Patent Application
20190337995
The present invention relates to methods for increasing carbon-based chemical product yield in an organism by increasing carbon uptake and/or altering a pathway to or from an overflow metabolite in the organism, nonnaturally occurring organisms having increased carbon-based chemical product yield with increased carbon uptake and/or an altered pathway to or from an overflow metabolite, and methods for producing a carbon-based chemical product with these organisms.
Under conditions of nutrient limitation, a phenomenon known as overflow metabolism (also known as energy spilling uncoupling or spillage) occurs in many bacteria (Schlegel and Vollbrecht Microbiology 1980 117:475-481). The range and quantity of overflow metabolites produced in a particular fermentation can depend upon the limitation applied (e.g. nitrogen, phosphate, oxygen), the extent of the limitation, the carbon source provided and the fermentation conditions such as, but not limited to, pH, source of phosphates or ammonia. See (Vollbrecht et al. European Journal of Applied Microbiology and Biotechnology 1978 6(2):145-155; Vollbrecht and Schlegel European Journal of Applied Microbiology and Biotechnology 1978 6(2):157-166; and Vollbrecht et al. European Journal of Applied Microbiology and Biotechnology 1979 7(3):267-276). Such overflow metabolites represent a net loss of carbon which could otherwise be converted into one or more desired compounds.
Tripartite tricarboxylate transporters (TTT) are carbon transporter proteins that use ion-electrochemical gradients to move substrates in a symporter mechanism (Rosa et al. Front Cell Infect. Microbiol. 2018 8:33; Winnen et al. Res. Microbiol. 2003 154(7):457-65).
Replacement of traditional chemical production processes relying on, for example fossil fuels and/or potentially toxic chemicals, with environmentally friendly and/or sustainable solutions is being considered, including work to identify suitable building blocks for such use in the manufacturing of such chemicals. Methods and organisms are needed which channel carbon into selected biosynthetic pathways by blocking undesirable pathways, thereby improving production of one or more desired compounds.
Methods for increasing product yield of organisms and organisms capable of increased product yield are provided.
An aspect of the present invention relates to methods for increasing carbon-based chemical product yield in an organism. These methods comprise modifying an organism selected from a species of Cupriavidus or Ralstonia with diminished polyhydroxybutyrate synthesis or an organism with properties similar thereto to increase carbon uptake and/or alter a pathway to or from an overflow metabolite. Organism are modified in accordance with the present invention by modulating activity of one or more polypeptides or functional fragments thereof functioning to increase carbon uptake and/or in a pathway to or from an overflow metabolite, thereby increasing carbon-based chemical product yield in the organism as compared to an organism without said modulated polypeptide activity.
In one nonlimiting embodiment, the organism is modified to increase carbon uptake via one or more modifications to alter expression and/or activity of a carbon transporter protein or functional fragment thereof.
In one nonlimiting embodiment, modifications to alter expression and/or activity of a carbon transporter protein or functional fragment thereof comprise altering expression and/or activity of one or more genes encoding a TctA, a TctB or a TctC.
In one nonlimiting embodiment, one or more genes as listed in Table 2 are modified.
In one nonlimiting embodiment, the organism is modified to alter a pathway to or from an overflow metabolite by disrupting one or more genes associated with the production of lactate, hydroxybutyrate, acetate and/or 2,3 butandiol, as shown in Table 3.
Another aspect of the present invention relates to nonnaturally occurring organisms capable of yielding a carbon-based chemical product. These nonnaturally occurring organisms are selected from a species of Cupriavidus or Ralstonia with diminished polyhydroxybutyrate synthesis or an organism with properties similar thereto and are modified to increase carbon uptake and/or alter a pathway to or from an overflow metabolite.
In one nonlimiting embodiment, the nonnaturally occurring organisms are modified to increase carbon uptake via one or more modifications to alter expression and/or activity of a carbon transporter protein or functional fragment thereof.
In one nonlimiting embodiment, one or more modifications to alter expression and/or activity of a carbon transporter protein or functional fragment thereof comprise altering expression and/or activity of one or more genes encoding a TctA, a TctB or a TctC is made to the organism.
In one nonlimiting embodiment, one or more genes as listed in Table 2 or Table 3 are modified.
Yet another aspect of the present invention relates to methods for producing a carbon-based chemical product. In these methods, a nonnaturally occurring organism of the present invention is fermented with a carbon source.
In one nonlimiting embodiment, the carbon source is derived from a biological or nonbiological feedstock. In one nonlimiting embodiment, the feedstock fed to the fermentation process comprises a gaseous or liquid stream. In one nonlimiting embodiment, the feedstock is selected from gases, sugars, sugar acids, carboxylic acids, aromatics, and alcohols. In one nonlimiting embodiment, the carbon source is derived from a by-product or waste stream of a food or agricultural industry.
The present invention provides methods of increasing carbon-based chemical product yield in an organism as well as nonnaturally occurring organisms modified to exhibit increased product yield as compared to unmodified organisms.
The methods of the present invention comprise modifying an organism selected from a species of Cupriavidus or Ralstonia with diminished polyhydroxybutyrate synthesis or an organism with properties similar thereto to increase carbon uptake and/or alter a pathway to or from an overflow metabolite. Organism are modified in accordance with the present invention by modulating activity of one or more polypeptides or functional fragments thereof functioning to increase carbon uptake and/or in a pathway to or from an overflow metabolite, thereby increasing carbon-based chemical product yield in the organism as compared to an organism without said modulated polypeptide activity. In one nonlimiting embodiment, genes in these pathways to or from an overflow metabolite may be modified. Such modifications may comprise overexpressing an endogenous or exogenous nucleic acid sequence in the organism. Alternatively, such modification may comprise downregulating, deleting or mutating an endogenous or exogenous nucleic acid sequence in the organism. The modified organisms are then cultured under conditions suitable for biosynthesis of the one or more products.
In certain aspects, the organism is modified by altering, engineering, or introducing one or more nucleic acid sequences within the organism to have one or more different characteristic properties relative to those of the corresponding unmodified wild type organism. The altering of modifying of the nucleic acid sequences can be, for example and without limitation, via genetic engineering, by adaptive mutation, or by selective isolation of naturally occurring mutant strains.
In some nonlimiting embodiments, one or more enzymes or nucleic acids of the organism are modified via non-direct or rational enzyme design approaches with aims of improving activity, improving specificity, reducing feedback inhibition, reducing repression, improving enzyme solubility, changing stereo-specificity, or changing co-factor specificity. In some embodiments, the enzymes in the pathways outlined herein can be gene dosed (i.e., overexpressed by having a plurality of copies of the gene in the host organism), into the resulting genetically modified organism via episomal or chromosomal integration approaches. In some nonlimiting embodiments, genome-scale system biology techniques such as Flux Balance Analysis can be utilized to devise genome scale attenuation or knockout strategies for directing carbon flux. Attenuation strategies include, but are not limited to, the use of transposons, homologous recombination (double cross-over approach), mutagenesis, enzyme inhibitors, and RNA interference (RNAi). In some embodiments, fluxomic, metabolomic and transcriptomal data can be utilized to inform or support genome-scale system biology techniques, thereby devising genome-scale attenuation or knockout strategies in directing carbon flux. In some embodiments, the tolerance of the host microorganism to high concentrations of the extracellular product can be improved through continuous cultivation in a selective environment.
The modified nucleic acid sequences of the organism can include, for example, one or more enzymes, one or more promoters, one or more transcription factors, or combinations thereof. The modifications can be to nucleic acids encoding polypeptides functioning as a transhydrogenase, reductase, dehydrogenase, or hydrogenase enzyme or functional fragments thereof. The modifications can be to nucleic acids not directly involved in encoding polypeptides functioning as a transhydrogenase, reductase, dehydrogenase, or hydrogenase enzyme or functional fragments thereof, but indirectly affecting the polypeptides through the interconnected metabolic network and metabolic control strategy of the organism. The modification of the nucleic acid sequences can include one or more deletions, one or more substitutions, one or more insertions, or combinations thereof.
Enzymes with substitutions will generally have not more than 50 (e.g., not more than 1, not more than 2, not more than 3, not more than 4, not more than 5, not more than 6, not more than 7, not more than 8, not more than 9, not more than 10, not more than 12, not more than 15, not more than 20, not more than 25, not more than 30, not more than 35, not more than 40, or not more than 50) amino acid substitutions (e.g., conservative or non-conservative substitutions). This applies to any of the enzymes described herein and functional fragments thereof. A conservative substitution is a substitution of one amino acid for another with similar characteristics. Conservative substitutions include substitutions within the following groups: valine, alanine and glycine; leucine, valine, and isoleucine; aspartic acid and glutamic acid; asparagine and glutamine; serine, cysteine, and threonine; lysine and arginine; and phenylalanine and tyrosine. The nonpolar hydrophobic amino acids include alanine, leucine, isoleucine, valine, proline, phenylalanine, tryptophan and methionine. The polar neutral amino acids include glycine, serine, threonine, cysteine, tyrosine, asparagine and glutamine. The positively charged (basic) amino acids include arginine, lysine and histidine. The negatively charged (acidic) amino acids include aspartic acid and glutamic acid. Any substitution of one member of the above-mentioned polar, basic, or acidic groups by another member of the same group can be deemed a conservative substitution. In contrast, a non-conservative substitution is a substitution of one amino acid for another with dissimilar characteristics. Deletion variants can, for example, lack 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 amino acid segments (of two or more amino acids) or non-contiguous single amino acids.
In one nonlimiting embodiment, modification of the organism is carried out by allele exchange. In this embodiment, genome edits are made in a Cupriavidus or Ralstonia organism with perturbed PHB synthesis or an organism with properties similar thereto by allele exchange (also referred to as allelic exchange). In one non-limiting embodiment, the organism is a ΔphaCAB H16 C. necator strain generated using allele exchange.
The term ‘allele’ is often used interchangeably with the term ‘gene’ more generally, and refers to a defined genomic locus. In allele exchange, a specific run of DNA sequence (i.e., the native allele) in a genome of an organism is literally exchanged for a recombinant, mutant, or synthetic run of DNA sequence (i.e., the recombinant allele). Depending on the nature of the recombinant allele, this allele exchange can result in a gene deletion, a gene substitution, or a gene insertion.
In one nonlimiting embodiment, recombinant/synthetic alleles can be constructed via gene synthesis and/or standard molecular biology techniques. These alleles are then cloned into a plasmid vector for transfer into the organism and execution of the allele exchange procedure.
In some nonlimiting embodiments, the organism is modified to include one or more exogenous nucleic acid sequences.
The term “exogenous” as used herein with reference to a nucleic acid (or a protein) and an organism refers to a nucleic acid that does not occur in (and cannot be obtained from) a cell of that particular type as it is found in nature or a protein encoded by such a nucleic acid. Thus, a non-naturally-occurring nucleic acid is considered to be exogenous to a host once in the host. It is important to note that non-naturally-occurring nucleic acids can contain nucleic acid subsequences or fragments of nucleic acid sequences that are found in nature provided the nucleic acid as a whole does not exist in nature. For example, a nucleic acid molecule containing a genomic DNA sequence within an expression vector is non-naturally-occurring nucleic acid, and thus is exogenous to a host cell once introduced into the host, since that nucleic acid molecule as a whole (genomic DNA plus vector DNA) does not exist in nature. Thus, any vector, autonomously replicating plasmid, or virus (e.g., retrovirus, adenovirus, or herpes virus) that as a whole does not exist in nature is considered to be non-naturally-occurring nucleic acid. It follows that genomic DNA fragments produced by PCR or restriction endonuclease treatment as well as cDNAs are considered to be non-naturally-occurring nucleic acid since they exist as separate molecules not found in nature. It also follows that any nucleic acid containing a promoter sequence and polypeptide-encoding sequence (e.g., cDNA or genomic DNA) in an arrangement not found in nature is non-naturally-occurring nucleic acid. A nucleic acid that is naturally-occurring can be exogenous to a particular host microorganism. For example, an entire chromosome isolated from a cell of yeast x is an exogenous nucleic acid with respect to a cell of yeast y once that chromosome is introduced into a cell of yeast y.
In contrast, the term “endogenous” as used herein with reference to a nucleic acid (e.g., a gene) (or a protein) and a host refers to a nucleic acid (or protein) that does occur in (and can be obtained from) that particular host as it is found in nature. Moreover, a cell “endogenously expressing” a nucleic acid (or protein) expresses that nucleic acid (or protein) as does a host of the same particular type as it is found in nature. Moreover, a host “endogenously producing” or that “endogenously produces” a nucleic acid, protein, or other compound produces that nucleic acid, protein, or compound as does a host of the same particular type as it is found in nature.
In certain aspects, the organism is modified to include one or more functional fragments of enzymes, other polypeptides, or nucleic acids. The phrase “functional fragment” as used herein refers to a peptide fragment of a polypeptide or a nucleic acid sequence fragment encoding a peptide fragment of a polypeptide that has at least 25%, e.g., at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 98%, at least 99%, or at least 100% of the activity of the corresponding mature, full-length, polypeptide. The functional fragment can generally, but not always, be comprised of a continuous region of the polypeptide, wherein the region has functional activity.
Tripartite tricarboxylate transporters (TTT) are carbon transporter proteins that use ion-electrochemical gradients to move substrates in a symporter mechanism. Each transporter is comprised of two transmembrane proteins and a periplasmic solute-binding protein. TctA is a well-conserved 12 transmembrane protein while TctB is a poorly conserved smaller transmembrane protein with 4 putative TMs domains. TctC is a periplasmic tricarboxylate-binding receptor. The TctC protein is highly represented in the protobacteria genomes possibly providing specificity to the transporter. Recent genome analysis of Ralstonia has shown an overrepresentation of tctC homologs. In one nonlimiting embodiment of the present invention, one or more modifications to increase carbon uptake comprise altering expression and/or activity of one or more of carbon transporter proteins or functional fragments thereof.
Within biotechnology the approach of redirecting carbon flux to a desired product by utilizing nutrient limitation is a well-established process. With Cupriavidus, it is the principle methodology for obtaining high polyhydroxyalkanoate (PHA) titers, as it exploits the organism's natural mechanism for intracellular storage of carbon and energy. To utilize Cupriavidus or Ralstonia for the purposes of generating other chemicals however, this natural mechanism is detrimental for obtaining high productivity and/or yields. Elimination or significant attenuation of PHA synthesis is therefore required, in order to maximize the efficiency of generating the desired product.
An unintended consequence of such an approach is that there is a cascade of effects upon metabolism due to high amounts of reducing equivalents and build-up of key central metabolites including pyruvate and acetyl-CoA. These manifestations include among others metabolic bottlenecks, heightened generation of overflow metabolites and a redox imbalance.
Furthermore, under conditions of nutrient limitation, a phenomenon known as overflow metabolism (also known as energy spilling uncoupling or spillage) occurs in many bacteria (Schlegel & Vollbrecht Microbiology 1980 117:475-481). In growth conditions in which there is a relative excess of carbon source and other nutrients (e.g. phosphorous, nitrogen and/or oxygen) are limiting cell growth, overflow metabolism results in the use of this excess energy (or carbon), not for biomass formation but for the excretion of metabolites, typically organic acids. Such overflow metabolites represent a net loss of carbon which could otherwise be converted into one or more desired compounds. Accordingly, in one nonlimiting embodiment of the method of the present invention, one or more modifications in a pathway to/from an overflow metabolite are made to increase carbon-based chemical product yield.
By “carbon-based chemical product” as used herein, it is meant to include C3 to C12 alkenes, alcohols, diols, monoacids, diacids, hydroxyacids, amino acids and diamines. In one nonlimiting embodiment, the carbon-based chemical product may be any C6-C12 difunctional aliphatic fatty acid or derivative thereof including, but not limited to, C6-C12 amino acids, C6-C12 diamines, C6-C12 hydroxyacids, C6-C12 diols, and C6-C12 diacids. Nonlimiting examples of carbon-based chemical products produced in accordance with this disclosure include 1,3-propanediol, 1,2-propanediol, methionine, threonine, lysine, glutamic acid, tryptophan, aspartic acid, leucine, isoleucine, valine, citric acid, maleic acid, succinic acid, isoprene, linalool, limonene, 3-hydroxypropanoic acid, malonic acid, lactic acid, n-butanol, 2-butanone, butadiene, 2-3 butanediol, 1-3 butanediol, benzoic acid, 1,4-benzenediamine, benzeneamine, pyridine, vanillin, hydroquinone, 1,4-diaminobutane, 2-hydroxyisobutyric acid, itaconic acid, 3-hydroxybutyrate and nylon intermediates.
In some nonlimiting embodiments, the organism has been modified to exhibit an increased synthesis of the extracellular product relative to that of the corresponding wild type organism.
In some nonlimiting embodiments, the carbon-based chemical product includes pimelic acid, 7-aminoheptanoate, 7-hydroxyheptanoate, heptamethylenediamine, 1,7-heptanediol, or a combination thereof. Additional descriptions of the synthesis of these carbon-based chemical products with Ralstonia, Cupriavidus, or an organism similar thereto can be found in U.S. Pat. No. 10,196,657, the disclosure of which is incorporated by reference herein in its entirety for all purposes.
In some nonlimiting embodiments, the carbon-based chemical product includes 1,4-butanediol, putrescine, 4-hydroxybutyrate, 4-aminobutyrate, or a combination thereof. Additional descriptions of the synthesis of these carbon-based chemical products with Ralstonia, Cupriavidus, or an organism related thereto can be found in U.S. Pat. Nos. 10,072,150 and 9,637,764, the disclosures of which are incorporated by reference herein in their entirety for all purposes.
In some nonlimiting embodiments, the carbon-based chemical product includes glutaric acid, 5-aminopentanoic acid, cadaverine (also known as 1,5 pentanediamine), 5-hydroxypentanoic acid, 1,5-pentanediol, glutarate semialdehyde (also known as 5-oxopentanoate), or a combination thereof. Additional descriptions of the synthesis of these carbon-based chemical products with Ralstonia, Cupriavidus, or an organism related thereto can be found in U.S. Pat. No. 9,920,339, the disclosure of which is incorporated by reference herein in its entirety for all purposes.
In some nonlimiting embodiments, the carbon-based chemical product includes isoprene. Additional descriptions of the synthesis of this carbon-based chemical product with Ralstonia, Cupriavidus, or an organism related thereto can be found in U.S. Pat. No. 9,862,973, the disclosure of which is incorporated by reference herein in its entirety for all purposes.
In some nonlimiting embodiments, the carbon-based chemical product includes adipic acid, 6-aminohexanoic acid, hexamethylenediamine, caprolactam, 1,6-hexanediol, or a combination thereof. Additional descriptions of the synthesis of these carbon-based chemical products with Ralstonia, Cupriavidus, or an organism related thereto can be found in U.S. Pat. No. 9,580,733, the disclosure of which is incorporated by reference herein in its entirety for all purposes.
For products of the present invention containing carboxylic acid groups such as organic monoacids, hydroxyacids, aminoacids and dicarboxylic acids, these products may be formed or converted to their ionic salt form when an acidic proton present in the parent product either is replaced by a metal ion, e.g., an alkali metal ion, an alkaline earth ion, or an aluminum ion; or coordinates with an organic base. Acceptable organic bases include ethanolamine, diethanolamine, triethanolamine, tromethamine, N-methylglucamine, and the like. Acceptable inorganic bases include aluminum hydroxide, calcium hydroxide, potassium hydroxide, sodium carbonate and/or bicarbonate, sodium hydroxide, ammonia and the like. The salt can be isolated as is from the system as the salt or converted to the free acid by reducing the pH to below the lowest pKa through addition of acid or treatment with an acidic ion exchange resin.
For products of the present invention containing amine groups such as but not limited to organic amines, aminoacids and diamine, these products may be formed or converted to their ionic salt form by addition of an acidic proton to the amine to form the ammonium salt, formed with inorganic acids such as hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, phosphoric acid, and the like; or formed with organic acids such as acetic acid, propionic acid, hexanoic acid, cyclopentanepropionic acid, glycolic acid, pyruvic acid, lactic acid, malonic acid, succinic acid, malic acid, maleic acid, fumaric acid, tartaric acid, citric acid, benzoic acid, 3-(4-hydroxybenzoyl)benzoic acid, cinnamic acid, mandelic acid, methanesulfonic acid, ethanesulfonic acid, 1,2-ethanedisulfonic acid, 2-hydroxyethanesulfonic acid, benzenesulfonic acid, 2-naphthalenesulfonic acid, 4-methylbicyclo-[2.2.2]oct-2-ene-1-carboxylic acid, glucoheptonic acid, 4,4′-methylenebis-(3-hydroxy-2-ene-1-carboxylic acid), 3-phenylpropionic acid, trimethylacetic acid, tertiary butylacetic acid, lauryl sulfuric acid, gluconic acid, glutamic acid, hydroxynaphthoic acid, salicylic acid, stearic acid or muconic acid. Acceptable inorganic bases are known in the art and include aluminum hydroxide, calcium hydroxide, potassium hydroxide, sodium carbonate and/or bicarbonate, ammonia, sodium hydroxide, and the like. The salt can be isolated as is from the system as a salt or converted to the free amine by raising the pH to above the lowest pKa through addition of base or treatment with a basic ion exchange resin.
For products of the present invention containing both amine groups and carboxylic acid groups such as but not limited to aminoacids, these products may be formed or converted to their ionic salt form by either 1) acid addition salts, formed with inorganic acids such as hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, phosphoric acid, and the like; or formed with organic acids such as acetic acid, propionic acid, hexanoic acid, cyclopentanepropionic acid, glycolic acid, pyruvic acid, lactic acid, malonic acid, succinic acid, malic acid, maleic acid, fumaric acid, tartaric acid, citric acid, benzoic acid, 3-(4-hydroxybenzoyl)benzoic acid, cinnamic acid, mandelic acid, methanesulfonic acid, ethanesulfonic acid, 1,2-ethanedisulfonic acid, 2-hydroxyethanesulfonic acid, benzenesulfonic acid, 2-naphthalenesulfonic acid, 4-methylbicyclo-[2.2.2]oct-2-ene-1-carboxylic acid, glucoheptonic acid, 4,4′-methylenebis-(3-hydroxy-2-ene-1-carboxylic acid), 3-phenylpropionic acid, trimethylacetic acid, tertiary butylacetic acid, lauryl sulfuric acid, gluconic acid, glutamic acid, hydroxynaphthoic acid, salicylic acid, stearic acid or muconic acid. Acceptable inorganic bases include aluminum hydroxide, calcium hydroxide, potassium hydroxide, sodium carbonate and/or bicarbonate, ammonia, sodium hydroxide, and the like or 2) when an acidic proton present in the parent compound either is replaced by a metal ion, e.g., an alkali metal ion, an alkaline earth ion, or an aluminum ion; or coordinates with an organic base. Acceptable organic bases are known in the art and include ethanolamine, diethanolamine, triethanolamine, tromethamine, N-methylglucamine, and the like. The salt can be isolated as is from the system or converted to the free acid by reducing the pH to below the pKa through addition of acid or treatment with an acidic ion exchange resin.
Nonnaturally occurring organism produced and used in accordance with the present invention are selected from a species of Cupriavidus or Ralstonia with diminished polyhydroxybutyrate synthesis or an organism with properties similar thereto.
For purposes of the present invention, by “diminishing” or “diminished” polyhydroxybutyrate synthesis, it is meant that the organism is altered to synthesize less polyhydroxybutyrate as compared to an unaltered wild-type organism of the same species. Organisms used in this disclosure can exhibit at least 20%, 25%, 30%, 40%, 50% or even greater decreased polyhydroxybutyrate synthesis as compared to an unperturbed wild-type organism of the same species.
Nonlimiting examples of species of Cupriavidus or Ralstonia useful in accordance with this disclosure include Cupriavidus necator, Cupriavidus metallidurans, Cupriavidus taiwanensis, Cupriavidus pinatubonensis, Cupriavidus basilensis and Ralstonia pickettii.
C. necator (also referred to as Hydrogenomonas eutrophus, Alcaligenes eutropha, Ralstonia eutropha, and Wautersia eutropha) is a Gram-negative, flagellated soil bacterium of the Betaproteobacteria class. This hydrogen-oxidizing bacterium is capable of growing at the interface of anaerobic and aerobic environments and easily adapts between heterotrophic and autotrophic lifestyles. Sources of energy for the bacterium include both organic compounds and hydrogen. Additional properties of C. necator include microaerophilicity, copper resistance (Makar, N. S. & Casida, L. E. Int. J. of Systematic Bacteriology 1987 37(4): 323-326), bacterial predation (Byrd et al. Can J Microbiol 1985 31:1157-1163; Sillman, C. E. & Casida, L. E. Can J Microbiol 1986 32:760-762; Zeph, L. E. & Casida, L. E. Applied and Environmental Microbiology 1986 52(4):819-823) and polyhydroxybutyrate (PHB) synthesis. In addition, the cells have been reported to be capable of either aerobic or nitrate dependent anaerobic growth. A nonlimiting example of a C. necator organism useful in the present invention is a C. necator of the H16 strain. In one nonlimiting embodiment, a C. necator host of the H16 strain with at least a portion of the phaC1AB1 gene locus knocked out (ΔphaCAB) is used. In one nonlimiting embodiment, the organism is further modified to eliminate phaCAB, involved in PHBs production and/or H16-A0006-9 encoding endonucleases thereby improving transformation efficiency as described in U.S. patent application Ser. No. 15/717,216, teachings of which are incorporated herein by reference. However, other means of eliminating PHB synthesis are included within the scope of the invention.
By “an organism with properties similar thereto” it is meant an organism having one or more of the above-mentioned properties of C. necator.
In the process described herein, a fermentation strategy can be used that entails anaerobic, micro-aerobic or aerobic cultivation coupled with nutrient limitation such as iron, sulphate, nitrogen, potassium, oxygen, phosphorus, carbon and/or or NADP limitations, gradients thereof and any combinations thereof.
A cell retention strategy using a ceramic hollow fiber membrane can also be employed to achieve and maintain a high cell density during fermentation.
The principal carbon source fed to the fermentation can derive from a biological or non-biological feedstock. In one nonlimiting embodiment, the feedstock is fed to the fermentation as a gaseous or liquid stream.
Feedstocks for fermentation may be gases such as carbon dioxide or hydrogen; sugars such as glucose, xylose or fructose; sugar acids such as gluconate; fatty acids or fats/oils, carboxylic acids such as propionic acid, lactic acid, and formic acid; amino acids, aromatics such as phenol and benzoic acid and/or alcohols such as glycerol.
The feedstocks may be carbon sources derived from by-product or waste streams such as brewing, dairy, plant oil, ethanol, corn, soy, fish, or sugar industries or any other food or agricultural waste such as used cooking oil.
The biological feedstock can be, or can derive from, monosaccharides, disaccharides, lignocellulose, hemicellulose, cellulose, paper-pulp waste, black liquor, lignin, levulinic acid and formic acid, triglycerides, glycerol, fatty acids, agricultural waste, thin stillage, condensed distillers' solubles or waste streams from the food processing or dairy industries municipal waste such as fruit peel/pulp or whey. The non-biological feedstock can be, or can derive from, natural gas, syngas, CO2/H2, CO, H2, O2, methanol, ethanol, waste streams from processes to produce monomers for the Nylon-66 and Nylon-6 industries such as but not limited to non-volatile residues (NVRs) and caustic wash waste streams from the cyclohexane oxidation process used to manufacture adipic acid or caprolactam or waste stream from other chemical industry processes such as, but not limited to a carbon black industry or a hydrogen-refining industry, or petrochemical industry, a nonlimiting example being a PTA-waste stream.
In one nonlimiting embodiment, at least one of the enzymatic conversions of the production method comprises gas fermentation within the modulated Ralstonia or Cupriavidus organism or other organism with properties similar thereto. In this embodiment, the gas fermentation may comprise at least one of natural gas, syngas, CO, H2, O2, CO2/H2, methanol, ethanol, non-volatile residue, caustic wash from cyclohexane oxidation processes, or waste stream from a chemical industry such as, but not limited to a carbon black industry or a hydrogen-refining industry, or petrochemical industry. In one nonlimiting embodiment, the gas fermentation comprises CO2/H2.
The methods of the present invention may further comprise recovering produced product from the organism. Once produced, any method can be used to isolate these products or derivatives or compounds related thereto.
The isolation of at least one product can involve any one or more downstream processes generally known to be suitable for the at least partial separation and/or isolation of material from a reaction or bioprocess. The collection can, for example, involve centrifugations, cell disruptions, concentrations, precipitations, extractions, filtrations, crystallizations, distillations, chemical conversions, or combinations thereof. One or more biosynthetic products can be collected from the liquid or solid phase of the culture, or from the gas phase present in the headspace of a bioreactor or the off-gas.
The present invention also provides nonnaturally occurring organisms and methods for producing the nonnaturally occurring organisms modified to comprise one or more modifications to increase carbon uptake and/or one or more modifications in a pathway to/from an overflow metabolite. Such modification may comprise overexpressing an endogenous or exogenous nucleic acid sequence in the organism. Alternatively, such modification may comprise downregulating, deleting or mutating an endogenous or exogenous nucleic acid sequence in the organism. These nonnaturally occurring organisms exhibit increased product yield as compared to product yield in the same organism without modification to comprise one or more modifications to increase carbon uptake and/or one or more modifications in a pathway to/from an overflow metabolite. The nonnaturally occurring organisms are selected from a species of Cupriavidus or Ralstonia with diminished polyhydroxybutyrate synthesis or an organism with properties similar thereto.
Nonlimiting examples of species of Cupriavidus or Ralstonia useful in accordance with this disclosure include Cupriavidus necator, Cupriavidus metallidurans, Cupriavidus taiwanensis, Cupriavidus pinatubonensis, Cupriavidus basilensis and Ralstonia pickettii.
In one nonlimiting embodiment, the present invention relates to a substantially pure culture of the nonnaturally occurring organism modified to comprise one or more modifications to increase carbon uptake and/or one or more modifications in a pathway to/from an overflow metabolite.
As used herein, a “substantially pure culture” of an altered organism is a culture of that microorganism in which less than about 40% (i.e., less than about 35%; 30%; 25%; 20%; 15%; 10%; 5%; 2%; 1%; 0.5%; 0.25%; 0.1%; 0.01%; 0.001%; 0.0001%; or even less) of the total number of viable cells in the culture are viable cells other than the altered microorganism, e.g., bacterial, fungal (including yeast), mycoplasmal, or protozoan cells. The term “about” in this context means that the relevant percentage can be 15% of the specified percentage above or below the specified percentage. Thus, for example, about 20% can be 17% to 23%. Such a culture of nonnaturally occurring microorganisms includes the cells and a growth, storage, or transport medium. Media can be liquid, semi-solid (e.g., gelatinous media), or frozen. The culture includes the cells growing in the liquid or in/on the semi-solid medium or being stored or transported in a storage or transport medium, including a frozen storage or transport medium. The cultures are in a culture vessel or storage vessel or substrate (e.g., a culture dish, flask, or tube or a storage vial or tube).
In addition, the present invention provides bio-derived, bio-based, or fermentation-derived products produced using the methods and/or nonnaturally occurring organisms disclosed herein. Examples of such products include, but are not limited to, compositions comprising at least one bio-derived, bio-based, or fermentation-derived compound or any combination thereof, as well as molded substances, formulations and semi-solid or non-semi-solid streams comprising one or more of the bio-derived, bio-based, or fermentation-derived compounds or compositions, combinations or products thereof.
While the invention has been described in detail, in some instances making reference to a specific aspect thereof, it is apparent to one of skill in the art that various changes and modifications can be made thereto without departing from its spirit and scope. The following section provides further illustration of the methods and materials of the present invention. These Examples are illustrative only and are not intended to limit the scope of the invention in any way.
In one nonlimiting embodiment, R. eutropha is grown in different carbon sources and RNAseq and/or proteomic experiments are performed to identify Tcts that are affected on different carbon sources. The Tcts are then validated by altering expression and/or activity and carbon utilization assessed. By modifying particular tcts, assimilation of different carbon sources can be altered. Such modifications may comprise overexpressing an endogenous or exogenous nucleic acid sequence in the organism. Alternatively, such modification may comprise downregulating, deleting or mutating an endogenous or exogenous nucleic acid sequence in the organism. For example, tctC genes H16_A1360, H16_A3350, H16_B1846 and H16_B1848 are induced through growth on pimelate, whilst H16_B0202 and H16_B1474 are induced through growth on adipate. TctC genes H16_A0036, H16_A1555, H16_B1078 and H16_B1448 are induced by growth on adipate and pimelate. TctC genes H16_A2384 and H16_B2116 are induced on fructose relative to pimelate and adipate. In addition, tctA gene H16_A2775 is induced on fructose relative to pimelate and adipate whilst H16_B2053 is induced on pimelate and adipate. TctB gene H16_B2054 is induced on pimelate and adipate whilst H16_A2774 is induced on fructose. RNA expression levels of selected C. necator H16 genes encoding Tct family transport components upon growth with fructose, adipate and pimelate as sole carbon sources are shown in Table 1. Gene expression levels were measured by RNAseq and are expressed as relative expression units (REU) that are normalized to total transcript levels.
Nonlimiting examples of putative TTT transporter genes that can be altered in accordance with the present invention are set forth in Table 2.
Nonlimiting examples of pathways that can be blocked to increase yield of the desired product are set forth in
Cupriavidus necator
Cupriavidus necator
Cupriavidus necator
This patent application claims the benefit of priority from U.S. Provisional Application Ser. No. 62/665,800 filed May 2, 2018, teachings of which are herein incorporated by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62665800 | May 2018 | US |
