Microorganism culturing system and method for culturing in said system by recycling off-gas

Abstract

The present invention provides a microorganism culturing system, the culturing system comprising a culturing tank, a recycled gas adjustment unit, a first gas circulation line having one end connected to an upper part of the culturing tank and the other end connected to the recycled gas adjustment unit, and a second gas circulation line having one end connected to the recycled gas adjustment unit and the other end connected so as to supply the recycled gas into the culturing tank, wherein the recycled gas adjustment unit mixes one or more gas components selected from the group consisting of combustible gas, combustion-supporting gas, and incombustible gas with at least a portion of off-gas discharged from the culturing tank so that the concentration of the combustion-supporting gas in the recycled gas falls within a predetermined range. The present invention also provides a method for culturing in a culturing system that uses microorganisms by recycling off-gas.

Description

Microbial cultivation system and method for culturing by recycling off-gas in the system

[0001] The present invention relates to a microbial cultivation system and a cultivation method in which off-gas is recycled in the system.

[0002] Microorganisms are used industrially to convert carbon-rich gases such as carbon dioxide, carbon monoxide, and methane into various chemical products such as fuel, proteins, alcohol, and organic acids through their fermentation process. Gas fermentation can utilize a variety of raw materials, including household waste, industrial waste, and agricultural waste, and can reduce dependence on fossil-derived carbon sources and contribute to the reduction of greenhouse gas emissions. It is therefore a technology that is attracting attention for its potential to realize a sustainable society.

[0003] Microorganisms grow in response to various conditions in the fermenter (e.g., temperature, pH, pressure, agitation, aeration, etc.). Some microorganisms grow under anaerobic conditions, while others grow under aerobic conditions. For microorganisms that grow under aerobic conditions, air is generally used as the oxygen source, but oxygen-enriched air or pure oxygen can also be used for their growth.

[0004] To optimize the productivity of a product produced by a fermentation process using microorganisms grown under aerobic conditions, it is generally desirable to cultivate the product under the highest possible oxygen concentration, which increases the amount of dissolved oxygen from the gas phase to the liquid phase and enhances the biosynthetic reactions of the aerobic microorganisms.

[0005] Some types of microorganisms used in fermentation require flammable gases (e.g., hydrogen gas) as the fermentation substrate. Flammable gases can cause gas explosions if an ignition source is nearby, so the cultivation process must be carried out in a way that prevents explosions. However, it is difficult to completely eliminate ignition sources such as static electricity, so the gas composition is usually controlled to be outside the explosive composition range, i.e., the oxygen concentration in the gas composition is controlled so that it does not fall within the explosive limit oxygen concentration.

[0006] In a fermentation culture process of microorganisms using combustible gases, development of a culture system that contributes to improving productivity of the final product and reducing operating costs while preventing gas explosions is underway. For example, Patent Document 1 and Non-Patent Document 1 disclose a system for efficient culture by measuring the gas composition of off-gas accumulated in the headspace of a fermentation culture tank after culture, supplying the off-gas back to the fermentation culture tank, and simultaneously mixing components of the gas composition consumed by fermentation (e.g., hydrogen gas, oxygen gas, carbon dioxide gas, etc.) and supplying the mixed gas to the fermentation culture tank.

[0007] International Publication No. 2019 / 191767

[0008] Garcia-Gonzalez, L., et al., Sustainable autotrophic production of polyhydroxybutyrate (PHB) from CO2 using a two-stage cultivation system., Catalysis Today, 257 (2015), pp.237-245

[0009] The object of the present invention is to provide a novel microbial culture system and method that enable safe and efficient culture.

[0010] In conventional microbial culture systems (e.g., Non-Patent Document 1), when off-gas accumulated in the headspace of a culture tank is reused, the gas components required for culture that are in short supply are premixed separately as makeup gas and supplied to the culture tank. However, when using this system and a combustible gas is used, there is a possibility that the composition of the makeup gas supplied to the culture tank may fall within the explosive composition range. Therefore, we investigated a new microbial culture system and method that enable safer and more efficient fermentation culture.

[0011] As a result of extensive research to solve the above problems, the inventors have developed a system and method for a microbial culture system that enables safe and efficient fermentation culture by adjusting the recycle gas from the off-gas to a desired gas component so that the concentration of a combustion-supporting gas in the recycle gas falls within a predetermined range.

[0012] [1] A microorganism cultivation system comprising: a cultivation tank; a recycle gas adjustment unit; a first gas circulation line having one end connected to an upper portion of the cultivation tank and the other end connected to the recycle gas adjustment unit; and a second gas circulation line having one end connected to the recycle gas adjustment unit and the other end connected to supply a recycled gas into the cultivation tank; wherein the recycle gas adjustment unit is connected to one or more gas supply units selected from the group consisting of a combustible gas supply unit, a combustion-supporting gas supply unit, and a non-combustible gas supply unit, and the recycle gas adjustment unit mixes one or more gas components selected from the group consisting of a combustible gas, a combustion-supporting gas, and a non-combustible gas with at least a portion of the off-gas discharged from the cultivation tank so that the concentration of the combustion-supporting gas in the recycled gas falls within a predetermined range. [2] The culture system according to item 1, further comprising a first gas concentration meter in the second gas circulation line for measuring the concentration of at least a combustion-supporting gas in the recycled gas, wherein the recycled gas adjustment unit performs feedback adjustment based on the concentration of the combustion-supporting gas measured by the first gas concentration meter so that the concentration of the combustion-supporting gas in the recycled gas falls within a predetermined range. [3] The culture system according to item 1 or 2, wherein the combustible gas supply unit is independently connected to the recycled gas adjustment unit. [4] The culture system according to any one of items 1 to 3, wherein the recycled gas adjustment unit mixes the gas components so that the concentrations of the combustible gas and / or the non-combustible gas in the recycled gas fall within a predetermined range. [5] The culture system according to any one of items 1 to 4, further comprising a second gas concentration meter in an upper portion of the culture tank and / or the first gas circulation line for measuring the concentration of at least a combustion-supporting gas in the off-gas. [6] The culture system according to any one of items 1 to 5, wherein the combustion-supporting gas supply unit and the non-combustible gas supply unit are connected to the recycle gas adjustment unit so that the combustion-supporting gas and the non-combustible gas are premixed before being mixed with the off-gas. [7] The culture system according to any one of items 1 to 6, wherein the microorganism is an aerobic fermentation bacterium.[8] The culture system according to item 7, wherein the aerobic fermentation bacteria are hydrogen-oxidizing bacteria and the combustible gas is hydrogen gas. [9] The culture system according to any one of items 1 to 8, wherein the combustion-supporting gas is oxygen gas.

[10] The culture system according to any one of items 1 to 9, wherein the non-combustible gas is carbon dioxide gas and / or nitrogen gas.

[11] The culture system according to any one of items 1 to 10, wherein the pressure inside the culture tank is atmospheric pressure or higher.

[12] The culture system according to any one of items 1 to 11, wherein the first gas circulation line is provided with a compressor.

[13] The culture system according to any one of items 1 to 12, wherein the recycle gas adjusting unit includes: one or more gas mixers; a first gas adjusting unit for adjusting the supply amount of combustible gas from the combustible gas supply unit; a second gas adjusting unit for adjusting the supply amount of combustion supporting gas from the combustion supporting gas supply unit; and a third gas adjusting unit for adjusting the supply amount of non-combustible gas from the non-combustible gas supply unit; and the combustible gas supply unit, the combustion supporting gas supply unit, and the non-combustible gas supply unit are connected to the gas mixers.

[0013]

[14] A method for culturing by recycling off-gas in a culturing system using microorganisms, comprising the following steps: (1) culturing a culture provided in a culture tank of the culturing system, the culture comprising microorganisms and a medium, by supplying a feed gas containing a combustible gas, a combustion-supporting gas, and a non-combustible gas; (2) mixing at least a portion of the off-gas discharged from the step (1) with one or more gas components selected from the group consisting of the combustible gas, the combustion-supporting gas, and the non-combustible gas to prepare a recycled gas, the mixed gas being such that the concentration of the combustion-supporting gas in the recycled gas falls within a predetermined range; and (3) carrying out the step (1), supplying the recycled gas obtained in the step (2) as the feed gas to the culture.

[15] The method according to item 14, comprising, after the step (2) and before the step (3), a step (2') of measuring the concentration of at least the combustion assisting gas in the recycled gas, and feedback-adjusting the concentration of the combustion assisting gas in the step (2) so that it falls within a predetermined range based on the concentration of the combustion assisting gas measured in the step (2').

[16] The method according to item 14 or 15, wherein the combustible gas is mixed independently with the off-gas.

[17] The method according to any one of items 14 to 16, wherein the combustible gas and / or the non-combustible gas is mixed with the gas components so that the concentration falls within a predetermined range in the recycled gas.

[18] The method according to any one of items 14 to 17, comprising, after the step (1) and before the step (2), a step (1') of measuring the concentration of at least the combustion assisting gas in the off-gas discharged from the step (1).

[19] The method according to any one of items 14 to 18, wherein in step (2), the combustion-supporting gas and the non-combustible gas are premixed before being mixed with the off-gas.

[20] The method according to any one of items 14 to 19, wherein the microorganism is an aerobic fermentation bacterium.

[21] The method according to item 20, wherein the aerobic fermentation bacterium is a hydrogen-oxidizing bacterium and the combustible gas is hydrogen gas.

[22] The method according to any one of items 14 to 21, wherein the combustion-supporting gas is oxygen gas.

[23] The method according to any one of items 14 to 22, wherein the non-combustible gas is carbon dioxide gas and / or nitrogen gas.

[24] The method according to any one of items 14 to 23, wherein the pressure inside the culture tank is atmospheric pressure or higher.

[0014] According to the present invention, it is possible to provide a highly safe culture system and a culture method in which the risk of explosion is lower than conventional systems when adjusting recycled gas by reusing off-gas in the fermentation culture of microorganisms.

[0015] Fig. 1 is a schematic diagram showing an example of the configuration of a culture system of the present invention. Fig. 2 is a schematic diagram showing an example of the configuration of a culture system of the present invention. Fig. 3 is a schematic diagram showing an example of the configuration of a culture system of the present invention.

[0016] Hereinafter, embodiments for carrying out the present invention will be described, but the technical scope of the present invention is not limited to the following embodiments. The prior art documents cited in this specification are incorporated herein by reference. The present invention can be modified, for example, by adding, deleting, or substituting constituent elements of the present invention, provided that the modifications do not depart from the spirit of the present invention.

[0017] In this specification, terms such as "first," "second," "third," etc. are used to distinguish one element from another; for example, a first element may be expressed as a second element, and similarly, a second element may be expressed as a first element, without departing from the scope of the present invention.

[0018] Unless otherwise defined, all terms (technical and scientific) used herein have the same meaning as commonly understood by one of ordinary skill in the art.

[0019] <Microbial Culture System> Figures 1 to 3 are schematic diagrams illustrating a microbial culture system (1, 1a, 1b) in one embodiment. However, the configurations shown in the drawings of the present application are merely examples, and the configuration of the culture system of the present invention is not limited thereto. In this specification, elements with the same reference numerals are basically used to indicate the same elements. Furthermore, depending on the purpose and necessity, only some of the elements constituting the culture system 1, 1a, or 1b may be employed, or any combination may be employed. The description of each element of the culture system of the present invention also applies, as appropriate, to the method of the present invention described later.

[0020] In one embodiment, a culture system 1 of the present invention (e.g., FIG. 1) comprises: a culture tank 10; a recycled gas adjustment unit; a first gas circulation line 12 having one end connected to the top of the culture tank and the other end connected to the recycled gas adjustment unit; and a second gas circulation line 13 having one end connected to the recycled gas adjustment unit and the other end connected to supply recycled gas into the culture tank.

[0021] In the culture system 1 of the present invention, a recycle gas adjustment unit (e.g., gas mixer 11) is connected to one or more gas supply units selected from the group consisting of a combustible gas supply unit 14, a combustion-supporting gas supply unit 15, and a non-combustible gas supply unit 16, and the recycle gas adjustment unit is configured to mix one or more gas components selected from the group consisting of a combustible gas, a combustion-supporting gas, and a non-combustible gas (also referred to as an "inert gas") with at least a portion of the off-gas discharged from the culture tank 10 so that the concentration of the combustion-supporting gas in the recycle gas falls within a predetermined range.

[0022] The culture tank 10 employed in the culture system 1 of the present invention can be a culture tank suitable for the type of microorganism to be cultured and for achieving the purpose (e.g., optimal conditions for producing a desired substance produced by the microorganism). The capacity and shape of the culture tank 10 are not limited and can be selected according to the application, purpose, etc., but for example, cylindrical, bale-shaped, spherical, and other culture tanks can be used. The culture tank 10 may be equipped with a stirring blade for stirring the medium, may circulate the medium and stir it by liquid flow, or may be equipped with a stirring device that rocks the culture tank 10 itself. The culture tank 10 may also be equipped with a temperature control device (e.g., a heater, cooling coil, etc.) for maintaining the temperature of the medium at a desired temperature. The culture tank 10 may also be equipped with a pH sensor, a dissolved oxygen (DO) sensor, and / or a pressure sensor for monitoring the conditions of the medium in the culture tank 10, and a combination of devices and sensors installed in known culture tanks can be used according to the application and purpose.

[0023] The culture system 1 of the present invention can be applied particularly to fermentation culture using a combustible gas. Combustible gases that can be applied to the culture system 1 of the present invention (and the method of the present invention) include, but are not limited to, gases such as hydrogen, ammonia, and hydrogen sulfide, as well as volatile hydrocarbons (for example, but not limited to, methane, or hydrocarbons with a carbon number (C) of 2 or more (for example, C ２－８ Alkanes of C ３－８ Acyclolcan, C ２－８ Alkenes of C ３－８ or a cycloalkene of C ２－８ Examples of suitable gases include gases obtained by volatilization of organic compounds (e.g., alkynes, benzene, etc.), and for example, when the microorganism used for fermentation is a hydrogen-oxidizing bacterium, hydrogen gas can be used.

[0024] To prevent gas explosions of gas compositions containing combustible gases, it is important to (i) eliminate ignition sources and (ii) ensure that the gas composition does not fall within the explosive composition range. However, removing ignition sources is not easy, and ignition can occur due to, for example, static electricity, making it difficult to implement complete countermeasures. Therefore, the latter countermeasure, i.e., gas composition management, is usually prioritized. Generally, combustible gases pose an extremely low risk of combustion or explosion on their own. For combustible gases to combust or explode, they must be mixed with a combustion-supporting gas (combustible component) such as oxygen in a certain ratio, and combustion and explosion will occur when certain conditions, such as temperature (or an ignition source), are met.

[0025] As used herein, the term "combustion-stimulating gas" refers to a gas that does not burn by itself but has the property of promoting combustion when mixed with a combustible gas, and includes, for example, oxygen, ozone, nitrous oxide, nitric oxide, nitrogen dioxide, fluorine, chlorine, chlorine dioxide, nitrogen trifluoride, chlorine trifluoride, silicon tetrachloride, and oxygen difluoride. The combustion-stimulating gas applicable to the culture system 1 of the present invention (and the method of the present invention) can be any of the above gases, but considering that it is used to culture microorganisms, it is preferable that it contains oxygen gas or be oxygen gas. In some cases, air containing oxygen gas can also be used as the combustion-stimulating gas applicable to the culture system 1 of the present invention (and the method of the present invention). When adjusting the recycle gas by adding air to the off-gas, the concentration of other gas components (e.g., nitrogen gas) contained in the air can be adjusted. In this specification, the term "single combustion-supporting gas" does not mean that it does not contain any components other than the combustion-supporting gas, but rather means that it may contain components other than the combustion-supporting gas in an amount of, for example, less than 5%, preferably less than 4%, 3%, 2%, 1%, 0.5%, or 0.1%.

[0026] For example, in the case of a mixture of two components, a combustible gas and a combustion-supporting gas, combustion and explosion can be prevented by keeping the concentration of the combustible gas below the lower explosion limit or above the upper explosion limit of the mixture. The lower explosion limit refers to the lowest concentration of the combustible gas at which combustion can continue, and the upper explosion limit refers to the lowest concentration of the combustion-supporting gas at which combustion can continue. Therefore, when the composition of the upper explosion limit is expressed in terms of the concentration of the combustion-supporting gas, explosion can be prevented by keeping the concentration of the combustion-supporting gas in this mixture below that concentration. When the combustion-supporting gas is oxygen gas, the oxygen concentration at the upper explosion limit is specifically referred to as the "explosive limit oxygen concentration" (see: Shozo Yagyu, "Explosive Limit Oxygen Concentration with the Addition of Inert Gas," Safety Engineering, Vol. 25, No. 4 (1986)).

[0027] Therefore, in the culture system 1 (and the method) of the present invention, the amount of gas components added by the recycle gas adjusting unit is adjusted so that the concentration of the combustion-supporting gas in the recycle gas is within a predetermined range, i.e., below the explosive limit concentration (e.g., below the explosive limit oxygen concentration), thereby preventing the recycle gas from exploding and enabling safe and efficient fermentation culture. The explosive limit concentration varies depending on the gas components that may be contained in the recycle gas, and can be appropriately set based on publicly known information depending on the purpose of the fermentation culture and the means used (e.g., the type of microorganism, the type of combustible gas, the type of non-combustible gas). (See, for example, Shozo Yagyu, "Explosive Limit Oxygen Concentration in the Addition of Inert Gas," Safety Engineering, Vol. 25, No. 4 (1986), etc.)

[0028] When the off-gas or recycled gas contains at least three components, including a combustible gas, a combustion-supporting gas, and a non-combustible gas, the mixture ratio of each of the three components can be determined based on publicly known information so as not to fall within the explosion limit range (see, for example, Shozo Yagyu, "Explosion Limit Oxygen Concentration with Inert Gas Addition," Safety Engineering, Vol. 25, No. 4 (1986) and Shozo Yagyu, "Explosion Range of Mixed Gases (2)," Safety Engineering, Vol. 1, No. 2 (1962)). For example, but not limited to, if the gas components contained in the off-gas or recycled gas are composed of hydrogen gas (combustible gas), carbon dioxide gas (non-combustible gas), and oxygen gas (combustible gas), under normal temperature and pressure conditions, the oxygen gas concentration is hardly affected by the ratio of the other two components, and the upper explosion limit is approximately 5%. Furthermore, if it is necessary to increase the oxygen gas concentration, the hydrogen gas concentration can be reduced to 8% or less to fall outside the explosion limit. Furthermore, if the carbon dioxide gas concentration is 80%, the hydrogen gas and carbon dioxide gas concentrations can be up to 10% each. Therefore, the mixing ratio of each gas component can be adjusted depending on the type and growth state of the microorganism to which the present invention is applied, the types of combustible and non-combustible gases contained in the off-gas or recycled gas, etc. At least from the viewpoint of safety, the concentration of the combustion-supporting gas (e.g., oxygen gas) can be controlled to be within a predetermined range, preferably below the explosive limit oxygen concentration. For example, when the combustible gas is hydrogen gas, the oxygen concentration is preferably adjusted to be less than 5%. The concentrations of other gas components in the recycled gas are preferably adjusted to be within a predetermined range depending on the type of microorganism used and the efficient production of the desired substance.

[0029] In the culture system 1 of the present invention (and the method of the present invention), the non-combustible gas may be, for example, helium gas, nitrogen gas, water vapor, carbon dioxide gas, carbon tetrachloride gas, or the like, or a combination of these non-combustible gases may be used. The explosion range of the non-combustible gas changes depending on the non-combustible gas, so the non-combustible gas can be selected appropriately depending on the purpose. In the culture system 1 of the present invention (and the method of the present invention), the non-combustible gas may include carbon dioxide gas and / or nitrogen gas. Furthermore, the non-combustible gas used in the present invention may serve as a substrate used in microbial fermentation and may be selected appropriately depending on the type of microorganism. For example, carbon dioxide gas may be used as a fermentation substrate for the microorganism.

[0030] In one embodiment, the second gas circulation line 13 may further include a first gas concentration meter 23 for measuring the concentration of at least the combustion-stimulating gas in the recycled gas (see, for example, FIGS. 2 and 3). Based on the concentration of the combustion-stimulating gas measured by the first gas concentration meter 23, the recycled gas adjustment unit performs feedback adjustment so that the concentration of the combustion-stimulating gas in the recycled gas is within a predetermined range (for example, below the explosion limit concentration). This allows the concentration of the combustion-stimulating gas in the recycled gas introduced into the culture tank to be controlled so as not to exceed a predetermined concentration, thereby preventing the concentration of the combustion-stimulating gas in the entire culture system (1a, 1b) of the present invention from exceeding a predetermined concentration, thereby further improving safety.

[0031] In one embodiment, the combustible gas supply unit 14 can be independently connected to the recycle gas adjustment unit. The combustible gas supply unit 14 contains a single combustible gas and is substantially free of other components, such as a combustion-supporting gas. Therefore, the composition of the combustible gas contained therein is not within the explosive composition range. Furthermore, because the combustible gas supply unit 14 is independently connected to the recycle gas adjustment unit, the concentration of the combustion-supporting gas is kept below the explosion limit even in the line connecting the combustible gas supply unit 14 to the recycle gas adjustment unit, thereby ensuring safety. Note that, in this specification, the term "single combustible gas" does not mean that the gas contains no components other than the combustible gas, but rather means that the gas may contain components other than the combustible gas at a concentration of, for example, less than 5%, preferably less than 4%, 3%, 2%, 1%, 0.5%, or 0.1%.

[0032] In one embodiment, the recycle gas adjustment unit may be configured to mix combustible and / or non-combustible gas components in the recycle gas so that the concentrations of these gas components are within a predetermined range. The concentrations of the combustible and / or non-combustible gas are preferably adjusted to fall within a predetermined range, depending on the type of microorganism used and the desired substance to be produced. This adjusts the concentrations of gases other than the combustion-supporting gas in the recycle gas, allowing the recycle gas to be supplied to the culture tank under conditions more suitable for microbial fermentation, thereby allowing fermentation to proceed efficiently.

[0033] In one embodiment, the upper portion of the culture tank 10 and / or the first gas circulation line 12 may further include a second gas concentration meter 24 for measuring the concentration of at least the combustion-stimulating gas in the off-gas (see, for example, FIGS. 2 and 3). This allows for advance detection of abnormalities, for example, when the culture state of the microorganisms suddenly changes and the concentration of the combustion-stimulating gas (e.g., oxygen gas) contained in the off-gas deviates from the concentration range expected during normal culture (e.g., when the oxygen concentration in the off-gas does not decrease below the concentration range expected during normal culture). Based on the detected abnormality, for example, the amount of gas components added by the recycle gas adjustment unit can be adjusted, preventing the concentration of the combustion-stimulating gas from falling outside the predetermined range and further enhancing safety. Therefore, in one embodiment, the culture system (1a, 1b) may have a mechanism in which the recycle gas adjustment unit performs feedforward adjustment based on the concentration of the combustion-stimulating gas measured by the second gas concentration meter 24 so that the concentration of the combustion-stimulating gas in the recycle gas is within a predetermined range.

[0034] The first gas concentration meter 23 and / or the second gas concentration meter 24 may further have a function of measuring the concentrations of combustible gas and / or non-combustible gas, thereby making it possible to confirm that the concentrations of combustible gas and / or non-combustible gas contained in the off-gas and / or recycled gas are within a predetermined range, in particular, that they are in a culture condition suitable for culturing microorganisms.

[0035] In one embodiment, the combustion-stimulating gas supply unit 15 and the non-combustible gas supply unit 16 may be connected to a recycle gas adjustment unit so that the combustion-stimulating gas and the non-combustible gas are premixed before being mixed with the off-gas (FIGS. 2 and 3). For example, the combustion-stimulating gas supply line 150 connected to the combustion-stimulating gas supply unit 15 and the non-combustible gas supply line 160 connected to the non-combustible gas supply unit 16 may be joined to form the combustion-stimulating gas / non-combustible gas supply line 170, which may be connected to a recycle gas adjustment unit (e.g., gas mixer 11, 11b). This allows the combustion-stimulating gas and the non-combustible gas to be premixed before being mixed with the off-gas. Premixing the combustion-stimulating gas and the non-combustible gas reduces the concentration of the combustion-stimulating gas provided at a high concentration, reducing the risk of combustion due to the flammable range when mixed with the off-gas, and reducing the risk of combustion or corrosion of metal materials caused by the combustion-stimulating gas.

[0036] Microorganisms that can be cultured in the culture system 1 of the present invention (and the method of the present invention) are not particularly limited, and may be, for example, aerobic fermentation bacteria or anaerobic fermentation bacteria. Examples of aerobic fermentation bacteria that can be used include hydrogen-oxidizing bacteria.

[0037] Hydrogen-oxidizing bacteria is a general term for bacteria that oxidize free hydrogen and use the energy generated by the reaction to perform carbon dioxide assimilation.

[0038] Examples of hydrogen-oxidizing bacteria include, but are not limited to, Achromobacter, Acidithiobacillus, Acidovorax, Alcaligenes, Anabaena, Aquifex, Arthrobacter, Azospirillum, Bacillus, Bradyrhizobium, Cupriavidus, and the like. idus), Derxia, Helicobacter, Herbaspirillum, Hydrogenobacter, Hydrogenobaculum, Hydrogenophaga, Hydrogenophilus, Hydrogenothermus, Hydrogenovibrio, Ideonella sp. O1, Ideonella sp. O1), Kyrpidia, Metallosphaera, Methanobrevibacter, Mycobacterium, Nocardia, Oligotropha, Paracoccus, Pelomonas, Polaromonas, Pseudomonas, Schizosaccharomyces cerevisiae ... Pseudonocardia, Rhizobium, Rhodococcus, Rhodopseudomonas, Rhodospirillum, Streptomyces, Thiocapsa, Treponema, Variovorax, Xanthobacter,Alternatively, it may be a bacterium of the genus Autersia, or a combination of two or more of these.

[0039] In one embodiment of the culture system 1 of the present invention (and the method of the present invention), the interior of the culture tank 10 can be adjusted to a pressure equal to or higher than atmospheric pressure by any pressurizing means (e.g., a pump or compressor). This allows the recycled gas supplied to the culture tank 10 to be efficiently dissolved in the medium, thereby promoting fermentation culture of the microorganisms. The pressure in the culture tank 10 may be, for example, a gauge pressure (differential pressure relative to atmospheric pressure), of 0.01 MPa to 1.0 MPa, 0.01 MPa to 0.5 MPa, 0.01 MPa to 0.2 MPa, or 0.05 MPa to 0.2 MPa.

[0040] In one embodiment of the culture system 1, a compressor may be provided in the first gas circulation line to circulate the off-gas. The compressor applicable to the present invention is not limited, but may be, for example, an axial compressor, a centrifugal compressor, a reciprocating compressor, or a rotary compressor, and may be appropriately selected in consideration of the purpose, the scale of the system, the gas composition of the off-gas and / or the recycled gas, etc.

[0041] In one embodiment of the culture system 1, the recycle gas adjustment unit may be, for example, one or more gas mixers (11, 11a, 11b) (FIGS. 1 to 3). Operation of the gas mixers (11, 11a, 11b) mixes the combustible gas, combustion-stimulating gas, and / or non-combustible gas supplied from the combustible gas supply unit 14, the combustion-stimulating gas supply unit 15, and / or the non-combustible gas supply unit 16 with the off-gas, adjusting the concentration of the combustion-stimulating gas in the recycle gas to be within a predetermined range (e.g., below the explosive limit of oxygen concentration). A single gas mixer (11) may be connected to the combustible gas supply unit 14 via a combustible gas supply line 140, the combustion-stimulating gas supply unit 15 via a combustion-stimulating gas supply line 150, and the non-combustible gas supply unit 16 via a non-combustible gas supply line 160. Furthermore, the combustible gas supply unit 14, the combustion supporting gas supply unit 15, and the non-combustible gas supply unit 16 may be connected to multiple gas mixers (11a, 11b), respectively. For example, the combustible gas supply unit 14, the combustion supporting gas supply unit 15, and the non-combustible gas supply unit 16 may be connected to three gas mixers, respectively. Furthermore, for example, of two gas mixers (11a, 11b), the combustible gas supply unit 14 may be connected to one gas mixer 11a, and the combustion supporting gas supply unit 15 and the non-combustible gas supply unit 16 may be connected to the other gas mixer 11b.

[0042] In one embodiment of the culture system (1a, 1b) (e.g., Figures 2 to 3), the recycle gas adjusting unit may include: one or more gas mixers (11, 11a, 11b); a first gas adjusting unit 141 for adjusting the amount of combustible gas supplied from the combustible gas supply unit 14; a second gas adjusting unit 151 for adjusting the amount of combustion-supporting gas supplied from the combustion-supporting gas supply unit 15; and a third gas adjusting unit 161 for adjusting the amount of non-combustible gas supplied from the non-combustible gas supply unit 16.

[0043] The first gas adjustment unit 141, the second gas adjustment unit 151, and / or the third gas adjustment unit 161 may be provided along the combustible gas supply line 140, the combustion supporting gas supply line 150, and / or the non-combustible gas supply line 160 (e.g., FIGS. 2 and 3 ), or may be provided at the gas outlet of the combustible gas supply unit 14, the combustion supporting gas supply unit 15, and / or the non-combustible gas supply unit 16. The first gas adjustment unit 141, the second gas adjustment unit 151, and / or the third gas adjustment unit 161 can adjust the amount of gas components supplied using an opening / closing mechanism such as a valve (e.g., a solenoid valve). The first gas adjustment unit 141, the second gas adjustment unit 151, and / or the third gas adjustment unit 161 are feedback-adjusted as appropriate in accordance with the gas composition of the recycled gas measured by the first gas concentration meter 23, thereby preventing the gas composition of the recycled gas from falling within the explosive range and further improving safety.

[0044] <Cultivation Method Using Off-Gas Recycling in a Microorganism-Based Cultivation System> In one embodiment, the method of the present invention may include the following steps: (1) culturing a culture containing a microorganism and a culture medium provided in a culture tank of the culture system by supplying a feed gas containing a combustible gas, a combustion-supporting gas, and a non-combustible gas; (2) preparing a recycled gas by mixing at least a portion of the off-gas discharged from step (1) with one or more gas components selected from the group consisting of the combustible gas, the combustion-supporting gas, and the non-combustible gas, wherein the concentration of the combustion-supporting gas in the recycled gas is within a predetermined range; and (3) carrying out step (1), supplying the recycled gas obtained in step (2) as the feed gas to the culture. The method of the present invention can be implemented, for example, by employing the above-described culture system. However, the configuration of the culture system is not limited to the above-described configuration as long as the method of the present invention can be implemented. Note that the components described in the above <Microorganism Cultivation System> may be applied to the configuration applicable to the method of the present invention.

[0045] In one embodiment of the method, the culture medium used in the system and method of the present invention is selected appropriately depending on the type of microorganism used, and is not particularly limited, as it may be any known culture medium or a culture medium whose composition is appropriately modified depending on the purpose.

[0046] In one embodiment, in the step (2), one or more gas components selected from the group consisting of a combustible gas, a combustion-supporting gas, and a non-combustible gas are mixed with at least a portion of the off-gas discharged from the step (1) to prepare a recycled gas. As described above, the concentration of the combustion-supporting gas in the recycled gas may be controlled to be within a predetermined range, and from a safety standpoint, it is more preferable to control it to be below the explosion limit concentration. The concentrations of other gas components in the recycled gas are preferably adjusted to be within their respective predetermined ranges depending on the type of microorganism used and the efficient production of the desired substance.

[0047] In one embodiment, the method of the present invention includes, after step (2) and before step (3), (2') measuring the concentration of at least the combustion-stimulating gas in the recycled gas, and based on the concentration of the combustion-stimulating gas measured in step (2'), feedback adjustment may be performed so that the concentration of the combustion-stimulating gas in step (2) is within a predetermined range (e.g., below the explosion limit concentration). This allows the concentration of the combustion-stimulating gas in the recycled gas introduced into the culture tank to be controlled so as not to exceed a predetermined concentration, thereby preventing the combustion-stimulating gas concentration from exceeding a predetermined concentration in the entire system to which the method of the present invention is applied, thereby further improving safety.

[0048] In one embodiment, the combustible gas to be mixed in the method of the present invention is preferably mixed independently with the off-gas. By independently supplying a single combustible gas to the off-gas, the concentration of the combustion-supporting gas in the combustible gas is kept below the explosion limit concentration until it is mixed with the off-gas, thereby ensuring safety.

[0049] In one embodiment, the combustible gas and / or non-combustible gas mixed by the method of the present invention is mixed with the gas components in the recycled gas so that the gas components fall within a predetermined range. The concentrations of the combustible gas and / or non-combustible gas are preferably adjusted to fall within a predetermined range, respectively, depending on the type of microorganism used and the desired substance to be produced. In this way, by adjusting the concentrations of gases other than the combustion-supporting gas in the recycled gas, gases suitable for fermentation can be supplied to the culture tank, allowing fermentation to proceed efficiently.

[0050] In one embodiment, the method of the present invention may further include the step of: (1') measuring the concentration of at least the combustion-supporting gas in the off-gas discharged from step (1) after step (1) and before step (2). This makes it possible to detect a sudden change in the oxygen concentration in the off-gas due to a sudden change in the culture state of the microorganism (for example, when the oxygen concentration does not decrease) before the recycle gas is generated, thereby preventing the concentration of the combustion-supporting gas in the recycle gas from falling outside a predetermined range, and is expected to further enhance safety.

[0051] Therefore, one embodiment of the method of the present invention may include the following step after step (1) and before step (2): (1'') measuring the concentration of at least the combustion-supporting gas in the off-gas discharged from step (1), and performing feedforward adjustment so that the concentration of the combustion-supporting gas in step (2) falls within a predetermined range based on the concentration of the combustion-supporting gas measured in step (1'').

[0052] In one embodiment of the present invention, in each step, the concentration of combustible gas and / or non-combustible gas contained in the off-gas and / or recycled gas may be measured, and the concentration of the combustible gas and / or non-combustible gas may be adjusted to fall within a predetermined range, particularly to provide culture conditions suitable for culturing microorganisms.

[0053] In one embodiment of the method of the present invention, in step (2), the combustion-supporting gas and the non-combustible gas may be premixed before being mixed with the off-gas, thereby reducing the concentration of the combustion-supporting gas provided at a high concentration, thereby reducing the risk of combustion due to a flammable range when mixed with the off-gas, and also reducing the risk of combustion or corrosion of metal materials due to the combustion-supporting gas.

[0054] DESCRIPTION OF SYMBOLS 1, 1a, 1b Cultivation system 10 Cultivation tank 11, 11a, 11b Gas mixer 12 First gas circulation line 13 Second gas circulation line 14 Combustible gas supply unit 15 Combustion-supporting gas supply unit 16 Non-combustible gas supply unit 17 Microorganism 18 Culture medium 19 Off-gas 20 Off-gas flow direction 21 Recycle gas flow direction 22 Compressor 23 First gas concentration meter 24 Second gas concentration meter 140 Combustible gas supply line 141 First gas adjustment unit 142 Feedback control signal to first gas adjustment unit 150 Combustion-supporting gas supply line 151 Second gas adjustment unit 152 Feedback control signal to second gas adjustment unit 160 Non-combustible gas supply line 161 Third gas adjustment unit 162 Feedback control signal to third gas adjustment unit 170 Combustible gas / non-combustible gas supply line

Claims

1. A microbial culture system, which includes the following: Culture tank and; Recycle gas adjustment unit and; A first gas circulation line, one end of which is connected to the upper part of the culture tank and the other end of which is connected to the recycle gas adjustment unit; A second gas circulation line, one end of which is connected to the recycle gas adjustment unit and the other end of which is connected to supply recycle gas into the culture tank; It is equipped with, In this culture system, the recycled gas adjustment unit is connected to a combustible gas supply unit, a combustion-supporting gas supply unit, and a non-combustible gas supply unit, and the recycled gas adjustment unit mixes one or more gas components selected from the group consisting of combustible gas, combustion-supporting gas, and non-combustible gas into at least a portion of the off-gas discharged from the culture tank so that the concentration of combustion-supporting gas in the recycled gas is within a predetermined range.

2. The second gas circulation line is further equipped with a first gas concentration meter for measuring the concentration of at least combustion-supporting gases in the recycled gas. The culture system according to claim 1, wherein the recycled gas adjustment unit provides feedback adjustment based on the concentration of the combustion-supporting gas measured by the first gas concentration meter so that the concentration of the combustion-supporting gas in the recycled gas falls within a predetermined range.

3. The culture system according to claim 1 or 2, wherein the combustible gas supply unit is independently connected to the recycle gas adjustment unit.

4. The culture system according to claim 1 or 2, wherein the recycled gas adjustment unit mixes the gas components so that the concentration of the combustible gas and / or non-combustible gas in the recycled gas is within a predetermined range.

5. The culture system according to claim 1 or 2, further comprising a second gas concentration meter for measuring the concentration of at least combustion-supporting gases in the off-gas, located above the culture tank and / or in the first gas circulation line.

6. The culture system according to claim 1 or 2, wherein the combustion-supporting gas supply unit and the non-combustible gas supply unit are connected to the recycle gas adjustment unit so that the combustion-supporting gas and the non-combustible gas are premixed before being mixed with the off-gas.

7. The culture system according to claim 1 or 2, wherein the microorganism is an aerobic fermenting bacterium.

8. The culture system according to claim 7, wherein the aerobic fermentation bacteria are hydrogen-oxidizing bacteria, and the combustible gas is hydrogen gas.

9. The culture system according to claim 1 or 2, wherein the combustion-supporting gas is oxygen gas.

10. The culture system according to claim 1 or 2, wherein the non-combustible gas is carbon dioxide gas and / or nitrogen gas.

11. The culture system according to claim 1 or 2, wherein the pressure inside the culture tank is greater than or equal to atmospheric pressure.

12. The culture system according to claim 1 or 2, further comprising a compressor in the first gas circulation line.

13. The aforementioned recycled gas adjustment unit With one or more gas mixers; A first gas adjustment unit for adjusting the amount of combustible gas supplied from the combustible gas supply unit; A second gas adjustment unit for adjusting the amount of combustion-supporting gas supplied from the aforementioned combustion-supporting gas supply unit; A third gas adjustment unit for adjusting the amount of non-combustible gas supplied from the aforementioned non-combustible gas supply unit; Includes, The culture system according to claim 1 or 2, wherein the combustible gas supply unit, the combustion-supporting gas supply unit, and the non-combustible gas supply unit are connected to the gas mixer.

14. A method for culturing microorganisms by recycling off-gas in a culture system, the following: (1) A step of culturing a culture, which includes microorganisms and culture medium, in a culture tank of a culture system by supplying a supply gas containing a combustible gas, a combustion-supporting gas, and a non-combustible gas; (2) A step of preparing a recycled gas by mixing at least a portion of the off-gas discharged from step (1) with one or more gas components selected from the group consisting of the combustible gas, the combustion-supporting gas and the non-combustible gas, wherein the mixing is performed such that the concentration of the combustion-supporting gas in the recycled gas is within a predetermined range; and (3) A step of carrying out step (1) above, wherein the recycled gas obtained in step (2) above is supplied to the cultured material as the supply gas. Methods that include...

15. After step (2) and before step (3), (2') A step of measuring the concentration of at least combustion-supporting gas in the recycled gas. The method according to claim 14, further comprising, and based on the concentration of the combustion-supporting gas measured in step (2'), feedback adjustment is performed so that the concentration of the combustion-supporting gas in step (2) is within a predetermined range.

16. The method according to claim 14 or 15, wherein the flammable gas is independently mixed with at least a portion of the off-gas.

17. The method according to claim 14 or 15, wherein the combustible gas and / or the non-combustible gas are mixed with the gas components such that they are within a predetermined concentration range in the recycled gas.

18. After step (1) and before step (2), (1') A step of measuring the concentration of at least combustion-supporting gas in the off-gas discharged from step (1) above. The method according to claim 14 or 15, including the method described in claim 14 or 15.

19. The method according to claim 14 or 15, wherein in step (2), the combustion-supporting gas and the non-combustible gas are premixed before being mixed with at least a portion of the off-gas.

20. The method according to claim 14 or 15, wherein the microorganism is an aerobic fermenting bacterium.

21. The method according to claim 20, wherein the aerobic fermenting bacteria are hydrogen-oxidizing bacteria, and the combustible gas is hydrogen gas.

22. The method according to claim 14 or 15, wherein the combustion-supporting gas is oxygen gas.

23. The method according to claim 14 or 15, wherein the non-combustible gas is carbon dioxide gas and / or nitrogen gas.

24. The method according to claim 14 or 15, wherein the pressure inside the culture vessel is greater than or equal to atmospheric pressure.