JP2011223888A - Method for producing acetic acid by microorganism - Google Patents

Abstract

It is an object of the present invention to provide a method for producing acetic acid by anaerobic microorganisms using carbon dioxide and hydrogen as raw materials.
[MEANS FOR SOLVING PROBLEMS] The present inventors have studied microorganisms suitable for producing acetic acid using microorganisms of the genus Moorella as an example of anaerobic microorganisms.
As a result, the specific growth rate of the cells was found to be faster at higher temperatures (60 ° C), but at a lower temperature (specifically around 50 ° C) than the appropriate temperature for growth, It was revealed that acetic acid accumulation concentration increased, that is, acetic acid production efficiency increased.
That is, the present inventors have succeeded in establishing suitable culture conditions in acetic acid production using anaerobic microorganisms.
[Selection figure] None

Description

  The present invention relates to a method for producing acetic acid by an anaerobic microorganism having the ability to produce acetic acid.

  In recent years, carbon dioxide released through human economic activities has been pointed out as a possible cause of global warming, and it has become an international issue to control its release into the atmosphere. The so-called low-carbon society has been called out. In addition to environmental issues, the effective use of carbon dioxide means the provision of new resources and energy sources, and is an important theme not only for Japan but also for the global chemical industry. Under such a background, the present inventors have studied various methods for directly using carbon dioxide as an industrial raw material instead of using it via biomass. As a result, we focused on the fact that acetic acid can be produced from carbon dioxide and hydrogen under mild conditions by using microorganisms that grow by assimilating carbon dioxide.

Many microorganisms that produce acetic acid using carbon dioxide as a carbon source have been reported so far. For example, the following microorganisms have been found.
Acetobacterium genus Clostridium genus Eubacterium genus Bacteroides genus Sporomusa genus Acetogenium genus Moorella genus Thermoanaerobhalo genus Atherohalobacter Genus

  These microorganisms are classified as so-called absolute autotrophic bacteria. Therefore, these microorganisms are generally obligately anaerobic, and when oxygen is present in the growth system, their growth tends to be inhibited. In addition, these microorganisms produce acetic acid under conditions of almost normal temperature and normal pressure while growing using carbon dioxide as a carbon source and hydrogen gas as an energy source. At this time, it is known that microorganisms produce 1 mol of acetic acid from 2 mol of carbon dioxide and 4 mol of hydrogen according to the reaction shown below (Patent Document 1, Non-Patent Documents 1 and 2, etc.).

2CO ₂ + 4H ₂ → CH ₃ COOH + 2H ₂ O

  Despite the fact that acetic acid can be produced from carbon dioxide by utilizing the metabolism of microorganisms, the majority of acetic acid currently produced industrially in the world is chemically synthesized. It is a thing.

  As a method for synthesizing acetic acid, a method utilizing oxidation of acetaldehyde, butane, naphtha, ethylene or the like is known. At present, the methanol method in which acetic acid is synthesized by carbonylation of methanol is the mainstream. In the methanol method, methanol and carbon monoxide are mixed at high temperature and high pressure in the presence of a metal catalyst such as rhodium or iridium, which are also rare metals, and acetic acid is produced according to the following reaction formula.

CH ₃ OH + CO → CH ₃ COOH

  If a method for industrially producing acetic acid using microorganisms is provided instead of a chemical synthesis method, acetic acid can be produced from carbon dioxide at about normal temperature and normal pressure. If microorganisms are used, a high temperature and high pressure are not required for the reaction, and thus an acetic acid synthesis method excellent in energy efficiency can be realized. In addition, the method for synthesizing acetic acid using microorganisms does not require a catalyst such as a rare metal, so that it can be said to be a method having a low environmental load even for raw materials.

  So far, methods for producing acetic acid using microorganisms have been studied (Patent Document 2, Non-Patent Document 3), but selection of more suitable types of microorganisms and culture conditions is required when acetic acid is produced. It was done.

Japanese Unexamined Patent Publication No. 01-098472 JP2003-339371

J. Biosci. Bioeng., 2005, 99, 252-258 Next Generation Industrial Technology Research and Development System, Bioreactor Research and Development Summary Report, 1981-63 (p195-229) Biotechnology Letters, 2004, 26, 1607-1612

  The present invention has been made in view of such circumstances, and its purpose is to cultivate at a temperature 8 to 12 ° C. lower than the culture temperature showing the optimum specific growth rate of the microorganism, utilizing the action of the microorganism. The present invention relates to a method for efficiently producing acetic acid using a gas such as carbon dioxide as a raw material under conditions.

  In order to solve the above problems, the present inventors have conducted intensive research.

  The present inventors examined a suitable culture condition for producing acetic acid using a microorganism belonging to the genus Moorella as an example of an anaerobic microorganism.

  Specifically, Morella SP HUC22-1 strain is cultured in the presence of hydrogen / carbon dioxide gas [4: 1] and under a pressure of 0 to 0.5 MPa, and the culture temperature is selected between 45 to 60 ° C. Thus, a suitable culture temperature in acetic acid production was examined.

  As a result, it was found that the specific growth rate of bacterial cells was higher at higher temperatures (60 ° C), but acetic acid was lower at a temperature lower than the appropriate temperature for growth (specifically, around 50 ° C). It was revealed that the accumulated concentration increased, that is, acetic acid production efficiency increased.

  That is, the present inventors have succeeded in establishing suitable culture conditions for acetic acid production using anaerobic microorganisms, thereby completing the present invention.

More specifically, the present invention provides the following [1] to [7].
[1] A method for producing acetic acid by an anaerobic microorganism having the ability to produce acetic acid, comprising the following steps;
(1) a step of culturing the anaerobic microorganism in the presence of a gaseous carbon compound at a temperature 8 to 12 ° C. lower than the culture temperature showing the optimum specific growth rate; and (2) anaerobic of step (1). A process of collecting acetic acid produced by microorganisms.
[2] The method for producing acetic acid according to [1], wherein the culturing is performed in the presence of a mixed gas containing a gaseous carbon compound and / or hydrogen in the step (1).
[3] The method for producing acetic acid according to [1] or [2], wherein the gaseous carbon compound is a compound selected from carbon monoxide and carbon dioxide.
[4] The production of acetic acid according to any one of [1] to [3], wherein the anaerobic microorganism is a bacterium classified into the genus Moorella and / or the genus Clostridium. Method.
[5] Any one of [1] to [3], wherein the anaerobic microorganism is Moorella sp. HUC22-1 strain (NITE P-866) or a related bacterium thereof A process for producing acetic acid as described in 1.
[6] The acetic acid according to any one of [1] to [3], wherein the anaerobic microorganism is Moorella sp. HUC22-1 strain (NITE P-866). Production method.
[7] Mororella sp. HUC22-1 strain (NITE P-866).

  It has long been known academically that acetic acid is produced by the metabolism of anaerobic microorganisms. And if it could be applied to industrial acetic acid production technology, it was thought that it would be a production method with a small environmental load. However, anaerobic microorganisms and culture conditions suitable for acetic acid production have not been established so far.

  According to the present invention, an efficient method for producing acetic acid using carbon dioxide as a raw material utilizing anaerobic microbial metabolism has been realized.

  Acetic acid is the most widely produced acid in the world and is widely used as a raw material for vinyl acetate, acetic anhydride, and other acetates. According to the special issue “Chemical Economy” in August 2008, demand for vinyl acetate monomer, the biggest demand area for acetic acid, is strong, and acetic acid consumption is expected to grow significantly. With the establishment and enhancement of a high-purity terephthalic acid plant, demand for acetic acid is expected to grow as a raw material for the production of high-purity terephthalic acid.

  INDUSTRIAL APPLICABILITY According to the present invention, an industrial production technique for acetic acid utilizing anaerobic microbial metabolism is provided, and the demand for acetic acid as an industrial raw material can be met. Carbon dioxide is one of the causes of global warming. Therefore, in the preferable aspect, the present invention provides a carbon dioxide immobilization technique and contributes to the maintenance of the global environment.

The present invention relates to a method for producing acetic acid by an anaerobic microorganism having the ability to produce acetic acid, comprising the following steps.
(1) a step of culturing the anaerobic microorganism in the presence of a gaseous carbon compound at a temperature 8 to 12 ° C. lower than the culture temperature showing the optimum specific growth rate; and (2) anaerobic of step (1). A process of collecting acetic acid produced by microorganisms.

  The anaerobic microorganism used for the production of acetic acid in the present invention is an anaerobic microorganism having an acetic acid-producing ability at a temperature of 40 ° C. or higher. The culture temperature for producing preferable acetic acid of the acetic acid-producing microorganism is 40-60 ° C, more preferably 48-52 ° C. The optimum temperature for growth (culture temperature showing the optimum specific growth rate) is 48 ° C or higher, preferably 48 ° C to 72 ° C, more preferably 56 ° C to 60 ° C.

  In the present invention, the pressurizing condition for culturing the anaerobic microorganism is not particularly limited as long as the microorganism can grow, but as a preferable pressurizing condition, a range of 0.1 to 0.5 MPa, Particularly preferred pressure conditions include a range of 0.1 to 0.2 MPa (more specifically 0.15 MPa).

  The acetic acid-producing microorganism used in the present invention is preferably one having the ability to produce acetic acid from a gaseous (also referred to as gas) carbon compound as a raw material. Examples of the carbon compound include carbon monoxide and carbon dioxide. Among these, one or two selected from carbon monoxide and carbon dioxide are preferable. In addition to these carbon compounds, hydrogen, hydrogen sulfide and the like can be used in combination. Examples of the mixed gas include a mixed gas of carbon monoxide and hydrogen, a mixed gas of carbon dioxide and hydrogen, a mixed gas of carbon monoxide, carbon dioxide and hydrogen, and the like. At that time, even if an inert gas such as nitrogen, another type of gas such as methane gas or hydrogen sulfide is mixed, there is no particular problem as long as the production of acetic acid is not hindered.

  These carbon compounds can be added in the form of a gas, but carbon dioxide may be generated in the culture solution by adding a substance that can be a carbon dioxide generating source such as carbonate. Among these, the use of carbon dioxide and hydrogen has the highest effect of reducing greenhouse gases. The carbon dioxide and carbon monoxide in the present invention include carbon-containing raw materials, that is, those produced by oxidation of a gas such as methane or ethane, or an organic substance such as coal or wood. The hydrogen in the present invention includes those produced by oxidizing a substance containing hydrogen such as hydrogen sulfide and methane.

The present invention includes a step of bringing hydrogen and carbon dioxide obtained by gasification of a hydrocarbon compound into contact with anaerobic microorganisms capable of producing acetic acid. In the present invention, anaerobic microorganisms that assimilate carbon dioxide and hydrogen and produce acetic acid can be used. For example, microorganisms classified into a genus selected from the following group are known to have acetic acid producing ability.
Acetobacterium genus Clostridium genus Eubacterium genus Bacteroides genus Sporomusa genus Acetogenium genus Moorella genus Thermoanaerobhalo genus Atherohalobacter Genus

Therefore, microorganisms selected from microorganisms classified into these genera and producing acetic acid by anaerobic fermentation using hydrogen and carbon dioxide are preferred microorganisms in the present invention. Among them, microorganisms belonging to the genus Acetobacterium, the genus Clostridium, or the genus Moorella are preferable as microorganisms having the ability to produce acetic acid in the present invention. The production of acetic acid by a microorganism can be confirmed by lowering the pH of the culture solution or by anaerobically culturing the microorganism in the presence of hydrogen and carbon dioxide and detecting the acetic acid produced in the culture. More specifically, for example, the following microorganisms can be used as microorganisms having the ability to produce acetic acid in the present invention.
Acetobacterium sp. No.446, FERM P-7017
(Acetobacterium sp. No.446, FERM P-7017)
Acetobacterium sp. MA-1, FERM P-8676
(Acetobacterium sp. MA-1, FERM P-8676)
Acetobacterium woody, ATCC 29683
(Acetobacterium Woodii, ATCC 29683)
Clostridium acetylicam, DSM 1496
(Clostridium aceticum, DSM 1496)
Clostridium glycolicum, ATCC29797
(Clostridium glycolicum, ATCC29797)
Clostridium SP No.307, FERM P-7487
(Clostridium sp. No.307 FERM P-7487)
Clostridium SP No.484, FERM P-7488
(Clostridium sp. No.484, FERM P-7488)
Clostridium SP No.68-2, FERM, P-7367
(Clostridium sp. No.68-2 FERM, P-7367)
Clostridium SP No.670, FERM P-8047
(Clostridium sp. No.670, FERM P-8047)
Clostridium SP No.672, FERM P-8049
(Clostridium sp. No.672, FERM P-8049)
Eubacterium SP No.477, FERM P-8045
(Eubacterium sp. No.477, FERM P-8045)
Eubacterium Rimosum, ATCC 8486
(Eubacterium limosum, ATCC 8486)
Eubacterium limosam, ATCC 10825
(Eubacterium limosum, ATCC10825)
Bacteroides SP No.669, FERM P-8046
(Bacteroides sp. No.669, FERM P-8046)
Bacteroides SP No.671, FERM P-8048
(Bacteroides sp. No.671, FERM P-8048)
Bacteroides ovatas, ATCC 8483
(Bacteroides ovatus, ATCC 8483)
Spolomucer Sphaeroides, DSM 2875
(Sporomusa sphaeroides, DSM 2875)
Spolomucer Ovata, DSM-2662
(Sporomusa ovata, DSM-2662)
Acetogenium kivi, ATCC 33488
(Acetogenium kivui, ATCC 33488)
Morella Thermosetica, ATCC 31490
(Moorella thermoacetica, ATCC 31490)
Morella Thermosetica, ATCC 35608
(Moorella thermoacetica, ATCC 35608)
Morella Thermosetica, ATCC 39073
(Moorella thermoacetica, ATCC 39073)
Morella Thermosetica, ATCC 39289
(Moorella thermoacetica, ATCC 39289)
Morella Thermosettica, ATCC 49707
(Moorella thermoacetica, ATCC 49707)
Morella Thermoautotropica, ATCC 33924
(Moorella thermoautotrophica, ATCC 33924)
Thermoana Aerobacter Kibui, DSM 2030
(Thermoanaerobacter kivui, DSM 2030)
Acethalobium arabachicam, DSM 5501
(Acetohalobium arabaticum, DSM 5501)

In particular, the Mororella sp. HUC22-1 strain (NITE P-866) described below or a similar strain having properties as a species similar to these strains can be used more preferably.
(1) NITE P-866
(I) Depositary institution: National Institute for Product Evaluation Technology Patent Microorganism Depositary Center (Location: 2-5-8 Kazusa Kamashi, Kisarazu City, Chiba Prefecture, Japan Postal Code 292-0818)
(B) Contract date: January 20, 2010 (C) Contract number: Moorella sp. HUC22-1 (NITE P-866)

The microorganism can be obtained from the depository indicated by the deposit number. Each deposit number indicates that the microorganism is deposited at the next depository.
FERM Patent Organism Depositary; International Patent Organism Depositary (IPOD)
http://unit.aist.go.jp/pod/ci/index.html
ATCC American Type Culture Collection (ATCC)
http://www.atcc.org/
DSM German Collection of Microorganisms and Cell Cultures (DSMZ)
http://www.dsmz.de/
NITE National Institute for Product Evaluation Technology Patent Microorganism Depositary Center (NPMD)
http://www.nbrc.nite.go.jp/npmd/

  In the present invention, anaerobic microorganisms capable of producing acetic acid are brought into contact with hydrogen and carbon dioxide under conditions suitable for acetic acid production and cultured. The condition suitable for the production of acetic acid in the present invention means that the anaerobic microorganism having acetic acid producing activity is maintained. More specifically, it means that anaerobic conditions that allow anaerobic microorganisms to survive are maintained, and nutrients are provided to support the activity and growth of the microorganisms. Various medium compositions suitable for the survival of anaerobic microorganisms are known. Therefore, those skilled in the art can select an appropriate medium composition for the anaerobic microorganisms having the ability to produce acetic acid described above.

For example, a water-soluble organic substance can be added as a carbon source to the medium used in the present invention. The following compounds can be listed as water-soluble organic substances.
Sorbose fructose glucose methanol

  The concentration of the organic substance added to the medium as a carbon source can be appropriately adjusted in order to efficiently grow microorganisms in the medium. Generally, excess and deficiency can be avoided by selecting the addition amount from the range of 0.1 to 10 wt / vol%.

  In addition to the above carbon source, a nitrogen source is added to the medium. In the present invention, various nitrogen compounds that can be used for normal fermentation can be used as the nitrogen source. Preferred nitrogen sources are ammonium salts and nitrates. More preferred nitrogen sources are ammonium chloride and sodium nitrate.

Furthermore, in addition to a carbon source and a nitrogen source, other organic substances or inorganic substances suitable for culturing microorganisms can be added to the medium. For example, in some cases, the growth or activity of microorganisms can be enhanced by adding inorganic compounds such as cofactors such as vitamins and various salts to the medium. For example, the following can be mentioned as microbial growth cofactors derived from inorganic compounds, vitamins and animals and plants.
Inorganic compounds Vitamins Potassium dihydrogen phosphate Biotin Magnesium sulfate Folic acid Manganese sulfate Pyridoxine Sodium chloride Thiamine Cobalt Riboflavin Calcium chloride Nicotinic acid Zinc sulfate Pantothenic acid Copper sulfate Vitamin B12
Alum Thiooctanoic acid Sodium molybdate p-Aminobenzoic acid Potassium chloride Boric acid Nickel chloride Sodium tungstate Sodium selenate Ammonium ferrous sulfate Animal and plant-derived microorganism growth factor Yeast extract Meat extract Peptones

  Methods for producing a culture solution by adding these inorganic compounds, vitamins, or growth cofactors are known. The medium can be liquid, semi-solid, or solid. In the method for producing acetic acid of the present invention, a preferred medium form is a liquid medium.

  In the present invention, the anaerobic microorganism can be cultured according to a known anaerobic microorganism culture method. For industrial production, a continuous fermentation system that can continuously supply a medium and a substrate gas and has a mechanism for recovering the culture is suitable.

  In the culture of anaerobic microorganisms, it is necessary to prevent oxygen from being mixed into the continuous culture system. As the incubator, a commonly used culture tank can be used as it is. Culture tanks that can also be used for culturing anaerobic microorganisms are commercially available. An anaerobic atmosphere can be created by replacing oxygen mixed in the culture tank with an inert gas such as nitrogen or a substrate gas.

  For example, an anaerobic jar can be a bioreactor for culturing anaerobic microorganisms. The anaerobic culture jar is composed of an airtight container made of metal, glass, or synthetic resin, and can block the inside from oxygen in the atmosphere. Furthermore, the anaerobic culture jar can be equipped with a mechanism for removing molecular oxygen contained in the space inside the anaerobic culture jar or in the culture solution. For example, by connecting a vacuum pump that sucks the inside of the anaerobic culture jar and sucking it, and supplying a gas other than oxygen, the inside can be maintained in an anaerobic state.

  In the present invention, an additional function can be given to the culture tank. For example, in addition to a commonly used stirred mixing tank, a bubble column type or draft tube type culture tank can also be used. Microorganisms are released and dispersed by carbon dioxide and hydrogen blown into the liquid medium, and the microorganisms and the medium can be sufficiently brought into contact with each other. In addition, microorganisms inhabit while dripping moisture on a highly breathable slag like a biotrickling filter, other ceramic-based inorganic fillers, or packed layers of organic synthetic materials such as polypropylene, It can also be cultured while aeration of gas. Furthermore, the microorganisms to be used can be used by immobilizing them on carrageenan gel, alginic acid gel, acrylamide gel, chitin, cellulose, agar, etc. by a conventional method.

  A person skilled in the art can use a known method for separating the produced microorganism and the culture product solution. A preferable separation method is a method using a hollow fiber type ultrafiltration or microfiltration membrane having filtration performance and concentration performance. In addition, in order to obtain a filtration rate sufficient for separating the microorganism and the product solution, a membrane having an appropriate fractional molecular weight may be selected according to the microorganism used. Acetic acid can be recovered from the culture solution separated from the culture tank through the ultrafiltration membrane. Methods for purifying acetic acid are known. For example, the culture can be removed by centrifugation, etc., acidified with mineral acids, extracted with a solvent such as amines, trioctylphosphine oxide, ethyl acetate, benzene, and then distilled. it can.

In the present invention, the combination of carbon compounds supplied to the anaerobic microorganism is not particularly limited. For example, hydrogen (H ₂ ) and carbon dioxide (CO ₂ ) can be mixed and used as a raw material.

In the above case, the ratio of hydrogen (H ₂ ) and carbon dioxide (CO ₂ ) supplied to the anaerobic microorganism is preferably 1: 1 to 10: 1 in terms of molar ratio of hydrogen / carbon dioxide. More preferably, hydrogen / carbon dioxide is in a molar ratio of 1.5: 1 to 4: 1. Moreover, in order to collect | recover acetic acid efficiently, 0.2-20 gas amount / liquid amount / min is preferable for the amount of ventilation | gas_flowing of the substrate gas to the culture tank.

  Depending on the shape of the culture tank, a stirrer or the like can be used to sufficiently stir the medium. By stirring the culture in the culture tank, it is possible to increase the chance of contacting the medium components and the substrate gas with the anaerobic microorganisms, and to optimize the production efficiency of acetic acid. The substrate gas can also be supplied as nanobubbles.

  For sufficient growth of microorganisms, the pH of the culture is preferably 3.0 to 8.0, more preferably 4.5 to 7.5. In order to increase the recovery amount of acetic acid, the temperature of the culture tank is preferably 25 ° C to 70 ° C, more preferably 30 ° C to 60 ° C. As described above, it is preferable to set the culture tank at a temperature 8 to 12 ° C. lower than the optimum temperature for growth (culture temperature showing the optimum specific growth rate). In the continuous culture system, fresh culture medium is continuously supplied to the culture tank. In order to efficiently recover acetic acid, the amount of fresh medium supplied to the culture tank is preferably such that the dilution rate in the culture in the culture tank is 0.04 to 2 / hr per hour. A more preferable dilution rate is 0.08 to 1 / hr.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

[Example 1]
Mororella sp. HUC 22-1 strain (NITE P-866) was cultured as follows. After preparing the medium shown in Table 1, it was placed in a boiling water bath for 20 minutes and degassed. After cooling with carbon dioxide gas, dispense 20 mL each into a 100 mL vial (manufactured by Maruemu), seal with a butyl rubber stopper, and sterilize at 121 ° C. for 15 minutes. After cooling, the gas phase was sufficiently replaced with a sterile hydrogen / carbon dioxide gas [4: 1] gas, and further pressurized to 0.15 MPa. Subsequently, 1 mL of the culture solution of the same bacterium previously cultured in the same medium was added with a sterile syringe and cultured with shaking at 45, 50, 55, and 60 ° C. at 160 spm for 7 days. During the culture period, 1 mL was sampled every 24 hours, and the growth (turbidity), pH, and acetic acid concentration of the bacteria were measured. If the gas phase had a negative pressure, hydrogen / carbon dioxide gas [4: 1] was replenished and pressurized again to 0.15 MPa.

  The sampled culture broth was separated from the cells with a centrifuge, and the supernatant was appropriately diluted with a mobile phase, and then acetic acid was quantified by high performance liquid chromatography. The results of comparing the maximum acetic acid concentration at each temperature are shown in Table 2. From this result, it was found that the acetic acid concentration was highest at 50 ° C.

[Example 2]
A medium similar to that in Example 1 was prepared. Next, 1 mL of the culture solution of Morella sp. HUC 22-1 strain (NITE P-866) previously cultured in the same medium was added with a sterile syringe. The cells were cultured at 60 ° C. with shaking at 160 spm. Sampling was performed at 0, 24, 36, 48, 70, and 96 hours after the start of culture, and the growth of bacteria (turbidity at 660 nm) was measured, and the specific growth rate at each temperature in the logarithmic growth phase was measured. The results are shown in Table 3. The growth at 60 ° C. was found to be the fastest, and when combined with Example 1, it was found that the acetic acid accumulation concentration increased at a temperature lower than the temperature suitable for growth.

  Until now, in culture of this microorganism, a culture temperature of 55 ° C. has been adopted from the time of isolation (Biotechnology Letters, 2004, 26, 1607-1612). This is because the growth of this microorganism was carried out in the range of 45 to 60 ° C., almost no growth was observed at 45 ° C. or lower, and the higher the temperature, the better the growth state.

  From these facts, it was speculated that the optimum culture temperature condition in the production of acetic acid is optimal at a high temperature (55 to 60 ° C.) than when the growth state is good. However, it was first revealed in the present invention that around 50 ° C. where the growth state slightly decreases contrary to expectation is suitable for acetic acid production.

The specific growth rate is expressed by the following formula.

Example 3
A medium similar to that in Example 1 was prepared. Subsequently, 1 mL of a bacterial culture solution of Morella sp. HUC 22-1 strain previously cultured in the same medium was added with a sterile syringe and cultured at 50 ° C. with shaking at 160 spm. Sampling was performed every 24 hours after the start of culture, and the growth (turbidity), pH, and acetic acid concentration of the bacteria were measured. If the gas phase had a negative pressure, hydrogen / carbon dioxide gas [4: 1] was replenished and pressurized again to 0.15 MPa.

  The course of the culture [pH, turbidity (OD660), acetic acid concentration] is shown in Table 4.

Example 4
The culture solution cultured in Example 3 was taken out, and the bacteria were removed with a centrifuge. After adjusting 10 mL of this to pH 2 with sulfuric acid, 10 mL of a solution obtained by diluting trioctylphosphine oxide to 15 wt% with kerosene was added as an extractant, and the mixture was sufficiently shaken and separated. As a result of quantitative determination by gas chromatography, 2.41 g / L of acetic acid was extracted in the organic solvent layer.
[Gas chromatography conditions]
Column: Gasclopack 54 (60/80, 1 m x 3 mm)
Carrier gas: Helium flow rate: 44 mL / min
Inlet temperature: 230 ° C
Column temperature: 180 ° C
Detection: FID
Sample volume: 1 μL

  According to the present invention, acetic acid can be produced with good efficiency using anaerobic microorganisms.

  Furthermore, when carbon dioxide or the like is used as a raw material, carbon dioxide in the atmosphere can be fixed to acetic acid according to the present invention. Furthermore, if acetic acid produced according to the present invention is used as an industrial raw material for the synthesis of various compounds, as a result, atmospheric carbon dioxide is fixed in a stable state. Therefore, the method for producing acetic acid of the present invention can also be used as a technique for fixing carbon dioxide in the atmosphere.

Claims (7)

A method for producing acetic acid by an anaerobic microorganism having the ability to produce acetic acid, comprising the following steps;
(1) a step of culturing the anaerobic microorganism in the presence of a gaseous carbon compound at a temperature 8 to 12 ° C. lower than the culture temperature showing the optimum specific growth rate; and (2) anaerobic of step (1). A process of collecting acetic acid produced by microorganisms.   The method for producing acetic acid according to claim 1, wherein the culturing is carried out in the presence of a mixed gas containing a gaseous carbon compound and / or hydrogen in the step (1).   The method for producing acetic acid according to claim 1 or 2, wherein the gaseous carbon compound is a compound selected from carbon monoxide and carbon dioxide.   The method for producing acetic acid according to any one of claims 1 to 3, wherein the anaerobic microorganism is a bacterium classified into the genus Mororella and / or the genus Clostridium.   The acetic acid according to any one of claims 1 to 3, wherein the anaerobic microorganism is Moorella sp. HUC22-1 strain (NITE P-866) or a related bacterium. Production method.   The method for producing acetic acid according to any one of claims 1 to 3, wherein the anaerobic microorganism is Mororella sp. HUC22-1 strain (NITE P-866).   Mororella sp. HUC22-1 strain (NITE P-866).