.S. Pat. No. 6,057,375 (Foam suppressing agents); and U.S. Pat. No. 7,118,773 (Edible emulsion spreads).
One skilled in the art will recognize that various processes may be used to hydrogenate carbohydrates. One suitable method includes contacting the carbohydrate with hydrogen or hydrogen mixed with a suitable gas and a catalyst under conditions sufficient in a hydrogenation reactor to form a hydrogenated product. The hydrogenation catalyst generally can include Cu, Re, Ni, Fe, Co, Ru, Pd, Rh, Pt, Os, Ir, and alloys or any combination thereof, either alone or with promoters such as W, Mo, Au, Ag, Cr, Zn, Mn, Sn, B, P, Bi, and alloys or any combination thereof. Other effective hydrogenation catalyst materials include either supported nickel or ruthenium modified with rhenium. In an embodiment, the hydrogenation catalyst also includes any one of the supports, depending on the desired functionality of the catalyst. The hydrogenation catalysts may be prepared by methods known to those of ordinary skill in the art.
In some embodiments the hydrogenation catalyst includes a supported Group VIII metal catalyst and a metal sponge material (e.g., a sponge nickel catalyst). Raney nickel provides an example of an activated sponge nickel catalyst suitable for use in this invention. In other embodiment, the hydrogenation reaction in the invention is performed using a catalyst comprising a nickel-rhenium catalyst or a tungsten-modified nickel catalyst. One example of a suitable catalyst for the hydrogenation reaction of the invention is a carbon-supported nickel-rhenium catalyst.
In an embodiment, a suitable Raney nickel catalyst may be prepared by treating an alloy of approximately equal amounts by weight of nickel and aluminum with an aqueous alkali solution, e.g., containing about 25 weight % of sodium hydroxide. The aluminum is selectively dissolved by the aqueous alkali solution resulting in a sponge shaped material comprising mostly nickel with minor amounts of aluminum. The initial alloy includes promoter metals (i.e., molybdenum or chromium) in the amount such that about 1 to 2 weight % remains in the formed sponge nickel catalyst. In another embodiment, the hydrogenation catalyst is prepared using a solution of ruthenium(III) nitrosylnitrate, ruthenium (III) chloride in water to impregnate a suitable support material. The solution is then dried to form a solid having a water content of less than about 1% by weight. The solid may then be reduced at atmospheric pressure in a hydrogen stream at 300° C. (uncalcined) or 400° C. (calcined) in a rotary ball furnace for 4 hours. After cooling and rendering the catalyst inert with nitrogen, 5% by volume of oxygen in nitrogen is passed over the catalyst for 2 hours.
In certain embodiments, the catalyst described includes a catalyst support. The catalyst support stabilizes and supports the catalyst. The type of catalyst support used depends on the chosen catalyst and the reaction conditions. Suitable supports for the invention include, but are not limited to, carbon, silica, silica-alumina, zirconia, titania, ceria, vanadia, nitride, boron nitride, heteropolyacids, hydroxyapatite, zinc oxide, chromia, zeolites, carbon nanotubes, carbon fullerene and any combination thereof.
The catalysts used in this invention can be prepared using conventional methods known to those in the art. Suitable methods may include, but are not limited to, incipient wetting, evaporative impregnation, chemical vapor deposition, wash-coating, magnetron sputtering techniques, and the like.
The conditions for which to carry out the hydrogenation reaction will vary based on the type of starting material and the desired products. One of ordinary skill in the art, with the benefit of this disclosure, will recognize the appropriate reaction conditions. In general, the hydrogenation reaction is conducted at temperatures of 80° C. to 250° C., and preferably at 90° C. to 200° C., and most preferably at 100° C. to 150° C. In some embodiments, the hydrogenation reaction is conducted at pressures from 500 KPa to 14000 KPa.
The hydrogen used in the hydrogenolysis reaction of the current invention may include external hydrogen, recycled hydrogen, in situ generated hydrogen, and any combination thereof. As used herein, the term “external hydrogen” refers to hydrogen that does not originate from the biomass reaction itself, but rather is added to the system from another source.
In some embodiments of the invention, it is desirable to convert the starting carbohydrate to a smaller molecule that will be more readily converted to desired higher hydrocarbons. One suitable method for this conversion is through a hydrogenolysis reaction. Various processes are known for performing hydrogenolysis of carbohydrates. One suitable method includes contacting a carbohydrate with hydrogen or hydrogen mixed with a suitable gas and a hydrogenolysis catalyst in a hydrogenolysis reactor under conditions sufficient to form a reaction product comprising smaller molecules or polyols. As used herein, the term “smaller molecules or polyols” includes any molecule that has a smaller molecular weight, which can include a smaller number of carbon atoms or oxygen atoms than the starting carbohydrate. In an embodiment, the reaction products include smaller molecules that include polyols and alcohols. Someone of ordinary skill in the art would be able to choose the appropriate method by which to carry out the hydrogenolysis reaction.
In some embodiments, a 5 and/or 6 carbon sugar or sugar alcohol may be converted to propylene glycol, ethylene glycol, and glycerol using a hydrogenolysis catalyst. The hydrogenolysis catalyst may include Cr, Mo, W, Re, Mn, Cu, Cd, Fe, Co, Ni, Pt, Pd, Rh, Ru, Ir, Os, and alloys or any combination thereof, either alone or with promoters such as Au, Ag, Cr, Zn, Mn, Sn, Bi, B, O, and alloys or any combination thereof. The hydrogenolysis catalyst may also include a carbonaceous pyropolymer catalyst containing transition metals (e.g., chromium, molybdemum, tungsten, rhenium, manganese, copper, cadmium) or Group VIII metals (e.g., iron, cobalt, nickel, platinum, palladium, rhodium, ruthenium, iridium, and osmium). In certain embodiments, the hydrogenolysis catalyst may include any of the above metals combined with an alkaline earth metal oxide or adhered to a catalytically active support. In certain embodiments, the catalyst described in the hydrogenolysis reaction may include a catalyst support as described above for the hydrogenation reaction.
The conditions for which to carry out the hydrogenolysis reaction will vary based on the type of starting material and the desired products. One of ordinary skill in the art, with the benefit of this disclosure, will recognize the appropriate conditions to use to carry out the reaction. In general, they hydrogenolysis reaction is conducted at temperatures of 110° C. to 300° C., and preferably at 170° C. to 220° C., and most preferably at 200° C. to 225° C. In some embodiments, the hydrogenolysis reaction is conducted under basic conditions, preferably at a pH of 8 to 13, and even more preferably at a pH of 10 to 12. In some embodiments, the hydrogenolysis reaction is conducted at pressures in a range between 60 KPa and 16500 KPa, and preferably in a range between 1700 KPa and 14000 KPa, and even more preferably between 4800 KPa and 11000 KPa.
The hydrogen used in the hydrogenolysis reaction of the current invention can include external hydrogen, recycled hydrogen, in situ generated hydrogen, and any combination thereof.
In some embodiments, the reaction products discussed above may be converted into higher hydrocarbons through a condensation reaction in a condensation reactor. In such embodiments, condensation of the reaction products occurs in the presence of a catalyst capable of forming higher hydrocarbons. While not intending to be limited by theory, it is believed that the production of higher hydrocarbons proceeds through a stepwise addition reaction including the formation of carbon-carbon, or carbon-oxygen bond. The resulting reaction products include any number of compounds containing these moieties, as described in more detail below.
In certain embodiments, suitable condensation catalysts include an acid catalyst, a base catalyst, or an acid/base catalyst. As used herein, the term “acid/base catalyst” refers to a catalyst that has both an acid and a base functionality. In some embodiments the condensation catalyst can include, without limitation, zeolites, carbides, nitrides, zirconia, alumina, silica, aluminosilicates, phosphates, titanium oxides, zinc oxides, vanadium oxides, lanthanum oxides, yttrium oxides, scandium oxides, magnesium oxides, cerium oxides, barium oxides, calcium oxides, hydroxides, heteropolyacids, inorganic acids, acid modified resins, base modified resins, and any combination thereof. In some embodiments, the condensation catalyst can also include a modifier. Suitable modifiers include La, Y, Sc, P, B, Bi, Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, and any combination thereof. In some embodiments, the condensation catalyst can also include a metal. Suitable metals include Cu, Ag, Au, Pt, Ni, Fe, Co, Ru, Zn, Cd, Ga, In, Rh, Pd, Ir, Re, Mn, Cr, Mo, W, Sn, Os, alloys, and any combination thereof.
In certain embodiments, the catalyst described in the condensation reaction may include a catalyst support as described above for the hydrogenation reaction. In certain embodiments, the condensation catalyst is self-supporting. As used herein, the term “self-supporting” means that the catalyst does not need another material to serve as support. In other embodiments, the condensation catalyst in used in conjunction with a separate support suitable for suspending the catalyst. In an embodiment, the condensation catalyst support is silica.
The conditions under which the condensation reaction occurs will vary based on the type of starting material and the desired products. One of ordinary skill in the art, with the benefit of this disclosure, will recognize the appropriate conditions to use to carry out the reaction. In some embodiments, the condensation reaction is carried out at a temperature at which the thermodynamics for the proposed reaction are favorable. The temperature for the condensation reaction will vary depending on the specific starting polyol or alcohol. In some embodiments, the temperature for the condensation reaction is in a range from 80° C. to 500° C., and preferably from 125° C. to 450° C., and most preferably from 125° C. to 250° C. In some embodiments, the condensation reaction is conducted at pressures in a range between 0 Kpa to 9000 KPa, and preferably in a range between 0 KPa and 7000 KPa, and even more preferably between 0 KPa and 5000 KPa.
The higher alkanes formed by the invention include, but are not limited to, branched or straight chain alkanes that have from 4 to 30 carbon atoms, branched or straight chain alkenes that have from 4 to 30 carbon atoms, cycloalkanes that have from 5 to 30 carbon atoms, cycloalkenes that have from 5 to 30 carbon atoms, aryls, fused aryls, alcohols, and ketones. Suitable alkanes include, but are not limited to, butane, pentane, pentene, 2-methylbutane, hexane, hexene, 2-methylpentane, 3-methylpentane, 2,2,-dimethylbutane, 2,3-dimethylbutane, heptane, heptene, octane, octene, 2,2,4-trimethylpentane, 2,3-dimethyl hexane, 2,3,4-trimethylpentane, 2,3-dimethylpentane, nonane, nonene, decane, decene, undecane, undecene, dodecane, dodecene, tridecane, tridecene, tetradecane, tetradecene, pentadecane, pentadecene, nonyldecane, nonyldecene, eicosane, eicosene, uneicosane, uneicosene, doeicosane, doeicosene, trieicosane, trieicosene, tetraeicosane, tetraeicosene, and isomers thereof. Some of these products may be suitable for use as fuels.
In some embodiments, the cycloalkanes and the cycloalkenes are unsubstituted. In other embodiments, the cycloalkanes and cycloalkenes are mono-substituted. In still other embodiments, the cycloalkanes and cycloalkenes are multi-substituted. In the embodiments comprising the substituted cycloalkanes and cycloalkenes, the substituted group includes, without limitation, a branched or straight chain alkyl having 1 to 12 carbon atoms, a branched or straight chain alkylene having 1 to 12 carbon atoms, a phenyl, and any combination thereof. Suitable cycloalkanes and cycloalkenes include, but are not limited to, cyclopentane, cyclopentene, cyclohexane, cyclohexene, methyl-cyclopentane, methyl-cyclopentene, ethyl-cyclopentane, ethyl-cyclopentene, ethyl-cyclohexane, ethyl-cyclohexene, isomers and any combination thereof.
In some embodiments, the aryls formed are unsubstituted. In another embodiment, the aryls formed are mono-substituted. In the embodiments comprising the substituted aryls, the substituted group includes, without limitation, a branched or straight chain alkyl having 1 to 12 carbon atoms, a branched or straight chain alkylene having 1 to 12 carbon atoms, a phenyl, and any combination thereof. Suitable aryls for the invention include, but are not limited to, benzene, toluene, xylene, ethyl benzene, para xylene, meta xylene, and any combination thereof.
The alcohols produced in the invention have from 4 to 30 carbon atoms. In some embodiments, the alcohols are cyclic. In other embodiments, the alcohols are branched. In another embodiment, the alcohols are straight chained. Suitable alcohols for the invention include, but are not limited to, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, undecanol, dodecanol, tridecanol, tetradecanol, pentadecanol, hexadecanol, heptyldecanol, octyldecanol, nonyldecanol, eicosanol, uneicosanol, doeicosanol, trieicosanol, tetraeicosanol, and isomers thereof.
The ketones produced in the invention have from 4 to 30 carbon atoms. In an embodiment, the ketones are cyclic. In another embodiment, the ketones are branched. In another embodiment, the ketones are straight chained. Suitable ketones for the invention include, but are not limited to, butanone, pentanone, hexanone, heptanone, octanone, nonanone, decanone, undecanone, dodecanone, tridecanone, tetradecanone, pentadecanone, hexadecanone, heptyldecanone, octyldecanone, nonyldecanone, eicosanone, uneicosanone, doeicosanone, trieicosanone, tetraeicosanone, and isomers thereof.
Another such chemical modification is interesterification. Naturally produced glycerolipids do not have a uniform distribution of fatty acid constituents. In the context of oils, interesterification refers to the exchange of acyl radicals between two esters of different glycerolipids. The interesterification process provides a mechanism by which the fatty acid constituents of a mixture of glycerolipids can be rearranged to modify the distribution pattern. Interesterification is a well-known chemical process, and generally comprises heating (to about 200° C.) a mixture of oils for a period (e.g., 30 minutes) in the presence of a catalyst, such as an alkali metal or alkali metal alkylate (e.g., sodium methoxide). This process can be used to randomize the distribution pattern of the fatty acid constituents of an oil mixture, or can be directed to produce a desired distribution pattern. This method of chemical modification of lipids can be performed on materials provided herein, such as extracted microbial oil or microbial biomass with a percentage of dry cell weight as lipid at least 20%.
Directed interesterification, in which a specific distribution pattern of fatty acids is sought, can be performed by maintaining the oil mixture at a temperature below the melting point of some TAGs which might occur. This results in selective crystallization of these TAGs, which effectively removes them from the reaction mixture as they crystallize. The process can be continued until most of the fatty acids in the oil have precipitated, for example. A directed interesterification process can be used, for example, to produce a product with a lower calorie content via the substitution of longer-chain fatty acids with shorter-chain counterparts. Directed interesterification can also be used to produce a product with a mixture of fats that can provide desired melting characteristics and structural features sought in food additives or products (e.g., margarine) without resorting to hydrogenation, which can produce unwanted trans isomers.
Interesterification of oils produced by the methods described herein can be performed in conjunction with one or more of the methods and/or materials, or to produce products, as reported in the following: U.S. Pat. No. 6,080,853 (Nondigestible fat substitutes); U.S. Pat. No. 4,288,378 (Peanut butter stabilizer); U.S. Pat. No. 5,391,383 (Edible spray oil); U.S. Pat. No. 6,022,577 (Edible fats for food products); U.S. Pat. No. 5,434,278 (Edible fats for food products); U.S. Pat. No. 5,268,192 (Low calorie nut products); U.S. Pat. No. 5,258,197 (Reduce calorie edible compositions); U.S. Pat. No. 4,335,156 (Edible fat product); U.S. Pat. No. 7,288,278 (Food additives or medicaments); U.S. Pat. No. 7,115,760 (Fractionation process); U.S. Pat. No. 6,808,737 (Structural fats); U.S. Pat. No. 5,888,947 (Engine lubricants); U.S. Pat. No. 5,686,131 (Edible oil mixtures); and U.S. Pat. No. 4,603,188 (Curable urethane compositions).
In one embodiment in accordance with the invention, transesterification of the oil, as described above, is followed by reaction of the transesterified product with polyol, as reported in U.S. Pat. No. 6,465,642, to produce polyol fatty acid polyesters. Such an esterification and separation process may comprise the steps as follows: reacting a lower alkyl ester with polyol in the presence of soap; removing residual soap from the product mixture; water-washing and drying the product mixture to remove impurities; bleaching the product mixture for refinement; separating at least a portion of the unreacted lower alkyl ester from the polyol fatty acid polyester in the product mixture; and recycling the separated unreacted lower alkyl ester.
Transesterification can also be performed on microbial biomass with short chain fatty acid esters, as reported in U.S. Pat. No. 6,278,006. In general, transesterification may be performed by adding a short chain fatty acid ester to an oil in the presence of a suitable catalyst and heating the mixture. In some embodiments, the oil comprises about 5% to about 90% of the reaction mixture by weight. In some embodiments, the short chain fatty acid esters can be about 10% to about 50% of the reaction mixture by weight. Non-limiting examples of catalysts include base catalysts, sodium methoxide, acid catalysts including inorganic acids such as sulfuric acid and acidified clays, organic acids such as methane sulfonic acid, benzenesulfonic acid, and toluenesulfonic acid, and acidic resins such as Amberlyst 15. Metals such as sodium and magnesium, and metal hydrides also are useful catalysts.
Another such chemical modification is hydroxylation, which involves the addition of water to a double bond resulting in saturation and the incorporation of a hydroxyl moiety. The hydroxylation process provides a mechanism for converting one or more fatty acid constituents of a glycerolipid to a hydroxy fatty acid. Hydroxylation can be performed, for example, via the method reported in U.S. Pat. No. 5,576,027. Hydroxylated fatty acids, including castor oil and its derivatives, are useful as components in several industrial applications, including food additives, surfactants, pigment wetting agents, defoaming agents, water proofing additives, plasticizing agents, cosmetic emulsifying and/or deodorant agents, as well as in electronics, pharmaceuticals, paints, inks, adhesives, and lubricants. One example of how the hydroxylation of a glyceride may be performed is as follows: fat may be heated, preferably to about 30-50° C. combined with heptane and maintained at temperature for thirty minutes or more; acetic acid may then be added to the mixture followed by an aqueous solution of sulfuric acid followed by an aqueous hydrogen peroxide solution which is added in small increments to the mixture over one hour; after the aqueous hydrogen peroxide, the temperature may then be increased to at least about 60° C. and stirred for at least six hours; after the stirring, the mixture is allowed to settle and a lower aqueous layer formed by the reaction may be removed while the upper heptane layer formed by the reaction may be washed with hot water having a temperature of about 60° C.; the washed heptane layer may then be neutralized with an aqueous potassium hydroxide solution to a pH of about 5 to 7 and then removed by distillation under vacuum; the reaction product may then be dried under vacuum at 100° C. and the dried product steam-deodorized under vacuum conditions and filtered at about 50° to 60° C. using diatomaceous earth.
Hydroxylation of microbial oils produced by the methods described herein can be performed in conjunction with one or more of the methods and/or materials, or to produce products, as reported in the following: U.S. Pat. No. 6,590,113 (Oil-based coatings and ink); U.S. Pat. No. 4,049,724 (Hydroxylation process); U.S. Pat. No. 6,113,971 (Olive oil butter); U.S. Pat. No. 4,992,189 (Lubricants and lube additives); U.S. Pat. No. 5,576,027 (Hydroxylated milk); and U.S. Pat. No. 6,869,597 (Cosmetics).
Hydroxylated glycerolipids can be converted to estolides. Estolides consist of a glycerolipid in which a hydroxylated fatty acid constituent has been esterified to another fatty acid molecule. Conversion of hydroxylated glycerolipids to estolides can be carried out by warming a mixture of glycerolipids and fatty acids and contacting the mixture with a mineral acid, as described by Isbell et al., JAOCS 71(2):169-174 (1994). Estolides are useful in a variety of applications, including without limitation those reported in the following: U.S. Pat. No. 7,196,124 (Elastomeric materials and floor coverings); U.S. Pat. No. 5,458,795 (Thickened oils for high-temperature applications); U.S. Pat. No. 5,451,332 (Fluids for industrial applications); U.S. Pat. No. 5,427,704 (Fuel additives); and U.S. Pat. No. 5,380,894 (Lubricants, greases, plasticizers, and printing inks).
Other chemical reactions that can be performed on microbial oils include reacting triacylglycerols with a cyclopropanating agent to enhance fluidity and/or oxidative stability, as reported in U.S. Pat. No. 6,051,539; manufacturing of waxes from triacylglycerols, as reported in U.S. Pat. No. 6,770,104; and epoxidation of triacylglycerols, as reported in “The effect of fatty acid composition on the acrylation kinetics of epoxidized triacylglycerols”, Journal of the American Oil Chemists' Society, 79:1, 59-63, (2001) and Free Radical Biology and Medicine, 37:1, 104-114 (2004).
The generation of oil-bearing microbial biomass and the extraction or separation of the oil for fuel and chemical products as described above results in the production of delipidated biomass meal. Delipidated meal is a byproduct of preparing algal oil and is useful as animal feed for farm animals, e.g., ruminants, poultry, swine and aquaculture. The resulting meal, although of reduced oil content, still contains high quality proteins, carbohydrates, fiber, ash, residual oil and other nutrients appropriate for an animal feed. Because the cells are predominantly lysed by the oil separation process, the delipidated meal is easily digestible by such animals. Delipidated meal can optionally be combined with other ingredients, such as grain, in an animal feed. Because delipidated meal has a powdery consistency, it can be pressed into pellets using an extruder or expander or another type of machine, which are commercially available.
The present invention provides methods of chemical modification of lipid-containing biomass other than transesterification that yield products useful in a variety of industrial and other applications. For example, the hydrogenation, interesterification, hydroxylation, and hydrolysis plus derivatization reactions described above in connection with making fuels from microbial oil extracted or otherwise separated from microbial biomass, can be carried out directly on high oil containing microbial biomass in accordance with the methods of the invention. Thus, in a manner similar to that described above with reference to transesterification, these chemical modifications can also be performed on biomass generated from the microbial cultures described herein.
In some embodiments, the biomass may comprise biomass combined from two or more cultures of distinct strains or species of microorganisms. In some embodiments, the distinct strains or species have different glycerolipid profiles. In some methods of the invention, the microbial biomass is first harvested from the culture medium, and then subjected to a chemical reaction that covalently modifies at least 1% of the lipid. In some embodiments, at least 2%, at least 3%, at least 4%, at least 5%, at least 10%, at least 20%, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, or at least 90% of the lipid is modified by the chemical process.
A. Hydrogenation: Saturation of Double Bonds
Hydrogenation is the addition of hydrogen to double bonds in the fatty acid constituents of glycerolipids or of free fatty acids. The hydrogenation process permits the transformation of liquid oils into semi-solid or solid fats, which may be more suitable for specific applications. Hydrogenation is a well-known chemical process, and generally comprises contacting an oil mixture with a finely divided transition metal (e.g., nickel, palladium, platinum, or rhodium) catalyst at an elevated temperature (e.g., 140-225° C.) in the presence of hydrogen.
Hydrogenation of biomass produced by the methods described herein can be performed in conjunction with one or more of the methods and/or materials provided herein, including microbial biomass with a percentage of DCW as lipid at least 20%, or to produce products, as reported in the following: U.S. Pat. No. 7,288,278 (food additives or medicaments); U.S. Pat. No. 5,346,724 (lubrication products); U.S. Pat. No. 5,475,160 (fatty alcohols); U.S. Pat. No. 5,091,116 (edible oils); U.S. Pat. No. 6,808,737 (structural fats for margarine and spreads); U.S. Pat. No. 5,298,637 (reduced-calorie fat substitutes); U.S. Pat. No. 6,391,815 (hydrogenation catalyst and sulfur adsorbent); U.S. Pat. No. 5,233,099 and U.S. Pat. No. 5,233,100 (fatty alcohols); U.S. Pat. No. 4,584,139 (hydrogenation catalysts); U.S. Pat. No. 6,057,375 (foam suppressing agents); and U.S. Pat. No. 7,118,773 (edible emulsion spreads), each of which is incorporated herein by reference.
B. Interesterification: Interchanging Fatty Acid Components of Glycerolipids
Naturally produced glycerolipids typically do not have a uniform distribution of fatty acid constituents. In the context of oils, interesterification refers to the exchange of acyl radicals between two esters of different glycerolipids. The interesterification process provides a mechanism by which the fatty acid constituents of a mixture of glycerolipids can be rearranged to modify the distribution pattern. Interesterification is a well-known chemical process, and generally comprises heating (to about 200° C.) a mixture of oils for a period (e.g, 30 minutes) in the presence of a catalyst, such as an alkali metal or alkali metal alkylate (e.g., sodium methoxide). This process can be used to randomize the distribution pattern of the fatty acid constituents of an oil mixture, or can be directed to produce a desired distribution pattern. This method of chemical modification of lipids can be performed on materials provided herein, such as microbial biomass with a lipid percentage of DCW of at least 20%.
Directed interesterification, in which a specific distribution pattern of fatty acids is sought, can be performed by maintaining the oil mixture at a temperature below the melting point of some TAGs that might be present. This results in selective crystallization of these TAGs, which effectively removes them from the reaction mixture as they crystallize. The process can be continued until most of the fatty acids in the oil have precipitated. A directed interesterification process can be used to produce, for example, a product with a lower calorie content via the substitution of longer-chain fatty acids with shorter-chain counterparts. Directed interesterification can also be used to produce a product with a mixture of fats that can provide desired melting characteristics and structural features sought in food additives or food products (e.g., margarine) without resorting to hydrogenation, which can produce unwanted trans isomers.
Interesterification of biomass produced by the methods described herein can be performed in conjunction with one or more of the methods and/or materials, or to produce products, as reported in the following: U.S. Pat. No. 6,080,853 (nondigestible fat substitutes); U.S. Pat. No. 4,288,378 (peanut butter stabilizer); U.S. Pat. No. 5,391,383 (edible spray oil); U.S. Pat. No. 6,022,577 (edible fats for food products); U.S. Pat. No. 5,434,278 (edible fats for food products); U.S. Pat. No. 5,268,192 (low calorie nut products); U.S. Pat. No. 5,258,197 (reduced calorie edible compositions); U.S. Pat. No. 4,335,156 (edible fat product); U.S. Pat. No. 7,288,278 (food additives or medicaments); U.S. Pat. No. 7,115,760 (fractionation process); U.S. Pat. No. 6,808,737 (structural fats); U.S. Pat. No. 5,888,947 (engine lubricants); U.S. Pat. No. 5,686,131 (edible oil mixtures); and U.S. Pat. No. 4,603,188 (curable urethane compositions), each of which is incorporated herein by reference. repeat of 289 above
In one embodiment of the invention, transesterification of the biomass, as described above, is followed by reaction of the transesterified product with polyol, as reported in U.S. Pat. No. 6,465,642, incorporated herein by reference, to produce polyol fatty acid polyesters. Transesterification can also be performed on microbial biomass with short chain fatty acid esters, as reported in U.S. Pat. No. 6,278,006, incorporated herein by reference.
C. Hydroxylation: Saturation via the Addition of Water to Double Bonds
Hydroxylation involves the addition of water to a double bond resulting in saturation and the incorporation of a hydroxyl moiety. The hydroxylation process provides a mechanism for converting one or more fatty acid constituents of a glycerolipid to a hydroxy fatty acid. Hydroxylation can be performed, for example, via the method reported in U.S. Pat. No. 5,576,027, incorporated herein by reference. Hydroxylated fatty acids, including castor oil and its derivatives, are useful as components in several industrial applications, including as food additives, surfactants, pigment wetting agents, defoaming agents, water proofing additives, plasticizing agents, cosmetic emulsifying and/or deodorant agents, as well as in electronics, pharmaceuticals, paints, inks, adhesives, and lubricants.
Hydroxylation of microbial biomass produced by the methods described herein can be performed in conjunction with one or more of the methods and/or materials, or to produce products, as reported in the following: U.S. Pat. No. 6,590,113 (oil-based coatings and ink); U.S. Pat. No. 4,049,724 (hydroxylation process); U.S. Pat. No. 6,113,971 (olive oil butter); U.S. Pat. No. 4,992,189 (lubricants and lube additives); U.S. Pat. No. 5,576,027 (hydroxylated milk); and U.S. Pat. No. 6,869,597 (cosmetics), each of which is incorporated herein by reference.
Hydroxylated glycerolipids can be converted to estolides. Estolides consist of a glycerolipid in which a hydroxylated fatty acid constituent has been esterified to another fatty acid molecule. Conversion of hydroxylated glycerolipids to estolides can be carried out by warming a mixture of glycerolipids and fatty acids and contacting the mixture with a mineral acid, as described by Isbell et al., JAOCS 71(2):169-174 (1994), incorporated herein by reference. Estolides are useful in a variety of applications, including without limitation those reported in the following: U.S. Pat. No. 7,196,124 (elastomeric materials and floor coverings); U.S. Pat. No. 5,458,795 (thickened oils for high-temperature applications); U.S. Pat. No. 5,451,332 (fluids for industrial applications); U.S. Pat. No. 5,427,704 (fuel additives); and U.S. Pat. No. 5,380,894 (lubricants, greases, plasticizers, and printing inks), each of which is incorporated herein by reference.
D. Hydrolysis plus Derivatization: Cleavage and Modification of Free Fatty Acids
Hydrolysis of the fatty acid constituents from the glycerolipids produced by the methods of the invention yields free fatty acids that can be derivatized to produce other useful chemical entities. Hydrolysis occurs in the presence of water and an acid or base catalyst. The liberated free fatty acids can be derivatized to yield a variety of products, as reported in the following: U.S. Pat. No. 5,304,664 (highly sulfated fatty acids); U.S. Pat. No. 7,262,158 (cleansing compositions); U.S. Pat. No. 7,115,173 (fabric softener compositions); U.S. Pat. No. 6,342,208 (emulsions for treating skin); U.S. Pat. No. 7,264,886 (water repellant compositions); U.S. Pat. No. 6,924,333 (paint additives); U.S. Pat. No. 6,596,768 (lipid-enriched ruminant feedstock); and U.S. Pat. No. 6,380,410 (surfactants for detergents and cleaners), each of which is incorporated herein by reference.
E. Additional Chemical Reactions to Modify Lipid-Containing Microbial Biomass
Other chemical reactions that can be performed on lipid-containing microbial biomass include reacting triacylglycerols with a cyclopropanating agent to enhance fluidity and/or oxidative stability, as reported in U.S. Pat. No. 6,051,539; manufacturing of waxes from triacylglycerols, as reported in U.S. Pat. No. 6,770,104; and epoxidation of triacylglycerols, as reported in “The effect of fatty acid composition on the acrylation kinetics of epoxidized triacylglycerols”, Journal of the American Oil Chemists' Society, 79:1, 59-63, (2001) and Free Radical Biology and Medicine, 37:1, 104-114 (2004), each of which is incorporated herein by reference.
In some methods, the first step of modification is hydroprocessing to saturate double bonds, followed by deoxygenation at elevated temperature in the presence of hydrogen and a catalyst. In some methods, hydrogenation and deoxygenation occur in the same reaction. In other methods deoxygenation occurs before hydrogenation. Isomerization is then optionally performed, also in the presence of hydrogen and a catalyst. Finally, gases and naphtha components can be removed if desired. For example, see U.S. Pat. No. 5,475,160 (hydrogenation of triglycerides); U.S. Pat. No. 5,091,116 (deoxygenation, hydrogenation and gas removal); U.S. Pat. No. 6,391,815 (hydrogenation); and U.S. Pat. No. 5,888,947 (isomerization), each of which is incorporated herein by reference.
F. Saponification of Oil-Bearing Microbial Biomass and Extracted Oil
1. Basic Chemistry of Saponification
Animal and plant oils are typically made of triacylglycerols (TAGs), which are esters of fatty acids with the trihydric alcohol, glycerol. In an alkaline hydrolysis reaction, the glycerol in a TAG is removed, leaving three carboxylic acid anions that can associate with alkali metal cations such as sodium or potassium to produce fatty acid salts. A typical reaction scheme is as follows:
In this scheme, the carboxylic acid constituents are cleaved from the glycerol moiety and replaced with hydroxyl groups. The quantity of base (e.g., KOH) that is used in the reaction is determined by the desired degree of saponification. If the objective is, for example, to produce a soap product that comprises some of the oils originally present in the TAG composition, an amount of base insufficient to convert all of the TAGs to fatty acid salts is introduced into the reaction mixture. Normally, this reaction is performed in an aqueous solution and proceeds slowly, but may be expedited by the addition of heat. Precipitation of the fatty acid salts can be facilitated by addition of salts, such as water-soluble alkali metal halides (e.g., NaCl or KCl), to the reaction mixture. Preferably, the base is an alkali metal hydroxide, such as NaOH or KOH. Alternatively, other bases, such as alkanolamines, including for example triethanolamine and aminomethylpropanol, can be used in the reaction scheme. In some embodiments, these alternatives may be preferred to produce a clear soap product.
2. Saponification of Oil Bearing Biomass
Saponification of oil bearing microbial biomass can be performed in accordance with the methods of the invention on intact biomass or biomass that has been disrupted prior to being subjected to the alkaline hydrolysis reaction. In the former case, intact microbial biomass generated via the culturing of microorganisms as described herein can be directly contacted with a base to convert ester-containing lipid components of the biomass to fatty acid salts. In some embodiments, all or a portion of the water in which the microbes have been cultured is removed and the biomass is resuspended in an aqueous solution containing an amount of base sufficient to saponify the desired portion of the glycerolipid and fatty acid ester components of the biomass. In some embodiments, less than 100% of the glycerolipids and fatty acid esters in the biomass are converted to fatty acid salts.
In some methods of the invention, the biomass is disrupted prior to being subjected to the alkaline hydrolysis reaction. Disruption of the biomass can be accomplished via any one or more of the methods described above for lysing cells, including heat-induced lysis, mechanical lysis, or the like, to make the intracellular contents of the microorganisms more readily accessible to the base. This can help to facilitate the conversion of TAGs or fatty acid esters to fatty acid salts. Although acid-induced lysis can be used to disrupt the biomass prior to saponification, other methods may be more desirable to reduce the possibility that additional base will be consumed to neutralize any remaining acid during the alkaline hydrolysis reaction, which may impact the conversion efficiency to fatty acid salts. Because the application of heat can expedite the alkaline hydrolysis reaction, heat-induced lysis can be used prior to or during the saponification reaction to produce the fatty acid salts.
In some embodiments of the invention, the biomass is not subjected to any treatment, or any treatment other than disruption, prior to being subjected to the alkaline hydrolysis reaction. In some embodiments, prior enrichment of the biomass to increase the ratio of lipid to non-lipid material in the biomass to more than 50% (or by more than 50%) by weight, is performed as described herein. In other embodiments, the biomass is subjected to the alkaline hydrolysis reaction without a step of prior enrichment. In some embodiments, the biomass subjected to the alkaline hydrolysis reaction contains components other than water in the same relative proportions as the biomass at the point of harvesting. In those embodiments in which substantially all of the water has been removed, the biomass comprises a cellular emulsion or substantially-dried emulsion concentrate.
Any of the microorganisms described herein can be used to produce lipid-containing biomass for the production of saponified oils. In some embodiments, the microorganisms can also impart other characteristics to the saponified-oil compositions produced from the methods described herein. For example, microalgae of different species, as well as microalgae grown under different conditions, vary in color, including green, yellow, orange, red, and the like. Small quantities of the compounds that impart these colors to the microalgae can be purposefully retained so that the resulting saponified-oil compositions and thereby provide natural colorants. In some embodiments, other constituents of the biomass, including carotenoids and xanthophylls, can also be retained in small quantities in the saponified-oil compositions.
The extent of saponification of the biomass can vary in the methods of the invention. In some embodiments, it is desirable to produce a saponified-oil composition that also includes glycerolipid constituents of the biomass. The appropriate quantity of base (e.g., NaOH) for use in the alkaline hydrolysis reaction can be determined based on an analysis of the glycerolipid and fatty acid ester content of the biomass. In some embodiments, it is preferable to use an excess of base to saponify lipid-containing biomass directly, because some of the base may be consumed by reaction with other constituents of the biomass. In some embodiments, the use of excess quantities of base to saponify the ester-containing lipid constituents of the biomass results in a saponified oil composition that is undesirably alkaline. In these instances, the composition can be purified to reduce the alkalinity of the composition by boiling the saponified oil composition in water and re-precipitating the fatty acid salts via addition of salts such as NaCl, KCl, or the like. The purified soap composition can then be subjected to further processing, such as removing excess water, introducing various additives into the soap composition, molding the soap into bars or other shapes, and the like.
In some embodiments, the fatty acid salts (also referred to as saponified oils) generated from the methods described herein can be combined with one or more additives selected from essential oils, fragrance oils, flavor oils, botanicals, extracts, CO2 extracts, clays, colorants, titanium dioxide, micas, tinting herbs, glitters, exfoliants, fruit seeds, fibers, grain powders, nut meals, seed meals, oil beads, wax beads, herbs, hydrosols, vitamins, milk powders, preservatives, antioxidants, tocopherols, salts, sugars, vegetable oils, waxes, glycerin, sea vegetables, nutritive oils, moisturizing oils, vegetable butters, propylene glycol, parabens, honey, bees wax, aloe, polysorbate, cornstarch, cocoa powder, coral powder, humectants, gums, emulsifying agents, and thickeners, or any other additives described herein.
3. Saponification of Extracted Oil
The degree of saponification of extracted lipid constituents of the biomass can be more readily controlled because of a reduced probability that the base will be consumed through interaction with components other than glycerolipids or fatty acid esters present in the extracted oil. Extraction of the lipid constituents can be performed via conventional hexane-extraction procedures, or via an oil-extraction or solventless-extraction procedure.
Conventional hexane-extraction (other suitable organic solvents can also be used) generally comprises contacting the biomass or lysate with hexane in an amount and for a period of time sufficient to allow the lipid to form a solution with the hexane. The mixture can then be filtered and the hexane removed by, for example, rotoevaporation. Hexane extraction methods are well known in the art.
Oil extraction includes the addition of an oil directly to a lysate without prior separation of the lysate components. After addition of the oil, the lysate separates either of its own accord or as a result of centrifugation or the like into different layers. The layers can include in order of decreasing density: a pellet of heavy solids, an aqueous phase, an emulsion phase, and an oil phase. The emulsion phase is an emulsion of lipids and aqueous phase. Depending on the percentage of oil added with respect to the lysate (w/w or v/v), the force of centrifugation, if any, volume of aqueous media and other factors, either or both of the emulsion and oil phases can be present. Incubation or treatment of the cell lysate or the emulsion phase with the oil is performed for a time sufficient to allow the lipid produced by the microorganism to become solubilized in the oil to form a heterogeneous mixture.
In various embodiments, the oil used in the extraction process is selected from the group consisting of oil from soy, rapeseed, canola, palm, palm kernel, coconut, corn, waste vegetable oil, Chinese tallow, olive, sunflower, cotton seed, chicken fat, beef tallow, porcine tallow, microalgae, macroalgae, Cuphea, flax, peanut, choice white grease (lard), Camelina sativa mustard seedcashew nut, oats, lupine, kenaf, calendula, hemp, coffee, linseed, hazelnut, euphorbia, pumpkin seed, coriander, camellia, sesame, safflower, rice, tung oil tree, cocoa, copra, pium poppy, castor beans, pecan, jojoba, jatropha, macadamia, Brazil nuts, and avocado. The amount of oil added to the lysate is typically greater than 5% (measured by v/v and/or w/w) of the lysate with which the oil is being combined. Thus, a preferred v/v or w/w of the oil is greater than 5%, or at least 6%, at least 7%, at least 10%, at least 20%, at least 25%, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, and at least 95% of the cell lysate.
Lipids can also be extracted from a lysate via a solventless extraction procedure without substantial or any use of organic solvents or oils by cooling the lysate. In such methods, the lysate is preferably produced by acid treatment in combination with above room temperature. Sonication can also be used, particularly if the temperature is between room temperature and 65° C. Such a lysate on centrifugation or settling can be separated into layers, one of which is an aqueous:lipid layer (the “emulsion” layer). Other layers can include a solid pellet, an aqueous layer, and a lipid layer. Lipid can be extracted from the emulsion layer by freeze thawing or otherwise cooling the emulsion. In such methods, it is not necessary to add any organic solvent or oil. If any solvent or oil is added, it can be below 5% v/v or w/w of the lysate.
The separated or extracted lipids are then subjected to an alkaline hydrolysis reaction as described above, in which the amount of base added to the reaction mixture can be tailored to saponify a desired amount of the glycerolipid and fatty acid ester constituents of the lipid composition. A close approximation or quantification of the amount of esterified lipid in the composition can be used to tailor the amount of base needed to saponify a specified portion of the oil, thereby providing an opportunity to modulate the amount of unsaponified oil remaining in the resulting composition. In some embodiments, at least 1%, at least 2%, at least 3%, at least 4%, at least 5%, at least 6%, at least 7%, at least 8%, at least 9%, or at least 10% of the oil, by weight, remains unsaponified in the resulting composition. In other embodiments, it may be desirable to saponify all or substantially all of the oil, such that the resulting composition contains no more than 10%, no more than 9%, no more than 8%, no more than 7%, no more than 6%, no more than 5%, no more than 4%, no more than 3%, no more than 2%, no more than 1%, or no more than 0.5% unsaponified oil by weight.
In various embodiments of the invention, the microbial biomass or oil can contain lipids with varying carbon chain lengths, and with varying levels of saturation. The characteristics of the lipids can result from the natural glycerolipid profiles of the one or more microorganism populations used to generate the biomass or oil subjected to the saponification reaction, or can be the result of lipid pathway engineering, as described herein, in which transgenic strains of microorganisms that produce particular lipids in greater proportions are produced.
The microbial biomass subjected to transesterification or other chemical modification, as described herein, can optionally be subjected to a process of prior enrichment that increases the ratio of the lipids to the dry weight of the microbes. In some embodiments, the ratio of lipids to non-lipid materials in the biomass is increased by more than 10%, by more than 20%, by more than 30%, by more than 40%, by more than 50%, by more than 60%, by more than 70%, by more than 80%, by more than 90%, or by more than 100% by weight. In some methods of the invention, the biomass is subjected to the chemical reaction without a step of prior enrichment, or, in some embodiments, without a step of prior enrichment that increases the ratio by more than 50%. Enrichment of the ratio of lipids to non-lipid material can be accomplished by, for example, the addition of lipids obtained from a source other than the microbial biomass (e.g., from a second microbial biomass culture, from a plant or seed-oil source, or the like). Whether or not subjected to optional enrichment, the lipid component comprises no more than 50%, no more than 60%, no more than 70%, no more than 80%, no more than 90%, or no more than 95% of the biomass subjected to the chemical reaction, and preferably the lipid component comprises no less than 15%, no less than 20%, no less than 30%, no less than 35%, no less than 40%, or no less than 45% of the biomass. In some embodiments, the harvested biomass comprises a lipid content of at least 5%, at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, or at least 90% by DCW.
In some embodiments, water is removed from the biomass prior to subjecting the biomass to the saponification (or other chemical modification) reaction. In some embodiments of the invention, the microbial biomass is not subjected to any treatment, other than removing water and/or lysis, prior to subjecting the biomass to the saponification(or other chemical modification) reaction. In some embodiments, the biomass subjected to the chemical reaction contains components other than water in the same relative proportions as the biomass at the point of harvesting from the fermentation. In this context, “the same relative proportions” means that the proportions of the components remain substantially the same after having accounted for changes associated with the cells' use or metabolic conversion of some components following harvesting of the biomass, chemical conversion of some components within the harvested biomass (without the application of exogenous reagents or catalysts), the escape of gases from the harvested biomass, and/or similar modifications of the relative proportions that are not readily controllable. The phrase “the same relative proportions” is also meant to account for some level of experimental variability, e.g, ±5%.
In some methods of the invention, the covalently modified lipid is separated from other components of the biomass following chemical modification of the lipid. In some embodiments, separating the lipid comprises a phase separation whereby the covalently modified lipids form a lighter non-aqueous phase and components of the biomass form one or more heavier phases. The lighter non-aqueous phase can then be removed to isolate the covalently modified lipid components. In some embodiments, separation of a lipophilic phase containing the covalently modified lipids from hydrophilic cell material of the biomass can be facilitated by centrifugation or other techniques. The ratio of the covalently modified lipid to the biomass from which it is separated can be between 10% lipid to 90% biomass and 90% lipid to 10% biomass by dry weight.
4. Advantages of Biomass with Higher Saturated Oil Content and Fewer Colored Impurities
Although biomass and/or extracted oil for use in the saponification methods described herein can be derived from any one of a number of microorganisms with varying glycerolipid profiles and varying ratios of other constituents such as pigments, in a preferred embodiment, the biomass and/or the extracted oil comprises a relatively high ratio of saturated fatty acids within the TAGs and a relatively low ratio of constituents that impart a color to the oil (e.g., pigments). In one embodiment, the biomass and/or extracted oil is derived from microalgae of the genus Prototheca.
The saturation characteristics of the fatty acid constituents of a saponified oil, as well as the presence of colored constituents, impact the shelf-life of compositions comprising the saponified oil, as well as their aesthetic qualities. Saturated fatty acids are less prone to oxidation than their unsaturated counterparts. Thus, use of saponified oils with a relatively higher ratio of saturated:unsaturated fatty acid constituents in the preparation of saponified oil products results in a longer overall shelf-life and minimizes the development of oxidation products, which often have an unpleasant odor. Similarly, the relative absence of colored impurities, which, upon oxidation tend to change the appearance of the saponified oil composition in which they are incorporated, improves the aesthetic qualities of the composition and consumer satisfaction with such products, particularly over an extended shelf-life. Consumers of the resulting soap tend to associate a particular color or lack of color with a brand of soap and come to expect the same color of product every time. The lack of color in the saponified oil allows for more consistency in the resulting saponified oil.
Higher ratios of saturated fatty acids are particularly advantageous in the preparation of saponified compositions, discussed below, in which a portion of the glycerolipids within the biomass (or the extracted oil) remains unsaponified. As discussed previously, a percentage of the glycerolipids can remain unmodified (unsaponified) by adjusting the quantity of base used in the saponification reaction, thus producing a soap product that retains some proportion of the originally present glycerolipids. The presence of an excess of glycerolipids in a saponification reaction is commonly referred to as “superfatting.” The extra oils remaining in the product following the saponification reaction impart moisturizing properties to the composition, but like any oil, are subject to oxidation, which can lead to the development of an unpleasant-smelling composition. Use of a higher ratio of saturated:unsaturated fatty acid constituents as the “superfatting” components of the reaction mixture results in a product with a relatively longer shelf-life and minimizes the production of malodorous oxidative products.
In various embodiments, saturated fatty acid constituents comprise from 1-100% of the ester-containing lipid components of the microbial biomass or extracted oil subjected to an alkaline hydrolysis reaction in accordance with the methods of the present invention. In preferred embodiments, saturated fatty acid constituents comprise at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%, or at least 99% of the ester-containing lipid components in the alkaline hydrolysis reaction.
In some embodiments, color-generating impurities (e.g., carotenoids) are present in the microbial biomass or the extracted oil at a concentration of no more than 500 ppm, no more than 250 ppm, no more than 100 ppm, no more than 75 ppm, or no more than 25 ppm. Color-generating impurities include carotenoids such as lutein, beta carotene, zeaxanthin, astaxanthin and chlorophyll. In other embodiments, the amount of chlorophyll that is present in the microbial biomass or the extracted oil is less than 0.1 mg/kg, less than 0.05 mg/kg, or less than 0.01 mg/kg.
In some embodiments, the microbial oil or soap, before or after saponification, respectively, contains less than 60 micrograms, less than 59 micrograms, less than 58 micrograms, less than 57 micrograms, less than 56 micrograms, less than 55 micrograms, less than 54 micrograms, less than 53 micrograms, less than 52 micrograms, less than 51 micrograms, less than 50 micrograms, less than 49 micrograms, less than 48 micrograms, less than 47 micrograms, less than 46 micrograms, less than 45 micrograms, less than 44 micrograms, less than 43 micrograms, less than 42 micrograms, less than 41 micrograms, less than 40 micrograms, less than 39 micrograms, less than 38 micrograms, less than 37 micrograms, less than 36 micrograms, less than 35 micrograms, less than 34 micrograms, less than 33 micrograms, less than 32 micrograms, less than 31 micrograms, less than 30 micrograms, less than 29 micrograms, less than 28 micrograms, less than 27 micrograms, less than 26 micrograms, less than 25 micrograms, less than 24 micrograms, less than 23 micrograms, less than 22 micrograms, less than 21 micrograms, less than 20 micrograms, less than 19 micrograms, less than 18 micrograms, less than 17 micrograms, less than 16 micrograms, less than 15 micrograms, less than 14 micrograms, less than 13 micrograms, less than 12 micrograms, less than 11 micrograms, less than 10 micrograms, less than 9 micrograms, less than 8 micrograms, less than 7 micrograms, less than 6 micrograms, less than 5 micrograms or less than 4 micrograms carotenoids per gram of saponified oil.
Microalgae of the genus Prototheca, including without limitation, Prototheca wickerhamii, Prototheca stagnora, Prototheca portoricensis, Prototheca moriformis, and Prototheca zopfii naturally produce higher ratios of saturated lipid constituents, as illustrated in Example 28. Moreover, oils extracted from microalgae of the genus Prototheca generally include fewer color-generating impurities, allowing for the production of colorless compositions comprising the saponified oils. Thus, use of such microorganisms as the source of biomass or oil for practicing saponification methods in accordance with the present invention is preferred.
Unless otherwise noted, all strains described in this and the following Examples were obtained from the University of Texas Culture Collection of Algae (Austin, Tex.). In this Example, Prototheca strains were cultivated to achieve a high percentage of oil by dry cell weight. Cryopreserved cells were thawed at room temperature and 500 ul of cells were added to 4.5 ml of medium (4.2 g/L K2HPO4, 3.1 g/L NaH2PO4, 0.24 g/L MgSO4.7H2O, 0.25 g/L Citric Acid monohydrate, 0.025 g/L CaCl2 2H2O, 2 g/L yeast extract) plus 2% glucose and grown for 7 days at 28° C. with agitation (200 rpm) in a 6-well plate. Dry cell weights were determined by centrifuging 1 ml of culture at 14,000 rpm for 5 min in a pre-weighed Eppendorf tube. The culture supernatant was discarded and the resulting cell pellet washed with 1 ml of deionized water. The culture was again centrifuged, the supernatant discarded, and the cell pellets placed at −80° C. until frozen. Samples were then lyophilized for 24 hrs and dry cell weights calculated. For determination of total lipid in cultures, 3 ml of culture was removed and subjected to analysis using an Ankom system (Ankom Inc., Macedon, N.Y.) according to the manufacturer's protocol. Samples were subjected to solvent extraction with an Amkom XT10 extractor according to the manufacturer's protocol. Total lipid was determined as the difference in mass between acid hydrolyzed dried samples and solvent extracted, dried samples. Percent oil dry cell weight measurements are shown in Table 2.
Prototheca stagnora
Prototheca moriformis
Prototheca moriformis
Prototheca strains were genotyped. Genomic DNA was isolated from algal biomass as follows. Cells (approximately 200 mg) were centrifuged from liquid cultures 5 minutes at 14,000×g. Cells were then resuspended in sterile distilled water, centrifuged 5 minutes at 14,000×g and the supernatant discarded. A single glass bead ˜2 mm in diameter was added to the biomass and tubes were placed at −80° C. for at least 15 minutes. Samples were removed and 150 μl of grinding buffer (1% Sarkosyl, 0.25 M Sucrose, 50 mM NaCl, 20 mM EDTA, 100 mM Tris-HCl, pH 8.0, RNase A 0.5 ug/ul) was added. Pellets were resuspended by vortexing briefly, followed by the addition of 40 ul of 5M NaCl. Samples were vortexed briefly, followed by the addition of 66 μl of 5% CTAB (Cetyl trimethylammonium bromide) and a final brief vortex. Samples were next incubated at 65° C. for 10 minutes after which they were centrifuged at 14,000×g for 10 minutes. The supernatant was transferred to a fresh tube and extracted once with 300 μl of Phenol:Chloroform:Isoamyl alcohol 12:12:1, followed by centrifugation for 5 minutes at 14,000×g. The resulting aqueous phase was transferred to a fresh tube containing 0.7 vol of isopropanol (˜190 μl), mixed by inversion and incubated at room temperature for 30 minutes or overnight at 4° C. DNA was recovered via centrifugation at 14,000×g for 10 minutes. The resulting pellet was then washed twice with 70% ethanol, followed by a final wash with 100% ethanol. Pellets were air dried for 20-30 minutes at room temperature followed by resuspension in 50 μl of 10 mM TrisCl, 1 mM EDTA (pH 8.0).
Five μl of total algal DNA, prepared as described above, was diluted 1:50 in 10 mM Tris, pH 8.0. PCR reactions, final volume 20 μl, were set up as follows. Ten μl of 2× iProof HF master mix (BIO-RAD) was added to 0.4 μl primer SZ02613 (5′-TGTTGAAGAATGAGCCGGCGAC-3′ (SEQ ID NO: 1) at 10 mM stock concentration). This primer sequence runs from position 567-588 in Gen Bank accession no. L43357 and is highly conserved in higher plants and algal plastid genomes. This was followed by the addition of 0.4 μl primer SZ02615 (5′-CAGTGAGCTATTACGCACTC-3′ (SEQ ID NO: 2) at 10 mM stock concentration). This primer sequence is complementary to position 1112-1093 in Gen Bank accession no. L43357 and is highly conserved in higher plants and algal plastid genomes. Next, 5 μl of diluted total DNA and 3.2 μl dH2O were added. PCR reactions were run as follows: 98° C., 45″; 98° C., 8″; 53° C., 12″; 72° C., 20″ for 35 cycles followed by 72° C. for 1 min and holding at 25° C. For purification of PCR products, 20 μl of 10 mM Tris, pH 8.0, was added to each reaction, followed by extraction with 40 μl of Phenol:Chloroform:isoamyl alcohol 12:12:1, vortexing and centrifuging at 14,000×g for 5 minutes. PCR reactions were applied to S-400 columns (GE Healthcare) and centrifuged for 2 minutes at 3,000×g. Purified PCR products were subsequently TOPO cloned into PCR8/GW/TOPO and positive clones selected for on LB/Spec plates. Purified plasmid DNA was sequenced in both directions using M13 forward and reverse primers. In total, twelve Prototheca strains were selected to have their 23S rRNA DNA sequenced and the sequences are listed in the Sequence Listing. A summary of the strains and Sequence Listing Numbers is included below. The sequences were analyzed for overall divergence from the UTEX 1435 (SEQ ID NO: 7) sequence. Two pairs emerged (UTEX 329/UTEX 1533 and UTEX 329/UTEX 1440) as the most divergent. In both cases, pairwise alignment resulted in 75.0% pairwise sequence identity. The percent sequence identity to UTEX 1435 is also included below.
Prototheca kruegani
Prototheca wickerhamii
Prototheca stagnora
Prototheca moriformis
Prototheca moriformis
Prototheca wikerhamii
Prototheca moriformis
Prototheca zopfii
Prototheca moriformis
Lipid samples from a subset of the above-listed strains were analyzed for lipid profile using FAME GC/FID detection methods. Results are shown below in Table 3.
A. Extraction of Oil from Microalgae Using an Expeller Press and a Press Aid
Microalgal biomass containing 38% oil by DCW was dried using a drum dryer resulting in resulting moisture content of 5-5.5%. The biomass was fed into a French L250 press. 30.4 kg (67 lbs.) of biomass was fed through the press and no oil was recovered. The same dried microbial biomass combined with varying percentage of switchgrass as a press aid was fed through the press. The combination of dried microbial biomass and 20% w/w switchgrass yielded the best overall percentage oil recovery. The pressed cakes were then subjected to hexane extraction and the final yield for the 20% switchgrass condition was 61.6% of the total available oil (calculated by weight). Biomass with above 50% oil dry cell weight did not require the use of a pressing aid such as switchgrass in order to liberate oil.
Oil extracted from wildtype Prototheca moriformis UTEX 1435 (via solvent extraction or using an expeller press was analyzed for carotenoids, chlorophyll, tocopherols, other sterols and tocotrienols. The results are summarized below in Table 4.
B. Monosaccharide Composition of Delipidated Prototheca moriformis Biomass
Prototheca moriformis (UTEX 1435) was grown in conditions and nutrient media (with 4% glucose) as described in Example 1 above. The microalgal biomass was then harvested and dried using a drum dryer. The dried algal biomass was lysed and the oil extracted using an expeller press as described above. The residual oil in the pressed biomass was then solvent extracted using petroleum ether. Residual petroleum ether was evaporated from the delipidated meal using a Rotovapor (Buchi Labortechnik AG, Switzerland). Glycosyl (monosaccharide) composition analysis was then performed on the delipidated meal using combined gas chromatography/mass spectrometry (GC/MS) of the per-O-trimethylsily (TMS) derivatives of the monosaccharide methyl glycosides produced from the sample by acidic methanolysis. A sample of delipidated meal was subjected to methanolysis in 1M HCl in methanol at 80° C. for approximately 20 hours, followed by re-N-acetylation with pyridine and acetic anhydride in methanol (for detection of amino sugars). The samples were then per-O-trimethylsiylated by treatment with Tri-Sil (Pierce) at 80° C. for 30 minutes (see methods in Merkle and Poppe (1994) Methods Enzymol. 230:1-15 and York et al., (1985) Methods Enzymol. 118:3-40). GC/MS analysis of the TMS methyl glycosides was performed on an HP 6890 GC interfaced to a 5975b MSD, using a All Tech EC-1 fused silica capillary column (30 m×0.25 mm ID). The monosaccharides were identified by their retention times in comparison to standards, and the carbohydrate character of these are authenticated by their mass spectra. 20 micrograms per sample of inositol was added to the sample before derivatization as an internal standard. The monosaccharide profile of the delipidated Prototheca moriformis (UTEX 1435) biomass is summarized in Table 5 below. The total percent carbohydrate from the sample was calculated to be 28.7%.
The carbohydrate content and monosaccharide composition of the delipidated meal makes it suitable for use as an animal feed or as part of an animal feed formulation. Thus, in one aspect, the present invention provides delipidated meal having the product content set forth in the table above.
A. Production of Biodiesel from Prototheca Oil
Degummed oil from Prototheca moriformis UTEX 1435, produced according to the methods described above, was subjected to transesterification to produce fatty acid methyl esters. Results are shown below:
The lipid profile of the oil was:
The Cold Soak Filterability by the ASTM D6751 A1 method of the biodiesel produced was 120 seconds for a volume of 300 ml. This test involves filtration of 300 ml of B 100, chilled to 40° F. for 16 hours, allowed to warm to room temp, and filtered under vacuum using 0.7 micron glass fiber filter with stainless steel support. Oils of the invention can be transesterified to generate biodiesel with a cold soak time of less than 120 seconds, less than 100 seconds, and less than 90 seconds.
B. Production of Renewable Diesel
Degummed oil from Prototheca moriformis UTEX 1435, produced according to the methods described above and having the same lipid profile as the oil used to make biodiesel above, was subjected to transesterification to produce renewable diesel.
The oil was first hydrotreated to remove oxygen and the glycerol backbone, yielding n-paraffins. The n-parrafins were then subjected to cracking and isomerization. A chromatogram of the material is shown in
The T10-T90 of the material produced was 57.9° C. Methods of hydrotreating, isomerization, and other covalent modification of oils disclosed herein, as well as methods of distillation and fractionation (such as cold filtration) disclosed herein, can be employed to generate renewable diesel compositions with other T10-T90 ranges, such as 20, 25, 30, 35, 40, 45, 50, 60 and 65° C. using triglyceride oils produced according to the methods disclosed herein.
The T10 of the material produced was 242.1° C. Methods of hydrotreating, isomerization, and other covalent modification of oils disclosed herein, as well as methods of distillation and fractionation (such as cold filtration) disclosed herein, can be employed to generate renewable diesel compositions with other T10 values, such as T10 between 180 and 295, between 190 and 270, between 210 and 250, between 225 and 245, and at least 290.
The T90 of the material produced was 300° C. Methods of hydrotreating, isomerization, and other covalent modification of oils disclosed herein, as well as methods of distillation and fractionation (such as cold filtration) disclosed herein can be employed to generate renewable diesel compositions with other T90 values, such as T90 between 280 and 380, between 290 and 360, between 300 and 350, between 310 and 340, and at least 290.
The FBP of the material produced was 300° C. Methods of hydrotreating, isomerization, and other covalent modification of oils disclosed herein, as well as methods of distillation and fractionation (such as cold filtration) disclosed herein, can be employed to generate renewable diesel compositions with other FBP values, such as FBP between 290 and 400, between 300 and 385, between 310 and 370, between 315 and 360, and at least 300.
Five Prototheca strains were cultivated in media with 2% glucose and grown for 7 days at 28° C. with agitation (200 rpm) in a 6-well plate. Lipid profiles were determined using standard HPLC methods. The lipid profile for a particular strain did not change significantly when grown in different culture media. The results are shown in Table 8, below.
Prototheca
stagnora
Prototheca
moriformis
Prototheca
moriformis
Prototheca
moriformis
Prototheca
moriformis
Biomass from UTEX 1435 was subjected to hexane extraction. The extracted oil contained very little coloration.
Although this invention has been described in connection with specific embodiments thereof, it will be understood that it is capable of further modifications. This application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth.
All references cited herein, including patents, patent applications, GenBank sequences, and publications are hereby incorporated by reference in their entireties, whether previously incorporated or not. The publications mentioned therein are cited for purpose of describing and disclosing reagents, methodologies and concepts that may be used in connection with the present invention. Nothing herein is to be construed as an admission that these references are prior art in relation to the inventions described therein. In particular, the following patent applications are hereby incorporated by reference in their entireties for all purposes: U.S. Provisional Application No. 61/043,620 filed Apr. 9, 2008, entitled “Direct Chemical Modification of Microbial Biomass”; U.S. Provisional Application No. 61/074,610, filed Jun. 20, 2008, entitled “Soaps and Cosmetic Products Produced from Oil-Bearing Microbial Biomass and Oils”; International publication number WO 2008/151149; U.S. Patent Application No. 61/118,590, filed Nov. 28, 2008, entitled “Production of Oil in Microorganisms”; U.S. Provisional Patent Application No. 61/118,994, filed Dec. 1, 2008, entitled “Production of Oil in Microorganisms”; U.S. Provisional Patent Application No. 61/174,357, filed Apr. 3, 2009, entitled “Production of Oil in Microorganisms”; U.S. Provisional Patent Application No. 61/219,525, filed Jun. 23, 2009, entitled “Production of Oil in Microorganisms”; U.S. patent application Ser. No. 12/628,149, filed Nov. 30, 2009, entitled “Renewable Chemical Production from Novel Fatty Acid Feedstocks”, and International Application No. PCT/US2009/66142, filed Nov. 30, 2009, entitled “Production of Tailored Oils in Heterotrophic Microorganisms”.
The present application is a continuation of U.S. application Ser. No. 12/642,487, filed Dec. 18, 2009, which is a continuation-in-part of U.S. application Ser. No. 12/499,033, filed Jul. 7, 2009, now U.S. Pat. No. 8,119,583, which is a continuation of International Application No. PCT/US2009/040123, filed Apr. 9, 2009, which claims the benefit under 35 U.S.C. 119(e) of U.S. Provisional Application No. 61/043,620, filed Apr. 9, 2008 and U.S. Provisional Patent Application No. 61/074,610, filed Jun. 20, 2008. U.S. application Ser. No. 12/642,487 is also a continuation-in-part of International Application No. PCT/US2009/066142, filed Nov. 30, 2009, which claims the benefit under 35 U.S.C. 119(e) of U.S. Provisional Application No. 61/118,590, filed Nov. 28, 2008, U.S. Provisional Application No. 61/118,994, filed Dec. 1, 2008, U.S. Provisional Application No. 61/174,357, filed Apr. 30, 2009, and U.S. Provisional Application No. 61/219,525, filed Jun. 23, 2009. Each of the applications referenced above is incorporated by reference herein in its entirety for all purposes.
| Number | Date | Country | |
|---|---|---|---|
| 61043620 | Apr 2008 | US | |
| 61074610 | Jun 2008 | US | |
| 61118590 | Nov 2008 | US | |
| 61118994 | Dec 2008 | US | |
| 61174357 | Apr 2009 | US | |
| 61219525 | Jun 2009 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12642487 | Dec 2009 | US |
| Child | 14260013 | US | |
| Parent | PCT/US2009/040123 | Apr 2009 | US |
| Child | 12499033 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12499033 | Jul 2009 | US |
| Child | 12642487 | US | |
| Parent | PCT/US2009/066142 | Nov 2009 | US |
| Child | 12642487 | US |
