WO2013022070A1 - 連続培養によるイソプロピルアルコール製造方法 - Google Patents
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- WO2013022070A1 WO2013022070A1 PCT/JP2012/070377 JP2012070377W WO2013022070A1 WO 2013022070 A1 WO2013022070 A1 WO 2013022070A1 JP 2012070377 W JP2012070377 W JP 2012070377W WO 2013022070 A1 WO2013022070 A1 WO 2013022070A1
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- C12P7/02—Preparation of oxygen-containing organic compounds containing a hydroxy group
- C12P7/04—Preparation of oxygen-containing organic compounds containing a hydroxy group acyclic
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- the present invention relates to a method for producing isopropyl alcohol.
- Propylene is an important basic raw material for synthetic resins such as polypropylene and petrochemical products, and is widely used in automotive bumpers, food containers, films, medical equipment, and so on.
- Isopropyl alcohol produced from plant-derived materials is promising as a carbon-neutral propylene material because it can be converted to propylene through a dehydration step.
- Kyoto Protocol it is obliged to reduce greenhouse gas emissions by 5% compared to 1990 in the developed countries as a whole between 2008 and 2012.
- Carbon neutral propylene is extremely environmentally friendly due to its versatility. is important.
- Microorganisms that assimilate plant-derived materials to produce isopropyl alcohol are already known.
- International Publication No. 2009/008377 discloses that isopropyl alcohol is produced using Escherichia coli modified to produce isopropyl alcohol using glucose as a raw material while performing semi-batch culture by sequential addition of a substrate solution.
- This isopropyl alcohol-producing Escherichia coli is described as having excellent properties as a biocatalyst for industrial production because of the high selectivity of isopropyl alcohol.
- the produced isopropyl alcohol is expelled from the culture solution into the gas by gas stripping, and the isopropyl alcohol contained in the gas is recovered using water as a capture solution.
- An Erlenmeyer flask is used as the culture tank, and the specific surface area is increased by charging a small amount of culture solution of 1/10 or less of the flask volume.
- the culture solution is also evaporated, the amount of the culture solution is reduced and a long operation time of 240 hours is possible.
- acetic acid is by-produced in aerobic culture in which oxygen gas or oxygen-containing gas is used, using Escherichia coli. Incurs a decline. Therefore, in order to suppress high acetic acid accumulation, the DO-Stat method is well known in which the aeration or stirring speed is controlled so that the dissolved oxygen concentration in the culture tank is controlled to several ppm. Biotech. Bioeng. , 36, pp. In 750-758, (1990), acetic acid accumulation was 35 g / L at the 48th hour in normal half-batch culture, and 17 g / L at the 36th hour under the control by the DO-Stat method. It is reported that the Balanced DO-Stat method, in which the concentration of glucose in the culture tank is controlled by controlling the addition rate of the substrate solution in the half-batch culture in addition to the control of the oxygen concentration, does not produce acetic acid.
- An object of this invention is to provide the manufacturing method of isopropyl alcohol which manufactures isopropyl alcohol by continuous culture simply and stably for a long time with high productivity.
- Each aspect of the present invention provides the following isopropyl alcohol production method.
- [1] Ability to produce isopropyl alcohol introduced or modified by genetic recombination while continuously supplying a substrate solution containing plant-derived materials to the culture vessel and continuously removing the culture solution containing the product from the culture vessel Culturing isopropyl alcohol-producing Escherichia coli having the above-mentioned conditions under the cell growth conditions in which the Escherichia coli stably grows in the isopropyl alcohol production period and maintaining the number of cells in the culture tank; The isopropyl alcohol-producing Escherichia coli and the plant-derived raw material were brought into contact with each other to produce isopropyl alcohol, and the isopropyl alcohol-producing Escherichia coli was produced from the culture solution containing the product extracted from the culture tank.
- Recovering isopropyl alcohol; and a method for producing isopropyl alcohol [2] The production method according to [1], wherein the cell growth condition is a condition that a specific growth rate is 0.015 / h or more. [3] The production method according to [1] or [2], wherein the culture is performed at an oxygen uptake rate of 10 mmol / L / h to 250 mmol / L / h. [4] The production method according to any one of [1] to [3], wherein the cell growth condition is a condition that a specific growth rate is 0.02 / h or more.
- 6 is a graph showing changes over time in the rate of plasmid loss in Examples 2 to 4 and Comparative Example 2 of the present invention.
- 6 is a graph showing the correlation between OUR and isopropyl alcohol yield in Examples 5 to 10 of the present invention.
- 6 is a graph showing the correlation between OUR and isopropyl alcohol production rate in Examples 5 to 10 of the present invention. It is a graph which shows the time-dependent change of the isopropyl alcohol production mass in Example 5, Example 7, and Example 9 of this invention.
- It is a graph which shows the time-dependent change of the dissolved oxygen in the culture tank in Example 5 of this invention.
- It is a graph which shows the time-dependent change of the dissolved oxygen in the culture tank in Example 7 of this invention.
- a substrate solution containing a plant-derived raw material is continuously supplied to a culture vessel, and a culture solution containing a product is continuously extracted from the culture vessel, or introduced by genetic recombination.
- the isopropyl alcohol-producing Escherichia coli and the plant-derived raw material are contacted in the culture tank to produce isopropyl alcohol, and from the culture solution containing the product extracted from the culture tank, the isopropyl alcohol Recovering isopropyl alcohol produced by the production E. coli, Russia is a pill alcohol production method.
- the present invention has the ability to produce isopropyl alcohol introduced or modified by genetic recombination while continuously supplying the substrate solution into the culture vessel and withdrawing the culture solution containing the product from the culture vessel. Maintaining the number of cells of isopropyl alcohol-producing Escherichia coli, and maintaining the number of cells in the culture tank under the cell growth conditions in which the Escherichia coli stably grows during the isopropyl alcohol production period. Incubate the production E. coli.
- isopropyl alcohol is produced while continuously cultivating isopropyl alcohol-producing Escherichia coli under the predetermined cell growth conditions while maintaining the number of cells, so even in continuous culture using isopropyl alcohol-producing Escherichia coli, In addition, isopropyl alcohol can be produced with high productivity stably for a long time.
- the present invention focuses on the behavior of isopropyl alcohol-producing Escherichia coli in the isopropyl alcohol-producing period after a predetermined time from the start of culture, not at the beginning of the introduction of isopropyl alcohol-producing Escherichia coli into the culture tank.
- the culture conditions are adjusted to conditions under which the bacterial cells can stably grow. This reduces isopropyl alcohol productivity of isopropyl alcohol-producing Escherichia coli in aerobic culture without complicated control of dissolved oxygen concentration and glucose concentration in the culture tank by DO-Stat method and Balanced DO-stat method. Therefore, isopropyl alcohol can be produced over a long period of time by a simple culture method. Furthermore, isopropyl alcohol can be produced more efficiently by adjusting the aeration / stirring conditions within a range suitable for isopropyl alcohol production.
- a numerical range indicated by using “to” indicates a range including the numerical values described before and after “to” as the minimum value and the maximum value, respectively.
- the term “process” is not limited to an independent process, and is included in the term if the intended purpose of this process is achieved even when it cannot be clearly distinguished from other processes. .
- the amount of each component in the composition when there are a plurality of substances corresponding to each component in the composition, the plurality present in the composition unless otherwise specified. Means the total amount of substances. The present invention will be described below.
- the isopropyl alcohol-producing Escherichia coli according to the present invention is an Escherichia coli equipped with an isopropyl alcohol production system for producing isopropyl alcohol. Since Escherichia coli originally does not have a system for producing isopropyl alcohol, the isopropyl alcohol-producing Escherichia coli according to the present invention is an Escherichia coli having the ability to produce isopropyl alcohol introduced or modified by genetic recombination. Such an isopropyl alcohol production system may be any system as long as the target Escherichia coli produces isopropyl alcohol.
- At least a part of the isopropyl alcohol production system is introduced or modified by genetic recombination.
- introduction or modification by gene recombination a known method can be used, and examples thereof include homologous recombination into the genome and introduction by a plasmid.
- the isopropyl alcohol-producing Escherichia coli according to the present invention is preferably Escherichia coli having enhanced enzyme activity involved in the production of isopropyl alcohol.
- “By genetic recombination” means that the base sequence is changed by insertion of a foreign base sequence having a different sequence from the base sequence of the native gene, or by substitution, deletion or a combination of a part of the gene. Any occurrences may be included, for example, may be obtained as a result of mutation.
- isopropyl alcohol-producing Escherichia coli In the isopropyl alcohol-producing Escherichia coli according to the present invention, four types of enzyme activities of acetoacetate decarboxylase activity, isopropyl alcohol dehydrogenase activity, CoA transferase activity, and thiolase activity are imparted from outside the cell body, or the expression is enhanced in the cell body, or these More preferably, both are made.
- the thiolase in the present invention is classified into enzyme number 2.3.1.9 based on the report of the International Biochemical Union (I.U.B.) Enzyme Committee, and a reaction for producing acetoacetyl CoA from acetyl CoA.
- the acetoacetate decarboxylase in the present invention is classified into enzyme number 4.1.1.4 based on the report of the International Biochemical Union (I.U.B.) Enzyme Committee and produces acetone from acetoacetate.
- the generic name of the enzyme that catalyzes The isopropyl alcohol dehydrogenase in the present invention is classified into enzyme number 1.1.1.180 according to the report of the International Biochemical Union (I.U.B.) Enzyme Committee, and a reaction for producing isopropyl alcohol from acetone.
- the CoA transferase in the present invention is classified into enzyme number 2.8.3.8 based on the report of the International Biochemical Union (IUB) Enzyme Committee, and generates acetoacetate from acetoacetyl CoA.
- Examples of the isopropyl alcohol-producing Escherichia coli provided with the isopropyl alcohol production system in the present invention include the pIPA / B strain or pIaaa / B strain described in WO2009 / 008377.
- the Escherichia coli is enhanced by enhancing the expression of each gene on the genome of the Escherichia coli to enhance CoA transferase activity and thiolase activity. Enhancement of acetate decarboxylase activity includes strains in which expression of each gene is enhanced with a plasmid (sometimes referred to as pIa / B :: atoDAB strain).
- Recombinant E. coli that has effectively improved isopropyl alcohol productivity may also be used, such as inactivated GntR activity, inactivated glucose-6-phosphate isomerase (Pgi) activity, Examples include inactivated phosphogluconate dehydrogenase (Gnd) activity and enhanced glucose-6-phosphate-1-dehydrogenase (Zwf) activity.
- inactivated GntR activity inactivated glucose-6-phosphate isomerase (Pgi) activity
- examples include inactivated phosphogluconate dehydrogenase (Gnd) activity and enhanced glucose-6-phosphate-1-dehydrogenase (Zwf) activity.
- Glucose-6-phosphate isomerase (Pgi) in the present invention is classified into enzyme number 5.3.1.9 according to the report of the International Biochemical Union (I.U.B.) Enzyme Committee.
- Glucose-6-phosphate-1-dehydrogenase (Zwf) in the present invention is classified into enzyme number 1.1.1.149 according to the report of the International Biochemical Union (IUB) enzyme committee. , A generic term for enzymes that catalyze the reaction of producing D-glucono-1,5-lactone-6-phosphate from D-glucose-6-phosphate.
- the glucose-6-phosphate-1-dehydrogenase (Zwf) gene used in the present invention is based on DNA having a base sequence of a gene encoding a thiolase obtained from each of the aforementioned derived organisms or a known base sequence thereof. Synthetic DNA sequences synthesized in this way can be used.
- the phosphogluconate dehydrogenase (Gnd) in the present invention is classified into enzyme number 1.1.1.144 according to the report of the International Biochemical Union (I.U.B.) Enzyme Committee, and 6-phospho-D A generic term for enzymes that catalyze the reaction of producing D-ribulose-5-phosphate and CO 2 from gluconic acid.
- a strain obtained by inactivating the GntR activity of the pIPA / B strain, pIaa / B strain or pIa / B :: atoDAB strain or the GntR activity of the pIA / B :: atoDAB strain And a strain in which glucose-6-phosphate isomerase (Pgi) activity is inactivated and glucose-6-phosphate-1-dehydrogenase (Zwf) activity is enhanced, or GntR activity and glucose-6 of pIa / B :: atoDAB strain -A strain in which phosphate isomerase (Pgi) activity and phosphogluconate dehydrogenase (Gnd) activity are inactivated, and glucose-6-phosphate-1-dehydrogenase (Zwf) activity is enhanced.
- Pgi glucose-6-phosphate isomerase
- Zwf glucose-6-phosphate-1-dehydrogenase
- the method for producing isopropyl alcohol of the present invention is to produce isopropyl alcohol from plant-derived materials by continuous culture using the above-mentioned isopropyl alcohol-producing Escherichia coli.
- the method for producing isopropyl alcohol includes the step of continuously supplying a substrate solution containing a plant-derived raw material to a culture tank and continuously removing the culture solution containing a product from the culture tank.
- a culturing step Culturing the produced Escherichia coli under microbial growth conditions in which the Escherichia coli stably grows during the isopropyl alcohol production period and maintaining the number of microbial cells in the culture tank (hereinafter referred to as a culturing step), Producing isopropyl alcohol by contacting the isopropyl alcohol-producing Escherichia coli with plant-derived raw materials in a culture tank (hereinafter referred to as “production process”), and a culture solution containing the product extracted from the culture tank Recovering isopropyl alcohol produced by the isopropyl alcohol-producing Escherichia coli (hereinafter referred to as a recovery step); Including the.
- the culture of the isopropyl alcohol-producing E. coli in the production method is performed under cell growth conditions for stably growing the isopropyl alcohol-producing E. coli while maintaining the number of cells. Maintenance of the number of cells is achieved by supplying the substrate solution and extracting the culture solution and culturing under the cell growth conditions. As a result, the ability of the Escherichia coli to grow can be maintained even during the isopropyl alcohol production period, and as a result, production of isopropyl alcohol can be maintained even during continuous culture.
- the production process of producing isopropyl alcohol by contacting the isopropyl alcohol-producing Escherichia coli with the plant-derived raw material in a culture tank proceeds simultaneously with the culture process.
- simple culture for growing or maintaining isopropyl alcohol-producing Escherichia coli that does not depend on the cell growth conditions may not be performed simultaneously with the production process.
- the recovery step recovers isopropyl alcohol produced by isopropyl alcohol-producing Escherichia coli from a culture solution containing the product extracted from the culture tank, the recovery step is performed simultaneously with the culture step and the production step. It may not be simultaneous with the culture process and the production process.
- the culturing step is performed after the microbial cell concentration at the initial stage of culture reaches a microbial cell concentration that can stably maintain the microbial cell number.
- the “cell concentration that can stably maintain the number of cells” at the beginning of the culture is not particularly limited as long as it is a cell concentration that can maintain the growth of the E. coli after the start of continuous culture. A cell concentration corresponding to 4 g-dry cell / L is sufficient.
- continuous culture refers to “Fundamental engineering” (PF Stanbury, Society Press, 1988, p14-p15, [Principles of Fermentation Technology (Stanbury, Peter F .; Whitaker, Allan )])
- the substrate solution is continuously supplied to the culture tank (hereinafter sometimes referred to as “feed”), and the culture solution containing the product is continuously withdrawn, It means that cells are cultured and the desired product is produced from the cells.
- the amount of the culture solution equal to that of the supplied substrate solution is withdrawn from the culture vessel, so that the amount of the solution becomes substantially constant in the culture vessel.
- the feeding method is not particularly limited, and examples thereof include a chemo stat method for feeding at a constant rate and a method for intermittently feeding in order to reduce loss of a carbon source (plant-derived material).
- Examples of the intermittent feeding method include a pHstat method. In this pHstat method, when the carbon source (plant-derived raw material) is fed and stopped once the carbon source (plant-derived raw material) in the culture tank is depleted, the pH rises, the dissolved oxygen concentration rises, the exhaust carbon dioxide concentration This is a method of resuming the feed using the decrease in the index as an index.
- the term “continuous supply” or “continuous extraction” includes any form of feed method as long as the amount of liquid in the culture tank is maintained substantially constant.
- the amount of liquid in the culture tank is almost constant means that the fluctuation of the liquid volume when compared to the amount of liquid in the culture tank at the start of isopropyl alcohol production is within the range of 0 to 10% by volume. From the viewpoint of the stability of continuous operation, it is preferably in the range of 0% to 5% by volume.
- isopropyl alcohol production period refers to a period during which isopropyl alcohol is produced after cell growth reaches a steady state.
- the cells are divided into an induction period in which the cells hardly grow immediately after the start of production and a subsequent logarithmic growth phase, depending on the state of growth of the cells.
- “cell growth reaches a steady state” means a state in which, in the logarithmic growth phase, the amount of cells extracted with the withdrawal of the culture solution is balanced with the amount of newly grown cells. .
- the cell concentration in the culture tank is constant.
- the time until the cell growth reaches a steady state varies depending on the cell concentration and state at the start of the culture, the volume of the culture solution, and the concentration of the supplied carbon source, but the cell concentration at the start of the culture is 0. 0.08 g-dry cell / L, carbon source concentration of 2 g / L, and culture medium volume of 0.5 L, it is generally 24 to 48 hours after the start of culture, so the isopropyl alcohol production phase is after the start of culture. It can be 24 hours or more, preferably 48 hours or more.
- the cell growth condition means a condition for growing a cell after reaching the logarithmic growth phase. That is, in the culture system in the culture tank, at least the cell density of the isopropyl alcohol-producing Escherichia coli, the substrate solution concentration, and the product concentration are maintained within a range that does not inhibit the growth of isopropyl alcohol-producing Escherichia coli. It is necessary.
- the growth of isopropyl alcohol-producing Escherichia coli is stagnant or inhibited when at least one of an excess of cell density or an increase in the number of killed isopropyl alcohol-producing Escherichia coli, an excessive substrate solution concentration, or an excessive product concentration occurs. Therefore, the growth of isopropyl alcohol-producing E. coli cannot be maintained. As a result, the ability to produce isopropyl alcohol in the entire culture system is impaired.
- the cell growth conditions are preferably conditions that give a specific growth rate of 0.015 / h or more from the viewpoint of maintaining a steady state. If the specific growth rate is 0.015 / h or more, the cell density, substrate solution concentration and product concentration of isopropyl alcohol-producing Escherichia coli can be adjusted easily and effectively, and the isopropyl alcohol-producing Escherichia coli in the culture system can be adjusted. There is a tendency to maintain proliferation ability. From the viewpoint of increasing the production rate of isopropyl alcohol, the specific growth rate is more preferably 0.02 / h or more, further preferably 0.025 / h or more, and 0.03 / h or more. It is particularly preferred. Yes.
- the upper limit of the specific growth rate is not particularly limited, but is preferably 4 / h or less, more preferably 1 / h or less, more preferably 0.5 / h or less in consideration of the generation time of E. coli. Is more preferable, and 0.2 / h or less is particularly preferable.
- a numerical range comprised from the preferable upper limit mentioned above and a preferable lower limit what is necessary is just a combination of any one of the upper limits mentioned above and any lower limit.
- This formula 1 is applied to the specific growth rate in the present invention.
- ⁇ F / V ⁇ : Specific growth rate (h ⁇ 1 )
- F Substrate liquid supply rate (L / h) ⁇ culture solution extraction rate (L / h)
- V Liquid volume in the culture tank (L)
- the supply rate of the substrate solution and the extraction rate of the culture solution vary depending on the amount of solution in the culture tank.
- the amount of solution in the culture tank is 1 L, 0.015 L / h
- it is preferably 0.02 L / h to 4 L / h, and more preferably 0.025 L / h to 1 L / h.
- 0.015 m 3 / h can be a ⁇ 4m 3 / h, 0.02 m from the viewpoint of enhancing the production rate of isopropyl alcohol 3 / h to 4 m 3 / h is preferable, and 0.025 m 3 / h to 1 m 3 / h is more preferable.
- capacitance (size) of the said culture tank The culture tank normally used for substance production is applicable. Further, the amount of the liquid filled in the culture tank can be appropriately set according to the capacity of the culture tank used.
- the specific growth rate should just be in the said range in the isopropyl alcohol production period.
- the specific growth rate in a period other than the isopropyl alcohol production period is not particularly limited, and may be the same as or different from the above-described range. In the case where the range is different from the above range, for example, it can be set to 0.015 / h or less.
- the conditions other than the specific growth rate for maintaining the steady state include the sugar concentration of the substrate solution, the temperature in the culture tank, the pH, etc., but there is no particular limitation as long as the steady state can be maintained, and the person skilled in the art can easily guess. Conditions are acceptable.
- isopropyl alcohol is preferably aerobic culture from the viewpoint of production efficiency.
- the aerobic culture means culture performed in the presence of air or oxygen, and refers to a state of oxygen in which the oxygen uptake rate of the bacterial cells is 1 mmol / L / h or more.
- Oxygen uptake rate (OUR) indicates the amount of oxygen consumed by cells per unit culture solution per unit time. OUR obtained from the following formula 2 by the exhaust gas analysis method is used.
- OUR varies depending on the aeration amount, stirring rotation speed, temperature, pressure, pH, and the like because the amount of cells and the amount of oxygen consumed per cell change during the culture period. Therefore, in order to adjust the OUR within the above-described range, the air flow rate, the air pressure, etc. may be adjusted appropriately. A person skilled in the art can appropriately adjust the target OUR based on Equation 2 above.
- OUR is preferably 10 mmol / L / h to 250 mmol / L / h, more preferably 20 mmol / L / h to 200 mmol / L / h, and 50 mmol / L / h to 200 mmol / L.
- / H is more preferable, and 100 mmol / L / h to 180 mmol / L / h is still more preferable. If OUR is 10 mmol / L / h or more, by-products such as lactic acid and organic acids such as lactic acid and organic acid and ethanol can be reduced, and if it is 250 mmol / L / h or less, by-products such as carbon dioxide are reduced. There is a tendency to be able to.
- each condition in the culture is as follows: (1) When the amount of the liquid in the culture tank is 1 L, the substrate liquid supply rate and the culture liquid extraction rate are 0.02 L / h to 4 L / h, and the specific growth rate is 0.02 / h. 4 / h or less, and OUR is 20 mmol / L / h to 200 mmol / L / h. (2) When the amount of the liquid in the culture tank is 1 L, the substrate solution supply rate and the culture solution withdrawal rate are 0.02 L / h to 1 L / h, and the specific growth rate is 0.02 / h.
- the substrate liquid supply rate and the culture liquid extraction rate are 0.02 L / h to 0.5 L / h, and the specific growth rate is 0.02 / H or more and 0.5 / h or less, and OUR is 20 mmol / L / h to 200 mmol / L / h (4)
- the supply rate of the substrate solution and the culture The liquid withdrawal rate is 0.02 L / h to 0.5 L / h
- the specific growth rate is 0.02 / h to 0.5 / h
- the OUR is 50 mmol / L / h to 200 mmol / L.
- the substrate solution supply rate and the culture solution withdrawal rate are 0.02 L / h to 0.5 L / h, and the specific growth rate is Is 0.02 / h or more and 0.5 / h or less, and OUR is 100 mmol / L / h to 80 mmol / L / h (6)
- the substrate solution supply rate and the culture solution withdrawal rate are 0.02 L / h to 0.2 L / h
- the specific growth rate is 0.02 / h or more and 0.2 / h or less
- the OUR is 20 mmol / L / h to 200 mmol / L / h (7)
- the substrate solution supply rate and the culture solution withdrawal rate are 0.02 L / h to 0.2 L / h
- the specific growth rate is 0.02 / h to 0.2 / h
- the OUR is
- the specific growth rate is 0.025 / h or more and 0.2 / h or less
- the OUR is 20 mmol / L / h to 200 mmol / L / h (10)
- the amount of liquid in the culture tank is 1 L
- the substrate solution supply rate and the culture solution withdrawal rate are 0.025 L / h to 1 L / h
- the specific growth rate is 0.025 / h to 0.2 / h
- OUR (11) When the amount of the liquid in the culture tank is 1 L, the supply rate of the substrate solution and the extraction rate of the culture solution are 0.025 L / h to 1 L / h. h, and the specific growth rate is 0.025 / h. It is more than 0.2 / h and OUR is 100 mmol / L / h to 180 mmol / L / h.
- the culture conditions of (1) above can be applied to isopropyl alcohol production using any of the following isopropyl alcohol-producing E. coli: (A) pIPA / B strain, pIaaa / B strain, (B) a strain in which the GntR activity of the pIa / B :: atoDAB strain is inactivated, (C) a strain in which the GntR activity and glucose-6-phosphate isomerase (Pgi) activity of pIa / B :: atoDAB strain are inactivated and the glucose-6-phosphate-1-dehydrogenase (Zwf) activity is enhanced, and (D) Inactivating the GntR activity, glucose-6-phosphate isomerase (Pgi) activity, and phosphogluconate dehydrogenase (Gnd) activity of the pIa / B :: atoDAB strain to produce glucose-6-phosphate-1-dehydrogenase ( Zwf) A strain with enhanced activity
- the culture condition of (2) can be applied to isopropyl alcohol production using the isopropyl alcohol-producing Escherichia coli of any one of (a) to (d).
- the above (a) to (d) can be applied to isopropyl alcohol production using the isopropyl alcohol-producing Escherichia coli, and the culture condition of (4) is any of the above (a) to (d).
- the cultivating conditions of (5) above can be applied to the production of isopropyl alcohol using the isopropyl alcohol-producing Escherichia coli of any one of (a) to (d) above. Can be applied.
- the culture condition of (6) can be applied to isopropyl alcohol production using the isopropyl alcohol-producing Escherichia coli of any one of (a) to (d), and the culture condition of (7) is The isopropyl alcohol-producing E. coli of any of the above (a) to (d) can be applied to the production of isopropyl alcohol, and the culture condition of (8) is the same as that of any of (a) to (d) above.
- the culture condition of (9) is applied to isopropyl alcohol production using any of the isopropyl alcohol-producing Escherichia coli described in (a) to (d) above.
- the isopropyl alcohol-producing E. coli according to any one of (a) to (d) above is used as the culture condition of (10) above.
- the culture conditions of (11) can be applied in isopropyl alcohol production using either isopropyl alcohol-producing Escherichia coli of (a) ⁇ (d).
- the plant-derived raw material used in the production process is a carbon source obtained from a plant, and is not particularly limited as long as it is a plant-derived raw material.
- it refers to organs such as roots, stems, trunks, branches, leaves, flowers, seeds, plants containing them, degradation products of these plant organs, and further from plant bodies, plant organs, or degradation products thereof.
- the obtained carbon sources those that can be used as a carbon source in culture by microorganisms are also included in plant-derived materials.
- Carbon sources included in such plant-derived materials generally include sugars such as starch, sucrose, glucose, fructose, xylose, and arabinose, and herbaceous degradation products and cellulose hydrolysates that contain a large amount of these components.
- sugars such as starch, sucrose, glucose, fructose, xylose, and arabinose
- herbaceous degradation products and cellulose hydrolysates that contain a large amount of these components.
- glycerin or fatty acid derived from vegetable oil may be included in the carbon source in the present invention.
- Examples of plant-derived raw materials in the present invention can preferably include crops such as cereals, corn, rice, wheat, soybeans, sugar cane, beet, cotton, and the like, and combinations thereof. There are no particular restrictions on raw products, juice, pulverized products, and the like. Moreover, the form of only the above-mentioned carbon source may be sufficient.
- pH and temperature conditions are not particularly limited. For example, pH 4 to 9, preferably pH 6 to 8, temperature 20 ° C. to 50 ° C., preferably 25 ° C. to 42 ° C., pressure 0 to 5 MPa, preferably The culture can be performed while appropriately controlling the pH and temperature within the range of 0 to 3 MPa.
- the substrate solution supplied to the culture tank may be only a solution containing a plant-derived raw material that becomes a carbon source, or may be a mixed solution of a solution containing a plant-derived raw material that becomes a carbon source and the medium. Good. In order to perform more efficient culture, it is preferable to use a medium containing the plant-derived raw material as a substrate solution.
- the solutions in the culture tank in which continuous culture is performed may be simply referred to as “culture solution”.
- the amount of the plant-derived raw material in the substrate solution can be 60% by mass or less as a carbon source from the viewpoint of the solubility of the raw material, and from 5% by mass to isopropyl alcohol productivity. It can be 50 mass%.
- the amount of gas aeration into the culture solution is not particularly limited, but in the case of culturing in an aeration and stirring tank and using only air as the gas, generally 0.02 vvm to 3.0 vvm (vvm; aeration capacity) [ML] / liquid volume [mL] / hour [min]), preferably 0.1 vvm to 2.0 vvm.
- the amount of aeration for adjusting to a suitable OUR differs depending on the type of culture apparatus, for example, adjustment to 0.02 vvm to 10.0 vvm is an example of the amount of aeration when culturing in a bubble column.
- the method for producing isopropyl alcohol of the present invention includes a pre-culture step for bringing the isopropyl alcohol-producing Escherichia coli to be used into an appropriate number of cells or a moderately active state before the culture step for isopropyl alcohol production. May be.
- the pre-culture process may be a culture under the culture conditions normally used according to the type of isopropyl alcohol-producing bacterium.
- isopropyl alcohol produced by isopropyl alcohol-producing Escherichia coli is collected from a culture solution containing the product extracted from the culture tank (hereinafter also referred to as “extraction solution”).
- extraction solution a culture solution containing the product extracted from the culture tank
- the isopropyl alcohol which is a product can be collect
- the method for recovering isopropyl alcohol contained in the extraction liquid is not particularly limited. For example, after removing bacterial cells from the extraction liquid by centrifugation or the like, isopropyl alcohol is extracted by a normal separation method such as distillation or membrane separation. A method of separating alcohol can be employed. When the recovered isopropyl alcohol is in an aqueous solution state, the method for producing isopropyl alcohol may further include a dehydration step in addition to the recovery step. Isopropyl alcohol can be dehydrated by a conventional method.
- the culturing step may be a step of culturing isopropyl alcohol-producing Escherichia coli while supplying gas into the mixture containing the isopropyl alcohol-producing bacteria and the plant-derived raw material, and generating isopropyl alcohol using the Escherichia coli.
- the recovery process includes a gaseous isopropyl alcohol collection process for collecting isopropyl alcohol in the gas volatilized from the culture medium by supplying gas, and a recovery process for isolating isopropyl alcohol from the collected gaseous isopropyl alcohol. Including both.
- Examples of the method for collecting gaseous isopropyl alcohol include cooling condensation with a condenser, trapping with a scrubber or trap tube, and adsorption with a filter having a high isopropyl alcohol adsorption capability, such as an active fiber filter.
- a recovery method for isolating isopropyl alcohol after collection the above-described recovery method can be used as it is, and can be appropriately selected based on the collection method.
- the recovery step may include recovering not only gaseous isopropyl alcohol but also liquid isopropyl alcohol.
- a culture tank As an apparatus applicable for culturing isopropyl alcohol-producing Escherichia coli while supplying gas to the mixture, a culture tank, a supply path connected to the culture tank and supplying gas into the mixed liquid in the culture tank, And a recovery path that is connected to the culture tank and recovers the gas in the culture tank.
- the production apparatus shown in FIG. 1 of International Publication No. 2009/008377 can be given.
- an infusion tube for injecting gas from the outside of the apparatus is connected to a culture tank in which a culture medium containing isopropyl alcohol-producing bacteria and plant-derived raw materials is accommodated, and aeration can be performed on the culture medium. Yes.
- the trap tank in which the trap liquid as a capture liquid is accommodated is connected to the culture tank via a connecting tube. At this time, the gas or liquid moved to the trap tank comes into contact with the trap liquid and bubbling occurs. Thereby, the isopropyl alcohol produced
- acetone which is a precursor of isopropyl alcohol
- the obtained acetone is preferably converted to isopropyl alcohol by purification using a known method and then using a known method (for example, the method described in Japanese Patent No. 2786272). Thereby, the conversion efficiency from the sugar raw material to isopropyl alcohol can be further increased.
- FIG. 1 shows an example of a manufacturing apparatus applicable to the present invention.
- 10 is a production apparatus
- 12 is a fermentation tank
- 48 is a substrate liquid tank
- 50 is a pump
- 54 is a controller
- 56 is a sampling liquid tank
- 58 is a pump
- 62 is a trap tank.
- the production apparatus 10 includes a culture tank 12 as an aeration and agitation tank for containing microbial cells and plant-derived materials and producing isopropyl alcohol.
- the production apparatus 10 includes a mass flow meter 14 for supplying air from the air inlet to the inside of the culture tank 12, and a capacitor 16 for discharging the air in the tank from the exhaust port.
- An in-tank pressure gauge 18 and an exhaust gas analyzer 20 are connected between the condenser 16 and the exhaust port, and the pressure in the tank and the oxygen partial pressure at the outlet can be measured.
- the exhaust port is guided into the trap tank 62 and opened in the trap liquid accommodated in the trap tank 62.
- a temperature sensor 22 In the culture tank 12, a temperature sensor 22, a dissolved oxygen sensor 24 and a pH sensor 26 are arranged.
- a disc turbine blade 28 as a stirrer is disposed in the culture tank 12, and the disc turbine blade 28 is stirred and controlled by a magnetic stirrer 44.
- a band heater 38 is provided around the culture tank 12, and a cooling rod 36 is provided therein, and a circulating cooling device 40 and a cooling water channel control electromagnetic valve 42 are connected to the cooling rod 36.
- a neutralizer tank 30 filled with a pH adjusting agent is provided outside the culture tank 12.
- the neutralizer tank 30 is provided with a balance 34.
- the neutralizer tank 30 can supply a pH adjuster to the culture tank 12 via a pump 32.
- the culture tank 12 is provided with a controller 54 for controlling the whole.
- the controller 54 is connected to the temperature sensor 22, the dissolved oxygen sensor 24 and the pH sensor 26, and can input information on the temperature, DO (dissolved oxygen) and pH in the reaction solution in the culture tank 12 from each sensor. It has become.
- the controller 54 is connected to the band heater 38 and the cooling water passage control electromagnetic valve 42.
- the controller 54 controls the temperature by operating the band heater 38 and the cooling water passage control electromagnetic valve 42 according to information from various sensors, and controls the pH of the pump 32 by operating.
- the manufacturing apparatus 10 is provided with a substrate liquid tank 48 and a sampling liquid tank 56.
- the substrate liquid tank 48 and the extraction liquid tank 56 are provided with balances 52 and 60, respectively.
- the substrate liquid tank 48 contains a substrate liquid, and the substrate liquid tank 48 is connected to the culture tank 12 via a pump 50.
- the substrate solution is fed from the substrate solution tank 48 to the culture tank 12 via the pump 50.
- feed controls such as chemo stat and pH stat can be performed by the setting of the controller 54, and the pump 50 is operated by a signal from the controller 54.
- the extraction liquid tank 56 is connected to the culture tank 12 via a pump 58, and the culture liquid is extracted from the culture tank 12 by the operation of the pump 58, guided to the extraction liquid tank 56, and stored.
- the extraction port is fixed at a fixed position in the culture tank, and is controlled so that the liquid level in the culture tank is constant.
- the trap tank 62 is filled with water (trap liquid), and is maintained at a predetermined temperature, for example, 5 ° C., for vaporizing the vaporized isopropyl alcohol. Isopropyl alcohol volatilized in the culture tank 12 by aeration and stirring is guided from the culture tank 12 to the trap tank 62 by the operation of the condenser 16 and trapped in the trap tank 62.
- isopropyl alcohol can be produced over a long period of time. Isopropyl alcohol can be produced more efficiently than isopropyl alcohol.
- the productivity of isopropyl alcohol of the present invention enables continuous culture for 240 h or more, for example. In this case, for example, a production rate of 0.7 g / L / h or more is possible, and a production rate of 1.0 g / L / h or more is preferable.
- the Escherichia coli producing isopropyl alcohol is not limited to the cells used in the examples, and is not particularly limited as long as it is Escherichia coli producing isopropyl alcohol. In the description, “%” is based on mass unless otherwise specified.
- GAPDH The glyceraldehyde 3-phosphate dehydrogenase (hereinafter referred to as GAPDH) derived from Escherichia coli described in 397-440 in the base sequence information of GenBank accession number X02662 as the base sequence of the promoter necessary for expressing the above gene Promoter sequences) may be used.
- GAPDH promoter the genomic DNA of Escherichia coli MG1655 strain was used as a template, and cgctcaattgcaatgattgaccacattttccg (SEQ ID NO: 1) and agagaattcgctattttgttgtgattagagt (SEQ ID NO: 2) were obtained by the PCR method.
- a DNA fragment encoding the GAPDH promoter of about 100 bp was obtained by digestion with EcoRI.
- the resulting DNA fragment was mixed with plasmid pUC19 (GenBank accession number X02514) digested with restriction enzyme EcoRI and further treated with alkaline phosphatase, and ligase was used for binding, followed by Escherichia coli DH5 ⁇ strain competent cell ( Toyobo Co., Ltd. DNA-903) was transformed to obtain transformants that grow on LB agar plates containing ampicillin 50 ⁇ g / mL.
- the genomic DNA of Escherichia coli MG1655 strain was used as a template to obtain cgaattcgctggtggagaatatatgaaaaaaaatgacatatacaagac (SEQ ID NO: 3), and the DNA fragment obtained by the gcggtactttatttttgtctctgtgtgtggt restriction method. Digestion with EcoRI and KpnI yielded an approximately 690 bp atoD fragment.
- This DNA fragment was mixed with pUCgapP previously digested with restriction enzymes EcoRI and KpnI, ligated with ligase, transformed into Escherichia coli DH5 ⁇ competent cell (Toyobo Co., Ltd. DNA-903), and ampicillin.
- a transformant that grows on an LB agar plate containing 50 ⁇ g / mL was obtained.
- a plasmid was recovered from the obtained cells, and it was confirmed that atoD was correctly inserted. This plasmid was named pGAPatoD.
- Escherichia coli MG1655 strain can be obtained from the American Type Culture Collection.
- a primer of SEQ ID NO: 4 prepared based on the sequence information of ggtctagagcaatgattagaacgagtccccg (SEQ ID NO: 7) prepared based on the sequence information of the GAPDH promoter of Escherichia coli MG1655 strain and atoD of Escherichia coli MG1655 strain was used. Then, PCR was performed using the expression vector pGAPatoD prepared earlier as a template to obtain a DNA fragment of about 790 bp consisting of the GAPDH promoter and atoD.
- the fragments obtained above were digested with restriction enzymes PstI and XbaI, XbaI and KpnI, respectively, and this fragment was temperature-sensitive plasmid pTH18cs1 (GenBank accession number AB019610) [Hashimoto-Gotoh, T., Gene, 241, 185-191 (2000)] was mixed with a fragment obtained by digesting with PstI and KpnI, ligated with ligase, transformed into DH5 ⁇ strain, and applied to an LB agar plate containing 10 ⁇ g / ml of chloramphenicol at 30 ° C. A growing transformant was obtained. The obtained colony was cultured overnight at 30 ° C.
- acetoacetate decarboxylase gene (adc) of Clostridium bacteria is described in GenBank accession number M55392, and the isopropyl alcohol dehydrogenase gene (IPAdh) is described in GenBank accession number AF157307.
- IPAdh isopropyl alcohol dehydrogenase gene
- a base sequence of a promoter necessary for expressing the above gene group glyceraldehyde 3-phosphate dehydrogenase derived from Escherichia coli described in 397 to 440 in the base sequence information of GenBank accession number X02662 Promoter sequence (sometimes referred to as GAPDH).
- Cgagctatacatgcaatgattgacagattttccg (SEQ ID NO: 8) and cgcgcgcatgtctttttgttgatagaag (SEQ ID NO: 9) were obtained by PCR using the genomic DNA of Escherichia coli MG1655 strain as a template, and amplified by the PCR method.
- a DNA fragment corresponding to the GAPDH promoter of about 110 bp was obtained by digestion with SphI.
- the resulting DNA fragment and the plasmid pBR322 (GenBank accession number J01749) were mixed with fragments obtained by digesting with restriction enzymes NdeI and SphI, ligated with ligase, and then Escherichia coli DH5 ⁇ strain competent cell (Toyo) Spinning Co., Ltd. DNA-903) was transformed to obtain a transformant that grew on an LB agar plate containing 50 ⁇ g / mL of ampicillin. The obtained colonies were cultured overnight at 37 ° C. in an LB liquid medium containing 50 ⁇ g / mL of ampicillin, and the plasmid pBRgapP was recovered from the obtained cells.
- IPAdh * codon-modified isopropyl alcohol dehydrogenase gene
- a isopropyl alcohol dehydrogenase gene that was codon-modified based on the amino acid sequence of the isopropyl alcohol dehydrogenase gene of Clostridium beijerinckii NRRL B-593 was designed, and DNA synthesis was performed to A DNA fragment (SEQ ID NO: 10) was prepared. The sequence is described below.
- the prepared DNA fragment is used as a template, and is amplified by PCR using acatgcatgcatgaaaggtttttgcaatgctg (SEQ ID NO: 11) and acgcgtcgactataataactactgctttaa (SEQ ID NO: 12), and the obtained DNA fragment is digested with restriction enzymes SphI and SalI. A 1 kbp codon modified isopropyl alcohol dehydrogenase fragment was obtained.
- the obtained DNA fragment and the fragment obtained by digesting plasmid pUC119 with restriction enzymes SphI and SalI were mixed and ligated using ligase, and then Escherichia coli DH5 ⁇ strain competent cell (DNA-903, Toyobo Co., Ltd.). And a transformant that grows on an LB agar plate containing 50 ⁇ g / mL of ampicillin was obtained.
- the obtained colony was cultured overnight at 37 ° C. in an LB liquid medium containing 50 ⁇ g / mL of ampicillin, and the plasmid was recovered from the obtained bacterial cells to confirm that the codon-modified IPAdh * was correctly inserted.
- This plasmid was named pUC-I * .
- a fragment containing IPAdh * obtained by digesting plasmid pUC-I * with restriction enzymes SphI and EcoRI and a fragment obtained by digesting plasmid pBRgapP with restriction enzymes SphI and EcoRI are mixed and ligated using ligase. Then, Escherichia coli DH5 ⁇ strain competent cells (Toyobo Co., Ltd. DNA-903) were transformed to obtain transformants that grew on LB agar plates containing ampicillin 50 ⁇ g / mL. The obtained colonies were cultured overnight at 37 ° C.
- the plasmid was recovered from the obtained bacterial cells to confirm that the codon-modified IPAdh * was correctly inserted.
- the plasmid was named pGAP-I * .
- a codon-modified acetoacetate decarboxylase gene (adc * )
- a codon-modified acetoacetate decarboxylase gene was designed based on the amino acid sequence of the acetoacetate decarboxylase gene of Clostridium acetobutylicum ATCC824 and A DNA fragment (SEQ ID NO: 13) was prepared. The sequence is described below.
- the DNA fragment obtained by digesting the DNA by the digestion method b using the PCR method I obtained by digesting the DNA obtained by the PCR method with the DNA obtained by digesting the DNA with the digestion method b by the digestion method b with the enzyme method b A codon-modified acetoacetate decarboxylase fragment was obtained.
- the obtained DNA fragment and the previously prepared plasmid pGAP-I * were digested with restriction enzymes SalI and XbaI, mixed and ligated with ligase, and then Escherichia coli DH5 ⁇ strain competent cell ( Toyobo Co., Ltd.
- DNA-903 was transformed to obtain transformants that grew on LB agar plates containing 50 ⁇ g / mL ampicillin.
- the obtained colony was cultured overnight at 37 ° C. in an LB liquid medium containing 50 ⁇ g / mL of ampicillin, the plasmid was recovered from the obtained bacterial cells, and it was confirmed that adc * was correctly inserted. It was named pI * a * .
- Escherichia coli B strain genomic DNA (GenBank accession No. CP000819) was used as a template.
- the resulting DNA fragment was digested with restriction enzymes BamHI and XbaI to obtain an about 1500 bp glucose 6-phosphate 1-dehydrogenase fragment.
- the obtained DNA fragment and the previously prepared plasmid pI * a * were mixed with the fragments obtained by digesting with the restriction enzymes XbaI and BamHI, ligated with ligase, and then Escherichia coli DH5 ⁇ strain competent cell (Toyo Spinning Co., Ltd.
- DNA-903 was transformed to obtain transformants that grew on LB agar plates containing 50 ⁇ g / mL of ampicillin. The obtained colonies were cultured overnight at 37 ° C. in an LB liquid medium containing 50 ⁇ g / mL of ampicillin, and the plasmid pI * a * z was recovered from the obtained cells.
- nucleotide sequence region near the gene (1,650Bp) encoding pgi oligos shown in Shieijijiaattcgctatatctggctctgcacg (SEQ ID NO: 18), cagtctagagcaatactcttctgattttgag (SEQ ID NO: 19), cagtctagatcatcgtcgatatgtaggcc (SEQ ID NO: 20) and Jieishishitgcagatcatccgtcagctgtacgc (SEQ ID NO: 21) Four types of nucleotide primers were synthesized.
- the primer of SEQ ID NO: 18 has an EcoRI recognition site on the 5 ′ end side
- the primers of SEQ ID NOS: 19 and 20 have an XbaI recognition site on the 5 ′ end side
- the primer of SEQ ID NO: 21 has a PstI recognition site on the 5 ′ end side, respectively.
- a genomic DNA of Escherichia coli MG1655 strain was prepared, and the obtained genomic DNA was used as a template, and a DNA fragment of about 1.0 kb was amplified by PCR using the primer pair of SEQ ID NO: 18 and SEQ ID NO: 19. (Hereinafter sometimes referred to as pgi-L fragment).
- a DNA fragment of about 1.0 kb was amplified by PCR using the primer pair of SEQ ID NO: 20 and SEQ ID NO: 21 (hereinafter sometimes referred to as pgi-R fragment).
- a transformant was obtained that grew on an LB agar plate containing 10 ⁇ g / ml of chloramphenicol at 30 ° C.
- a plasmid was recovered from the obtained transformant, and it was confirmed that two fragments, a 5 'upstream vicinity fragment and a 3' downstream vicinity fragment of the gene encoding pgi were correctly inserted into pTH18cs1.
- the obtained plasmid was digested with XbaI, and then blunt-ended with T4 DNA polymerase.
- This DNA fragment and the pUC4K plasmid (GenBank accession number X06404) (Pharmacia) digested with EcoRI and the kanamycin resistance gene further blunt-ended with T4 DNA polymerase were ligated using T4 DNA ligase. did. Thereafter, the cells were transformed into Escherichia coli DH5 ⁇ competent cells to obtain transformants that grew at 30 ° C. on LB agar plates containing chloramphenicol 10 ⁇ g / ml and kanamycin 50 ⁇ g / ml.
- the plasmid was recovered from the obtained transformant, and it was confirmed that the kanamycin resistance gene was correctly inserted between the 5 ′ upstream neighboring fragment and the 3 ′ downstream neighboring fragment of the gene encoding pgi, and pTH18cs1-pgi and did.
- B :: atoDAB ⁇ pgi strain The resulting Escherichia coli B strain, B :: atoDAB, was transformed with plasmid pTH18cs1-pgi, and cultured overnight at 30 ° C. on an LB agar plate containing 10 ⁇ g / ml of chloramphenicol and 50 ⁇ g / ml of kanamycin. Got the body. The obtained transformant was inoculated into an LB liquid medium containing kanamycin 50 ⁇ g / ml and cultured at 30 ° C. overnight.
- ⁇ Preparation of plasmid pTH18cs1-gntR> The entire base sequence of the genomic DNA of Escherichia coli B strain is known (GenBank accession No. CP000819), and the base sequence encoding GntR is GenBank accession No.
- the genome sequence of Escherichia coli B strain described in CP000819 is described in 3509184 to 3510179.
- a genomic DNA of Escherichia coli B strain (GenBank accession No. CP000819) was prepared, and the obtained genomic DNA was used as a template, and PCR was performed with a primer pair of SEQ ID NO: 22 and SEQ ID NO: 23 to obtain about 1.0 kb.
- a DNA fragment was amplified (hereinafter sometimes referred to as a gntR-L fragment).
- a DNA fragment of about 1.0 kb was amplified by PCR using the primer pair of SEQ ID NO: 24 and SEQ ID NO: 25 (hereinafter sometimes referred to as gntR-R fragment).
- DNA fragments were separated and collected by agarose electrophoresis, and PCR was performed using the gntR-L and gntR-R fragments as a template and the primer pair of SEQ ID NO: 22 and SEQ ID NO: 25 to obtain a DNA fragment of about 2.0 kb.
- was amplified hereinafter sometimes referred to as a “gntR-LR fragment”.
- the gntR-LR fragment was separated and collected by agarose electrophoresis, digested with EcoRI, mixed with an EcoRI digest of the temperature sensitive plasmid pTH18cs1 (GenBank accession number AB019610), reacted with T4 DNA ligase, and then Escherichia coli.
- DH5 ⁇ competent cells manufactured by Toyobo Co., Ltd.
- Toyobo Co., Ltd. were transformed to obtain transformants that grew at 30 ° C. on LB agar plates containing 10 ⁇ g / ml of chloramphenicol.
- a plasmid was recovered from the obtained transformant, and it was confirmed that the gntLR fragment was correctly inserted into pTH18cs1, and this plasmid was designated as pTH18cs1-gntR.
- the primer of SEQ ID NO: 26 has an NdeI recognition site on the 5 ′ end side
- the primers of SEQ ID NO: 27 and SEQ ID NO: 28 have a SacI recognition site on the 5 ′ end side
- the primer of SEQ ID NO: 29 has a BamHI recognition site on the 5 ′ end side.
- a genomic DNA (GenBank accession No. CP000819) of Escherichia coli B strain was prepared, and a DNA fragment of about 1.0 kb was amplified by PCR using the primer pair of SEQ ID NO: 26 and SEQ ID NO: 27 (hereinafter referred to as gnd-). Sometimes called L fragment).
- gnd-R fragment a DNA fragment of about 1.0 kb was amplified by PCR using the primer pair of SEQ ID NO: 28 and SEQ ID NO: 29 (hereinafter sometimes referred to as gnd-R fragment).
- the plasmid was recovered from the obtained transformant, and it was confirmed that two fragments of the 5 ′ upstream neighboring fragment and the 3 ′ downstream neighboring fragment of the gene encoding gnd were correctly inserted into pTH18cs1, and pTH18cs1-gnd and did.
- B :: atoDAB ⁇ pgi ⁇ gnd strain The resulting Escherichia coli B strain, B :: atoDAB ⁇ pgi strain, was transformed with plasmid pTH18cs1-gnd, and cultured on an LB agar plate containing 10 ⁇ g / ml of chloramphenicol at 30 ° C. overnight. Obtained. The obtained transformant was inoculated into an LB liquid medium containing 10 ⁇ g / ml of chloramphenicol and cultured at 30 ° C. overnight.
- B :: atoDAB ⁇ pgi ⁇ gnd ⁇ gntR strain The prepared B :: atoDAB ⁇ pgi ⁇ gnd strain competent cell was transformed with the plasmid pTH18cs1-gntR, and cultured on an LB agar plate containing 10 ⁇ g / ml of chloramphenicol at 30 ° C. overnight to obtain a transformant. It was. The obtained transformant was inoculated into an LB liquid medium containing 10 ⁇ g / ml of chloramphenicol and cultured at 30 ° C. overnight.
- a strain capable of amplifying an about 2.0 kbp fragment due to deletion of the gntR gene was selected by PCR, and the obtained strain was selected as B :: atoDAB ⁇ pgi ⁇ gnd. It was named ⁇ gntR strain.
- Example 1 Continuous culture of isopropyl alcohol ⁇ Pre-culture> LB medium (Difco TM LB Broth Miller) was placed in an Erlenmeyer flask in an amount 1/5 of the flask volume, and autoclaved at 121 ° C. for 15 minutes. The autoclave-sterilized medium was inoculated with 0.1 vol% of the Escherichia coli pGAPIaa / B strain described in WO2009 / 008377. Shaking culture was performed for 16 hours in a constant temperature room at 35 ° C. to grow seed cells.
- isopropyl alcohol was produced using the production apparatus 10 shown in FIG.
- the culture tank 12 was 5 L, and the substrate liquid tank 48 and the extraction liquid tank 56 were 20 L.
- the trap tank 62 was filled with 20 L of water and kept at 5 ° C.
- a culture tank containing 750 mL of an autoclave-sterilized medium having the composition shown in Table 1 was inoculated with 38 mL of the preculture solution.
- a substrate solution having the composition shown in Table 2 was fed at 11 g / h until 8 hours after the start of the culture, and thereafter at a feed rate of 22.5 g / h.
- the extraction speed of the culture solution in the culture tank 12 was the same as the feed speed, and the amount of the culture solution in the culture tank 12 was controlled to 750 mL.
- the specific gravity of the substrate solution is 1 g / cm 3 and the steady state specific growth rate is 0.03 / h.
- the 48th hour after the start of the culture is the time when the number of bacteria was determined based on the turbidity by OD660 and the number of bacteria became constant, so that it was determined to be in the isopropyl alcohol production period.
- the isopropyl alcohol concentration in the obtained culture broth was measured by gas chromatography according to a conventional method.
- the cell mass was calculated as [g-drydcell]. The results are shown in FIGS.
- Example 2 [Preparation of Isopropyl Alcohol Producing Escherichia coli] Pre-culture was performed in the same manner as in Example 1 using the pI * a * z / B :: atoDAB ⁇ pgi ⁇ gnd ⁇ gntR strain. Next, isopropyl alcohol was produced using the production apparatus 10 shown in FIG.
- the culture tank 12 was a 1-L container, and the substrate liquid tank 48 and the extraction liquid tank 56 were 4 L-volume.
- the trap tank 62 was filled with 4 L of water and maintained at 5 ° C.
- a culture tank containing 500 mL of an autoclave-sterilized medium having the composition shown in Table 1 was inoculated with 25 mL of the preculture solution.
- the amount of the culture solution was controlled to be 500 mL.
- a substrate solution having the composition shown in Table 4 was fed at a rate of 5 g / h until 8 hours after the start of culture, and thereafter at a feed rate of 60.6 g / h.
- the specific gravity of the substrate solution was 1 g / cm 3 and the steady state specific growth rate was 0.1212 / h.
- the isopropyl alcohol concentration and the cell mass in the culture solution were obtained. The results are shown in FIGS. 4 and 5 and Tables 5 and 6.
- LB Broth agar medium 1 and LB Broth agar medium 2 containing 100 ⁇ L / mL ampicillin were prepared, and the diluted culture solution in the culture tank was applied and kept at 30 ° C. The number of colonies after 24 hours was counted.
- Example 3 Continuous culture was performed in the same manner as in Example 2 except that the feed rate after 8 hours was changed to 23.5 g / h. At this time, the specific growth rate in the steady state was 0.0470 / h.
- the isopropyl alcohol concentration and the cell mass in the culture solution were obtained, and in the same manner as in Example 2, the plasmid dropout rate was obtained. The results are shown in FIGS. 4, 5, 6, Table 5 and Table 6.
- Example 4 Continuous culture was performed in the same manner as in Example 2 except that the feed rate after 8 hours was changed to 12.4 g / h. At this time, the specific growth rate in the steady state was 0.0247 / h. In the same manner as in Example 1, the isopropyl alcohol concentration and the cell mass in the culture solution were obtained, and in the same manner as in Example 2, the plasmid dropout rate was obtained. The results are shown in FIGS. 4, 5, 6, Table 5 and Table 6.
- the total mass of isopropyl alcohol is a value obtained by dividing the total mass of isopropyl alcohol by the amount of culture solution in the culture tank during the operation time (here, 0.5 L).
- the production rate is an average isopropyl alcohol production rate calculated from the isopropyl alcohol integrated mass, and the same applies hereinafter.
- FIG. 4 black circles indicate Example 2
- white circles indicate Example 3
- black triangles indicate Example 4
- white triangles indicate Comparative Example 2.
- FIG. 4 specific growth rate of 0.0147 [h ⁇ 1 ]
- the number of bacterial cells in the culture tank was not maintained or propagated after 48 hours (FIG. 4), and the steady state was not reached. It was also found that isopropyl alcohol production stopped after 96 hours (FIG. 5). It is clear from FIG. 6 that the plasmid shedding rate at this time is 80% or more (see FIG. 6).
- Example 2 to Example 4 in which the culture was performed under a condition where the specific growth rate was higher than 0.0147 [h ⁇ 1 ], the cell growth reached a steady state, and continuous operation for a long time was possible. Isopropyl alcohol could be produced stably.
- Example 5 The substrate solution composition shown in Table 7 was changed, and the stirring rotation speed was changed to 500 rpm. Otherwise, continuous culture was performed in the same manner as in Example 2.
- the value of the mass flow meter 14 was adopted as the air flow rate at the air inlet, and the value of the mass flow meter 14 was adopted as the range where the decrease due to oxygen consumption was negligible.
- the values of the pressure gauge 18 in the tank were adopted for the air pressure at the air inlet and outlet.
- the absolute temperature at the air inlet and outlet is the value of the temperature sensor 22 in the tank.
- the oxygen mole fraction at the air inlet was 0.209, and the value of the exhaust gas analyzer 20 was adopted as the oxygen mole fraction at the outlet.
- the value of the dissolved oxygen sensor 24 in the tank was adopted.
- the air flow rate at the air inlet and outlet was 1.0 L / min
- the air pressure at the air inlet and outlet was normal pressure
- the temperature of the air inlet and outlet was 30 ° C.
- OUR the average value in the steady state after the 24th hour of the value calculated according to the above-described equation 2
- the calculated OUR of this example was 50 mmol / L / h.
- the isopropyl alcohol concentration in the culture solution was obtained, and the isopropyl alcohol yield and the isopropyl alcohol production rate with respect to the calculated OUR were determined.
- the results are shown in FIGS. 7, 8, 9, 10, Table 8 and Table 9.
- the specific growth rate was 0.1200 / h.
- Example 6 The continuous rotation was performed in the same manner as in Example 5 except that the stirring rotation speed was changed to 600 rpm. At this time, the calculated OUR was 107 mmol / L / h. Further, in the same manner as in Example 5, the isopropyl alcohol concentration in the culture broth was obtained, and the isopropyl alcohol yield and the isopropyl alcohol production rate with respect to the calculated OUR were determined. The results are shown in FIGS. 7 and 8 and Table 8. The steady state specific growth rate was 0.1203 / h.
- Example 7 Continuous culture was performed in the same manner as in Example 5 except that the stirring rotation speed was 700 rpm. At this time, the calculated OUR was 153 mmol / L / h. Further, in the same manner as in Example 5, the isopropyl alcohol concentration in the culture broth was obtained, the isopropyl alcohol yield and the isopropyl alcohol production rate with respect to the calculated OUR were determined, and the dissolved oxygen concentration was obtained. The results are shown in FIGS. 7, 8, 9, 11, Table 8 and Table 9. The steady state specific growth rate was 0.1200 / h.
- Example 8 Continuous culture was performed in the same manner as in Example 5 except that the stirring speed was 800 rpm. At this time, the calculated OUR was 187 mmol / L / h. Further, in the same manner as in Example 5, the isopropyl alcohol concentration in the culture broth was obtained, and the isopropyl alcohol yield and the isopropyl alcohol production rate with respect to the calculated OUR were determined. The results are shown in FIGS. The steady state specific growth rate was 0.1210 / h.
- Example 9 Continuous culture was performed in the same manner as in Example 5 except that the stirring rotation speed was 900 rpm. At this time, the calculated OUR was 196 mmol / L / h. Further, in the same manner as in Example 5, the isopropyl alcohol concentration in the culture broth was obtained, the isopropyl alcohol yield and the isopropyl alcohol production rate with respect to the calculated OUR were determined, and the dissolved oxygen concentration was obtained. The results are shown in FIG. 7, FIG. 8, FIG. 9, FIG. The steady state specific growth rate was 0.1210 / h.
- Example 10 Continuous culture was performed in the same manner as in Example 5 except that the stirring rotation speed was 400 rpm. At this time, the calculated OUR was 20 mmol / L / h. Further, in the same manner as in Example 5, the isopropyl alcohol concentration in the culture broth was obtained, and the isopropyl alcohol yield and the isopropyl alcohol production rate with respect to the calculated OUR were determined. The results are shown in FIGS. 7 and 8 and Table 8. The steady state specific growth rate was 0.1200 / h.
- FIG. 9 the time-dependent change of the integrated mass of isopropyl alcohol is shown in FIG.
- black circles indicate Example 5
- black diamonds indicate Example 7, and black triangles indicate Example 9.
- FIG. 10 The time-dependent changes in the dissolved oxygen concentration in the culture tank are shown in FIG. 10 for Example 5, FIG. 11 for Example 7, and FIG. 12 for Example 9.
- the acetic acid production rate is low and the isopropyl alcohol production rate is kept high even if the dissolved oxygen concentration in the culture tank is 0 ppm or the dissolved oxygen concentration fluctuates around 0-1 ppm.
- Example 11 The composition of the substrate solution was changed to Table 10, and the substrate solution was fed at 5 g / h until 8 hours after the start of culture, and thereafter fed at an average feed rate of 42 g / h.
- the pHstat method was adopted in order to minimize the outflow of the substrate to the extraction liquid.
- continuous culture was performed in the same manner as in Example 2.
- OUR was 200 mmol / L / h.
- the isopropyl alcohol concentration and the microbial mass in the culture solution were obtained, and the plasmid dropout rate was obtained in the same manner as in Example 2.
- the results are shown in FIG. 13, FIG. 14, Table 11 and Table 12.
- the specific growth rate was 0.083 / h.
- the cell mass in the culture tank was constant after 24 hours, and the average cell concentration from 24 hours to 840 hours was 12 g-dry cell / L. From FIG. 14, it can be seen that 35 days of continuous operation is possible by optimizing the fermentation conditions.
- the integrated mass of isopropyl alcohol was 1315 g / L / 840h, and the production rate was 1.57 g / L / h. Furthermore, the production rate was 2.40 g / L / h by the sixth day and 2.15 g / L / h by the tenth day.
- the plasmid dropout rate of recombinant E. coli was as low as 20% or less until the 27th day, 47% on the 29th day and 77% on the 35th day, and the plasmid was retained for a long time. It has been found.
- isopropyl alcohol can be produced easily and stably for a long time with high production efficiency by continuous culture using isopropyl alcohol-producing Escherichia coli.
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Abstract
Description
植物由来原料から製造されたイソプロピルアルコールは、脱水工程を経てプロピレンに変換できることから、カーボンニュートラルなプロピレンの原料として有望である。京都議定書によって2008年から2012年の間に先進国全体で温室効果ガス排出量を1990年比で5%削減することが義務付けられている現在、カーボンニュートラルなプロピレンはその汎用性から地球環境上極めて重要である。
例えば国際公開2009/008377号には、グルコースを原料としてイソプロピルアルコールを生産するように改変された大腸菌を用いて、基質液の逐次添加による半回分式培養を行いながらイソプロピルアルコールを生産することが開示されている。このイソプロピルアルコール生産大腸菌は、イソプロピルアルコールの選択性が高いことから工業生産用生体触媒として優れた性質を持つと記載されている。
このために、例えば、生物化学工学会誌,71(1),pp.9-14,(1993)には、土壌から分離したClostridium属に属する微生物を用いたブタノール・イソプロピルアルコールの連続培養が報告されている。ここでは、30日間の連続培養を行っているが、本微生物は遺伝子組換えによる改変を行っておらず、イソプロピルアルコールの選択率は約25%と低い。
菌体増殖の観点においても、半回分培養では16時間から48時間程度で菌体の増殖がほとんど停止し、培養時間が更に長くなるとイソプロピルアルコールの生産速度は低下することが知られている。J.Biosci.Bioeng.,110(6),pp.696-701,(2010)に記載された技術においても、240時間以降は濃縮栄養培地を添加してもイソプロピルアルコールの生産が停止することが報告されている。
本発明は、連続培養によってイソプロピルアルコールを簡便にかつ長時間安定的に高い生産性で製造するイソプロピルアルコールの製造方法を提供することを目的とする。
〔1〕 植物由来原料を含有する基質液を培養槽に連続的に供給し且つ生産物を含む培養液を該培養槽から連続的に抜き取りながら、遺伝子組換えにより導入又は改変したイソプロピルアルコール生産能力を保有するイソプロピルアルコール生産大腸菌を、イソプロピルアルコール生産期に該大腸菌が安定的に増殖する菌体増殖条件で、且つ前記培養槽内の菌体数を維持して、培養することと、前記培養槽内で前記イソプロピルアルコール生産大腸菌と植物由来原料とを接触させて、イソプロピルアルコールを生産することと、前記培養槽から抜き取られた前記生産物を含む培養液から、前記イソプロピルアルコール生産大腸菌により生産されたイソプロピルアルコールを回収することと、を含むイソプロピルアルコール製造方法。
〔2〕 前記菌体増殖条件が、比増殖速度0.015/h以上となる条件である〔1〕記載の製造方法。
〔3〕 前記培養を、10mmol/L/h~250mmol/L/hの酸素摂取速度で行う〔1〕又は〔2〕に記載の製造方法。
〔4〕 前記菌体増殖条件が、比増殖速度0.02/h以上となる条件である〔1〕~〔3〕のいずれかに記載の製造方法。
また、例えば、Biotech.Bioeng.,36,pp.750-758,(1990)に開示された技術では、大腸菌を用いた運転時間2日の好気による半回分培養が行われている。酸素摂取速度に関する記載はないものの、ファーメンターを用いて空気又は純酸素を1vvmで通気、攪拌回転数は最大1350rpmであり、酸素摂取速度が高いことは当該業者であれば、容易に推測できる。培養2日程度ではプラスミドの脱落の影響はほとんどないものの、好気培養では酢酸の高蓄積による増殖阻害や目的物の生産速度が低下するため、DO-Stat法やBalanced DO-stat法などにより溶存酸素濃度を制御しなければならないことが記載されている。
更に通気・攪拌条件をイソプロピルアルコール生産に適した範囲内に調整することによって、より効率よくイソプロピルアルコールを製造することができる。
本明細書において「工程」との語は、独立した工程だけでなく、他の工程と明確に区別できない場合であっても本工程の所期の目的が達成されれば、本用語に含まれる。
また、本発明において、組成物中の各成分の量について言及する場合、組成物中に各成分に該当する物質が複数存在する場合には、特に断らない限り、組成物中に存在する当該複数の物質の合計量を意味する。
以下、本発明について説明する。
本発明におけるアセト酢酸デカルボキシラーゼとは、国際生化学連合(I.U.B.)酵素委員会報告に準拠した酵素番号4.1.1.4に分類され、アセト酢酸からアセトンを生成する反応を触媒する酵素の総称を指す。
本発明におけるイソプロピルアルコールデヒドロゲナーゼとは、国際生化学連合(I.U.B.)酵素委員会報告に準拠した酵素番号1.1.1.80に分類され、アセトンからイソプロピルアルコールを生成する反応を触媒する酵素の総称を指す。
本発明におけるCoAトランスフェラーゼとは、国際生化学連合(I.U.B.)酵素委員会報告に準拠した酵素番号2.8.3.8に分類され、アセトアセチルCoAからアセト酢酸を生成する反応を触媒する酵素の総称を指す。
前記イソプロピルアルコール製造方法は、具体的には、植物由来原料を含有する基質液を培養槽に連続的に供給し且つ生産物を含む培養液を該培養槽から連続的に抜き取りながら、前記イソプロピルアルコール生産大腸菌を、イソプロピルアルコール生産期に該大腸菌が安定的に増殖する菌体増殖条件で、且つ前記培養槽内の菌体数を維持して、培養すること(以下、培養工程という)と、前記培養槽内で前記イソプロピルアルコール生産大腸菌と植物由来原料とを接触させて、イソプロピルアルコールを生産すること(以下、「生産工程」という)と、前記培養槽から抜き取られた前記生産物を含む培養液から、前記イソプロピルアルコール生産大腸菌により生産されたイソプロピルアルコールを回収すること(以下、回収工程という)と、を含む。
また、前記回収工程は、前記培養槽から抜き取られた前記生産物を含む培養液から、イソプロピルアルコール生産大腸菌により生産されたイソプロピルアルコールを回収するものであるため、前記培養工程及び生産工程と同時に行ってもよく、培養工程及び生産工程と同時でなくてもよい。
培養初期の「安定的に菌体数を維持できる菌体濃度」とは、連続培養開始後に前記大腸菌の増殖が維持できる菌体濃度であれば特に制限は無いが、例えば、乾燥質量として2.4g-dry cell/Lに相当する菌体濃度であれば十分である。
本発明における「連続的な供給」又は「連続的な抜き取り」との用語には、培養槽内の液量がほぼ一定に維持されている限り、如何なる態様のフィード方法も包含される。なお、「培養槽内の液量がほぼ一定」とは、イソプロピルアルコール製造開始における培養槽内の液量と比較したときの液量の変動が0容量%~10容量%の範囲内を意味し、連続運転の安定性の観点から好ましくは0容量%~5容量%の範囲内を意味する。
(式1)
μ=F/V
μ:比増殖速度(h-1)
F:基質液の供給速度(L/h)≒培養液の抜き取り速度(L/h)
V:培養槽中の液量(L)
前記培養槽の容量(大きさ)としては、特に制限はなく、物質生産に通常用いられる培養槽が適用可能である。また、培養槽に充填される液の液量は、用いられる培養槽の容量に応じて適宜設定可能である。
また、定常状態を保つ比増殖速度以外の条件としては、基質液の糖濃度や培養槽内の温度、pHなど挙げられるが、定常状態が維持できれば特に制限はなく、当該業者が容易に類推できる条件でよい。
本発明に製造方法では、イソプロピルアルコールを生産効率の観点から、好気培養であることが好ましい。本発明において好気培養とは、空気または酸素がある状態で行う培養を意味し、菌体の酸素摂取速度が1mmol/L/h以上となる酸素がある状態を指す。酸素摂取速度(oxygen uptake rate:OUR)とは、単位時間、単位培養液あたりに菌体が消費する酸素の量を示す。OURは排ガス分析法によって以下の式2から求めたものを用いる。
(式2)
OUR=7.22×106/V×(QiPiyi/Ti-QoPoyo/To)
V:培養槽中の液量(L)
Qi及びQo:空気入り口及び出口における空気流量(L/min)
Pi及びPo:空気入り口及び出口における空気圧(MPa)
Ti及びTo:空気入り口及び出口における絶対温度(K)
yi及びyo:空気入り口及び出口における酸素のモル分率
なお上記式2に基づいてOURを求める際に、空気流量、空気圧、絶対温度の値が空気入り口及び出口で無視できる程度の差しかないときには1カ所での測定値を適用してもよい。また、本発明でいう圧力及び空気圧は、絶対圧力を指す。
本発明において、OURは10mmol/L/h~250mmol/L/hであることが好ましく、20mmol/L/h~200mmol/L/hであることがより好ましく、50mmol/L/h~200mmol/L/hであることがより好ましく、100mmol/L/h~180mmol/L/hであることが更に好ましい。OURが10mmol/L/h以上であれば、乳酸や有機酸などの有機酸やエタノールなどの副生物をより少なくでき、250mmol/L/h以下であれば、二酸化炭素などの副生物をより少なくできる傾向がある。結果として、OURが10mmol/L/h以上、250mmol/L/h以下の範囲であれば、副生物の生成量の低減により、イソプロピルアルコール収率やイソプロピルアルコール生産速度が向上する傾向がある。
(1) 培養槽中の液量を1Lとしたときに、基質液の供給速度及び培養液の抜き取り速度が0.02L/h~4L/hであり、前記比増殖速度が0.02/h以上4/h以下であり、OURが20mmol/L/h~200mmol/L/hである。
(2) 培養槽中の液量を1Lとしたときに、基質液の供給速度及び培養液の抜き取り速度が0.02L/h~1L/hであり、前記比増殖速度が0.02/h以上1/h以下であり、OURが20mmol/L/h~200mmol/L/hである。
(3) 培養槽中の液量を1Lとしたときに、基質液の供給速度及び培養液の抜き取り速度が0.02L/h~0.5L/hであり、前記比増殖速度が0.02/h以上0.5/h以下であり、OURが20mmol/L/h~200mmol/L/hである
(4) 培養槽中の液量を1Lとしたときに、基質液の供給速度及び培養液の抜き取り速度が0.02L/h~0.5L/hであり、前記比増殖速度が0.02/h以上0.5/h以下であり、OURが50mmol/L/h~200mmol/L/hである
(5) 培養槽中の液量を1Lとしたときに、基質液の供給速度及び培養液の抜き取り速度が0.02L/h~0.5L/hであり、前記比増殖速度が0.02/h以上0.5/h以下であり、OURが100mmol/L/h~180mmol/L/hである
(6) 培養槽中の液量を1Lとしたときに、基質液の供給速度及び培養液の抜き取り速度が0.02L/h~0.2L/hであり、前記比増殖速度が0.02/h以上0.2/h以下であり、OURが20mmol/L/h~200mmol/L/hである
(7) 培養槽中の液量を1Lとしたときに、基質液の供給速度及び培養液の抜き取り速度が0.02L/h~0.2L/hであり、前記比増殖速度が0.02/h以上0.2/h以下であり、OURが50mmol/L/h~200mmol/L/hである
(8) 培養槽中の液量を1Lとしたときに、基質液の供給速度及び培養液の抜き取り速度が0.02L/h~0.2L/hであり、前記比増殖速度が0.02/h以上0.2/h以下であり、OURが100mmol/L/h~180mmol/L/hである
(9) 培養槽中の液量を1Lとしたときに、基質液の供給速度及び培養液の抜き取り速度が0.025L/h~1L/hであり、前記比増殖速度が0.025/h以上0.2/h以下であり、OURが20mmol/L/h~200mmol/L/hである
(10) 培養槽中の液量を1Lとしたときに、基質液の供給速度及び培養液の抜き取り速度が0.025L/h~1L/hであり、前記比増殖速度が0.025/h以上0.2/h以下であり、OURが50mmol/L/h~200mmol/L/hである
(11) 培養槽中の液量を1Lとしたときに、基質液の供給速度及び培養液の抜き取り速度が0.025L/h~1L/hであり、前記比増殖速度が0.025/h以上0.2/h以下であり、OURが100mmol/L/h~180mmol/L/hである
(a)pIPA/B株、pIaaa/B株、
(b)pIa/B::atoDAB株のGntR活性を不活化した株、
(c)pIa/B::atoDAB株のGntR活性とグルコース-6-リン酸イソメラーゼ(Pgi)活性を不活化し、グルコース-6-リン酸-1-デヒドロゲナーゼ(Zwf)活性を強化した株、及び
(d)pIa/B::atoDAB株のGntR活性とグルコース-6-リン酸イソメラーゼ(Pgi)活性とホスホグルコン酸デヒドロゲナーゼ(Gnd)活性を不活化し、グルコース-6-リン酸-1-デヒドロゲナーゼ(Zwf)活性を強化した株。
また同様に、上記(2)の培養条件を、上記(a)~(d)のいずれかのイソプロピルアルコール生産大腸菌を用いたイソプロピルアルコール生産に適用することができ、上記(3)の培養条件を、上記(a)~(d)のいずれかのイソプロピルアルコール生産大腸菌を用いたイソプロピルアルコール生産に適用することができ、上記(4)の培養条件を、上記(a)~(d)のいずれかのイソプロピルアルコール生産大腸菌を用いたイソプロピルアルコール生産に適用することができ、上記(5)の培養条件を、上記(a)~(d)のいずれかのイソプロピルアルコール生産大腸菌を用いたイソプロピルアルコール生産に適用することができる。
また同様に、(6)の培養条件を、上記(a)~(d)のいずれかのイソプロピルアルコール生産大腸菌を用いたイソプロピルアルコール生産に適用することができ、上記(7)の培養条件を、上記(a)~(d)のいずれかのイソプロピルアルコール生産大腸菌を用いたイソプロピルアルコール生産に適用することができ、上記(8)の培養条件を、上記(a)~(d)のいずれかのイソプロピルアルコール生産大腸菌を用いたイソプロピルアルコール生産に適用することができ、(9)の培養条件を、上記(a)~(d)のいずれかのイソプロピルアルコール生産大腸菌を用いたイソプロピルアルコール生産に適用することができ、上記(10)の培養条件を、上記(a)~(d)のいずれかのイソプロピルアルコール生産大腸菌を用いたイソプロピルアルコール生産に適用することができ、上記(11)の培養条件を、上記(a)~(d)のいずれかのイソプロピルアルコール生産大腸菌を用いたイソプロピルアルコール生産に適用することができる。
イソプロピルアルコール生産大腸菌の培養に用いられる培地としては、炭素源、窒素源、無機イオン、及びイソプロピルアルコールを生産するために微生物が要求する有機微量元素、核酸、ビタミン類等が含まれた通常用いられる培地であれば特に制限はない。
本発明の培養に際して、pH、温度条件は特別の制限はなく、例えばpH4~9、好ましくはpH6~8、温度20℃~50℃、好ましくは25℃~42℃、圧力0~5MPa、好ましくは0~3MPaの範囲内でpHと温度を適切に制御しながら培養することができる。
培養槽へ供給される場合、基質液における植物由来原料の量は、該原料の溶解度の観点から、炭素源として60質量%以下とすることができ、イソプロピルアルコール生産性の観点から5質量%~50質量%とすることができる。
前記抜取り液中に含まれるイソプロピルアルコールを回収する方法としては、特に制限はないが、例えば、前記抜取り液から菌体を遠心分離などで除去した後、蒸留や膜分離等通常の分離方法でイソプロピルアルコールを分離する方法が採用できる。回収されたイソプロピルアルコールが水溶液の状態である場合には、本イソプロピルアルコールの製造方法は、回収工程に加えて、脱水工程を更に含んでいてもよい。イソプロピルアルコールの脱水は、常法により行なうことができる。
なお、この形態においては、ガス状イソプロピルアルコールを収集工程と共に、液状イソプロピルアルコールを収集する工程を含めてもよい。この場合には、前記回収工程は、ガス状イソプロピルアルコールのみならず液状イソプロピルアルコールを回収することを含むものであってもよい。
このような装置としては、例えば、国際公開第2009/008377号パンフレットの図1に示される生産装置を挙げることができる。
この生産装置では、イソプロピルアルコール生産細菌と植物由来原料とを含む培地が収容された培養槽に、装置外部から気体を注入するための注入管が連結され、培地に対してエアレーションが可能となっている。
これにより、培養槽で通気培養により生成したイソプロピルアルコールは、エアレーションによって蒸散して培地から容易に分離される共に、トラップ槽においてトラップ液に捕捉される。この結果、イソプロピルアルコールを、より精製された形態で連続的に且つ簡便に生産することができる。
製造装置10には、菌体及び植物由来原料を収容してイソプロピルアルコールの生産を行うための、通気攪拌槽としての培養槽12が備えられている。製造装置10には、空気入り口から空気を培養槽12の内部に供給するためのマスフローメータ14と、槽内の空気を排気口から排出するためのコンデンサ16が備えられている。コンデンサ16と排気口との間には、槽内圧力計18及び排ガス分析計20が連結され、槽内の圧力及び出口の酸素モル分圧をそれぞれ測定可能になっている。また、排気口は、トラップ槽62の内部に誘導されて、トラップ槽62の内部に収容されたトラップ液中で開口している。培養槽12には、温度センサ22、溶存酸素センサ24及びpHセンサ26がそれぞれ配置されている。また、培養槽12には、攪拌機としてのディスクタービン翼28が配置されており、ディスクタービン翼28はマグネッティックスターラ44で攪拌・制御される。
また、培養槽12の周囲にはバンドヒータ38、内部には冷却棒36が備えられており、冷却棒36には循環冷却装置40、冷却水路制御用電磁弁42が接続されている。培養槽12の外側には、pH調整剤を充填した中和剤槽30が設けられている。中和剤槽30には天秤34が備えられている。中和剤槽30は、ポンプ32を介して培養槽12へpH調整剤を供給可能となっている。
培養槽12には、全体を制御するコントローラ54が備えられている。コンロトーラ54は、温度センサ22、溶存酸素センサ24及びpHセンサ26に連結されて、それぞれのセンサから、培養槽12内の反応液中の温度、DO(溶存酸素)及びpHの各情報が入力可能になっている。また、コントローラ54は、バンドヒータ38と冷却水路制御用電磁弁42に連結されている。コントローラ54は、各種センサからの情報に応じて、バンドヒータ38、冷却水路制御用電磁弁42を作動させて温度を制御すると共に、ポンプ32を作動によりpH制御するようになっている。
トラップ槽62には水(トラップ液)が充填されており、気化したイソプロピルアルコールが液化するための所定の温度、例えば5℃に維持されている。通気・攪拌により培養槽12内に揮発するイソプロピルアルコールは、コンデンサ16が作動することにより培養槽12からトラップ槽62に誘導されて、トラップ槽62でトラップされる。
なお、記載中の「%」は特に断らない限り、質量基準である。
<B::atoDAB株の作製>
エシェリヒア・コリMG1655株のゲノムDNAの全塩基配列は公知であり(GenBank accession number U00096)、エシェリヒア・コリMG1655株のCoAトランスフェラーゼ αサブユニットをコードする遺伝子(以下、atoDと略することがある)の塩基配列も報告されている。すなわちatoDはGenBank accession number U00096に記載のエシェリヒア・コリMG1655株ゲノム配列の2321469~2322131に記載されている。
なおエシェリヒア・コリMG1655株はアメリカンタイプカルチャーコレクションより入手することができる。
なお、エシェリシア・コリB株(ATCC11303)は細胞・微生物・遺伝子バンクであるアメリカンタイプカルチャーコレクションより入手することができる。
クロストリジウム属細菌のアセト酢酸デカルボキシラーゼ遺伝子(adc)はGenBank accession number M55392に、イソプロピルアルコールデヒドロゲナーゼ遺伝子(IPAdh)はGenBank accession number AF157307に記載されている。
上記の遺伝子群を発現させるために必要なプロモーターの塩基配列として、GenBank accession number X02662の塩基配列情報において、397-440に記されているエシェリヒア・コリ由来のグリセルアルデヒド3-リン酸デヒドロゲナーゼ(以下GAPDHと呼ぶことがある)のプロモーター配列を使用することができる。
ATGAAAGGTTTTGCAATGCTGGGTATTAATAAGCTGGGCTGGATCGAAAAAGAGCGCCCGGTTGCGGGTTCGTATGATGCGATTGTGCGCCCACTGGCCGTATCTCCGTGTACCTCAGATATCCATACCGTTTTTGAGGGAGCTCTTGGCGACCGCAAGAATATGATTTTAGGGCATGAAGCGGTGGGTGAAGTTGTGGAGGTAGGCAGTGAAGTGAAGGATTTCAAACCTGGTGACCGTGTTATCGTCCCTTGCACAACCCCGGATTGGCGGTCTTTGGAAGTTCAGGCTGGTTTTCAACAGCACTCAAACGGTATGCTCGCAGGATGGAAATTTTCCAACTTCAAGGATGGCGTCTTTGGTGAGTATTTTCATGTGAATGATGCGGATATGAATCTTGCGATTCTGCCTAAAGACATGCCCCTGGAAAACGCTGTTATGATCACAGATATGATGACTACGGGCTTCCACGGAGCCGAACTTGCAGATATTCAGATGGGTTCAAGTGTAGTGGTCATTGGCATTGGCGCGGTTGGCCTGATGGGGATAGCCGGTGCTAAATTACGTGGAGCAGGTCGGATCATTGGCGTGGGGAGCCGCCCGATTTGTGTCGAGGCTGCCAAATTTTACGGGGCCACCGACATTTTGAATTATAAAAATGGTCATATCGTTGATCAAGTCATGAAACTGACGAACGGAAAAGGCGTTGACCGCGTGATTATGGCAGGCGGTGGTAGCGAAACACTGTCCCAGGCCGTATCTATGGTCAAACCAGGCGGGATCATTTCGAATATAAATTATCATGGAAGTGGCGATGCGTTATTGATCCCGCGTGTGGAATGGGGGTGCGGAATGGCTCACAAGACTATCAAAGGCGGTCTTTGTCCCGGGGGACGTTTGAGAGCAGAGATGCTGCGAGATATGGTAGTGTACAACCGTGTTGATCTCAGCAAACTGGTCACGCATGTATATCATGGGTTCGATCACATCGAAGAAGCCCTGTTACTGATGAAAGACAAGCCAAAAGACCTGATTAAAGCAGTAGTTATATTATAA
ATGCTGAAAGATGAAGTGATTAAACAGATTAGCACGCCATTAACTTCGCCTGCATTTCCGCGCGGTCCGTATAAATTTCATAATCGTGAATATTTTAACATTGTATACCGTACCGATATGGACGCCCTGCGTAAAGTTGTGCCAGAGCCTCTGGAAATTGATGAGCCCTTAGTCCGGTTCGAAATCATGGCAATGCATGATACGAGTGGCCTGGGTTGCTATACAGAATCAGGTCAGGCTATTCCCGTGAGCTTTAATGGTGTTAAGGGCGACTACCTTCACATGATGTATCTGGATAACGAGCCGGCAATTGCCGTAGGTCGGGAATTAAGTGCATACCCTAAAAAGCTCGGGTATCCAAAGCTGTTTGTGGATTCAGACACTCTGGTGGGCACGTTAGACTATGGAAAACTGCGTGTTGCGACCGCGACAATGGGGTACAAACATAAAGCCCTGGATGCTAATGAAGCAAAGGATCAAATTTGTCGCCCGAACTATATGTTGAAAATCATCCCCAATTATGACGGCTCCCCTCGCATATGCGAGCTTATCAACGCGAAAATCACCGATGTTACCGTACATGAAGCTTGGACAGGACCGACTCGACTGCAGTTATTCGATCACGCTATGGCGCCACTGAATGACTTGCCGGTCAAAGAGATTGTTTCTAGCTCTCACATTCTTGCCGATATAATCTTGCCGCGCGCGGAAGTCATATACGATTATCTCAAGTAA
エシェリヒア・コリMG1655のゲノムDNAの全塩基配列は公知であり(GenBank accession number U00096)、エシェリヒア・コリのホスホグルコースイソメラーゼ(以下pgiと呼ぶことがある)をコードする遺伝子の塩基配列も報告されている(GenBank accession number X15196)。pgiをコードする遺伝子(1,650bp)の塩基配列近傍領域をクローニングするため、caggaattcgctatatctggctctgcacg(配列番号18)、cagtctagagcaatactcttctgattttgag(配列番号19)、cagtctagatcatcgtcgatatgtaggcc(配列番号20)及びgacctgcagatcatccgtcagctgtacgc(配列番号21)に示すオリゴヌクレオチドプライマーを4種合成した。配列番号18のプライマーは5’末端側にEcoRI認識部位を、配列番号19および20のプライマーは5’末端側にXbaI認識部位を、配列番号21のプライマーは5’末端側にPstI認識部位をそれぞれ有している。
作製したエシェリヒア・コリB株、B::atoDABにプラスミドpTH18cs1-pgiを形質転換し、クロラムフェニコール10μg/mlとカナマイシン50μg/mlを含むLB寒天プレートに30℃で一晩培養し、形質転換体を得た。得られた形質転換体をカナマイシン50μg/mlを含むLB液体培地に接種し、30℃で一晩培養した。次にこの培養液の一部をカナマイシン50μg/mlを含むLB寒天プレートに塗布し、42℃で生育するコロニーを得た。得られたコロニーをカナマイシン50μg/mlを含むLB液体培地で、30℃で24時間培養し、更にカナマイシン50μg/mlを含むLB寒天プレートに塗布して42℃で生育するコロニーを得た。
なおエシェリヒア・コリMG1655株およびエシェリヒア・コリB株はアメリカンタイプカルチャーコレクションより入手することができる。
エシェリヒア・コリB株のゲノムDNAの全塩基配列は公知であり(GenBank accession No.CP000819)、GntRをコードする塩基配列はGenBank accession No.CP000819に記載のエシェリヒア・コリB株ゲノム配列の3509184~3510179に記載されている。GntRをコードする塩基配列(gntR)の近傍領域をクローニングするため、ggaattcgggtcaattttcaccctctatc(配列番号22)、gtgggccgtcctgaaggtacaaaagagatagattctc(配列番号23)、ctcttttgtaccttcaggacggcccacaaatttgaag(配列番号24)、ggaattcccagccccgcaaggccgatggc(配列番号25)に示すオリゴヌクレオチドプライマーを4種合成した。配列番号22および25のプライマーは5’末端側にEcoRI認識部位をそれぞれ有している。
ホスホグルコン酸デヒドロゲナーゼをコードする遺伝子(gnd)の塩基配列近傍領域をクローニングするため、cgccatatgaatggcgcggcggggccggtgg(配列番号26)、tggagctctgtttactcctgtcaggggg(配列番号27)、tggagctctctgatttaatcaacaataaaattg(配列番号28)、cgggatccaccaccataaccaaacgacgg(配列番号29)に示すオリゴヌクレオチドプライマーを4種合成した。配列番号26のプライマーは5’末端側にNdeI認識部位を有し、配列番号27および配列番号28のプライマーは5’末端側にSacI認識部位を有している。また、配列番号29のプライマーは5’末端側にBamHI認識部位を有している。
作製したエシェリヒア・コリB株、B::atoDAB△pgi株にプラスミドpTH18cs1-gndを形質転換し、クロラムフェニコール10μg/mlを含むLB寒天プレートに30℃で一晩培養し、形質転換体を得た。得られた形質転換体をクロラムフェニコール10μg/mlを含むLB液体培地に接種し、30℃で一晩培養した。次にこの培養液の一部をカナマイシンクロラムフェニコール10μg/mlを含むLB寒天プレートに塗布し、42℃で生育するコロニーを得た。得られたコロニーをLB液体培地で、30℃で24時間培養し、更にLB寒天プレートに塗布して42℃で生育するコロニーを得た。
作製したB::atoDAB△pgi△gnd株コンピテントセルにプラスミドpTH18cs1-gntRを形質転換し、クロラムフェニコール10μg/mlを含むLB寒天プレートに30℃で一晩培養し、形質転換体を得た。得られた形質転換体をクロラムフェニコール10μg/mlを含むLB液体培地に接種し、30℃で一晩培養した。次にこの培養液の一部をカナマイシンクロラムフェニコール10μg/mlを含むLB寒天プレートに塗布し、42℃で生育するコロニーを得た。得られたコロニーをLB液体培地で、30℃で24時間培養し、更にLB寒天プレートに塗布して42℃で生育するコロニーを得た。
出現したコロニーの中から無作為に100コロニーをピックアップして、それぞれをLB寒天プレートと、クロラムフェニコール10μg/mlを含むLB寒天プレートに生育させ、クロラムフェニコール感受性のクローンを選んだ。更にこれらの目的クローンの染色体DNAからPCRにより、gntR遺伝子が欠失していることで約2.0kbp断片の増幅が得られる株を選抜し、得られた株をB::atoDAB△pgi△gnd△gntR株と命名した。
作製したエシェリヒア・コリB株、B::atoDAB△pgi△gnd△gntR株コンピテントセルにプラスミドpI*a*zを形質転換し、アンピシリン50μg/mLを含むLB Broth,Miller寒天プレートで37℃で一晩培養することにより、エシェリヒア・コリB株 pI*a*z/B::atoDAB△pgi△gnd△gntR株を得た。
<前培養>
LB培地(DifcoTM LB Broth Miller)を、三角フラスコにフラスコ容量の1/5量入れ、121℃、15分間オートクレーブ殺菌を行った。オートクレーブ殺菌後の培地に、WO2009/008377に記載のエシェリヒア・コリ pGAPIaaa/B株を0.1vol%接種した。35℃の恒温室にて16hr振盪培養を行い、種菌体を増殖させた。
次いで、図1に示される製造装置10を用いてイソプロピルアルコールの生産を行った。培養槽12は5L容のものを、基質液槽48、抜取り液槽56は20L容のものを使用した。トラップ槽62には、20Lの水を充填し、5℃に保温した。
表1に示す組成でオートクレーブ殺菌済みの培地750mLが入った培養槽に、上記の前培養液38mLを接種した。培養は常圧、攪拌回転速度700rpm、空気通気量1.0vvm、培養温度30℃、pH=7.0(アンモニア水で調整)に制御した。
表2に示す組成の基質液を培養開始後8時間目までは11g/hでフィードし、それ以降はフィード速度22.5g/hでフィードした。培養槽12内の培養液の抜き取り速度はフィード速度と同一とし、培養槽12内の培養液量は750mLに制御した。基質液の比重は1g/cm3であり、定常状態の比増殖速度は0.03/hである。
なお、培養開始後48時間目は、菌数をOD660による濁度に基づいて測定した場合に菌数が一定状態となったことから、イソプロピルアルコール生産期であると判断された時間である。
カラム温度:35℃7分、12℃/minで昇温、240℃5分、インジェクション温度:220℃、検出器温度:240℃、検出器:FID、キャリアーガス:窒素、流速:6mL/min、スプリットレス
図1のポンプ58を停止して抜取らないようにし、それ以外は実施例1と同様に培養を行った。144時間目の培養液量は3.8Lであった。実施例1と同様にして、培養液中のイソプロピルアルコール濃度と菌体質量を得た。結果を図2、図3、表3に示す。
上記[イソプロピルアルコール生産大腸菌の作製]pI*a*z/B::atoDAB△pgi△gnd△gntR株を用いて、実施例1と同様に前培養を行った。次いで、図1に示される製造装置10を用いてイソプロピルアルコールの生産を行った。培養槽12は1L容のものを、基質液槽48、抜取り液槽56は4L容のものを使用した。トラップ槽62には、4Lの水を充填し、5℃に維持した。
表4に示す組成の基質液を培養開始後8時間目までは5g/hでフィードし、それ以降はフィード速度60.6g/hでフィードした。基質液の比重は1g/cm3であり、定常状態の比増殖速度は0.1212/hであった。実施例1と同様にして、培養液中のイソプロピルアルコール濃度と菌体質量を得た。結果を図4、図5、及び表5、表6に示す。
また、プラスミドの脱落率を調べるため、LB Broth寒天培地1と、100μL/mL アンピシリンを含むLB Broth寒天培地2を作製し、希釈した培養槽内培養液を塗布し、30℃にて保温した。24時間後のコロニー数をカウントした。アンピシリン耐性を持つプラスミドを保持した大腸菌はアンピシリン含有寒天培地でも生育できるが、プラスミドが脱落した大腸菌はアンピシリン含有寒天培地では生育できないことが知られている。これより、各寒天培地におけるコロニー数から、プラスミド脱落率を下記の式3に従って算出した。結果を図6に示す。
(式3)
プラスミド脱落率=[(寒天培地1でのコロニー数)-(寒天培地2でのコロニー数)]/(寒天培地1でのコロニー数)
8時間目以降のフィード速度を23.5g/hに変更する以外は実施例2と同様に連続培養を行った。このとき定常状態の比増殖速度は0.0470/hであった。実施例1と同様にして、培養液中のイソプロピルアルコール濃度と菌体質量を得て、また実施例2と同様にしてプラスミド脱落率を得た。結果を図4、図5、図6、表5及び表6に示す。
8時間目以降のフィード速度を12.4g/hに変更する以外は実施例2と同様に連続培養を行った。このとき定常状態の比増殖速度は0.0247/hであった。実施例1と同様にして、培養液中のイソプロピルアルコール濃度と菌体質量を得て、また実施例2と同様にしてプラスミド脱落率を得た。結果を図4、図5、図6、表5及び表6に示す。
8時間目以降のフィード速度を7.4g/hに変更する以外は実施例2と同様に連続培養を行った。このとき式1から算出される比増殖速度は0.0147/hであった。実施例1と同様にして、培養液中のイソプロピルアルコール濃度と菌体質量を得て、また実施例2と同様にしてプラスミド脱落率を得た。結果を図4、図5、図6、表5及び表6に示す。
なお表6中、イソプロピルアルコール積算質量とは、記載の運転時間までの単位液量あたりのイソプロピルアルコールの生産量の総和、つまり培養槽内の培養液、抜取られた培養液、トラップ槽に含まれる全イソプロピルアルコール質量の総和を該運転時間における培養槽内の培養液量(ここでは0.5L)で除した値である。生産速度は、イソプロピルアルコール積算質量から算出した平均イソプロピルアルコール生産速度であり、以下、同様である。
比較例2(比増殖速度0.0147[h-1])では48時間目以降、培養槽内の菌体数は維持又は増殖されておらず(図4)、定常状態には至らなかった。また、イソプロピルアルコールの生産は96時間で停止することが判明した(図5)。このときのプラスミドの脱落率が80%以上であることが、図6より明らかである(図6参照)。
一方、比増殖速度が0.0147[h-1]より高い条件で培養を行った実施例2~実施例4では、菌体増殖は定常状態に至り、長時間の連続運転が可能であり、イソプロピルアルコールは安定的に生産できた。
表7に示す基質液組成に変更、攪拌回転速度を500rpmに変更し、それ以外は実施例2と同様に連続培養を行った。
OURの算出には、空気入り口の空気流量はマスフローメータ14の値を、また出口の空気流量も、酸素消費による減少分は無視できる範囲としてマスフローメータ14の値を採用した。同様に空気入り口及び出口の空気圧は共に槽内圧力計18の値を採用した。また空気入り口及び出口における絶対温度は共に槽内の温度センサ22の値を採用した。空気入り口の酸素モル分率は0.209とし、出口の酸素モル分率は排ガス分析計20の値を採用した。溶存酸素濃度は、槽内の溶存酸素センサ24の値を採用した。
攪拌回転速度を600rpmに変更し、それ以外は実施例5と同様に連続培養を行った。
このとき算出OURは107mmol/L/hであった。また実施例5と同様にして、培養液中のイソプロピルアルコール濃度を得て、算出OURに対するイソプロピルアルコール収率、イソプロピルアルコール生産速度を求めた。結果を図7、図8及び表8に示す。定常状態の比増殖速度は0.1203/hであった。
攪拌回転速度700rpmで、それ以外は実施例5と同様に連続培養を行った。このとき算出OURは153mmol/L/hであった。また実施例5と同様にして、培養液中のイソプロピルアルコール濃度を得て、算出OURに対するイソプロピルアルコール収率、イソプロピルアルコール生産速度を求め、また溶存酸素濃度を得た。結果を図7、図8、図9、図11、表8及び表9に示す。定常状態の比増殖速度は0.1200/hであった。
攪拌回転速度800rpmで、それ以外は実施例5と同様に連続培養を行った。このとき算出OURは187mmol/L/hであった。また実施例5と同様にして、培養液中のイソプロピルアルコール濃度を得て、算出OURに対するイソプロピルアルコール収率、イソプロピルアルコール生産速度を求めた。結果を図7、図8、表8に示す。定常状態の比増殖速度は0.1210/hであった。
攪拌回転速度900rpmで、それ以外は実施例5と同様に連続培養を行った。このとき算出OURは196mmol/L/hであった。また実施例5と同様にして、培養液中のイソプロピルアルコール濃度を得て、算出OURに対するイソプロピルアルコール収率、イソプロピルアルコール生産速度を求め、また溶存酸素濃度を得た。結果を図7、図8、図9、図12及び表8及び表9に示す。定常状態の比増殖速度は0.1210/hであった。
攪拌回転速度400rpmで、それ以外は実施例5と同様に連続培養を行った。このとき算出OURは20mmol/L/hであった。また実施例5と同様にして、培養液中のイソプロピルアルコール濃度を得て、算出OURに対するイソプロピルアルコール収率、イソプロピルアルコール生産速度を求めた。結果を図7、図8、及び表8に示す。定常状態の比増殖速度は0.1200/hであった。
図7及び表8より、OURを20mmol/L/h~200mmol/L/hの範囲に制御することにより、イソプロピルアルコール収率がより一層高くなることがわかる。また、図8及び表8よりOURを20mmol/L/h~200mmol/L/hの範囲に制御することにより、イソプロピルアルコール生産速度もより一層高くなることが判明した。
また、図には示さないものの、実施例5~10のいずれにおいても酢酸生産速度は0.6g/L/h以下、エタノール生産速度は0.1g/L/h以下であった。
いずれの実施例の結果から明らかなように、11日間の連続運転でも、生産速度は低下することなく連続的にイソプロピルアルコールを生産できることがわかる。
培養槽内の溶存酸素濃度の経時変化を実施例5は図10に、実施例7は図11に、実施例9は図12に各々示す。これにより、培養槽内の溶存酸素濃度が0ppmであっても、また、溶存酸素濃度が0~1ppm付近で変動していても、酢酸生産速度は低く、かつ、イソプロピルアルコールの生産速度は高く維持されており、特に溶存酸素濃度を制御するDO-Stat法やBalanced DO-stat法などの複雑な制御方法を採らなくても副生物の生成を抑制できることが分かった。
また、図には示さないものの、実施例5~実施例10において、培養槽内の菌体質量は24時間目以降一定であり、定常状態に達していた。
基質液の組成を表10に変更し、基質液を培養開始後8時間目までは5g/hでフィードし、それ以降は平均フィード速度42g/hでフィードした。ここでは基質が抜取り液へ流出するのを最小限にするため、pHstat法を採用した。それ以外は実施例2と同様に連続培養を実施した。このときOURは200mmol/L/hであった。また実施例1と同様にして、培養液中のイソプロピルアルコール濃度及び菌体質量を得て、また、実施例2と同様にプラスミド脱落率を得た。結果を図13、図14、表11及び表12に示す。比増殖速度は0.083/hであった。
本明細書に記載された全ての文献、特許出願、および技術規格は、個々の文献、特許出願、および技術規格が参照により取り込まれることが具体的かつ個々に記された場合と同程度に、本明細書中に援用されて取り込まれる。
Claims (4)
- 植物由来原料を含有する基質液を培養槽に連続的に供給し且つ生産物を含む培養液を該培養槽から連続的に抜き取りながら、遺伝子組換えにより導入又は改変したイソプロピルアルコール生産能力を保有するイソプロピルアルコール生産大腸菌を、イソプロピルアルコール生産期に該大腸菌が安定的に増殖する菌体増殖条件で、且つ前記培養槽内の菌体数を維持して、培養することと、
前記培養槽内で前記イソプロピルアルコール生産大腸菌と植物由来原料とを接触させて、イソプロピルアルコールを生産することと、
前記培養槽から抜き取られた前記生産物を含む培養液から、イソプロピルアルコール生産大腸菌により生産されたイソプロピルアルコールを回収することと、
を含むイソプロピルアルコール製造方法。 - 前記菌体増殖条件が、比増殖速度0.015/h以上となる条件である請求項1記載のイソプロピルアルコール製造方法。
- 前記培養を、10mmol/L/h~250mmol/L/hの酸素摂取速度で行う請求項1又は請求項2記載のイソプロピルアルコール製造方法。
- 前記菌体増殖条件が、比増殖速度0.02/h以上となる条件である請求項1~請求項3のいずれか1項記載のイソプロピルアルコール製造方法。
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US11129906B1 (en) | 2016-12-07 | 2021-09-28 | David Gordon Bermudes | Chimeric protein toxins for expression by therapeutic bacteria |
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