Patent Application
20200199559
The present invention relates to processes for producing fermentation products from starch-containing material. The invention also relates to a composition suitable for use in a process of the invention.
This application contains a Sequence Listing in computer readable form. The computer readable form is incorporated herein by reference.
Production of fermentation products, such as ethanol, from starch-containing material is well-known in the art. Industrially two different kinds of processes are used today. The most commonly used process, often referred to as a “conventional process”, includes liquefying gelatinized starch at high temperature using typically a bacterial alpha-amylase, followed by simultaneous saccharification and fermentation carried out in the presence of a glucoamylase and a fermentation organism. Another well-known process, often referred to as a “raw starch hydrolysis”-process (RSH process), includes simultaneously saccharifying and fermenting granular starch below the initial gelatization temperature typically in the presence of at least a glucoamylase.
Despite significant improvement of fermentation product production processes over the past decade a significant amount of residual starch material is not converted into the desired fermentation product, such as ethanol. At least some of the unconverted residual starch material, e.g., sugars and dextrins, is in the form of non-fermentable Maillard products.
Therefore, there is still a desire and need for providing processes for producing fermentation products, such as ethanol, from starch-containing material that can provide a higher fermentation product yield, or other advantages, compared to a conventional process.
The present invention relates to processes of producing fermentation products, such as ethanol, from starch-containing material using a fermenting organism.
In the first aspect the invention relates to processes for producing fermentation products, such as ethanol, from starch-containing material comprising the steps of:
i) liquefying the starch-containing material at a pH in the range between from above 5.0-7.0 at a temperature above the initial gelatinization temperature using:
an alpha-amylase;
a protease having a thermostability value of more than 20% determined as Relative Activity at 80° C./70° C.; and
optionally a carbohydrate-source generating enzyme;
ii) saccharifying using a carbohydrate-source generating enzyme;
iii) fermenting using a fermenting organism.
In a preferred embodiment liquefaction is carried out at a temperature between 80-90° C., such as around 85° C. In a preferred embodiment liquefaction is carried out at a pH in the range pH above 5.0 to 6.0.
In a second aspect the invention relates to an enzyme composition comprising:
i) an alpha-amylase;
ii) a protease having a thermostability value of more than 20% determined as Relative Activity at 80° C./70° C.; and
iii) optionally a carbohydrate-source generating enzyme.
The optional carbohydrate-source generating enzyme may be a thermostable glucoamylase, and/or a pullulanase. In an embodiment the carbohydrate-source generating enzyme, in particular a glucoamylase, is Penicillium oxalicum glucoamylase.
The Figure shows a comparison of the 54 hour ethanol fermentation yield (%) for Alpha-Amylase 1407 with and without Protease Pfu and/or Glucoamylase PE001 added during liquefaction at pH 5.4 and 5.8, respectively, at 85° C. for 2 hours.
The present invention relates to processes of producing fermentation products, such as ethanol from starch-containing material using a fermenting organism.
The inventors have found that an increased ethanol yield is obtained when liquefying starch-containing material with a mature Bacillus stearothermophilus alpha-amylase disclosed in SEQ ID NO: 1 herein having a double deletion (I181*+G182*) and substitution N193F together with Pyrococcus furiosus protease (pfu S) or thermostable variants of wild-type Thermoascus aurantiacus protease at 85° C., at pH 5.4 or 5.8 for 2 hours.
In the first aspect the invention relates to processes for producing fermentation products, preferably ethanol, comprising the steps of:
i) liquefying the starch-containing material at a pH in the range between from above 5.0-7.0 at a temperature above the initial gelatinization temperature using:
an alpha-amylase;
a protease having a thermostability value of more than 20% determined as Relative Activity at 80° C./70° C.; and optionally
a carbohydrate-source generating enzyme;
ii) saccharifying using a carbohydrate-source generating enzyme;
iii) fermenting using a fermenting organism.
Steps ii) and iii) are carried out either sequentially or simultaneously. In a preferred embodiment steps ii) and iii) are carried out simultaneously. The alpha-amylase, thermostable protease and optionally the carbohydrate-source generating enzyme, preferably glucoamylase, and/or optionally a pullulanase may be added before and/or during liquefaction step i). A composition of the invention may suitably be used in a process of the invention. However, the enzymes may also be added separately. Examples of alpha-amylases can be found in the “Alpha-Amylase Present and/or Added During Liquefaction”-section below. Examples of thermostable proteases can be found in the “Protease Present and/or Added During Liquefaction”-section below. Examples of suitable optional carbohydrate-source generating enzymes, preferably thermostable carbohydrate-source generating enzymes, in particular a thermostable glucoamylase, can be found in the “Carbohydrate-Source Generating Enzymes Present and/or Added During Liquefaction”-section below. A suitable optional pullulanase can be found in the “Pullulanase Present and/or Added During Liquefaction”-section below.
The pH during liquefaction is above 5.0, such as between above 5.0-6.5, such as between 5.2-6.2, such as between pH 5.0-6.0, such as around 5.2, such as around 5.4, such as around 5.6, such as around 5.8. In an embodiment the pH is between 5.0 and 5.5.
According to the invention the temperature is above the initial gelatinization temperature. The term “initial gelatinization temperature” refers to the lowest temperature at which solubilization of starch, typically by heating, begins. The temperature can vary for different starches.
In an embodiment the temperature during liquefaction step i) is in the range from 70-100° C., such as between 75-95° C., such as between 75-90° C., preferably between 80-90° C., such as around 85° C.
In an embodiment, the process of the invention further comprises, prior to the step i), the steps of:
a) reducing the particle size of the starch-containing material, preferably by dry milling;
b) forming a slurry comprising the starch-containing material and water.
The starch-containing starting material, such as whole grains, may be reduced in particle size, e.g., by milling, in order to open up the structure, to increase surface area and allowing for further processing. Generally there are two types of processes: wet and dry milling. In dry milling whole kernels are milled and used. Wet milling gives a good separation of germ and meal (starch granules and protein). Wet milling is often applied at locations where the starch hydrolysate is used in production of, e.g., syrups. Both dry and wet millings are well known in the art of starch processing. According to the present invention dry milling is preferred. In an embodiment the particle size is reduced to between 0.05 to 3.0 mm, preferably 0.1-0.5 mm, or so that at least 30%, preferably at least 50%, more preferably at least 70%, even more preferably at least 90% of the starch-containing material fit through a sieve with a 0.05 to 3.0 mm screen, preferably 0.1-0.5 mm screen. In another embodiment at least 50%, preferably at least 70%, more preferably at least 80%, especially at least 90% of the starch-containing material fit through a sieve with #6 screen.
The aqueous slurry may contain from 10-55 w/w-% dry solids (DS), preferably 25-45 w/w-% dry solids (DS), more preferably 30-40 w/w-% dry solids (DS) of starch-containing material.
The slurry may be heated to above the initial gelatinization temperature, preferably to between 80-90° C., between pH 5.0-7.0, preferably between 5.0 and 6.0, for 30 minutes to 5 hours, such as around 2 hours.
The alpha-amylase, thermostable protease and optional carbohydrate-source generating enzyme, in particular thermostable glucoamylase, and/or optional pullulanase may initially be added to the aqueous slurry to initiate liquefaction (thinning). In an embodiment only a portion of the enzymes is added to the aqueous slurry, while the rest of the enzymes are added during liquefaction step i).
Liquefaction step i) is according to the invention carried out for 0.5-5 hours, such as 1-3 hours, such as typically around 2 hours.
The aqueous slurry may in an embodiment be jet-cooked to further gelatinize the slurry before being subjected to liquefaction in step i). The jet-cooking may be carried out at a temperature between 110-145° C., preferably 120-140° C., such as 125-135° C., preferably around 130° C. for about 1-15 minutes, preferably for about 3-10 minutes, especially around about 5 minutes.
One or more carbohydrate-source generating enzymes, in particular glucoamylase, may be present and/or added during saccharification step ii) and/or fermentation step iii). The carbohydrate-source generating enzyme may preferably be a glucoamylase, but may also be an enzyme selected from the group consisting of: beta-amylase, maltogenic amylase and alpha-glucosidase. The carbohydrate-source generating enzyme added during saccharification step ii) and/or fermentation step iii) is typically different from the optional carbohydrate-source generating enzyme, in particular thermostable glucoamylase, optionally added during liquefaction step i). In an embodiment the carbohydrate-source generating enzymes, in particular glucoamylase, is added together with a fungal alpha-amylase.
Examples of carbohydrate-source generating enzymes, including glucoamylases, can be found in the “Carbohydrate-Source Generating Enzyme Present and/or Added During Saccharification and/or Fermentation”-section below.
When doing sequential saccharification and fermentation, saccharification step ii) may be carried out at conditions well-known in the art. For instance, the saccharification step ii) may last up to from about 24 to about 72 hours. In an embodiment pre-saccharification is done. Pre-saccharification is typically done for 40-90 minutes at a temperature between 30-65° C., typically about 60° C. Pre-saccharification is followed by saccharification during fermentation in simultaneous saccharification and fermentation (“SSF). Saccharification is typically carried out at temperatures from 20-75° C., preferably from 40-70° C., typically around 60° C., and at a pH between 4 and 5, normally at about pH 4.5.
Simultaneous saccharification and fermentation (“SSF”) is widely used in industrial scale fermentation product production processes, especially ethanol production processes. When doing SSF the saccharification step ii) and the fermentation step iii) are carried out simultaneously. There is no holding stage for the saccharification, meaning that a fermenting organism, such as yeast, and enzyme(s), may be added together. However, it is also contemplated to add the fermenting organism and enzyme(s) separately. SSF is according to the invention typically carried out at a temperature from 25° C. to 40° C., such as from 28° C. to 35° C., such as from 30° C. to 34° C., preferably around about 32° C. In an embodiment fermentation is ongoing for 6 to 120 hours, in particular 24 to 96 hours. In an embodiment the pH is between 3.5-5, in particular between 3.8 and 4.3.
“Fermentation media” or “fermentation medium” refers to the environment in which fermentation is carried out. The fermentation medium includes the fermentation substrate, that is, the carbohydrate source that is metabolized by the fermenting organism. According to the invention the fermentation medium may comprise nutrients and growth stimulator(s) for the fermenting organism(s). Nutrient and growth stimulators are widely used in the art of fermentation and include nitrogen sources, such as ammonia; urea, vitamins and minerals, or combinations thereof.
The term “Fermenting organism” refers to any organism, including bacterial and fungal organisms, especially yeast, suitable for use in a fermentation process and capable of producing the desired fermentation product. Especially suitable fermenting organisms are able to ferment, i.e., convert, sugars, such as glucose or maltose, directly or indirectly into the desired fermentation product, such as ethanol. Examples of fermenting organisms include fungal organisms, such as yeast. Preferred yeast includes strains of Saccharomyces spp., in particular, Saccharomyces cerevisiae.
Suitable concentrations of the viable fermenting organism during fermentation, such as SSF, are well known in the art or can easily be determined by the skilled person in the art. In one embodiment the fermenting organism, such as ethanol fermenting yeast, (e.g., Saccharomyces cerevisiae) is added to the fermentation medium so that the viable fermenting organism, such as yeast, count per mL of fermentation medium is in the range from 105 to 1012, preferably from 107 to 1010, especially about 5×107.
Examples of commercially available yeast includes, e.g., RED START™ and ETHANOL RED™ yeast (available from Fermentis/Lesaffre, USA), FALI (available from Fleischmann's Yeast, USA), SUPERSTART and THERMOSACC™ fresh yeast (available from Ethanol Technology, Wis., USA), BIOFERM AFT and XR (available from NABC—North American Bioproducts Corporation, Ga., USA), GERT STRAND (available from Gert Strand AB, Sweden), and FERMIOL (available from DSM Specialties).
Any suitable starch-containing material may be used according to the present invention. The starting material is generally selected based on the desired fermentation product. Examples of starch-containing materials, suitable for use in a process of the invention, include whole grains, corn, wheat, barley, rye, milo, sago, cassava, tapioca, sorghum, rice, peas, beans, or sweet potatoes, or mixtures thereof or starches derived therefrom, or cereals. Contemplated are also waxy and non-waxy types of corn and barley. In a preferred embodiment the starch-containing material, used for ethanol production according to the invention, is corn or wheat.
The term “fermentation product” means a product produced by a process including a fermentation step using a fermenting organism. Fermentation products contemplated according to the invention include alcohols (e.g., ethanol, methanol, butanol; polyols such as glycerol, sorbitol and inositol); organic acids (e.g., citric acid, acetic acid, itaconic acid, lactic acid, succinic acid, gluconic acid); ketones (e.g., acetone); amino acids (e.g., glutamic acid); gases (e.g., H2 and CO2); antibiotics (e.g., penicillin and tetracycline); enzymes; vitamins (e.g., riboflavin, B12, beta-carotene); and hormones. In a preferred embodiment the fermentation product is ethanol, e.g., fuel ethanol; drinking ethanol, i.e., potable neutral spirits; or industrial ethanol or products used in the consumable alcohol industry (e.g., beer and wine), dairy industry (e.g., fermented dairy products), leather industry and tobacco industry. Preferred beer types comprise ales, stouts, porters, lagers, bitters, malt liquors, happoushu, high-alcohol beer, low-alcohol beer, low-calorie beer or light beer. Preferably processes of the invention are used for producing an alcohol, such as ethanol. The fermentation product, such as ethanol, obtained according to the invention, may be used as fuel, which is typically blended with gasoline. However, in the case of ethanol it may also be used as potable ethanol.
Subsequent to fermentation, or SSF, the fermentation product may be separated from the fermentation medium. The slurry may be distilled to extract the desired fermentation product (e.g., ethanol). Alternatively the desired fermentation product may be extracted from the fermentation medium by micro or membrane filtration techniques. The fermentation product may also be recovered by stripping or other method well known in the art.
Alpha-Amylase Present and/or Added During Liquefaction
According to the invention an alpha-amylase is present and/or added during liquefaction together with a thermostable protease, and optionally a carbohydrate-source generating enzyme, in particular a thermostable glucoamylase, and/or optionally a pullulanase.
The alpha-amylase added during liquefaction step i) may be any alpha-amylase. Preferred are bacterial alpha-amylases, which typically are stable at temperature used during liquefaction.
The term “bacterial alpha-amylase” means any bacterial alpha-amylase classified under EC 3.2.1.1. A bacterial alpha-amylase used according to the invention may, e.g., be derived from a strain of the genus Bacillus, which is sometimes also referred to as the genus Geobacillus. In an embodiment the Bacillus alpha-amylase is derived from a strain of Bacillus amyloliquefaciens, Bacillus licheniformis, Bacillus stearothermophilus, or Bacillus subtilis, but may also be derived from other Bacillus sp.
Specific examples of bacterial alpha-amylases include the Bacillus stearothermophilus alpha-amylase of SEQ ID NO: 3 in WO 99/19467, the Bacillus amyloliquefaciens alpha-amylase of SEQ ID NO: 5 in WO 99/19467, and the Bacillus licheniformis alpha-amylase of SEQ ID NO: 4 in WO 99/19467 (all sequences are hereby incorporated by reference). In an embodiment the alpha-amylase may be an enzyme having a degree of identity of at least 60%, e.g., at least 70%, at least 80%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99% to any of the sequences shown in SEQ ID NOS: 3, 4 or 5, respectively, in WO 99/19467.
In an embodiment the alpha-amylase may be an enzyme having a degree of identity of at least 60%, e.g., at least 70%, at least 80%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99% to any of the sequences shown in SEQ ID NO: 3 in WO 99/19467 or SEQ ID NO: 1 herein.
In a preferred embodiment the alpha-amylase is derived from Bacillus stearothermophilus. The Bacillus stearothermophilus alpha-amylase may be a mature wild-type or a mature variant thereof. The mature Bacillus stearothermophilus alpha-amylases, or variant thereof, may be naturally truncated during recombinant production. For instance, the Bacillus stearothermophilus alpha-amylase may be a truncated so it has around 491 amino acids (compared to SEQ ID NO: 3 in WO 99/19467), such as from 480-495 amino acids.
The Bacillus alpha-amylase may also be a variant and/or hybrid. Examples of such a variant can be found in any of WO 96/23873, WO 96/23874, WO 97/41213, WO 99/19467, WO 00/60059, and WO 02/10355 (all documents are hereby incorporated by reference). Specific alpha-amylase variants are disclosed in U.S. Pat. Nos. 6,093,562, 6,187,576, 6,297,038, and 7,713,723 (hereby incorporated by reference) and include Bacillus stearothermophilus alpha-amylase (often referred to as BSG alpha-amylase) variants having a deletion of one or two amino acids at positions R179, G180, 1181 and/or G182, preferably a double deletion disclosed in WO 96/23873—see, e.g., page 20, lines 1-10 (hereby incorporated by reference), preferably corresponding to deletion of positions I181 and G182 compared to the amino acid sequence of Bacillus stearothermophilus alpha-amylase set forth in SEQ ID NO: 3 disclosed in WO 99/19467 or SEQ ID NO: 1 herein or the deletion of amino acids R179 and G180 using SEQ ID NO: 3 in WO 99/19467 or SEQ ID NO: 1 herein for numbering (which reference is hereby incorporated by reference). Even more preferred are Bacillus alpha-amylases, especially Bacillus stearothermophilus alpha-amylases, which have a double deletion corresponding to a deletion of positions 181 and 182 and further comprise a N193F substitution (also denoted I181*+G182*+N193F) compared to the wild-type BSG alpha-amylase amino acid sequence set forth in SEQ ID NO: 3 disclosed in WO 99/19467 or SEQ ID NO: 1 herein. The bacterial alpha-amylase may also have a substitution in a position corresponding to S239 in the Bacillus licheniformis alpha-amylase shown in SEQ ID NO: 4 in WO 99/19467, or a S242 variant of the Bacillus stearothermophilus alpha-amylase of SEQ ID NO: 3 in WO 99/19467 or SEQ ID NO: 1 herein.
In an embodiment the variant is a S242A, E or Q variant, preferably a S242Q variant, of the Bacillus stearothermophilus alpha-amylase (using SEQ ID NO: 1 herein for numbering).
In an embodiment the variant is a position E188 variant, preferably E188P variant of the Bacillus stearothermophilus alpha-amylase (using SEQ ID NO: 1 herein for numbering). The bacterial alpha-amylase may in an embodiment be a truncated Bacillus licheniformis alpha-amylase. Especially the truncation is so that the Bacillus stearothermophilus alpha-amylase shown in SEQ ID NO: 3 in WO 99/19467 or SEQ ID NO: 1 herein, is around 491 amino acids long, such as from 480-495 amino acids long.
Bacterial Hybrid Alpha-Amylases
The bacterial alpha-amylase may also be a hybrid bacterial alpha-amylase, e.g., an alpha-amylase comprising 445 C-terminal amino acid residues of the Bacillus licheniformis alpha-amylase (shown in SEQ ID NO: 4 of WO 99/19467) and the 37 N-terminal amino acid residues of the alpha-amylase derived from Bacillus amyloliquefaciens (shown in SEQ ID NO: 5 of WO 99/19467). In a preferred embodiment this hybrid has one or more, especially all, of the following substitutions:
In an embodiment the bacterial alpha-amylase is the mature part of the chimeric alpha-amylase disclosed in Richardson et al., 2002, The Journal of Biological Chemistry 277(29): 267501-26507, referred to as BD5088 or a variant thereof. This alpha-amylase is the same as the one shown in SEQ ID NO: 2 in WO 2007134207. The mature enzyme sequence starts after the initial “Met” amino acid in position 1.
According to the invention the alpha-amylase may be a thermostable alpha-amylase, such as a thermostable bacterial alpha-amylase, preferably from Bacillus stearothermophilus. In an embodiment the alpha-amylase used according to the invention has a T½ (min) at pH 4.5, 85° C., 0.12 mM CaCl2 of at least 10.
In an embodiment the thermostable alpha-amylase has a T½(min) at pH 4.5, 85° C., 0.12 mM CaCl2, of at least 15.
In an embodiment the thermostable alpha-amylase has a T½(min) at pH 4.5, 85° C., 0.12 mM CaCl2, of at least 20.
In an embodiment the thermostable alpha-amylase has a T½(min) at pH 4.5, 85° C., 0.12 mM CaCl2, of at least 25.
In an embodiment the thermostable alpha-amylase has a T½(min) at pH 4.5, 85° C., 0.12 mM CaCl2, of at least 30.
In an embodiment the thermostable alpha-amylase has a T½(min) at pH 4.5, 85° C., 0.12 mM CaCl2, of at least 40.
In an embodiment the thermostable alpha-amylase has a T½(min) at pH 4.5, 85° C., 0.12 mM CaCl2, of at least 50.
In an embodiment the thermostable alpha-amylase has a T½(min) at pH 4.5, 85° C., 0.12 mM CaCl2, of at least 60.
In an embodiment the thermostable alpha-amylase has a T½(min) at pH 4.5, 85° C., 0.12 mM CaCl2, between 10-70.
In an embodiment the thermostable alpha-amylase has a T½(min) at pH 4.5, 85° C., 0.12 mM CaCl2, between 15-70.
In an embodiment the thermostable alpha-amylase has a T½(min) at pH 4.5, 85° C., 0.12 mM CaCl2, between 20-70.
In an embodiment the thermostable alpha-amylase has a T½(min) at pH 4.5, 85° C., 0.12 mM CaCl2, between 25-70.
In an embodiment the thermostable alpha-amylase has a T½(min) at pH 4.5, 85° C., 0.12 mM CaCl2, between 30-70.
In an embodiment the thermostable alpha-amylase has a T½(min) at pH 4.5, 85° C., 0.12 mM CaCl2, between 40-70.
In an embodiment the thermostable alpha-amylase has a T½(min) at pH 4.5, 85° C., 0.12 mM CaCl2, between 50-70.
In an embodiment the thermostable alpha-amylase has a T½(min) at pH 4.5, 85° C., 0.12 mM CaCl2, between 60-70.
In an embodiment of the invention the alpha-amylase is an bacterial alpha-amylase, preferably derived from the genus Bacillus, especially a strain of Bacillus stearothermophilus, in particular the Bacillus stearothermophilus as disclosed in WO 99/19467 as SEQ ID NO: 3 (SEQ ID NO: 1 herein) with one or two amino acids deleted at positions R179, G180, 1181 and/or G182, in particular with R179 and G180 deleted, or with I181 and G182 deleted, with mutations in below list of mutations.
In preferred embodiments the Bacillus stearothermophilus alpha-amylases have double deletion I181 +G182, and optional substitution N193F, further comprising mutations selected from below list:
In a preferred embodiment the alpha-amylase is selected from the group of Bacillus stearomthermphilus alpha-amylase variants:
It should be understood that when referring to Bacillus stearothermophilus alpha-amylase and variants thereof they are normally produced in truncated form. In particular, the truncation may be so that the Bacillus stearothermophilus alpha-amylase shown in SEQ ID NO: 3 in WO 99/19467 or SEQ ID NO: 1 herein, or variants thereof, are truncated in the C-terminal and are typically around 491 amino acids long, such as from 480-495 amino acids long.
In a preferred embodiment the alpha-amylase variant may be an enzyme having a degree of identity of at least 60%, e.g., at least 70%, at least 80%, at least 90%, at least 95%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98% or at least 99%, but less than 100% to the sequence shown in SEQ ID NO: 3 in WO 99/19467 or SEQ ID NO: 1 herein.
Protease Present and/or Added During Liquefaction
According to the invention a thermostable protease is present and/or added during liquefaction together with an alpha-amylase, such as a thermostable alpha-amylase, and optionally a carbohydrate-source generating enzyme, in particular a thermostable glucoamylase, and/or optionally a pullulanase.
Proteases are classified on the basis of their catalytic mechanism into the following groups: Serine proteases (S), Cysteine proteases (C), Aspartic proteases (A), Metallo proteases (M), and Unknown, or as yet unclassified, proteases (U), see Handbook of Proteolytic Enzymes, A. J.Barrett, N. D.Rawlings, J. F.Woessner (eds), Academic Press (1998), in particular the general introduction part.
In a preferred embodiment the thermostable protease used according to the invention is a “metallo protease” defined as a protease belonging to EC 3.4.24 (metalloendopeptidases); preferably EC 3.4.24.39 (acid metallo proteinases).
To determine whether a given protease is a metallo protease or not, reference is made to the above “Handbook of Proteolytic Enzymes” and the principles indicated therein. Such determination can be carried out for all types of proteases, be it naturally occurring or wild-type proteases; or genetically engineered or synthetic proteases.
Protease activity can be measured using any suitable assay, in which a substrate is employed, that includes peptide bonds relevant for the specificity of the protease in question. Assay-pH and assay-temperature are likewise to be adapted to the protease in question. Examples of assay-pH-values are pH 6, 7, 8, 9, 10, or 11. Examples of assay-temperatures are 30, 35, 37, 40, 45, 50, 55, 60, 65, 70 or 80° C.
Examples of protease substrates are casein, such as Azurine-Crosslinked Casein (AZCL-casein). Two protease assays are described below in the “Materials & Methods”-section, of which the so-called “AZCL-Casein Assay” is the preferred assay.
In an embodiment the thermostable protease has at least 20%, such as at least 30%, such as at least 40%, such as at least 50%, such as at least 60%, such as at least 70%, such as at least 80%, such as at least 90%, such as at least 95%, such as at least 100% of the protease activity of the Protease 196 variant or Protease Pfu determined by the AZCL-casein assay described in the “Materials & Methods” section.
There are no limitations on the origin of the protease used in a process of the invention as long as it fulfills the thermostability properties defined below.
In one embodiment the protease is of fungal origin.
The protease may be a variant of, e.g., a wild-type protease as long as the protease has the thermostability properties defined herein. In a preferred embodiment the thermostable protease is a variant of a metallo protease as defined above. In an embodiment the thermostable protease used in a process of the invention is of fungal origin, such as a fungal metallo protease, such as a fungal metallo protease derived from a strain of the genus Thermoascus, preferably a strain of Thermoascus aurantiacus, especially Thermoascus aurantiacus CGMCC No. 0670 (classified as EC 3.4.24.39).
In an embodiment the thermostable protease is a variant of the mature part of the metallo protease shown in SEQ ID NO: 2 disclosed in WO 2003/048353 or the mature part of SEQ ID NO: 1 in WO 2010/008841 and shown as SEQ ID NO: 3 herein further with mutations selected from below list:
In an preferred embodiment the thermostable protease is a variant of the metallo protease disclosed as the mature part of SEQ ID NO: 2 disclosed in WO 2003/048353 or the mature part of SEQ ID NO: 1 in WO 2010/008841 or SEQ ID NO: 3 herein with the following mutations:
In an embodiment the protease variant has at least 75% identity preferably at least 80%, more preferably at least 85%, more preferably at least 90%, more preferably at least 91%, more preferably at least 92%, even more preferably at least 93%, most preferably at least 94%, and even most preferably at least 95%, such as even at least 96%, at least 97%, at least 98%, at least 99%, but less than 100% identity to the mature part of the polypeptide of SEQ ID NO: 2 disclosed in WO 2003/048353 or the mature part of SEQ ID NO: 1 in WO 2010/008841 or SEQ ID NO: 3 herein.
The thermostable protease may also be derived from any bacterium as long as the protease has the thermostability properties defined according to the invention.
In an embodiment the thermostable protease is derived from a strain of the bacterium Pyrococcus, such as a strain of Pyrococcus furiosus (pfu protease).
In an embodiment the protease is one shown as SEQ ID NO: 1 in U.S. Pat. No. 6,358,726-B1 (Takara Shuzo Company) and SEQ ID NO: 13 herein.
In another embodiment the thermostable protease is one disclosed in SEQ ID NO: 13 herein or a protease having at least 80% identity, such as at least 85%, such as at least 90%, such as at least 95%, such as at least 96%, such as at least 97%, such as at least 98%, such as at least 99% identity to SEQ ID NO: 1 in US Pat. No. 6,358,726-B1 or SEQ ID NO: 13 herein. The Pyrococcus furiosus protease can be purchased from Takara Bio, Japan.
The Pyrococcus furiosus protease is a thermostable protease according to the invention. The commercial product Pyrococcus furiosus protease (Pfu S) was found to have a thermostability of 110% (80° C./70° C.) and 103% (90° C./70° C.) at pH 4.5 determined as described in Example 2 herein.
In one embodiment a thermostable protease used in a process of the invention has a thermostability value of more than 20% determined as Relative Activity at 80° C./70° C. determined as described in Example 2.
In an embodiment the protease has a thermostability of more than 30%, more than 40%, more than 50%, more than 60%, more than 70%, more than 80%, more than 90%, more than 100%, such as more than 105%, such as more than 110%, such as more than 115%, such as more than 120% determined as Relative Activity at 80° C./70° C.
In an embodiment protease has a thermostability of between 20 and 50%, such as between 20 and 40%, such as 20 and 30% determined as Relative Activity at 80° C./70° C.
In an embodiment the protease has a thermostability between 50 and 115%, such as between 50 and 70%, such as between 50 and 60%, such as between 100 and 120%, such as between 105 and 115% determined as Relative Activity at 80° C./70° C.
In an embodiment the protease has a thermostability value of more than 10% determined as Relative Activity at 85° C./70° C. determined as described in Example 2. In an embodiment the protease has a thermostability of more than 10%, such as more than 12%, more than 14%, more than 16%, more than 18%, more than 20%, more than 30%, more than 40%, more that 50%, more than 60%, more than 70%, more than 80%, more than 90%, more than 100%, more than 110% determined as Relative Activity at 85° C./70° C.
In an embodiment the protease has a thermostability of between 10 and 50%, such as between 10 and 30%, such as between 10 and 25% determined as Relative Activity at 85° C./70° C.
In an embodiment the protease has more than 20%, more than 30%, more than 40%, more than 50%, more than 60%, more than 70%, more than 80%, more than 90% determined as Remaining Activity at 80° C.; and/or
In an embodiment the protease has more than 20%, more than 30%, more than 40%, more than 50%, more than 60%, more than 70%, more than 80%, more than 90% determined as Remaining Activity at 84° C.
Determination of “Relative Activity” and “Remaining Activity” is done as described in Example 2.
In an embodiment the protease may have a themostability for above 90, such as above 100 at 85° C. as determined using the Zein-BCA assay as disclosed in Example 3.
In an embodiment the protease has a themostability above 60%, such as above 90%, such as above 100%, such as above 110% at 85° C. as determined using the Zein-BCA assay. In an embodiment protease has a themostability between 60-120, such as between 70-120%, such as between 80-120%, such as between 90-120%, such as between 100-120%, such as 110-120% at 85° C. as determined using the Zein-BCA assay.
In an embodiment the thermostable protease has at least 20%, such as at least 30%, such as at least 40%, such as at least 50%, such as at least 60%, such as at least 70%, such as at least 80%, such as at least 90%, such as at least 95%, such as at least 100% of the activity of the JTP196 protease variant or Protease Pfu determined by the AZCL-casein assay.
Carbohydrate-Source Generating Enzyme Present and/or Added During Liquefaction
According to the invention a carbohydrate-source generating enzyme, in particular a glucoamylase, preferably a thermostable glucoamylase, may be present and/or added during liquefaction together with an alpha-amylase and a thermostable protease. As mentioned above, a pullulanase may also be present and/or added during liquefaction step i).
The term “carbohydrate-source generating enzyme” includes any enzymes generating fermentable sugars. A carbohydrate-source generating enzyme is capable of producing a carbohydrate that can be used as an energy-source by the fermenting organism(s) in question, for instance, when used in a process of the invention for producing a fermentation product, such as ethanol. The generated carbohydrates may be converted directly or indirectly to the desired fermentation product, preferably ethanol. According to the invention a mixture of carbohydrate-source source generating enzymes may be used. Specific examples include glucoamylase (being glucose generators), beta-amylase and maltogenic amylase (being maltose generators).
In a preferred embodiment the carbohydrate-source generating enzyme is thermostable. The carbohydrate-source generating enzyme, in particular thermostable glucoamylase, may be added together with or separately from the alpha-amylase and the thermostable protease.
In an embodiment the carbohydrate-source generating enzyme, preferably a thermostable glucoamylase, has a Relative Activity heat stability at 85° C. of at least 20%, at least 30%, preferably at least 35% determined as described in Example 4 (heat stability).
In an embodiment the carbohydrate-source generating enzyme is a glucoamylase having a relative activity pH optimum at pH 5.0 of at least 90%, preferably at least 95%, preferably at least 97%, such as 100% determined as described in Example 4 (pH optimum).
In an embodiment the carbohydrate-source generating enzyme is a glucoamylase having a pH stability at pH 5.0 of at least at least 80%, at least 85%, at least 90% determined as described in Example 4 (pH stability).
In a specific and preferred embodiment the carbohydrate-source generating enzyme is a thermostable glucoamylase, preferably of fungal origin, preferably a filamentous fungi, such as from a strain of the genus Penicillium, especially a strain of Penicillium oxalicum, in particular the Penicillium oxalicum glucoamylasedisclosed as SEQ ID NO: 2 in PCT/CN10/071753 published as WO 2011/127802 (which is hereby incorporated by reference) and shown in SEQ ID NO: 9 or 14 herein.
In an embodiment the thermostable glucoamylase has at least 80%, more preferably at least 85%, more preferably at least 90%, more preferably at least 91%, more preferably at least 92%, even more preferably at least 93%, most preferably at least 94%, and even most preferably at least 95%, such as even at least 96%, at least 97%, at least 98%, at least 99% or 100% identity to the mature polypeptide shown in SEQ ID NO: 2 in WO 2011/127802 or SEQ ID NOs: 9 or 14 herein.
In an embodiment the carbohydrate-source generating enzyme, in particular thermostable glucoamylase, is the Penicillium oxalicum glucoamylase.
In a preferred embodiment the carbohydrate-source generating enzyme is a variant of the Penicillium oxalicum glucoamylase disclosed as SEQ ID NO: 2 in WO 2011/127802 and shown in SEQ ID NO: 9 and 14 herein, having a K79V substitution (referred to as PE001) (using the mature sequence shown in SEQ ID NO: 14 for numbering). The K79V glucoamylase variant has reduced sensitivity to protease degradation relative to the parent as disclosed in co-pending U.S. application No. 61/531,189 or PCT/U.S. Ser. No. 12/053,779 (which are hereby incorporated by reference).
In an embodiment the thermostable glucoamylase is a variant of the Penicillium oxalicum glucoamylase disclosed as SEQ ID NO: 2 in WO 2011/127802 and shown in SEQ ID NO: 9 and 14 herein. In a preferred embodiment the Penicillium oxalicum glucoamylase is the one disclosed as SEQ ID NO: 2 in WO 2011/127802 and shown in SEQ ID NO: 9 and 14 herein having Val (V) in position 79 (using SEQ ID NO: 14 for numbering).
Contemplated Penicillium oxalicum glucoamylase variants are disclosed in co-pending PCT application #PCT/EP12/070127 (which is hereby incorporated by reference).
In an embodiment these variants have reduced sensitivity to protease degradation.
In an embodiment these variant have improved thermostability compared to the parent.
More specifically, in an embodiment the glucoamylase has a K79V substitution (using SEQ ID NO: 14 for numbering), corresponding to the PE001 variant, and further comprises at least one of the following substitutions or combination of substitutions:
In a preferred embodiment the Penicillium oxalicum glucoamylase variant has a K79V substitution (using SEQ ID NO: 14 for numbering), corresponding to the PE001 variant, and further comprises one of the following mutations:
The carbohydrate-source generating enzyme, in particular, may be added in amounts from 0.1-100 micrograms EP/g, such as 0.5-50 micrograms EP/g, such as 1-25 micrograms EP/g, such as 2-12 micrograms EP/g DS.
Pullulanase Present and/or Added During Liquefaction
Optionally a pullulanase may be present and/or added during liquefaction step i) together with an alpha-amylase and a thermostable protease. As mentioned above a carbohydrate-source generating enzyme, preferably a thermostable glucoamylase, may also be present and/or added during liquefaction step i).
The pullulanase may be present and/or added during liquefaction step i) and/or saccharification step ii) or simultaneous saccharification and fermentation.
Pullulanases (E.C. 3.2.1.41, pullulan 6-glucano-hydrolase), are debranching enzymes characterized by their ability to hydrolyze the alpha-1,6-glycosidic bonds in, for example, amylopectin and pullulan.
Contemplated pullulanases according to the present invention include the pullulanases from Bacillus amyloderamificans disclosed in U.S. Pat. No. 4,560,651 (hereby incorporated by reference), the pullulanase disclosed as SEQ ID NO: 2 in WO 01/151620 (hereby incorporated by reference), the Bacillus deramificans disclosed as SEQ ID NO: 4 in WO 01/151620 (hereby incorporated by reference), and the pullulanase from Bacillus acidopullulyticus disclosed as SEQ ID NO: 6 in WO 01/151620 (hereby incorporated by reference) and also described in FEMS Mic. Let. (1994) 115, 97-106.
Additional pullulanases contemplated according to the present invention included the pullulanases from Pyrococcus woesei, specifically from Pyrococcus woesei DSM No. 3773 disclosed in WO 92/02614.
In an embodiment the pullulanase is a family GH57 pullulanase. In an embodiment the pullulanase includes an X47 domain as disclosed in U.S. 61/289,040 published as WO 2011/087836 (which are hereby incorporated by reference). More specifically the pullulanase may be derived from a strain of the genus Thermococcus, including Thermococcus litoralis and Thermococcus hydrothermalis, such as the Thermococcus hydrothermalis pullulanase shown in SEQ ID NO: 11 truncated at site X4 right after the X47 domain (i.e., amino acids 1-782 in SEQ ID NOS: 11 and 12 herein). The pullulanase may also be a hybrid of the Thermococcus litoralis and Thermococcus hydrothermalis pullulanases or a T. hydrothermalis/T. litoralis hybrid enzyme with truncation site X4 disclosed in U.S. 61/289,040 published as WO 2011/087836 (which is hereby incorporated by reference) and disclosed in SEQ ID NO: 12 herein.
In another embodiment the pullulanase is one comprising an X46 domain disclosed in WO 2011/076123 (Novozymes).
The pullulanase may according to the invention be added in an effective amount which include the preferred amount of about 0.0001-10 mg enzyme protein per gram DS, preferably 0.0001-0.10 mg enzyme protein per gram DS, more preferably 0.0001-0.010 mg enzyme protein per gram DS. Pullulanase activity may be determined as NPUN. An Assay for determination of NPUN is described in the “Materials & Methods”-section below.
Suitable commercially available pullulanase products include PROMOZYME D, PROMOZYME™ D2 (Novozymes A/S, Denmark), OPTIMAX L-300 (Genencor Int., USA), and AMANO 8 (Amano, Japan).
Carbohydrate-Source Generating Enzyme Present and/or Added during Saccharification and/or Fermentation
According to the invention a carbohydrate-source generating enzyme, preferably a glucoamylase, is present and/or added during saccharification and/or fermentation.
In a preferred embodiment the carbohydrate-source generating enzyme is a glucoamylase, of fungal origin, preferably from a stain of Aspergillus, preferably A. niger, A. awamori, or A. oryzae; or a strain of Trichoderma, preferably T. reesei; or a strain of Talaromyces, preferably T. emersonii, Glucoamylase
According to the invention the glucoamylase present and/or added during saccharification and/or fermentation may be derived from any suitable source, e.g., derived from a microorganism or a plant. Preferred glucoamylases are of fungal or bacterial origin, selected from the group consisting of Aspergillus glucoamylases, in particular Aspergillus niger G1 or G2 glucoamylase (Boel et al. (1984), EMBO J. 3 (5), p. 1097-1102), or variants thereof, such as those disclosed in WO 92/00381, WO 00/04136 and WO 01/04273 (from Novozymes, Denmark); the A. awamori glucoamylase disclosed in WO 84/02921, Aspergillus oryzae glucoamylase (Agric. Biol. Chem. (1991), 55 (4), p. 941-949), or variants or fragments thereof. Other Aspergillus glucoamylase variants include variants with enhanced thermal stability: G137A and G139A (Chen et al. (1996), Prot. Eng. 9, 499-505); D257E and D293E/Q (Chen et al. (1995), Prot. Eng. 8, 575-582); N182 (Chen et al. (1994), Biochem. J. 301, 275-281); disulphide bonds, A246C (Fierobe et al. (1996), Biochemistry, 35, 8698-8704; and introduction of Pro residues in position A435 and S436 (Li et al. (1997), Protein Eng. 10, 1199-1204.
Other glucoamylases include Athelia rolfsii (previously denoted Corticium rolfsii) glucoamylase (see U.S. Pat. No. 4,727,026 and (Nagasaka et al. (1998) “Purification and properties of the raw-starch-degrading glucoamylases from Corticium rolfsii, Appl Microbiol Biotechnol 50:323-330), Talaromyces glucoamylases, in particular derived from Talaromyces emersonii (WO 99/28448), Talaromyces leycettanus (U.S. Pat. No. Re. 32,153), Talaromyces duponti, Talaromyces thermophilus (U.S. Pat. No. 4,587,215). In a preferred embodiment the glucoamylase used during saccharification and/or fermentation is the Talaromyces emersonii glucoamylase disclosed in WO 99/28448.
Bacterial glucoamylases contemplated include glucoamylases from the genus Clostridium, in particular C. thermoamylolyticum (EP 135,138), and C. thermohydrosulfuricum (WO 86/01831).
Contemplated fungal glucoamylases include Trametes cingulata, Pachykytospora papyracea; and Leucopaxillus giganteus all disclosed in WO 2006/069289; and Peniophora rufomarginata disclosed in WO2007/124285; or a mixture thereof. Also hybrid glucoamylase are contemplated according to the invention. Examples include the hybrid glucoamylases disclosed in WO 2005/045018. Specific examples include the hybrid glucoamylase disclosed in Table 1 and 4 of Example 1 (which hybrids are hereby incorporated by reference).
In an embodiment the glucoamylase is derived from a strain of the genus Pycnoporus, in particular a strain of Pycnoporus as described in U.S. 61/264,977 published as WO 2011/066576 (SEQ ID NOs 2, 4 or 6), or from a strain of the genus Gloephyllum, in particular a strain of Gloephyllum as described in U.S. 61/406,741 published as WO 2011/068803 (SEQ ID NO: 2, 4, 6, 8, 10, 12, 14 or 16) or a strain of the genus Nigrofomes, in particular a strain of Nigrofomes sp. disclosed in U.S. 61/411,044 or PCT/US10/058375 (SEQ ID NO: 2) (all references hereby incorporated by reference). Contemplated are also glucoamylases which exhibit a high identity to any of the above-mentioned glucoamylases, i.e., at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99% or even 100% identity to any one of the mature parts of the enzyme sequences mentioned above.
Glucoamylases may in an embodiment be added to the saccharification and/or fermentation in an amount of 0.0001-20 AGU/g DS, preferably 0.001-10 AGU/g DS, especially between 0.01-5 AGU/g DS, such as 0.1-2 AGU/g DS.
Commercially available compositions comprising glucoamylase include AMG 200L; AMG 300 L; SANT™ SUPER, SANT™ EXTRA L, SPIRIZYME™ PLUS, SPIRIZYME™ FUEL, SPIRIZYME™ B4U, SPIRIZYME™ ULTRA, SPIRIZYME™ EXCEL and AMG™ E (from Novozymes A/S); OPTIDEX™ 300, GC480, GC417 (from Genencor Int.); AMIGASE™ and AMIGASE™ PLUS (from DSM); G-ZYME™ G900, G-ZYME™ and G990 ZR (from Genencor Int.).
The carbohydrate-source generating enzyme present and/or added during saccharification and/or fermentation may also be a maltogenic alpha-amylase. A “maltogenic alpha-amylase” (glucan 1,4-alpha-maltohydrolase, E.C. 3.2.1.133) is able to hydrolyze amylose and amylopectin to maltose in the alpha-configuration. A maltogenic amylase from Bacillus stearothermophilus strain NCIB 11837 is commercially available from Novozymes A/S. Maltogenic alpha-amylases are described in U.S. Pat. Nos. 4,598,048, 4,604,355 and 6,162,628, which are hereby incorporated by reference. The maltogenic amylase may in a preferred embodiment be added in an amount of 0.05-5 mg total protein/gram DS or 0.05-5 MANU/g DS.
In a preferred embodiment the invention relates to a process for producing fermentation products from starch-containing material comprising the steps of:
i) liquefying the starch-containing material at a pH in the range between from above 5.0-7.0 at a temperature above the initial gelatinization temperature using:
ii) saccharifying using a glucoamylase enzyme;
iii) fermenting using a fermenting organism.
In another preferred embodiment the invention relates to a process for producing fermentation products from starch-containing material comprising the steps of:
i) liquefying the starch-containing material at a pH in the range between from above 5.0-7.0 at a temperature above the initial gelatinization temperature using:
a protease, preferably derived from Pyrococcus furiosus and/or Thermoascus aurantiacus, having a thermostability value of more than 20%, more than 30%, more than 40%, more than 50%, more than 60%, more than 70%, more than 80%, more than 90%, more than 100%, more than 105%, more than 110%, more than 115%, more than 120%; such as between 20 and 50%, between 20 and 40%, 20 and 30%, between 50 and 115%, between 50 and 70%, between 50 and 60%, between 100 and 120%, between 105 and 115% determined as Relative Activity at 80° C./70° C. determined as Relative Activity at 80° C./70° C.;
optionally a Penicillium oxalicum glucoamylase
ii) saccharifying using a glucoamylase enzyme;
iii) fermenting using a fermenting organism.
In another preferred embodiment the invention relates to a process for producing fermentation products from starch-containing material comprising the steps of:
i) liquefying the starch-containing material at a pH in the range between from above 5.0-6.0 at a temperature between 80-90° C. using:
an alpha-amylase, preferably derived from Bacillus stearothermophilus, having a T½ (min) at pH 4.5, 85° C., 0.12 mM CaCl2 of at least 10, at least 15, at least 20, at least 25, at least 30, at least 40, at least 50, at least 60, at least 70, such as between 10-70; such as between 15-70, such as between 20-70; such as between 25-70; such as between 30-70; such as between 40-70; such as between 50-70; such as between 60-70;
a protease, preferably derived from Pyrococcus furiosus and/or Thermoascus aurantiacus, having a thermostability value of more than 20%, more than 30%, more than 40%, more than 50%, more than 60%, more than 70%, more than 80%, more than 90%, more than 100%, more than 105%, more than 110%, more than 115%, more than 120%; such as between 20 and 50%, between 20 and 40%, 20 and 30%, between 50 and 115%, between 50 and 70%, between 50 and 60%, between 100 and 120%, between 105 and 115% determined as Relative Activity at 80° C./70° C. determined as Relative Activity at 80° C./70° C.;
optionally a Penicillium oxalicum glucoamylase
ii) saccharifying using a glucoamylase enzyme;
iii) fermenting using a fermenting organism.
In another preferred embodiment the invention relates to a process for producing fermentation products from starch-containing material comprising the steps of:
i) liquefying the starch-containing material at a pH in the range between from above 5.0-7.0 at a temperature above the initial gelatinization temperature using:
an alpha-amylase derived from Bacillus stearothermophilus having a double deletion I181+G182 and optionally substitution N193F; and optionally further one of the following set of substitutions:
E129V+K177L+R179E;
V59A+Q89R+E129V+K177L+R179E+H208Y+K220P+N224L+Q254S;
E129V+K177L+R179E+K220P+N224L+S242Q+Q254S (using SEQ ID NO: 1 herein for numbering).
a protease, preferably derived from Pyrococcus furiosus and/or Thermoascus aurantiacus, having a thermostability value of more than 20% determined as Relative Activity at 80° C./70° C.; and
optionally Penicillium oxalicum glucoamylase in SEQ ID NO: 14 having substitutions selected from the group of:
K79V;
K79V+P11F+T65A+Q327F; or
K79V+P2N+P4S+P11F+T65A+Q327F; or
K79V+P11F+D26C+K33C+T65A+Q327F; or
K79V+P2N+P4S+P11F+T65A+Q327W+E501V+Y504T; or
K79V+P2N+P4S+P11F+T65A+Q327F+E501V+Y504T; or
K79V+P11F+T65A+Q327W+E501V+Y504T (using SEQ ID NO: 14 for numbering);
ii) saccharifying using a glucoamylase enzyme;
iii) fermenting using a fermenting organism.
In another preferred embodiment the process for producing fermentation products from starch-containing material comprises the steps of:
i) liquefying the starch-containing material at a pH in the range between from above 5.0-6.0 at a temperature between 80-90° C. using:
an alpha-amylase derived from Bacillus stearothermophilus having a double deletion I181 +G182 and optional substitution N193F; and optionally further one of the following set of substitutions:
E129V+K177L+R179E;
V59A+Q89R+E129V+K177L+R179E+H208Y+K220P+N224L+Q254S;
E129V+K177L+R179E+K220P+N224L+S242Q+Q254S (using SEQ ID NO: 1 herein for numbering).
a protease, preferably derived from Pyrococcus furiosus and/or Thermoascus aurantiacus, having a thermostability value of more than 20% determined as Relative Activity at 80° C./70° C.; and
optionally a Penicillium oxalicum glucoamylase in SEQ ID NO: 14 having substitutions selected from the group of:
K79V;
K79V+P11F+T65A+Q327F; or
K79V+P2N+P4S+P11F+T65A+Q327F; or
K79V+P11F+D26C+K33C+T65A+Q327F; or
K79V+P2N+P4S+P11F+T65A+Q327W+E501V+Y504T; or
K79V+P2N+P4S+P11F+T65A+Q327F+E501V+Y504T; or
K79V+P11F+T65A+Q327W+E501V+Y504T (using SEQ ID NO: 14 for numbering);
ii) saccharifying using a glucoamylase enzyme;
iii) fermenting using a fermenting organism.
The alpha-amylase mentioned above derived from Bacillus stearothermophilus (SEQ ID NO: 1 herein), or a variant thereof, is the mature alpha-amylase or corresponding mature alpha-amylases having at least 80% identity, at least 90% identity, at least 95% identity at least 96% identity at least 97% identity at least 99% identity to the SEQ ID NO: 1.
The protease mentioned above, derived from Pyrococcus furiosus (SEQ ID NO: 13) and/or Thermoascus aurantiacus (SEQ ID NO: 3), or a variant thereof, is the mature protease or corresponding mature proteases having at least 80% identity, at least 90% identity, at least 95% identity at least 96% identity at least 97% identity at least 99% identity to the SEQ ID NO: 13 or SEQ ID NO: 3 respectively.
The glucoamylase mentioned above derived from Penicillium oxalicum (SEQ ID NO: 14 herein), or a variant thereof, is the mature glucoamylase or corresponding mature glucoamylase having at least 80% identity, at least 90% identity, at least 95% identity at least 96% identity at least 97% identity at least 99% identity to the SEQ ID NO: 14 herein.
A composition of the invention comprises an alpha-amylase, such as a thermostable alpha-amylase, and a thermostable protease. The composition may also further comprise a thermostable carbohydrate-source generating enzyme, in particular a glucoamylase, and/or optionally a pullulanase too.
Therefore, in this aspect the invention relates to composition comprising:
i) an alpha-amylase;
ii) a protease, preferably derived from Pyrococcus furiosus and/or Thermoascus aurantiacus, has a thermostability value of more than 20% determined as Relative Activity at 80° C./70° C.; and
iii) optionally a carbohydrate-source generating enzyme.
Alpha-amylase: The alpha-amylase may be any alpha-amylase, such as bacterial alpha-amylases, such as alpha-amylases derived from the genus Bacillus, such as Bacillus stearomthermphilus.
The alpha-amylase may be a thermostable alpha-amylase. The thermostable alpha-amylase may have a T½(min) at pH 4.5, 85° C., 0.12 mM CaCl2) of at least 10, such as at least 15, such as at least 20, such as at least 25, such as at least 30, such as at least 40, such as at least 50, such as at least 60, such as between 10-70, such as between 15-70, such as between 20-70, such as between 25-70, such as between 30-70, such as between 40-70, such as between 50-70, such as between 60-70.
In an embodiment the alpha-amylase is selected from the group of Bacillus stearomthermphilus alpha-amylase variants, in particular truncated to be 491 amino acids long, such as from 480 to 495 amino acids long, with mutations selected from the group of:
It should be understood that these alpha-amylases are only specific examples. Any alpha-amylase disclosed above in the “Alpha-Amylase Present and/or Added During Liquefaction”-section above may be used as the alpha-amylase component in a composition of the invention.
There is no limitation on the origin of the protease component as long as it fulfills the thermostability properties defined herein.
In a preferred embodiment the protease is a variant of the Thermoascus aurantiacus protease mentioned above having a thermostability value of more than 20% determined as Relative Activity at 80° C./70° C. determined as described in Example 2.
In a specific preferred embodiment the protease is a variant of the metallo protease derived from Thermoascus aurantiacus disclosed as the mature part of SEQ ID NO. 2 disclosed in WO 2003/048353 or the mature part of SEQ ID NO: 1 in WO 2010/008841 or SEQ ID NO: 3 herein with mutations selected from the group of:
D79L+S87P+A112P+D142L;
D79L+S87P+D142L; and
A27K+D79L+Y82F+S87G+D104P+A112P+A126V+D142L.
In another preferred embodiment the protease is derived from a strain of Pyrococcus furiosus, such as the one shown in SEQ ID NO: 1 in U.S. Pat. No. 6,358,726 or SEQ ID NO: 13 herein.
It should be understood that these proteases are only examples. Any protease disclosed above in the “Protease Present and/or Added During Liquefaction” section above may be used as the protease component in a composition of the invention.
Carbohydrate-source generating enzymes: A composition of the invention may further comprise a carbohydrate-source generating enzyme, in particular a glucoamylase, which has a heat stability at 85° C., pH 5.3, of at least 30%, preferably at least 35%.
Said carbohydrate-source generating enzyme may be a thermostable glucoamylase having a Relative Activity heat stability at 85° C. of at least 20%, at least 30%, preferably at least 35% determined as described in Example 4 (Heat stability).
In an embodiment the carbohydrate-source generating enzyme is a glucoamylase having a relative activity pH optimum at pH 5.0 of at least 90%, preferably at least 95%, preferably at least 97%, such as 100% determined as described in Example 4 (pH optimum).
In an embodiment the carbohydrate-source generating enzyme is a glucoamylase having a pH stability at pH 5.0 of at least at least 80%, at least 85%, at least 90% determined as described in Example 4 (pH stability).
In a preferred embodiment the carbohydrate-source generating enzyme is a thermostable glucoamylase, preferably of fungal origin, preferably a filamentous fungi, such as from a strain of the genus Penicillium, especially a strain of Penicillium oxalicum disclosed as SEQ ID NO: 2 in PCT/CN10/071753 published as WO 2011/127802 (which is hereby incorporated by reference), or a variant thereof, and shown in SEQ ID NO: 9 or 14 herein.
In an embodiment the glucoamylase, or a variant thereof, may have at least 80%, more preferably at least 85%, more preferably at least 90%, more preferably at least 91%, more preferably at least 92%, even more preferably at least 93%, most preferably at least 94%, and even most preferably at least 95%, such as even at least 96%, at least 97%, at least 98%, at least 99% or 100% identity to the mature polypeptide shown in SEQ ID NO: 2 in WO 2011/127802 or SEQ ID NO: 9 or 14 herein.
In a specific and preferred embodiment the carbohydrate-source generating enzyme is a variant of the Penicillium oxalicum glucoamylase disclosed as SEQ ID NO: 2 in WO 2011/127802 and shown in SEQ ID NO: 9 and 14 herein, having a K79V substitution (using the mature sequence shown in SEQ ID NO: 14 for numbering). The K79V glucoamylase variant has reduced sensitivity to protease degradation relative to the parent as disclosed in co-pending U.S. application No. 61/531,189 (which is hereby incorporated by reference).
Examples of suitable thermostable Penicillium oxalicum glucoamylase variants are listed above and in Examples 17 and 18 below.
In an embodiment the carbohydrate-source generating enzyme has pullulanase side activity.
It should be understood that these carbohydrate-source generating enzymes, in particular glucoamylases, are only examples. Any carbohydrate-source generating enzyme disclosed above in the “Carbohydrate-source generating enzyme Present and/or Added During Liquefaction” section above may be used as component in a composition of the invention.
Specifically the pullulanase may be derived from a strain from the genus Thermococcus, including Thermococcus litoralis and Thermococcus hydrothermalis or a hybrid thereof.
The pullulanase may be Thermococcus hydrothermalis pullulanase truncated at site X4 or a Thermococcus hydrothermalis/T. litoralis hybrid enzyme with truncation site X4 as disclosed in U.S. 61/289,040 published as WO 2011/087836.
The another embodiment the pullulanase is one comprising an X46 domain disclosed in WO 2011/076123(Novozymes).
It should be understood that these pullulanases are only specific examples. Any pullulanase disclosed above in the “Pullulanase Present and/or Added During Liquefaction” section above may be used as the optional pullulanase component in a composition of the invention.
In a preferred embodiment the composition of the invention comprises
an alpha-amylase derived from Bacillus stearothermophilus;
a protease preferably derived from Pyrococcus furiosus and/or Thermoascus aurantiacus having a thermostability value of more than 20% determined as Relative Activity at 80° C./70° C.; and
optionally a glucoamylase derived from Penicillium oxalicum.
In a preferred embodiment the composition of the invention comprises
an alpha-amylase, preferably derived from Bacillus stearothermophilus, having a T½ (min) at pH 4.5, 85° C., 0.12 mM CaCl2 of at least 10;
a protease, preferably derived from Pyrococcus furiosus or Thermoascus aurantiacus, having a thermostability value of more than 20% determined as Relative Activity at 80° C./70° C.;
optionally a glucoamylase derived from Penicillium oxalicum.
In a preferred embodiment the composition comprises
an alpha-amylase derived from Bacillus stearothermophilus having a double deletion I181 +G182 and optionally substitution N193F; and optionally further one of the following set of substitutions:
E129V+K177L+R179E;
V59A+Q89R+E129V+K177L+R179E+H208Y+K220P+N224L+Q254S;
E129V+K177L+R179E+K220P+N224L+S242Q+Q254S (using SEQ ID NO: 1 herein for numbering).
a protease, preferably derived from Pyrococcus furiosus and/or Thermoascus aurantiacus, having a thermostability value of more than 20% determined as Relative Activity at 80° C./70° C.; and
optionally a Penicillium oxalicum glucoamylase in SEQ ID NO: 14 having substitutions selected from the group of:
K79V;
K79V+P11F+T65A+Q327F; or
K79V+P2N+P4S+P11F+T65A+Q327F; or
K79V+P11F+D26C+K33C+T65A+Q327F; or
K79V+P2N+P4S+P11F+T65A+Q327W+E501V+Y504T; or
K79V+P2 N+P4S+P11F+T65A+Q327F+E501V+Y504T; or
K79V+P11F+T65A+Q327W+E501V+Y504T(using SEQ ID NO: 14 for numbering);
In an embodiment the Bacillus stearothermophilus alpha-amylase (SEQ ID NO: 1 herein), or a variant thereof, is the mature alpha-amylase or corresponding mature alpha-amylases having at least 80% identity, at least 90% identity, at least 95% identity at least 96% identity at least 97% identity at least 99% identity to the SEQ ID NO: 1.
In an embodiment the Pyrococcus furiosus protease (SEQ ID N01: 13) and/or Thermoascus aurantiacus protease (SEQ ID NO: 3), or a variant thereof, is the mature protease or corresponding mature protease having at least 80% identity, at least 90% identity, at least 95% identity at least 96% identity at least 97% identity at least 99% identity to the SEQ ID NO: 13 or SEQ ID NO: 3, respectively.
In an embodiment the Penicillium oxalicum glucoamylase (SEQ ID NO: 14 herein), or a variant thereof, is the mature glucoamylase or corresponding mature glucoamylase having at least 80% identity, at least 90% identity, at least 95% identity at least 96% identity at least 97% identity at least 99% identity to the SEQ ID NO: 14 herein.
In an embodiment the carbohydrate-source generating enzyme, in particular glucoamylase, is the Penicillium oxalicum glucoamylase. The glucoamylase may optionally be substituted or combined with a pullulanase, as described above in the “Pullulanase”-section, preferably derived from Thermococcus litoralis or Thermococcus hydrothermalis.
In a final aspect the invention relates to an alpha-amylase variant. The alpha-amylase variant is a thermostable variant suitable for use in a process of the invention. The alpha-amylase variant may also be an alpha-amylase (e.g., thermostable alpha-amylase) in a composition of the invention. The alpha-amylase variant has increased stability. The stability can be tested as described in Example 1 herein by comparison to a reference alpha-amylase. An alpha-amylase variant of the invention may be prepared as described in WO 2011/082425 (hereby incorporated by reference). A specifically contemplates variant (AA369) is used in Example 20 in a process of the invention.
In this aspect the invention relates to variant alpha-amylases, comprising mutations in positions corresponding to positions 59, 89, 129, 177, 179, 254, 284, wherein the variant has at least 65% and less than 100% sequence identity with the mature polypeptide of SEQ ID NO: 1, and the variant has alpha-amylase activity.
In an embodiment the variant of the invention comprises a substitution at a position corresponding to position 59 with Ala, Arg, Asn, Asp, Cys, Gln, Glu, Gly, His, Ile, Leu, Lys, Met, Phe, Pro, Ser, Thr, Trp, or Tyr, in particular with Ala, Gln, Glu, Gly, Ile, Leu, Pro, or Thr.
In an embodiment the variant of the invention comprises a substitution at a position corresponding to position 89 with Ala, Arg, Asn, Asp, Cys, Glu, Gly, His, Ile, Leu, Lys, Met, Phe, Pro, Ser, Thr, Trp, Tyr, or Val, in particular with Arg, His, or Lys.
In an embodiment the variant of the invention comprises a substitution at a position corresponding to position 129 with Ala, Arg, Asn, Asp, Cys, Gln, Gly, His, Ile, Leu, Lys, Met, Phe, Pro, Ser, Thr, Trp, Tyr, or Val, in particular with Ala, Thr, or Val.
In an embodiment the variant of the invention comprises a substitution at a position corresponding to position 177 with Ala, Arg, Asn, Asp, Cys, Gln, Glu, Gly, His, Ile, Leu, Met, Phe, Pro, Ser, Thr, Trp, Tyr, or Val, in particular with Arg, Leu, or Met.
In an embodiment the variant of the invention comprises a substitution at a position corresponding to position 179 with Ala, Asn, Asp, Cys, Gln, Glu, Gly, His, Ile, Leu, Lys, Met, Phe, Pro, Ser, Thr, Trp, Tyr, or Val, in particular with Gln, Glu, Ile, Leu, Lys, or Val.
In an embodiment the variant of the invention comprises a substitution at a position corresponding to position 254 with Ala, Arg, Asn, Asp, Cys, Glu, Gly, His, Ile, Leu, Lys, Met, Phe, Pro, Ser, Thr, Trp, Tyr, or Val, in particular with Ala, Ser, or Thr.
In an embodiment the variant of the invention comprises a substitution at a position corresponding to position 284 with Ala, Arg, Asn, Asp, Cys, Gln, Glu, Gly, His, Ile, Leu, Lys, Phe, Pro, Ser, Thr, Trp, Tyr, or Val, in particular with His, Thr, or Val.
In an embodiment the variant of the invention comprises or consists of the following mutations: V59A+Q89R+E129V+K177L+R179E+Q254S+M284V.
In an embodiment the variant of the invention is a variant of a parent alpha-amylase from a polypeptide with at least 60% sequence identity with the mature polypeptide of SEQ ID NO: 1 herein, or a fragment of the mature polypeptide of SEQ ID NO: 1, which has alpha-amylase activity.
In an embodiment the variant of the invention the parent alpha-amylase has at least 60%, e.g., at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, and 100% sequence identity with the mature polypeptide of SEQ ID NO: 1.
In an embodiment the variant of the invention the parent alpha-amylase comprises or consists of the amino acid sequence of the mature polypeptide of SEQ ID NO: 1.
In an embodiment the variant of the invention the parent alpha-amylase is a fragment of the amino acid sequence of the mature polypeptide of SEQ ID NO: 1, wherein the fragment has alpha-amylase activity.
In an embodiment the variant of the invention is a variant of a parent wild-type alpha-amylase.
In an embodiment the variant of the invention the parent alpha-amylase is a Bacillus alpha-amylase.
In an embodiment the parent alpha-amylase is a Bacillus stearothermophilus.
In an embodiment the parent alpha-amylase is the alpha-amylase shown in SEQ ID NO:
1 comprising the following mutations: double deletion of positions I181+G182 and optionally a N193F substitution, or double deletion of positions R179+G180.
In an embodiment the variant of the invention comprises or consists of the following mutations: I181*+G182*+N193F+V59A+Q89R+E129V+K177L+R179E+Q254S+M284V (using SEQ ID NO: 1 for numbering).
In an embodiment the variant of the invention the variant has a sequence identity of at least 65%, e.g., at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, but less than 100%, to the amino acid sequence of the parent alpha-amylase.
In an embodiment the variant of the invention the variant has a sequence identity of at least 65%, e.g., at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, and at least 99%, but less than 100%, with the mature polypeptide of SEQ ID NO: 1.
In an embodiment the alpha-amylase variant has the sequence shown in SEQ ID NO: 1 herein (naturally) truncated so it is around 491 amino acids long, such as from 480-495 amino acids long.
In a specific embodiment the alpha-amylase of the invention is a Bacillus stearothermophilus alpha-amylase with the mutations:
In one aspect the invention relates to the use of a variant of the invention for washing and/or dishwashing.
In one aspect the invention relates to the use of a variant of the invention for desizing a textile.
In one aspect the invention relates to the use of a variant of the invention for producing a baked product.
In one aspect the invention relates to the use of a variant of the invention for liquefying a starch-containing material.
In one aspect the invention relates to a method of producing liquefied starch, comprising liquefying a starch-containing material with a variant of the invention.
In one aspect the invention relates to an isolated polynucleotide encoding the variant of the invention.
In one aspect the invention relates to a nucleic acid construct comprising the polynucleotide of the invention.
In one aspect the invention relates to an expression vector comprising the nucleic acid construct of the invention.
In one aspect the invention relates to a host cell comprising the nucleic acid construct of the invention.
In one aspect the invention relates to a method of producing a variant alpha-amylase, comprising:
a. cultivating the host cell of the invention under conditions suitable for the expression of the variant; and
b. recovering the variant from the cultivation medium.
In an embodiment the invention relates to a transgenic plant, plant part or plant cell transformed with the polynucleotide of the invention.
In an embodiment the invention relates to a method for obtaining a variant alpha-amylase, comprising
a. introducing into a parent alpha-amylase a mutations in positions corresponding to positions 59, 89, 129, 177, 179, 254, 284, wherein the variant has at least 65% and less than 100% sequence identity with the mature polypeptide of SEQ ID NO: 1, and the variant has alpha-amylase activity; and
b. recovering the variant.
In an embodiment the mature polypeptide is the alpha-amylase shown in SEQ ID NO: 1 comprising the following mutations: double deletion of positions I181+G182, and optionally a N193F substitution,
Glucoamylase BL2: Blend comprising Talaromyces emersonii glucoamylase disclosed in WO99/28448, Trametes cingulata glucoamylase disclosed in WO 06/69289, and Rhizomucor pusillus alpha-amylase with Aspergillus niger glucoamylase linker and SBD disclosed as V039 in Table 5 in WO 2006/069290 as side activities (ratio about 65:15:1).
For purposes of the present invention the degree of identity between two amino acid sequences, as well as the degree of identity between two nucleotide sequences, may be determined by the program “align” which is a Needleman-Wunsch alignment (i.e. a global alignment). The program is used for alignment of polypeptide, as well as nucleotide sequences. The default scoring matrix BLOSUM50 is used for polypeptide alignments, and the default identity matrix is used for nucleotide alignments. The penalty for the first residue of a gap is −12 for polypeptides and −16 for nucleotides. The penalties for further residues of a gap are −2 for polypeptides, and −4 for nucleotides.
“Align” is part of the FASTA package version v20u6 (see W. R. Pearson and D. J. Lipman (1988), “Improved Tools for Biological Sequence Analysis”, PNAS 85:2444-2448, and W. R. Pearson (1990) “Rapid and Sensitive Sequence Comparison with FASTP and FASTA,” Methods in Enzymology 183:63-98). FASTA protein alignments use the Smith-Waterman algorithm with no limitation on gap size (see “Smith-Waterman algorithm”, T. F. Smith and M. S. Waterman (1981) J. Mol. Biol. 147:195-197).
Protease assays
A solution of 0.2% of the blue substrate AZCL-casein is suspended in Borax/NaH2PO4 buffer pH9 while stirring. The solution is distributed while stirring to microtiter plate (100 microL to each well), 30 microL enzyme sample is added and the plates are incubated in an Eppendorf Thermomixer for 30 minutes at 45° C. and 600 rpm. Denatured enzyme sample (100° C. boiling for 20min) is used as a blank. After incubation the reaction is stopped by transferring the microtiter plate onto ice and the coloured solution is separated from the solid by centrifugation at 3000 rpm for 5 minutes at 4° C. 60 microL of supernatant is transferred to a microtiter plate and the absorbance at 595 nm is measured using a BioRad Microplate Reader.
pNA-Assay
50 microL protease-containing sample is added to a microtiter plate and the assay is started by adding 100 microL 1 mM pNA substrate (5 mg dissolved in 100 microL DMSO and further diluted to 10 mL with Borax/NaH2PO4 buffer pH 9.0). The increase in OD405 at room temperature is monitored as a measure of the protease activity.
Glucoamylase activity may be measured in Glucoamylase Units (AGU). The Novo Glucoamylase Unit (AGU) is defined as the amount of enzyme, which hydrolyzes 1 micromole maltose per minute under the standard conditions 37° C., pH 4.3, substrate: maltose 23.2 mM, buffer: acetate 0.1 M, reaction time 5 minutes.
An autoanalyzer system may be used. Mutarotase is added to the glucose dehydrogenase reagent so that any alpha-D-glucose present is turned into beta-D-glucose. Glucose dehydrogenase reacts specifically with beta-D-glucose in the reaction mentioned above, forming NADH which is determined using a photometer at 340 nm as a measure of the original glucose concentration.
A folder (EB-SM-0131.02/01) describing this analytical method in more detail is available on request from Novozymes A/S, Denmark, which folder is hereby included by reference.
The alpha-amylase activity may be determined using potato starch as substrate. This method is based on the break-down of modified potato starch by the enzyme, and the reaction is followed by mixing samples of the starch/enzyme solution with an iodine solution. Initially, a blackish-blue color is formed, but during the break-down of the starch the blue color gets weaker and gradually turns into a reddish-brown, which is compared to a colored glass standard.
One Kilo Novo alpha amylase Unit (KNU) is defined as the amount of enzyme which, under standard conditions (i.e., at 37° C. +/−0.05; 0.0003 M Ca2+; and pH 5.6) dextrinizes 5260 mg starch dry substance Merck Amylum solubile.
A folder EB-SM-0009.02/01 describing this analytical method in more detail is available upon request to Novozymes A/S, Denmark, which folder is hereby included by reference.
Endo-pullulanase activity in NPUN is measured relative to a Novozymes pullulanase standard. One pullulanase unit (NPUN) is defined as the amount of enzyme that releases 1 micro mol glucose per minute under the standard conditions (0.7% red pullulan (Megazyme), pH 5, 40° C., 20 minutes). The activity is measured in NPUN/ml using red pullulan.
1 mL diluted sample or standard is incubated at 40° C. for 2 minutes. 0.5 mL 2% red pullulan, 0.5 M KCl, 50 mM citric acid, pH 5 are added and mixed. The tubes are incubated at 40° C. for 20 minutes and stopped by adding 2.5 ml 80% ethanol. The tubes are left standing at room temperature for 10-60 minutes followed by centrifugation 10 minutes at 4000 rpm. OD of the supernatants is then measured at 510 nm and the activity calculated using a standard curve.
The present invention is described in further detail in the following examples which are offered to illustrate the present invention, but not in any way intended to limit the scope of the invention as claimed. All references cited herein are specifically incorporated by reference for that which is described therein.
The stability of a reference alpha-amylase (Bacillus stearothermophilus alpha-amylase with the mutations I181*+G182*+N193F truncated to 491 amino acids (SEQ ID NO: 1 numbering)) and alpha-amylase variants thereof was determined by incubating the reference alpha-amylase and variants at pH 4.5 and 5.5 and temperatures of 75° C. and 85° C. with 0.12 mM CaCl2 followed by residual activity determination using the EnzChek® substrate (EnzChek® Ultra Amylase assay kit, E33651, Molecular Probes).
Purified enzyme samples were diluted to working concentrations of 0.5 and 1 or 5 and 10 ppm (micrograms/m1) in enzyme dilution buffer (10 mM acetate, 0.01% Triton X100, 0.12 mM CaCl2, pH 5.0). Twenty microliters enzyme sample was transferred to 48-well PCR MTP and 180 microliters stability buffer (150 mM acetate, 150 mM MES, 0.01% Triton X100, 0.12 mM CaCl2, pH 4.5 or 5.5) was added to each well and mixed. The assay was performed using two concentrations of enzyme in duplicates. Before incubation at 75° C. or 85° C., 20 microliters was withdrawn and stored on ice as control samples. Incubation was performed in a PCR machine at 75° C. and 85° C. After incubation samples were diluted to 15 ng/mL in residual activity buffer (100 mM Acetate, 0.01% Triton X100, 0.12 mM CaCl2, pH 5.5) and 25 microliters diluted enzyme was transferred to black 384-MTP. Residual activity was determined using the EnzChek substrate by adding 25 microliters substrate solution (100 micrograms/ml) to each well. Fluorescence was determined every minute for 15 minutes using excitation filter at 485-P nm and emission filter at 555 nm (fluorescence reader is Polarstar, BMG). The residual activity was normalized to control samples for each setup.
Assuming logarithmic decay half life time (T½ (min)) was calculated using the equation: T½ (min)=T(min)*LN(0.5)/LN(%RA/100), where T is assay incubation time in minutes, and % RA is % residual activity determined in assay.
Using this assay setup the half life time was determined for the reference alpha-amylase and variant thereof as shown in Table 1.
The results demonstrate that the alpha-amylase variants have a significantly greater half-life and stability than the reference alpha-amylase.
E. coli DH12S (available from Gibco BRL) was used for yeast plasmid rescue. pJTP000 is a S. cerevisiae and E. coli shuttle vector under the control of TPI promoter, constructed from pJC039 described in WO 01/92502, in which the Thermoascus aurantiacus M35 protease gene (WO 03/048353) has been inserted.
Saccharomyces cerevisiae YNG318 competent cells: MATa Dpep4[cir+] ura3-52, leu2-D2, his 4-539 was used for protease variants expression. It is described in J. Biol. Chem. 272 (15), pp 9720-9727, 1997.
Unless otherwise stated, DNA manipulations and transformations were performed using standard methods of molecular biology as described in Sambrook et al. (1989) Molecular cloning: A laboratory manual, Cold Spring Harbor lab. Cold Spring Harbor, N.Y.; Ausubel, F. M. et al. (eds.) “Current protocols in Molecular Biology”, John Wiley and Sons, 1995; Harwood, C. R. and Cutting, S. M. (Eds.).
Yeast transformation was performed using the lithium acetate method. 0.5 microL of vector (digested by restriction endnucleases) and 1 microL of PCR fragments is mixed. The DNA mixture, 100 microL of YNG318 competent cells, and 10 microL of YEAST MAKER carrier DNA (Clontech) is added to a 12 ml polypropylene tube (Falcon 2059). Add 0.6 ml PEG/LiAc solution and mix gently. Incubate for 30 min at 30° C., and 200 rpm followed by 30 min at 42° C. (heat shock). Transfer to an eppendorf tube and centrifuge for 5 sec. Remove the supernatant and resolve in 3 ml of YPD. Incubate the cell suspension for 45 min at 200 rpm at 30° C. Pour the suspension to SC-glucose plates and incubate 30° C. for 3 days to grow colonies. Yeast total DNA are extracted by Zymoprep Yeast Plasmid Miniprep Kit (ZYMO research).
E. coli transformation for DNA sequencing was carried out by electroporation (BIO-RAD Gene Pulser). DNA Plasmids were prepared by alkaline method (Molecular Cloning, Cold Spring Harbor) or with the Qiagen® Plasmid Kit. DNA fragments were recovered from agarose gel by the Qiagen gel extraction Kit. PCR was performed using a PTC-200 DNA Engine. The ABI PRISM™ 310 Genetic Analyzer was used for determination of all DNA sequences.
The Themoascus M35 protease gene was amplified with the primer pair Prot F (SEQ ID NO: 4) and Prot R (SEQ ID NO: 45). The resulting PCR fragments were introduced into S. cerevisiae YNG318 together with the pJC039 vector (described in WO2001/92502) digested with restriction enzymes to remove the Humicola insolens cutinase gene.
The Plasmid in yeast clones on SC-glucose plates was recovered to confirm the internal sequence and termed as pJTP001.
Library in yeast and site-directed variants were constructed by SOE PCR method (Splicing by Overlap Extension, see “PCR: A practical approach”, p. 207-209, Oxford University press, eds. McPherson, Quirke, Taylor), followed by yeast in vivo recombination.
The primers AM34 (SEQ ID NO:5) and AM35 (SEQ ID NO:6) were used to make DNA fragments containing any mutated fragments by the SOE method together with degenerated primers (AM34+Reverse primer and AM35+forward primer) or just to amplify a whole protease gene (AM34+AM35).
DNA fragments were recovered from agarose gel by the Qiagen gel extraction Kit. The resulting purified fragments were mixed with the vector digest. The mixed solution was introduced into Saccharomyces cerevisiae to construct libraries or site-directed variants by in vivo recombination.
Yeast clones on SC-glucose were inoculated to a well of a 96-well micro titre plate containing YPD+Zn medium and cultivated at 28° C. for 3 days. The culture supernatants were applied to a 96-well zein micro titer plate and incubated at at least 2 temperatures (ex. 60° C. and 65° C., 70° C. and 75° C., 70° C. and 80° C.) for more than 4 hours or overnight. The turbidity of zein in the plate was measured as A630 and the relative activity (higher/lower temperatures) was determined as an indicator of thermoactivity improvement. The clones with higher relative activity than the parental variant were selected and the sequence was determined.
Yeast clones on SC-glucose were inoculated to a well of a 96-well micro titre plate and cultivated at 28° C. for 3 days. Protease activity was measured at 65° C. using azo-casein (Megazyme) after incubating the culture supernatant in 20 mM sodium acetate buffer, pH 4.5, for 10 min at a certain temperature (80° C. or 84° C. with 4° C. as a reference) to determine the remaining activity. The clones with higher remaining activity than the parental variant were selected and the sequence was determined.
20 microL of samples were mixed with 150 microL of substrate solution (4 ml of 12.5% azo-casein in ethanol in 96 ml of 20 mM sodium acetate, pH 4.5, containing 0.01% triton-100 and 0.25 mM ZnSO4) and incubated for 4 hours or longer.
After adding 20 microL/well of 100% trichloroacetic acid (TCA) solution, the plate was centrifuge and 100 microL of supernatants were pipette out to measure A440.
Expression of Protease Variants in Aspergillus oryzae
The constructs comprising the protease variant genes were used to construct expression vectors for Aspergillus. The Aspergillus expression vectors consist of an expression cassette based on the Aspergillus niger neutral amylase II promoter fused to the Aspergillus nidulans triose phosphate isomerase non translated leader sequence (Pna2/tpi) and the Aspergillus niger amyloglycosidase terminator (Tamg). Also present on the plasmid was the Aspergillus selective marker amdS from Aspergillus nidulans enabling growth on acetamide as sole nitrogen source. The expression plasmids for protease variants were transformed into Aspergillus as described in Lassen et al. (2001), Appl. Environ. Microbiol. 67, 4701-4707. For each of the constructs 10-20 strains were isolated, purified and cultivated in shake flasks.
Selected variants showing good thermo-stability were purified and the purified enzymes were used in a zein-BCA assay as described below. The remaining protease activity was determined at 60° C. after incubation of the enzyme at elevated temperatures as indicated for 60 min.
Zein-BCA assay was performed to detect soluble protein quantification released from zein by variant proteases at various temperatures.
The results are shown in Table 5. All of the tested variants showed an improved thermo-stability as compared to the wt protease.
Characterization of Penicillium oxalicum glucoamylase
The Penicillium oxalicum glucoamylase is disclosed in SEQ ID NO: 9 herein.
From the results it can be seen that the optimal temperature for Penicillium oxalicum glucoamylase at the given conditions is between 50° C. and 70° C. and the glucoamylase maintains more than 80% activity at 95° C.
The results are shown in Table 7.
From the results it can be seen that Penicillium oxalicum glucoamylase is stable up to 70° C. after preincubation for 15 min in that it maintains more than 80% activity. pH optimum. To assess the pH optimum of the Penicillium oxalicum glucoamylase the Reaction condition assay described above was performed at pH 2.0, 3.0, 3.5, 4.0, 4.5, 5.0, 6.0 7.0, 8.0, 9.0, 10.0 and 11.0. Instead of using the acetate buffer described in the Reaction condition assay the following buffer was used 100 mM Succinic acid, HEPES, CHES, CAPSO, 1 mM CaCl2, 150 mM KCl, 0.01% Triton X-100, pH adjusted to 2.0, 3.0, 3.5, 4.0, 4.5, 5.0, 6.0 7.0, 8.0, 9.0, 10.0 or 11.0 with HCl or NaOH.
The results are shown in Table 8.
From the results it can be seen that Penicillium oxalicum glucoamylase at the given conditions has the highest activity at pH 5.0. The Penicillium oxalicum glucoamylase is active in a broad pH range in the it maintains more than 50% activity from pH 2 to 7.
The results are shown in Table 9.
From the results it can be seen that Penicillium oxalicum glucoamylase, is stable from pH 3 to pH 7 after preincubation for 20 hours and it decreases its activity at pH 8.
The thermostability of the Pyrococcus furiosus protease (Pfu S) purchased from Takara
Bio Inc, (Japan) was tested using the same methods as in Example 2. It was found that the thermostability (Relative Activity) was 110% at (80° C./70° C.) and 103% (90° C./70° C.) at pH 4.5.
Ethanol Production using Alpha-Amylase 1407 and Protease Pfu for Liquefaction
The purpose of this experiment was to evaluate the application performance of Protease Pfu derived from Pyrococcus furiosus added during liquefaction at pH 5.4 and 5.8, respectively, at 85° C. for 2 hours.
Each liquefaction received ground corn (84.19% DS), backset (6.27% DS), and tap water targeting a total weight of 100 g at 32.50% Dry Solids (DS). Backset was blended at 30% w/w of total slurry weight. Initial slurry pH was approximately 5.2 and was adjusted to pH 5.4 or 5.8 with 50% w/w sodium hydroxide prior to liquefaction. All enzymes were added according to the experimental design listed in Table 11 below. Liquefaction took place in a Labomat using the following conditions: 5° C./min. Ramp, 17 minute Ramp, 103 minute hold time at 85° C., 40 rpm for the entire run, 200 mL stainless steel canisters. After liquefaction, all canisters were cooled in an ice bath and prepared for fermentation based on the protocol listed below under SSF.
Each mash was adjusted to pH 5.0 with 50% w/w Sodium Hydroxide or 40% v/v sulfuric acid. Penicillin was applied to each mash to a total concentration of 3 ppm. The tubes were prepared with mash by aliquoting approximately 4.5 g of mash per 15 mL pre-drilled test tubes to allow CO2 release. The test tubes sat, overnight, at 4° C. until the next morning.
All test tubes of mash were removed from cold storage and warmed up to 32° C. in the walk-in incubation chamber. Once warmed, Glucoamylase BL2, was dosed to each tube of mash at 0.50 AGU/g DS, water was added so that all tubes received 120 μL of liquid and each mash sample received 100 μL of rehydrated yeast. Rehydrated yeast was prepared by mixing 5.5 g of Fermentis RED STAR into 100 mL of 32° C. tap water for at least 15 minutes. In monitoring CO2 weight-loss over time, each unit of CO2 generated and lost is converted to gram ethanol produced per gram of dry solids (g EtOH/g DS) by the following:
Fermentation sampling took place after 54 hours of fermentation by taking 3 tubes per treatment. Each sample was deactivated with 50 μL of 40% v/v H2SO4, vortexing, centrifuging at 1460×g for 10 minutes, and filtering through a 0.45 μm Whatman PP filter. 54 hour samples were analyzed under HPLC without further dilution. Samples were stored at 4° C. prior to and during HPLC analysis.
The method quantified analyte(s) using calibration standards for ethanol (% w/v). A four point calibration including the origin is used for quantification.
Where applicable, data were analyzed using JMP software (Cary, N.C.) with Oneway ANOVA of pairs using Tukey-Kramer HSD or Dunnett's. Error bars denoting the 95% confidence level were established by multiplying the standard error of Oneway Anova analysis by 1.96.
Ethanol Production with Alpha-Amylase A and Thermostable Protease 050 and Protease 036
The purpose of this experiment was to evaluate the application performance of two thermostable protease variants of the Thermoascus auranticus protease added during liquefaction at pH 5.4 at 85° C. for 2 hours.
Ground corn, backset and tap water were blended to 32.50% DS and adjusted to pH 5.4 with 50% v/v sodium hydroxide. Each respective protease was added, mixed well, and followed by Alpha-Amylase A addition at a dose of 0.02% (w/w) per g corn. Samples were incubated in a water bath set to 85° C. for two hours and received frequent mixing during the first 15 minutes of incubation, every 15 minutes thereafter. All mashes were refrigerated after liquefaction and remained there until fermentation.
Simultaneous Saccharification and Fermentation (SSF)
Mashes were adjusted to 32% DS with tap water prior to SSF as needed and dosed to a total concentration of 500 ppm urea and 3 ppm penicillin. No pH adjustment was made for SSF after liquefaction. Approximately 4.5 g of mash was added to 15 mL test tubes that were pre-drilled in the top to allow for CO2 release. Glucoamylase BL2 was dosed at 0.50 AGU/g DS, and water was added to each tube to ensure all samples were processed at equal solids. Rehydrated yeast was prepared by mixing 5.5 g of Fermentis RED STAR in 100 mL of 32° C. tap water for at least 15 minutes and each test tube was inoculated with 100 μL, corresponding to 30 million cells per mL of mash.
All 54 hour fermentation samples selected for HPLC analysis and were deactivated with 50 μL of 40% v/v H2SO4, vortexed, centrifuged at 1460×g for 10 min., and then filtered through a 0.45 μm Whatman filter. Samples were stored at 4° C. prior to HPLC analysis. HPLC analysis was done as described in Example 6.
In monitoring CO2 weight-loss over time, each unit of CO2 lost is converted to gram Ethanol produced per gram of dry solids (g EtOH/g DS) using the formula in Example 6.
All liquefactions included Alpha-Amylase A.
Cloning of Penicillium oxalicum Strain Glucoamylase Gene
Preparation of Penicillium oxalicum Strain cDNA.
The cDNA was synthesized by following the instruction of 3′ Rapid Amplifiction of cDNA End System (Invitrogen Corp., Carlsbad, Calif., USA).
Cloning of Penicillium oxalicum Strain Glucoamylase Gene.
The Penicillium oxalicum glucoamylase gene was cloned using the oligonucleotide primer shown below designed to amplify the glucoamylase gene from 5′ end.
The full length gene was amplified by PCR with Sense primer and AUAP (supplied by 3′ Rapid Amplifiction of cDNA End System) by using Platinum HIFI Taq DNA polymerase (Invitrogen Corp., Carlsbad, Calif., USA). The amplification reaction was composed of 5 μl of 10× PCR buffer, 2 μl of 25 mM MgCl2, 1 μl of 10 mM dNTP, 1 μl of 10 uM Sense primer, 1 μl of 10 uM AUAP, 2 μl of the first strand cDNA, 0.5 pl of HIFI Taq, and 37.5 pl of deionized water. The PCR program was: 94° C., 3 mins; 10 cycles of 94° C. for 40 secs, 60° C. 40 secs with 1° C. decrease per cycle, 68° C. for 2 min; 25 cycles of 94° C. for 40 secs, 50° C. for 40 secs, 68° C. for 2 min; final extension at 68° C. for 10 mins.
The obtained PCR fragment was cloned into pGEM-T vector (Promega Corporation, Madison, Wis., USA) using a pGEM-T Vector System (Promega Corporation, Madison, Wis., USA) to generate plasmid AMG 1. The glucoamylase gene inserted in the plasmid AMG 1 was sequencing confirmed. E. coli strain TOP10 containing plasmid AMG 1 (designated NN059173), was deposited with the Deutsche Sammlung von Mikroorganismen and Zellkulturen GmbH (DSMZ) on Nov. 23, 2009, and assigned accession number as DSM 23123.
Expression of Cloned Penicillium oxalicum Glucoamylase
The Penicillium oxalicum glucoamylase gene was re-cloned from the plasmid AMG 1 into an Aspergillus expression vector by PCR using two cloning primer F and primer R shown below, which were designed based on the known sequence and added tags for direct cloning by IN-FUSION™ strategy.
A PCR reaction was performed with plasmid AMG 1 in order to amplify the full-length gene. The PCR reaction was composed of 40 μg of the plasmid AMG 1 DNA, 1 μl of each primer (100 μM); 12.5 μl of 2×Extensor Hi-Fidelity master mix (Extensor Hi-Fidelity Master Mix, ABgene, United Kingdom), and 9.5 μl of PCR-grade water. The PCR reaction was performed using a DYAD PCR machine (Bio-Rad Laboratories, Inc., Hercules, Calif., USA) programmed for 2 minutes at 94° C. followed by a 25 cycles of 94° C. for 15 seconds, 50° C. for 30 seconds, and 72° C. for 1 minute; and then 10 minutes at 72° C.
The reaction products were isolated by 1.0% agarose gel electrophoresis using 1× TAE buffer where an approximately 1.9 kb PCR product band was excised from the gel and purified using a GFX® PCR DNA and Gel Band Purification Kit (GE Healthcare, United Kingdom) according to manufacturer's instructions. DNA corresponding to the Penicillium oxalicum glucoamylase gene was cloned into an Aspergillus expression vector linearized with BamHl and HindIII, using an IN-FUSION™ Dry-Down PCR Cloning Kit (BD Biosciences, Palo Alto, Calif., USA) according to the manufacturer's instructions. The linearized vector construction is as described in WO 2005/042735 A1.
A 2 μl volume of the ligation mixture was used to transform 25 μl of Fusion Blue E. coli cells (included in the IN-FUSION™ Dry-Down PCR Cloning Kit). After a heat shock at 42° C. for 45 sec, and chilling on ice, 250 pl of SOC medium was added, and the cells were incubated at 37° C. at 225 rpm for 90 min before being plated out on LB agar plates containing 50 μg of ampicillin per ml, and cultivated overnight at 37° C. Selected colonies were inoculated in 3 ml of LB medium supplemented with 50 μg of ampicillin per ml and incubated at 37° C. at 225 rpm overnight. Plasmid DNA from the selected colonies was purified using Mini JETSTAR (Genomed, Germany) according to the manufacturer's instructions. Penicillium oxalicum glucoamylase gene sequence was verified by Sanger sequencing before heterologous expression. One of the plasmids was selected for further expression, and was named XYZ XYZ1471-4.
Protoplasts of Aspergillus niger MBin118 were prepared as described in WO 95/02043. One hundred μl of protoplast suspension were mixed with 2.5 μg of the XYZ1471-4 plasmid and 250 microliters of 60% PEG 4000 (Applichem) (polyethylene glycol, molecular weight 4,000), 10 mM CaCl2, and 10 mM Tris-HCl pH 7.5 were added and gently mixed. The mixture was incubated at 37° C. for 30 minutes and the protoplasts were mixed with 6% low melting agarose (Biowhittaker Molecular Applications) in COVE sucrose (Cove, 1996, Biochim. Biophys. Acta 133:51-56) (1M) plates supplemented with 10 mM acetamid and 15 mM CsCl and added as a top layer on COVE sucrose (1M) plates supplemented with 10 mM acetamid and 15 mM CsCl for transformants selection (4 ml topagar per plate). After incubation for 5 days at 37° C. spores of sixteen transformants were picked up and seed on 750 μl YP-2% Maltose medium in 96 deepwell MT plates. After 5 days of stationary cultivation at 30° C., 10 μl of the culture-broth from each well was analyzed on a SDS-PAGE (Sodium dodecyl sulfate-polyacrylamide gel electrophoresis) gel, Griton XT Precast gel (BioRad, Calif., USA) in order to identify the best transformants based on the ability to produce large amount of glucoamylase. A selected transformant was identified on the original transformation plate and was preserved as spores in a 20% glycerol stock and stored frozen (−80° C.).
Cultivation. The selected transformant was inoculated in 100 ml of MLC media and cultivated at 30° C. for 2 days in 500 ml shake flasks on a rotary shaker. 3 ml of the culture broth was inoculated to 100 ml of M410 medium and cultivated at 30° C. for 3 days. The culture broth was centrifugated and the supernatant was filtrated using 0.2 μm membrane filters.
Alpha-cyclodextrin affinity gel. Ten grams of Epoxy-activated Sepharose 6B (GE Healthcare, Chalfont St. Giles, U.K) powder was suspended in and washed with distilled water on a sintered glass filter. The gel was suspended in coupling solution (100 ml of 12.5 mg/ml alpha-cyclodextrin, 0.5 M NaOH) and incubated at room temperature for one day with gentle shaking. The gel was washed with distilled water on a sintered glass filter, suspended in 100 ml of 1 M ethanolamine, pH 10, and incubated at 50° C. for 4 hours for blocking. The gel was then washed several times using 50 mM Tris-HCl, pH 8 and 50 mM NaOAc, pH 4.0 alternatively. The gel was finally packed in a 35-40 ml column using equilibration buffer (50 mM NaOAc, 150 mM NaCl, pH 4.5).
Purification of glucoamylase from culture broth. Culture broth from fermentation of A. niger MBin118 harboring the glucoamylase gene was filtrated through a 0.22 μm PES filter, and applied on a alpha-cyclodextrin affinity gel column previously equilibrated in 50 mM NaOAc, 150 mM NaCl, pH 4.5 buffer. Unbound material was washed off the column with equilibration buffer and the glucoamylase was eluted using the same buffer containing 10 mM beta-cyclodextrin over 3 column volumes.
The glucoamylase activity of the eluent was checked to see, if the glucoamylase had bound to the alpha-cyclodextrin affinity gel. The purified glucoamylase sample was then dialyzed against 20 mM NaOAc, pH 5.0. The purity was finally checked by SDS-PAGE, and only a single band was found.
Construction and Expression of a Site-Directed Variant of Penicillium oxalicum Glucoamylase (PE001)
Two PCR reactions were performed with plasmid XYZ1471-4, described in Example 9, using primers K79V F and K79VR shown below, which were desined to substitute lysine K at position 79 from the mature seequence to varin V and primers F-NP003940 and R-NP003940 shown below, which were designed based on the known sequence and added tags for direct cloning by IN-FUSlON™ strategy.
The PCR was performed using a PTC-200 DNA Engine under the conditions described below.
DNA fragments were recovered from agarose gel by the Qiagen gel extraction Kit according to the manufacturer's instruction. The resulting purified two fragments were cloned into an Aspergillus expression vector linearized with BamHI and HindIII, using an IN-FUSION™ Dry-Down PCR Cloning Kit (BD Biosciences, Palo Alto, Calif., USA) according to the manufacturer's instructions. The linearized vector construction is as described in WO 2005/042735 A1.
The ligation mixture was used to transform E. coli DH5αcells (TOYOBO). Selected colonies were inoculated in 3 ml of LB medium supplemented with 50 μg of ampicillin per ml and incubated at 37° C. at 225 rpm overnight. Plasmid DNA from the selected colonies was purified using Qiagen plasmid mini kit (Qiagen) according to the manufacturer's instructions. The sequence of Penicillium oxalicum glucoamylase site-directed variant gene sequence was verified before heterologous expression and one of the plasmids was selected for further expression, and was named pPoPE001.
Protoplasts of Aspergillus niger MBin118 were prepared as described in WO 95/02043. One hundred microliters of protoplast suspension were mixed with 2.5 μg of the pPoPE001 plasmid and 250 microliters of 60% PEG 4000 (Applichem) (polyethylene glycol, molecular weight 4,000), 10 mM CaCl2, and 10 mM Tris-HCl pH 7.5 were added and gently mixed. The mixture was incubated at 37° C. for 30 minutes and the protoplasts were mixed with 1% agarose L (Nippon Gene) in COVE sucrose (Cove, 1996, Biochim. Biophys. Acta 133:51-56) supplemented with 10 mM acetamid and 15 mM CsCl and added as a top layer on COVE sucrose plates supplemented with 10 mM acetamid and 15 mM CsCl for transformants selection (4 ml topagar per plate). After incubation for 5 days at 37° C. spores of sixteen transformants were picked up and seed on 750 μl YP-2% Maltose medium in 96 deepwell MT plates. After 5 days of stationary cultivation at 30° C., 10 μl of the culture-broth from each well was analyzed on a SDS-PAGE gel in order to identify the best transformants based on the ability to produce large amount of the glucoamylase.
The selected transformant of the variant and the strain expressing the wild type Penicillium oxalicum glucoamylase described in Example 8 was cultivated in 100 ml of YP-2% maltose medium and the culture was filtrated through a 0.22 μm PES filter, and applied on a alpha-cyclodextrin affinity gel column previously equilibrated in 50 mM NaOAc, 150 mM NaCl, pH 4.5 buffer. Unbound materias was washed off the column with equilibration buffer and the glucoamylase was eluted using the same buffer containing 10 mM beta-cyclodextrin over 3 column volumes.
The glucoamylase activity of the eluent was checked to see, if the glucoamylase had bound to the alpha-cyclodextrin affinity gel. The purified glucoamylase samples were then dialyzed against 20 mM NaOAc, pH 5.0.
40 μl enzyme solutions (1 mg/ml) in 50 mM sodium acetate buffer, pH 4.5, was mixed with 1/10 volume of 1mg/ml protease solutions such as aspergillopepsinl described in Biochem J. 1975 April; 147(1): 45-53 or the commercially availble product from Sigma and aorsin descrived in Biochemical journal [0264-6021] Ichishima, 2003, 371(2): 541 and incubated at 4 or 32° C. overnight. As a control experiment, H2O was added to the sample instead of proteases. The samples were loaded on SDS-PAGE to see if the glucoamylases are cleaved by proteases.
In SDS-PAGE, PE001 only showed one band corresponding to the intact molecule, while the wild type glucoamylase was degraded by proteases and showed a band at lower molecular size at 60 kCa.
Aspergillus transformant of the variant and the wild type Penicillium oxalicum glucoamylase were cultivated in 6-well MT plates containing 4× diluted YP-2% maltose medium supplemented with 10 mM sodium acetate buffer, pH4.5, at 32° C. for 1 week.
The culture supernatants were loaded on SDS-PAGE.
The wild type glucoamylase was cleaved by host proteasaes during fermentation, while the variant yielded only intact molecule.
The glucoamylase activity measures as AGU as described above was checked for the purified enzymes of the wild type Penicillium oxalicum and the variant glucoamylase.
The Glucoamylase Unit (AGU) was defined as the amount of enzyme, which hydrolyzes 1 micromole maltose per minute under the standard conditions (37° C., pH 4.3, substrate: maltose 100 mM, buffer: acetate 0.1 M, reaction time 6 minutes).
Penicillium oxalicum wt
Penicillium oxalicum PE001 (SEQ ID NO: 14 + V79K)
Purification of Glycoamylase Variants having Increased Thermostability
The variants showing increased thermostability may be constructed and expressed similar to the procedure described in Example 10. All variants were derived from the PE001. After expression in YPM medium, variants comprising the T65A or Q327F substitution was micro-purified as follows:
Mycelium was removed by filtration through a 0.22 μm filter. 50 μl column material (alpha-cyclodextrin coupled to Mini-Leak divinylsulfone-activated agarose medium according to manufacturers recommendations) was added to the wells of a filter plate (Whatman, Unifilter 800 μl, 25-30 μm MBPP). The column material was equilibrated with binding buffer (200 mM sodium acetate pH 4.5) by two times addition of 200 μl buffer, vigorous shaking for 10 min (Heidolph, Titramax 101, 1000 rpm) and removal of buffer by vacuum (Whatman, UniVac 3). Subsequently, 400 μl culture supernatant and 100 μl binding buffer was added and the plate incubated 30 min with vigorous shaking. Unbound material was removed by vacuum and the binding step was repeated. Normally 4 wells were used per variant. Three washing steps were then performed with 200 μl buffer of decreasing ionic strength added (50/10/5 mM sodium acetate, pH 4.5), shaking for 15 min and removal of buffer by vacuum. Elution of the bound AMG was achieved by two times addition of 100 pl elution buffer (250 mM sodium acetate, 0.1% alpha-cyclodextrin, pH 6.0), shaking for 15 min and collection of eluted material in a microtiter plate by vacuum. Pooled eluates were concentrated and buffer changed to 50 mM sodium acetate pH 4.5 using centrifugal filter units with 10 kDa cut-off (Millipore Microcon Ultracel YM-10). Micropurified samples were stored at −18° C. until testing of thermostability.
Protein thermal unfolding of the T65A and Q327F variants, was monitored using Sypro Orange (In-vitrogen, S-6650) and was performed using a real-time PCR instrument (Applied Biosystems; Step-One-Plus).
In a 96-well plate, 25 microliter micropurified sample in 50 mM Acetate pH4,5 at approx. 100 microgram/ml was mixed (5:1) with Sypro Orange (resulting conc. =5×; stock solution from supplier=5000×). The plate was sealed with an optical PCR seal. The PCR instrument was set at a scan-rate of 76° C. pr. hr, starting at 25° C. and finishing at 96° C. Protein thermal unfolding of the E501V+Y504T variant, was monitored using Sypro Orange (In-vitrogen, S-6650) and was performed using a real-time PCR instrument (Applied Biosystems; Step-One-Plus).
In a 96-well plate, 15 microliter purified sample in 50 mM Acetate pH4,5 at approx. 50 microgram/ml was mixed (1:1) with Sypro Orange (resulting conc.=5×; stock solution from supplier=5000×) with or without 200 ppm Acarbose (Sigma A8980). The plate was sealed with an optical PCR seal. The PCR instrument was set at a scan-rate of 76 degrees C. pr. hr, starting at 25° C. and finishing at 96° C.
Fluorescence was monitored every 20 seconds using in-built LED blue light for excitation and ROX-filter (610 nm, emission).
Tm-values were calculated as the maximum value of the first derivative (dF/dK) (ref.: Gregory et al., 2009, J. Biomol. Screen. 14: 700).
Additional site specific variants having substitutions and/or deletions at specific positions were constructed basically as described in Example 10 and purified as described in Example 11.
The thermostability of the purified Po-AMG PE001 derived variants were determined at pH 4.0 or 4.8 (50 mM Sodium Acetate) by Differential Scanning Calorimetry (DSC) using a VP-Capillary Differential Scanning Calorimeter (MicroCal Inc., Piscataway, N.J., USA). The thermal denaturation temperature, Td (° C.), was taken as the top of the denaturation peak (major endothermic peak) in thermograms (Cp vs. T) obtained after heating enzyme solutions in selected buffers (50 mM Sodium Acetate, pH 4.0 or 4.8)at a constant programmed heating rate of 200 K/hr.
Sample- and reference-solutions (approximately 0.3 ml) were loaded into the calorimeter (reference: buffer without enzyme) from storage conditions at 10° C. and thermally pre-equilibrated for 10 minutes at 20° C. prior to DSC scan from 20° C. to 110° C. Denaturation temperatures were determined with an accuracy of approximately +/−1° C.
The isolated variants and the DSC data are disclosed in Table 16 below.
Thermostability Analysis by Thermo-Strees Test and pNPG Assay
Starting from one of the identified substitution variants from Example 10, identified as PE008, additional variants were tested by a thermo-stress assay in which the supernatant from growth cultures were assayed for glucoamylase (AMG) activity after a heat shock at 83° C. for 5 min.
After the heat-shock the residual activity of the variant was measured as well as in a non-stressed sample.
Description of Po-AMG pNPG Activity Assay:
The Penicillium oxalicum glucoamylase pNPG activity assay is a spectrometric endpoint assay where the samples are split in two and measured thermo-stressed and non-thermo-stressed. The data output is therefore a measurement of residual activity in the stressed samples.
A sterile micro titer plate (MTP) was added 200 microliters rich growth media (FT X-14 without Dowfax) to each well. The strains of interest were inoculated in triplicates directly from frozen stocks to the MTP. Benchmark was inoculated in 20 wells. Non-inoculated wells with media were used as assay blanks. The MTP was placed in a plastic box containing wet tissue to prevent evaporation from the wells during incubation. The plastic box was placed at 34° C. for 4 days.
50 microliters supernatant was transferred to 50 microliters 0.5 M NaAc pH 4.8 to obtain correct sample pH.
50 microliters dilution was transferred to a PCR plate and thermo-stressed at 83° C. for 5 minutes in a PCR machine. The remaining half of the dilution was kept at RT.
20 microliters of both stressed and unstressed samples was transferred to a standard MTP. 20 microliters pNPG-substrate was added to start the reaction. The plate was incubated at RT for 1 h.
The reaction was stopped and the colour developed by adding 50 microliters 0.5 M Na2CO3. The yellow colour was measured on a plate reader (Molecular Devices) at 405 nm.
In Excel the raw Abs405 data from both stressed and unstressed samples were blank subtracted with their respective blanks. The residual activity (% res. act.=(Absunstressed(Absunstressed−Absstressed)Absunstressed*100%) was calculated and plotted relative to benchmark, Po-amg0008.
All of the above described variants disclosed in tables 16, 17, and 18 have been verified for Glucoamylase activity on culture supernatants using the pNPG assay described in Example 18.
The purpose of this experiment was to evaluate the application performance of Alpha-Amylase 1407 and Alpha-Amylase 369 in combination with Protease Pfu derived from Pyrococcus furiosus and added during liquefaction at pH 4.8, 5.3 and 5.8, at 85° C. for 2 hours.
Each liquefaction received ground corn (85.6% DS), backset (4.9% DS), and tap water targeting a total weight of 140 g at 32.50% Dry Solids (DS). Backset was blended at 30% w/w of total slurry weight. Initial slurry pH was approximately 5.2 and was adjusted to pH 4.8, 5.3 or 5.8 with 50% w/w sodium hydroxide or 40% v/v sulfuric acid prior to liquefaction. All enzymes were added according to the experimental design listed in Table 19 below. Liquefaction took place in a Labomat using the following conditions: 5° C./min. Ramp, 17 minute Ramp, 103 minute hold time, 40 rpm for the entire run, 200 mL stainless steel canisters. After liquefaction, all canisters were cooled in an ice bath and prepared for fermentation based on the protocol listed below under SSF.
Each mash was adjusted to pH 5.0 with 50% w/w Sodium Hydroxide or 40% v/v sulfuric acid. Penicillin was applied to each mash to a total concentration of 3 ppm. The tubes were prepared with mash by aliquoting approximately 4.5 g of mash per 15 mL pre-drilled test tubes to allow CO2 release.
Glucoamylase BL2 was dosed to each tube of mash at 0.54 AGU/g DS, minimal water was added to each tube to normalize solids, and each mash sample received 100 μL of rehydrated yeast. Rehydrated yeast was prepared by mixing 5.5 g of Fermentis RED STAR into 100 mL of 32° C. tap water for at least 15 minutes.
Fermentation sampling took place after approximately 54 hours of fermentation. Each sample was deactivated with 50 μL of 40% v/v H2SO4, vortexing, centrifuging at 1460×g for 10 minutes, and filtering through a 0.45 μm Whatman PP filter. 54 hour samples were analyzed under HPLC without further dilution. Samples were stored at 4° C. prior to and during HPLC analysis.
The method quantified analyte(s) using calibration standards for ethanol (% w/v). A four point calibration including the origin is used for quantification.
Where applicable, data were analyzed using JMP software (Cary, N.C.) with Oneway ANOVA of pairs using Tukey-Kramer HSD or Dunnett's. Error bars denoting the 95% confidence level were established by multiplying the standard error of Oneway Anova analysis by 1.96.
These results demonstrate that the thermostable alpha-amylase, glucoamylase, and thermostabe protease can be used together in liquefaction to increase ethanol yield compared to Alpha-Amylase A (AAA) alone.
The present invention is defined in the claims and accompanying description. For convenience, other aspects of the present invention are presented herein by way of numbered paragraphs:
The invention described and claimed herein is not to be limited in scope by the specific aspects herein disclosed, since these aspects are intended as illustrations of several aspects of the invention. Any equivalent aspects are intended to be within the scope of this invention. Indeed, various modifications of the invention in addition to those shown and described herein will become apparent to those skilled in the art from the foregoing description. Such modifications are also intended to fall within the scope of the appended claims. In the case of conflict, the present disclosure including definitions will control.
This application is a continuation of U.S. application Ser. No. 14/362,002 filed May 30, 2014, pending, which is a 35 U.S.C. 371 national application of PCT/US2012/067380 filed Nov. 30, 2012, which claims priority or the benefit under 35 U.S.C. 119 of U.S. provisional application No. 61/566,281 filed Dec. 2, 2011, the contents of which are fully incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61566281 | Dec 2011 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 14362002 | May 2014 | US |
| Child | 16811019 | US |
