Bacterial cultivation apparatus and bacterial cultivation method

Abstract

To improve the cultivation efficiency of bacteria nourished by inorganic gas containing an inorganic carbon source.SOLUTION: A bacterial cultivation apparatus 1 comprises: an inorganic culture solution 11 for bacteria nourished by inorganic gas containing an inorganic carbon source; bubble generating means 30 including a diffuser 31 and a pump 32 for generating bubbles of inorganic gas containing an inorganic carbon source in the inorganic culture solution 11; and a carrier 41 which includes a chemical fiber bundle, having voids between the chemical fiber fibers, is submerged in the inorganic culture solution 11, and allows bacteria to adhere thereto.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a bacterial culture apparatus and a bacterial culture method for culturing bacteria that use an inorganic gas containing an inorganic carbon source as a nutrient source, and in particular to a bacterial culture apparatus and a bacterial culture method that can improve the efficiency of bacterial culture. [Background technology]

[0002] In recent years, there has been concern about the impact of an increase in atmospheric carbon dioxide on global warming. In particular, chemical, cement, steel, and other manufacturing plants emit large amounts of gases, including carbon dioxide, generated by fuel combustion during the production process of industrial products, and release them into the atmosphere. As the problem of global warming becomes more serious, there is an ever-increasing demand to reduce carbon dioxide, a greenhouse gas, in order to achieve carbon neutrality. Therefore, in addition to reducing carbon dioxide emissions through the use of green energy and electrification, active research is being conducted into reducing carbon dioxide by fixing carbon dioxide contained in the atmosphere and exhaust gases using artificial photosynthesis and microorganisms, etc. In particular, technology to fix carbon dioxide using microorganisms is attracting a great deal of attention due to the possibility that microorganisms can convert carbon dioxide into organic matter that can be used as a resource.

[0003] For example, Patent Document 1 discloses a technology in which hydrogen bacteria in a culture medium are cultured while being supplied with hydrogen, carbon dioxide, and a substance that functions as the final electron acceptor for the hydrogen bacteria, while being supplied with electrons via an electron mediator substance that can take both oxidized and reduced forms, thereby controlling the metabolism of the hydrogen bacteria and increasing the amount of useful substances in the metabolic products produced by the hydrogen bacteria as carbon dioxide fixation products. Patent Document 2 discloses a technique for cultivating carbon monoxide-resistant bacteria in a mixed gas containing carbon dioxide, hydrogen, oxygen, and nitrogen while fixing carbon dioxide, and for causing the bacteria to accumulate and produce biodegradable plastics. Furthermore, Patent Document 3 discloses a method for culturing hydrogen bacteria that is safe to work with, does not inhibit bacterial growth, and exhibits good proliferation effects by adding fluorocarbon to an autotrophic medium that uses carbon dioxide as the only carbon source.

[0004] As shown in Patent Documents 1 to 3, in verifying the consumption of substrates by hydrogen bacteria and the amount of product produced, the hydrogen bacteria are inoculated into a culture solution (liquid medium), a mixed gas containing carbon dioxide as a carbon source is sealed in the head space (gas phase) of a container containing the culture solution, and the container containing the culture solution is shaken and stirred to dissolve the substrate gas into the culture solution. For this reason, the efficiency of bacterial cultivation is low, making it unsuitable for mass cultivation. On the other hand, Patent Document 4 describes the direct introduction of a substrate gas (gaseous resource) into a culture solution (fermentation solution) as bubbles. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2017-093465 A [Patent Document 2] JP 2004-051920 A [Patent Document 3] Japanese Patent Application Publication No. 04-271778 [Patent Document 4] JP 2012-100547 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, even if the substrate gas is directly introduced into the culture solution as gas bubbles, most of the supplied substrate gas simply passes through the culture solution as a gas and rises to the surface, and there is still a problem that the substrate gas cannot be efficiently utilized by the bacteria.

[0007] Therefore, an object of the present invention is to provide a bacterial culture apparatus and a bacterial culture method that can improve the culture efficiency of bacteria that use an inorganic gas containing an inorganic carbon source as a nutrient source. [Means for solving the problem]

[0008] The bacterial culture device of the invention of claim 1 comprises an inorganic culture solution for bacteria that uses an inorganic gas containing an inorganic carbon source as a nutrient source, a bubble generating means for generating bubbles of the inorganic gas containing the inorganic carbon source in the inorganic salt culture solution, and a carrier consisting of an aggregate of chemical fibers having voids between the chemical fibers, which is immersed in the inorganic salt culture solution and to which the bacteria adhere.

[0009] The bacteria that use inorganic gases containing the inorganic carbon source as a nutrient source are bacteria that use inorganic carbon sources such as carbon dioxide or carbon monoxide as a nutrient source, and convert inorganic carbon such as carbon dioxide into organic matter by reducing it using energy or light energy produced by the oxidation reaction of inorganic matter (energy source), and can grow in the absence of organic carbon. For example, chemoautotrophic bacteria that use carbon dioxide as an inorganic carbon source and reduced inorganic matter such as hydrogen, carbon monoxide, hydrogen sulfide, sulfur compounds, iron (II) oxide, nitrous acid, and ammonia as an energy source to grow, specifically, hydrogen bacteria (hydrogen oxidizing bacteria, hydrogen assimilating bacteria), acetic acid producing bacteria, methanogens, methane oxidizing bacteria, nitrate bacteria, nitrite bacteria, sulfur oxidizing bacteria, iron oxidizing bacteria, anammox bacteria, etc., carbon monoxide assimilating bacteria that use carbon monoxide as an inorganic carbon source and reduced inorganic matter such as hydrogen as an energy source to grow, and photoautotrophic bacteria that use carbon dioxide as an inorganic carbon source and light as an energy source to grow. The inorganic culture solution contains inorganic salts in water, and preferably contains a nitrogen source such as ammonium salts or nitrates.

[0010] The bubble generating means may be any means capable of generating bubbles of inorganic gas containing an inorganic carbon source in the inorganic culture solution. For example, inorganic gas bubbles may be generated in the inorganic culture solution by releasing the inorganic gas into the inorganic culture solution using an air pump or an aeration device, or the inorganic gas may be pressurized and dissolved in the inorganic culture solution at several atmospheric pressures, and the pressure may be rapidly reduced to atmospheric pressure using a pressure reducing valve or the like to cause the inorganic gas dissolved in excess of the pressure in the pressurized environment to precipitate as bubbles (reduced pressure foaming). Alternatively, bubbles may be generated by mixing and vibrating the outer surface of the gas-liquid mixture using a high-speed jet or swirling flow, or ultrasonic waves, etc., to entrain the inorganic gas in the gas phase in the inorganic culture solution and incorporate it as bubbles. Preferably, bubbles of inorganic gas are ejected into the inorganic culture solution using an air pump or an aeration device, etc., because bubbles can be generated at low cost.

[0011] The carrier preferably has a three-dimensional mesh structure formed by chemical fibers that meander irregularly in three dimensions and are bonded and entangled at various points, and consists of a fiber assembly with gaps between the chemical fibers.The carrier is immersed in an inorganic culture solution and allows bacteria to adhere to it.

[0012] The chemical fiber of the carrier of the bacteria culture device of the invention according to claim 2 is made of a hydrophobic resin. The hydrophobic resin is, for example, a thermoplastic resin exhibiting hydrophobicity, and may be a hydrophilic fiber whose surface has been subjected to a hydrophobic treatment.

[0013] The chemical fiber of the carrier of the bacterial culture device of the invention of claim 3 has a critical surface tension γc of the polymer of its constituent material preferably in the range of 12 mN / m or more and 60 mN / m or less, more preferably 15 mN / m or more and 60 mN / m or less, and even more preferably 25 mN / m or more and 55 mN / m or less. The above surface tension is the critical surface tension γc of the polymer of the chemical fiber that constitutes the carrier, and can be determined by a Zisman plot based on the measurement results of the contact angle (θ).

[0014] The porosity of the carrier immersed in the inorganic culture solution of the bacterial culture device of the invention of claim 4 is preferably in the range of 35.0% or more and 99.5% or less, more preferably 40.0% or more and 99.5% or less, and even more preferably 45.0% or more and 99.5% or less. The porosity is calculated by the following formula (1). Porosity (%) = 100 {1 - bulk density of carrier (Kg / L) / true density of carrier (Kg / L)} (1)

[0015] The carrier of the bacteria-cultivating device of the invention according to claim 5 is non-water-absorbent.

[0016] The bacterial culture method of the invention of claim 6 comprises immersing a carrier consisting of an aggregate of chemical fibers with voids between the chemical fibers in an inorganic culture solution for bacteria that use an inorganic gas containing an inorganic carbon source as a nutrient source, and culturing the bacteria by generating bubbles of the inorganic gas containing the inorganic carbon source in the inorganic culture solution.

[0017] The bacterial culture method of the invention of claim 7 comprises, after culturing the bacteria, separating and recovering the bacteria from the inorganic culture solution and the carrier, and recovering organic substances produced by the bacteria, such as bioplastics, proteins, organic acids, alcohols, aldehydes, esters, etc. The bacteria can be separated from the culture medium and the carrier by, for example, passing water or the like through the carrier to separate the bacteria from the carrier, or by using a centrifuge to separate the liquid and the bacteria from the liquid containing the bacteria. Effect of the Invention

[0018] According to the bacterial culture device of the invention of claim 1, bubbles of inorganic gas containing an inorganic carbon source are generated by the bubble generating means in the inorganic culture solution of bacteria that uses the inorganic gas containing an inorganic carbon source as a nutrient source, so that bacteria tend to aggregate at the inorganic gas bubble interface, and bacteria tend to grow because they can immediately take in the inorganic gas dissolved in water from the inorganic gas bubble interface. And, by immersing a carrier made of an aggregate of chemical fibers and having voids between the chemical fibers in the inorganic culture solution of bacteria, the inorganic gas bubbles tend to pass through the voids in the carrier and remain in the inorganic culture solution, and are dispersed and fined, and further, bacteria tend to attach to the carrier and grow and diffuse there, so that the contact efficiency (contact frequency) and contact area between the inorganic gas bubbles and bacteria can be increased, and bacteria tend to grow. Therefore, the efficiency of culturing bacteria that utilize the inorganic gas containing an inorganic carbon source as a nutrient source can be improved.

[0019] According to the bacterial culture apparatus of the invention of claim 2, the chemical fiber of the carrier is made of a hydrophobic resin, so in addition to the effect of claim 1, the bacteria adhering to the carrier can be easily separated and recovered from the carrier.

[0020] According to the bacterial culture apparatus of the invention of claim 3, the critical surface tension γc of the polymer constituting the carrier is preferably 12 mN / m or more and 60 mN / m or less, so that the bacteria in the inorganic culture solution can adhere, settle and grow there easily, and in addition to the effect described in claim 1, the bacteria can be cultured more efficiently.

[0021] According to the bacterial culture apparatus of the invention of claim 4, the carrier preferably has a porosity of 35.0% or more and 99.5% or less, so that the contact efficiency and contact area between the inorganic gas bubbles and the bacterial cells can be increased, and in addition to the effect described in claim 1, the bacteria can be cultured more efficiently.

[0022] According to the bacterial culture apparatus of the invention of claim 5, the carrier is non-water-absorbent and bacteria do not enter the carrier by absorbing water, so in addition to the effect of claim 1, it is easy to separate and recover the bacterial cells from the carrier.

[0023] According to the bacterial culture method of the invention of claim 6, inorganic gas bubbles containing an inorganic carbon source are generated in an inorganic culture solution for bacteria that use the inorganic gas containing an inorganic carbon source as a nutrient source, so that bacteria tend to aggregate at the inorganic gas bubble interface, and bacteria can readily take in the inorganic gas dissolved in water from the inorganic gas bubble interface, which facilitates bacteria proliferation. In addition, a carrier made of an aggregate of chemical fibers and having voids between the chemical fibers is immersed in an inorganic culture solution for bacteria, so that inorganic gas bubbles tend to pass through the voids in the carrier and remain in the inorganic culture solution, and are dispersed and miniaturized, and bacteria tend to attach to the carrier and proliferate and diffuse there, so that the contact efficiency (contact frequency) and contact area between the inorganic gas bubbles and bacteria can be increased, facilitating bacteria proliferation. Therefore, the efficiency of culturing bacteria that utilize the inorganic gas containing an inorganic carbon source as a nutrient source can be improved.

[0024] According to the bacterial culture method of the invention of claim 7, after culturing the bacteria, the bacteria are separated from the inorganic culture solution and the carrier, and the organic matter produced by the bacteria is recovered. Therefore, in addition to the effect described in claim 6, the cultured bacteria can be recovered without waste, and a large amount of the organic matter produced by the bacteria can be recovered. [Brief description of the drawings]

[0025] [Figure 1] FIG. 1 is a schematic diagram of a bacteria culture device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is an explanatory diagram of an experimental example in which bacteria were cultured using the bacterial culture apparatus according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the embodiments, the same symbols and the same reference numerals indicate parts having the same or corresponding functions, and therefore, detailed descriptions thereof will be omitted here.

[0027] [Embodiment Mode] First, a bacteria culture apparatus 1 according to an embodiment of the present invention will be described with reference to FIG. As shown diagrammatically in FIG. 1, the bacterial culture apparatus 1 of this embodiment includes an inorganic culture solution 11 for bacteria that uses an inorganic gas containing an inorganic carbon source as a nutrient source, a bubble generating means 30 for generating bubbles of the inorganic gas containing the inorganic carbon source in the inorganic culture solution 11, and a carrier 41 immersed in the inorganic culture solution 11.

[0028] Bacteria that use inorganic gases containing inorganic carbon sources as a nutrient source are bacteria that use inorganic carbon sources such as carbon dioxide or carbon monoxide as a nutrient source, and use energy from the oxidation reaction of inorganic substances (energy sources) or light energy to reduce inorganic carbon such as carbon dioxide to organic substances, thereby being able to grow in the absence of organic carbon. Examples of such bacteria include chemoautotrophic bacteria, photoautotrophic bacteria, and carbon monoxide-utilizing bacteria.

[0029] Chemoautotrophic bacteria are bacteria that synthesize organic matter within the bacterial cells by reducing carbon dioxide using energy from the oxidation reaction of inorganic substances, i.e., bacteria that obtain energy through the oxidation of inorganic substances and use that energy to synthesize necessary organic matter within the bacterial cells from carbon dioxide, and examples of such bacteria include hydrogen bacteria (hydrogen oxidizing bacteria, hydrogen assimilating bacteria), methanogens, methane oxidizing bacteria, nitrate bacteria, nitrite bacteria, sulfur oxidizing bacteria, iron oxidizing bacteria, anammox bacteria, acetic acid producing bacteria, etc. Inorganic substances used as energy sources by these chemoautotrophic bacteria include reduced inorganic substances such as hydrogen, carbon monoxide, hydrogen sulfide, sulfur compounds, iron oxide (II), nitrite, ammonia, etc. Photoautotrophic bacteria are bacteria that synthesize organic matter within the cells of their bodies by reducing carbon dioxide using light energy, and examples of such bacteria include purple sulfur bacteria, green sulfur bacteria, and cyanobacteria. These chemoautotrophic and photoautotrophic bacteria are bacteria that utilize carbon dioxide as an inorganic carbon source and perform carbon fixation (carbon assimilation, carbon assimilation, carbon fixation).

[0030] The inorganic culture solution 11 for culturing bacteria that use inorganic gases containing such inorganic carbon sources as a nutrient source contains water and inorganic substrates (e.g., nitrogen (N), phosphorus (P), potassium (K), iron (Fe), magnesium (M), nickel (Ni)) necessary for the growth and proliferation of bacteria, and contains, for example, nitrogen sources such as phosphates, ammonium salts, and nitrates, and inorganic ions such as phosphate ions, potassium ions, magnesium ions, iron ions, manganese ions, sulfate ions, and calcium ions. The types of inorganic salts such as nitrogen and minerals are appropriately selected depending on the type of bacteria to be cultured.

[0031] More specifically, the inorganic culture solution 11 is, for example, ammonium sulfate ((NH 4 ) 2 SO 4 ), potassium dihydrogen phosphate (KH 2 PO 4 ), dipotassium hydrogen phosphate (K 2 HPO 4 ), magnesium sulfate hydrate (MgSO 4 7H 2 O), ferrous sulfate (FeSO 4 7H 2 O), calcium chloride (CaCl 2 ), sodium chloride (NaCl), ammonium chloride (NH 4 Cl), magnesium chloride (MgCl 2 6H 2 O), iron chloride (FeCl 2 4H 2 O), nickel chloride, etc. Also contains trace elements (e.g., zinc sulfate (ZnSO 4 7H 2 O), copper sulfate (CuSO 4 5H 2 O), manganese sulfate (MnSO 4 5H 2 O), molybdenum oxide (MoO 3 ), Sodium molybdate (Na 2 MoO 4 2H 2 O), cobalt chloride (CoCl 2 6H 2 O), Nickel chloride (NiCl2 6H 2 O), boric acid (H 3 BO 3 )), micronutrients, buffering agents, etc.

[0032] For example, in the case of culturing hydrogen bacteria, the inorganic culture medium 11 is preferably sodium hydrogen phosphate (Na 2 HPO 4 ), Sodium dihydrogen phosphate (KH 2 PO 4 ) and sodium bicarbonate (NaHCO 3 ) or a pH buffering agent (e.g., HEPES) in the inorganic culture solution 11, the inorganic culture solution 11 can be endowed with pH buffering ability. That is, a drop in pH due to dissolved carbon dioxide or products such as hydrogen bacteria is prevented, and inhibition of growth and proliferation of the hydrogen bacteria and the like due to a drop in pH is prevented. When culturing hydrogen bacteria and the like, it is preferable to control the inorganic culture solution 11 to a pH of, for example, 2.0 to 12.0, preferably 4.0 to 9.5, and more preferably 6.5 to 7.5. For example, ammonia and the like can be used as a pH neutralizing component. Ammonia can also replenish the nitrogen source consumed in the inorganic culture solution 11 assimilated by the hydrogen bacteria and the like.

[0033] In the bacterial culture apparatus 1 of this embodiment, an aeration section 31 for bubbling an inorganic gas is disposed in the inorganic culture solution 11, and the inorganic gas is sent to the aeration section 31 by a pump 32, and the inorganic gas is ejected from a hole (opening) of the aeration section 31, thereby generating bubbles in the inorganic culture solution 11. That is, the bubble generating means 30 of this embodiment is composed of the pump 32 for sending the inorganic gas, the aeration section 31 for ejecting the inorganic gas sent from the pump 32 into the inorganic culture solution 11, and the like.

[0034] In this manner, when bubbles of inorganic gas containing a carbon source are supplied to the inorganic culture solution 11 using the bubble generating means 30, the bacteria in the inorganic culture solution 11 tend to aggregate at the bubble interface, and the bacteria can immediately take up the inorganic gas dissolved at the bubble interface, thereby allowing the inorganic gas to be efficiently taken up by the bacteria.

[0035] In the bacterial culture apparatus 1 of this embodiment, the carrier 41 is placed in the inorganic culture solution 11. The carrier 41 of this embodiment is made of a fiber assembly, which is a three-dimensional network structure formed by bonding (binder bonding, welding, etc.) and entangling chemical fibers, which are continuous filaments, in a three-dimensional irregular (random) manner, and has interconnected voids (spaces) between the fibers. Such a fiber assembly allows air bubbles and water to pass through by having interconnected voids between the fibers. It is preferably non-water-absorbent. It is also flexible, elastic (cushioning), and easily deformable. Furthermore, since it is made of a chemical fiber material, it is easy to process into a desired shape, lightweight, and available at low cost. The carrier 41, which is the three-dimensional network structure of this embodiment, is in the form of a three-dimensional nonwoven fabric, and can be made by processing fibers that have been curled into a lock (curly) shape into a nonwoven fabric; for example, resin is fed into a carding machine to form sheets, which are then stacked and entangled with needles to form a nonwoven fabric; or molten resin is extruded as a continuous filament in an extrusion molding machine, so that the resin curls and becomes randomly entangled and partially fused into a nonwoven fabric.

[0036] The chemical fibers constituting the carrier 41 are preferably hydrophobic synthetic fibers (hydrophobic fibers) from the viewpoint of ease of separation and recovery of the proliferated bacteria, and are, for example, resins such as polyester, polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, polyethylene, polyvinylidene chloride, polyvinyl chloride, polymethyl methacrylate, polyacrylamide, polystyrene, and polypropylene. Among them, polyester and polyvinylidene chloride resins are more preferable because they are inexpensively available, have high critical surface tension, and can improve wettability of the liquid containing bacteria. In addition, the fineness of the chemical fibers constituting the carrier 41 is, for example, 60 to 1500 dtx, and may be a single type or a mixture of multiple types. The cross-sectional shape of the fibers, whether solid or hollow, is not particularly important.

[0037] The carrier 41 made of the fiber aggregate, which is a three-dimensional network structure, has a specific gravity in the range of 0.8 to 2.0 and a bulk density of 0.01 to 0.2 g / cm. 3 Within the range of 4 to 30 m 2 / m 2 Within the range of 450~4000g / m 2 Preferably, a material within the range is used. Furthermore, the shape of the carrier 41 is not particularly limited, and for example, carriers formed into a sheet, plate, columnar, prismatic (rectangular parallelepiped, cubic), cylindrical, or square tube shape can be used.

[0038] By placing the carrier 41 made of a three-dimensional mesh-like fiber aggregate in the inorganic culture solution 11 for bacteria, the bacteria will adhere and settle there. In particular, since the carrier 41 is a three-dimensional mesh-like fiber aggregate and has a large surface area due to the gaps between the fibers, the bacteria inoculated in the inorganic culture solution 11 can easily adhere in large numbers. Therefore, the product substances secreted by the bacteria are also less likely to flow into the inorganic culture solution 11, and a protective film made of the product substances secreted by the bacteria, a so-called biofilm, is more likely to be formed on the carrier 41, making it easier for the bacteria to grow and spread on the carrier 41. As the bacterial growth area expands, the contact area and contact efficiency between the inorganic gas bubbles and the bacteria increase, making it easier for the bacteria to grow. Furthermore, by placing the carrier 41 made of an aggregate of chemical fibers in the inorganic culture solution 11, the inorganic gas bubbles generated from the aeration section 31 below the inorganic culture solution 11 rise through the gaps in the carrier 41 while colliding with or becoming entangled with the carrier 41, so the presence of the carrier 41 increases the resistance to passage of the inorganic gas bubbles generated from the aeration section 31, making it easier for the inorganic gas bubbles to remain. Furthermore, the interconnected gaps between the fibers of the carrier 41 also make it possible to disperse and refine the bubbles. This increases the contact area and contact efficiency between the inorganic gas bubbles and the bacteria, making it easier for the bacteria to grow.

[0039] In particular, the carrier 41, which is a chemical fiber assembly, preferably has a critical surface tension γc of the polymer of its constituent material of 12 mN / m or more and 60 mN / m or less, more preferably 15 mN / m or more and 60 mN / m or less, even more preferably 25 mN / m or more and 55 mN / m or less, and particularly preferably 28 mN / m or more and 50 mN / m or less. If it is within this range, even if the carrier 41 is made of hydrophobic fibers, the inorganic culture solution 11 will be well wetted, and the bacteria in the inorganic culture solution 11 will adhere to the carrier 41 and become easily fixed. Therefore, it is possible to increase the contact efficiency and contact area between the inorganic gas bubbles and the bacteria, and further increase the bacterial culture efficiency.

[0040] The porosity of the carrier 41, which is a fiber assembly, is preferably 35.0% or more and 99.5% or less, more preferably 40.0% or more and 99.5% or less, even more preferably 45.0% or more and 99.5% or less, and particularly preferably 50.0% or more and 99.0% or less. If it is within this range, it is possible to prevent the coalescence of bubbles in the voids of the carrier 41, and the surface area is large so that many bacteria can be attached, thereby increasing the contact efficiency and contact area between the inorganic gas bubbles and the bacteria, and further increasing the bacterial culture efficiency.

[0041] Thus, the bacterial culture device 1 of this embodiment includes an inorganic culture solution 11 for bacteria that uses an inorganic gas containing an inorganic carbon source as a nutrient source, a bubble generating means 30 consisting of an aeration unit 31 and a pump 32 that generate bubbles of the inorganic gas containing the inorganic carbon source in the inorganic culture solution 11, and a carrier 41 that is immersed in the inorganic culture solution 11. Usually, the inorganic culture solution 11 is contained in a container 21, the carrier 41 is immersed in the inorganic culture solution 11 in the container 21, and the aeration unit 31 is placed in the inorganic culture solution 11 in the container 21, and bubbles of the inorganic gas are supplied to the inorganic culture solution 11 by the aeration unit 31 from below the inorganic culture solution 11 in the container 21.

[0042] The container 21 for containing the inorganic culture solution 11 is not particularly limited in shape, size, material, etc., as long as the inorganic culture solution 11 does not leak to the outside. In terms of heat and moisture barrier properties, pressure resistance, corrosion resistance, etc., metal, resin, glass, etc. are preferably used, and a heat insulating material may be combined. The side surface may be curved to increase the aeration efficiency. In this embodiment, the inorganic culture solution 11 can be stirred by bubbling using the aeration unit 31, but it is preferable to further stir the inorganic culture solution 11 at a stirring speed of, for example, 50 rpm to 1500 rpm using stirring means 71 such as a stirring blade. This allows the inorganic gas bubbles to be dispersed and easily retained in the inorganic culture solution 11, thereby increasing the contact efficiency between the inorganic gas bubbles and bacteria.

[0043] Furthermore, it is preferable that the carrier 41 immersed in the inorganic culture solution 11 in the container 21 is held in a predetermined position without flowing in the inorganic culture solution 11, and in order to raise the bottom to avoid contact with the stirring means 71 or the aeration section 31, or to maintain a predetermined porosity, the carrier 41 may be held by a water-permeable reticulate, mesh, net-like or other holder (e.g., a container, etc.) and immersed in the inorganic culture solution 11. At this time, the carrier 41 does not have to be entirely immersed in the inorganic culture solution 11 when no inorganic gas bubbles are being generated; that is, it may be only partially immersed, and preferably, it is immersed to the extent that when inorganic gas bubbles are generated in the inorganic culture solution 11, the bubbles pass through the carrier 41 and reach the upper surface of the carrier 41. In addition, the cultivation of bacteria in the bacterial culture apparatus 1 is usually carried out in an airtight state, and while an inorganic gas is supplied continuously or intermittently, the pressure inside the apparatus may be adjustable by allowing the air inside the apparatus to be freely exhausted.

[0044] Here, the inorganic gas supplied to the inorganic culture liquid 11 contains at least an inorganic carbon source such as carbon dioxide or carbon monoxide. When chemoautotrophic bacteria such as hydrogen bacteria or carbon monoxide-utilizing bacteria are cultured as bacteria that use inorganic gas containing an inorganic carbon source as a nutrient source, the inorganic gas contains hydrogen, carbon monoxide, etc., which serve as energy sources used in the reduction of the inorganic carbon source. Furthermore, in the case of aerobic bacteria that obtain energy by aerobic oxidation of hydrogen, etc., that is, hydrogen bacteria that use oxygen as an electron acceptor and use the energy obtained by oxidizing inorganic substances such as hydrogen with oxygen to reduce carbon dioxide, the inorganic gas contains oxygen.

[0045] As a supply source of inorganic gases such as carbon dioxide, hydrogen, and oxygen, combustion gases emitted from heating, air-conditioning, warming, and cooling devices in factories, etc., and exhaust gases such as hydrogen exhaust gas emitted in the manufacturing process of industrial products, etc. can be used. For example, chemical industry factories that manufacture chemicals, cement, steel, etc., emit hydrogen exhaust gases such as by-product hydrogen (for example, hydrogen produced as a by-product during the manufacture of caustic soda, chlorine gas, ethylene, etc., during coke refining, during petroleum refining, during the dehydrogenation condensation reaction of silicone in the manufacture of chemical products, during chemical edging treatment, during die casting treatment, etc.) and combustion exhaust gases containing carbon dioxide, and in particular emit a large amount of carbon dioxide, a greenhouse gas.Factories also emit oxygen that is not used for combustion (surplus oxygen). That is, sources of carbon dioxide include, for example, exhaust gas from combustion gases, and exhaust gas containing carbon dioxide generated as a by-product during steelmaking, the manufacture of petrochemical products, or the manufacture of other products. Sources of hydrogen include, for example, hydrogen gas produced by steam reforming or partial oxidation reforming from fossil fuels such as natural gas or petroleum in a factory, hydrogen gas produced by electrolysis of water, and exhaust gas from hydrogen gas produced by reforming of methanol or ethanol. Sources of oxygen include exhaust gas and air discharged from a factory containing oxygen generated as a by-product during the electrolysis of water, etc. Therefore, by using exhaust gases from factories, etc. that contain carbon dioxide, hydrogen, and oxygen as substrate gases for bacteria, and consuming the carbon dioxide-containing exhaust gases emitted from factories, etc. as a substrate for bacteria, it is possible to reduce the amount of carbon dioxide emitted into the environment.

[0046] Incidentally, exhaust gas discharged from a factory or the like may be supplied directly to the aeration section 31 via pump 32, or may be supplied after being treated to remove impurities using a filter or the like or after being sterilized, or may be supplied after being concentrated, highly concentrated, and highly purified using a concentrator / separator or the like.

[0047] In this embodiment, bubbles of inorganic gas containing at least an inorganic carbon source are supplied to the inorganic culture solution 11, but when culturing bacteria that use inorganic substances such as hydrogen as an energy source or require oxygen for the oxidation of inorganic substances, bubbles of a mixed gas of an inorganic carbon source gas such as carbon dioxide and an inorganic energy source gas such as hydrogen gas or an electron acceptor oxygen gas may be supplied to the inorganic culture solution 11, or each gas may be bubbled separately and supplied to the inorganic culture solution 11. Alternatively, an inorganic energy source gas such as hydrogen gas or an electron acceptor oxygen gas may be supplied to the gas phase (head space) of the bacterial culture apparatus 1 without being bubbled.

[0048] Furthermore, the bacterial culture apparatus 1 of this embodiment may be provided with a circulation means for recovering the gas phase, sending it to the pump 32, sending it from the pump 32 to the aeration section 31, and supplying it again as air bubbles into the inorganic culture solution 11. By circulating the inorganic gas supplied to the bacterial culture apparatus 1 and repeatedly supplying it as air bubbles into the inorganic culture solution 11, the utilization rate of the inorganic gas can be increased and the amount of carbon dioxide and the like to be exhausted can be reduced.

[0049] The bacterial culture device 1 of this embodiment contains an inorganic culture solution 11 of bacteria that uses an inorganic gas containing an inorganic carbon source as a nutrient source in a container 21, and is provided with an aeration section 31 that generates bubbles of the inorganic gas containing the inorganic carbon source in the inorganic culture solution 11 contained in the container 21. Also, a carrier 41 made of an aggregate of chemical fibers is immersed in the inorganic culture solution 11. Bacteria are inoculated (inoculated) into the inorganic culture solution 11 and the carrier 41, and the inorganic gas bubbles are introduced into the inorganic culture solution 11 from the aeration section 31 via a pump 32, thereby culturing the bacteria. In addition, inoculation (inoculation) of bacteria into the inorganic culture solution 11 or the carrier 41 is carried out, for example, by adding bacterial powder, colonies, undiluted liquid, etc. to the inorganic culture solution 11, or by rubbing or painting bacterial powder, colonies, undiluted liquid, etc. onto the carrier 41.

[0050] According to the bacterial culture device 1 of this embodiment, which is composed of an inorganic culture solution 11 for bacteria that use inorganic gas containing such an inorganic carbon source as a nutrient source, a bubble generating means 30 consisting of an aeration section 31 and a pump 32 that generate bubbles of inorganic gas containing the inorganic carbon source in the inorganic culture solution 11, and a carrier 41 consisting of an aggregate of chemical fibers immersed in the inorganic culture solution 11, since inorganic gas bubbles are supplied into the inorganic culture solution 11, the bacteria in the inorganic culture solution 11 tend to aggregate at the bubble interface, and the bacteria tend to quickly take up the inorganic gas dissolved at the bubble interface, which increases the contact efficiency between the bacteria and the bubble gas and makes it easier for the bacteria to grow.

[0051] In particular, by immersing the carrier 41, which is made of an aggregate of chemical fibers and has gaps between the fibers, in the inorganic culture solution 11, the inorganic gas bubbles rise while passing through the gaps between the fibers of the carrier 41, and are therefore likely to remain in the culture solution 11 and are further likely to be dispersed and micronized. This increases the contact efficiency and contact area between the bacteria and the inorganic gas, making it easier for the bacteria to grow. Furthermore, by immersing the carrier 41, which is made of an aggregate of chemical fibers and has gaps between the fibers, in the inorganic culture solution 11, the bacteria in the inorganic culture solution 11 attach and settle on the carrier 41 made of chemical fibers, and grow there, expanding the growth area. In particular, in the case where the bacteria are suspended in the inorganic culture solution 11, the secretions from the bacteria are easily washed away, making it difficult to form a biofilm, whereas in the case where the bacteria are attached to the carrier 41 made of chemical fibers, the secretions from the bacteria are difficult to wash away, making it easier to form a biofilm, expanding the growth area of ​​the bacteria on the carrier 41 and increasing the contact efficiency and contact area with the inorganic gas. Therefore, the contact efficiency and contact area between the bacteria and the inorganic gas are further increased, making it easier for the bacteria to grow.

[0052] Thus, according to the bacterial culture device 1 of this embodiment, bacteria can easily take in inorganic gas, and bacterial culture efficiency can be improved. In particular, by immersing the carrier 41 made of an aggregate of chemical fibers in the inorganic culture solution 11, it is possible to retain air bubbles in the inorganic culture solution 11 for a long time and to disperse and refine the air bubbles. Furthermore, it is possible to attach and settle the bacteria on the carrier 41, thereby expanding the growth area there. This increases the contact efficiency and contact area between the bacteria and the inorganic gas, thereby increasing the bacterial culture efficiency without significantly increasing the energy consumption. In other words, the bacterial culture efficiency can be improved with an energy-saving design.

[0053] According to the bacterial culture device 1 of this embodiment, bacteria are cultured using inorganic gas containing an inorganic carbon source as a nutrient source, and since the bacteria consume carbon dioxide when assimilating carbon dioxide as an inorganic carbon source, if exhaust gas containing carbon dioxide from a factory or the like is supplied as inorganic gas, the emission of carbon dioxide into the outside air can be suppressed and carbon dioxide can be reduced. In particular, since the cultivation of hydrogen bacteria that use carbon dioxide as an inorganic carbon source and assimilate hydrogen as an energy source consumes carbon dioxide and hydrogen, if exhaust gas containing carbon dioxide and hydrogen from a factory or the like is supplied as inorganic gas, carbon dioxide can be reduced with little environmental load by effectively utilizing hydrogen such as by-product hydrogen, and inorganic resources can be effectively utilized.

[0054] When by-product hydrogen is effectively utilized as a fuel cell, there are problems with the quality of the battery, such as the stability of the amount of power generated and deterioration of the fuel cell stack, whereas in the embodiment, in which the by-product hydrogen is consumed by the hydrogen bacteria cultivated in the bacterial culture device 1, the hydrogen bacteria selectively use the carbon dioxide and hydrogen contained in the inorganic gas supplied, so that even if the hydrogen purity of the inorganic gas containing by-product hydrogen is low or the gas composition and supply amount are unstable and fluctuating, there are no quality problems as in the case of use in a fuel cell, etc. Therefore, even hydrogen exhaust gas with low hydrogen purity and unstable supply amount can be effectively utilized for environmental purification by consuming carbon dioxide using the by-product hydrogen contained therein.

[0055] In particular, in the bacterial culture device 1 of this embodiment, the fixation of carbon dioxide using inorganic compounds such as hydrogen as an energy source by chemoautotrophic bacteria such as hydrogen bacteria does not require a large and vast light receiving area or installation area to obtain sufficient light, unlike the consumption of carbon dioxide using photosynthesis by photosynthetic bacteria, that is, carbon fixation using photosynthesis. Therefore, it can be installed in both bright and dark places, and can be made compact, allowing carbon dioxide to be consumed and fixed in a small space and at low cost.

[0056] Furthermore, among the chemoautotrophic bacteria that fix carbon, hydrogen bacteria have better energy efficiency for carbon fixation than carbon fixation that uses light energy (photosynthesis), and some species have faster growth rates, which allows for higher carbon fixation efficiency and therefore higher efficiency in the consumption of hydrogen and carbon dioxide. Furthermore, hydrogen bacteria do not require a special nutrient substrate for cultivation, and can be cultivated using inexpensive materials that are easily available. In addition, the influence of fluctuations in the components of the inorganic culture solution 11, such as pH, is small, and it is possible to increase the amount of bacteria (increase the concentration of bacteria), and bacteria can be cultivated efficiently with less effort required to replace the inorganic culture solution 11 frequently. In addition, hydrogen bacteria have simple nutritional requirements, and under culture conditions where hydrogen is present in high concentration, the proliferation of miscellaneous bacteria due to contamination is unlikely to occur, and no harmful substances are discharged, so maintenance and management are easy, and disposal of the inorganic culture solution 11 is not complicated. In other words, in an environment with a high hydrogen concentration, the growth of other bacteria is suppressed, and hydrogen bacteria can be cultivated preferentially, so filter sterilization of the inorganic gas supplied is not necessarily required, and a simple configuration can be achieved. Therefore, carbon dioxide can be consumed at low cost.

[0057] Hydrogen bacteria use carbon dioxide as an inorganic carbon source and hydrogen as an energy source. They use the energy obtained by aerobic oxidation of hydrogen with oxygen, or by the oxidation of carbon dioxide and nitrate ions (NO 3 - ) as an electron acceptor and anaerobically oxidize hydrogen to obtain energy to fix carbon dioxide, grow, and proliferate. That is, the hydrogen bacteria used to fix carbon dioxide may be ones that use oxygen as an electron acceptor to aerobically oxidize hydrogen and assimilate carbon dioxide, or ones that use carbon dioxide or nitrate ions as electron acceptors to anaerobically oxidize hydrogen and assimilate carbon dioxide.

[0058] In particular, the hydrogen bacteria that oxidize hydrogen aerobically use the assimilated oxygen as an electron acceptor to aerobically oxidize (assimilate) free hydrogen, and further use the energy generated by the reaction to assimilate carbon dioxide (carbon dioxide gas) of the inorganic carbon source, and also assimilate inorganic nutrient substrates such as inorganic salts in the inorganic culture liquid 11 to grow and grow. Therefore, in the presence of hydrogen, carbon dioxide, and oxygen supplied as inorganic gases, and inorganic nutrient substrates such as inorganic salts, the bacteria aerobically oxidize hydrogen using oxygen, and further use the oxidation energy to absorb carbon dioxide and fix carbon dioxide, thereby growing and growing. In the hydrogen bacteria that oxidize hydrogen aerobically, carbon dioxide is also produced by aerobic respiration, but the amount produced by respiration is less than the amount of carbon dioxide fixed. When aerobic hydrogen bacteria are used, for example, the ratio of inorganic gases carbon dioxide, hydrogen, and oxygen is supplied at carbon dioxide:hydrogen:oxygen=1:7-8:1-2.

[0059] Examples of such hydrogen bacteria include those of the genera Alcaligenes, Aquaspirillum, Arthrobacter, Azospirillum, Bacillus, Bradyrhizobium, Burkholderia, Calderobacterium, Cupriavidus, Derxia, Flavobacterium, Frankia, Helicobacter, Hydrogenobacter, Hydrogenomonas, Hydrogenovibrio, Mycobacterium, Microcyclus, Norcadia, Paracoccus, Pseudmonas, Pyrinomonas, Streptomyces, Ralstonia, Renobacter, Rhizobium, Rhodococcus, Variovorax, and Xantobacter. Transformants may also be used. Hydrogen bacteria are generally short rods, gram-negative, asporogenous rods, and have polar hairs. For example, those isolated from soil or water can be used.

[0060] Among bacteria that use inorganic gases containing inorganic carbon sources as a nutrient source, there are some that reduce inorganic carbon sources such as carbon dioxide to produce a large amount of useful organic matter inside or outside the bacterial cell. For example, there are bacteria that produce organic resources such as organic acids (polyhydroxyalkanoic acid (PHA), polyhydroxybutyric acid (PHB), 4-hydroxybenzoic acid (PHBA), hydroxyisobutyric acid, hydroxybutyric acid, methylcitric acid, lactic acid, carboxylic acid, acetic acid, etc.), polysaccharides, amino acids, peptides, proteins (lysine, arginine, tryptophan, methionine, cyanophycin, organophosphorus hydrolase, etc.), fatty acids (linear saturated fatty acids, etc.), amines, esters (lactones, phosphate esters, etc.), nucleic acids, enzymes, vitamins, physiologically active substances, and bioplastics (polyesters, etc.). Therefore, according to the bacterial culture apparatus 1 of the present embodiment, the bacterial culture efficiency can be increased, and therefore the production efficiency of these organic resources can also be increased.

[0061] Regarding useful organic resources produced by specific bacteria, useful resources such as acids, proteins, bioplastics, etc. can be recovered by recovering the bacterial cells cultured in the bacterial culture device 1 of this embodiment and extracting and separating the above-mentioned organic resources such as acids, proteins, bioplastics, etc. from the bacterial cells. That is, in the bacterial culture apparatus 1 of this embodiment, the bacteria that use inorganic gases containing inorganic carbon sources as a nutrient source can fix carbon dioxide, a greenhouse gas, with the energy obtained when hydrogen and the like are oxidized, and can also convert these into useful resources. In particular, while carbon dioxide may be emitted in the industrial process when organic resources are produced by chemical synthesis, by using specific bacteria to convert carbon dioxide into organic matter, it is possible to obtain organic resources with little environmental impact.

[0062] At this time, in the bacterial culture device 1 of this embodiment, the carrier 41 is made of a chemical fiber assembly, has flexibility, elasticity, and is easily deformed. If the carrier 41 is non-water-absorbent, the liquid containing the bacteria attached inside the carrier 41 can be easily discharged to the outside by compressing and deforming the carrier 41. In particular, if the carrier 41 is made of hydrophobic fibers, the bacteria attached to the carrier 41 can be easily separated from the carrier 41 by running water through the carrier 41, and the bacteria attached to the carrier 41 can be recovered with a high recovery rate. Then, the liquid containing the washed-out bacteria and the inorganic culture liquid 41 containing the bacteria can be easily separated into the bacteria (sediment) and the liquid (supernatant) by centrifuging, and only the bacteria (sediment) can be recovered. Furthermore, the organic matter produced by the bacteria can be recovered by appropriately extracting the recovered bacteria (sediment). Thus, in the bacterial culture apparatus 1 of this embodiment, the grown bacteria can be easily recovered from the carrier 41 and the inorganic culture solution 11 at a high recovery rate, and a large amount of product (organic resource) can be recovered from the bacteria.

[0063] Furthermore, the carrier 41 of this embodiment is a fiber assembly of a three-dimensional network structure formed by chemical fibers that are three-dimensionally irregularly meandering and bonded and entangled at various points, so it is strong, resistant to corrosion, and has good durability. Also, preferably, the carrier 41 is not moved in the inorganic culture solution 11 but is held in a predetermined position, so there is no wear due to abrasion between the carriers 41. Therefore, the carrier 41 can be made to last a long time, and can be used repeatedly even after the bacteria that have grown on the carrier 41 are collected.

[0064] When bacteria are mass-cultured using the bacterial culture device 1 of this embodiment, the temperature, humidity, pressure, water level of the inorganic culture solution 11, pH, inorganic component concentration (e.g., nitrogen), etc. in the device are preferably controlled and managed within a predetermined range. At this time, such information can be detected by sensors and computer-controlled. The culture temperature of bacteria in the bacteria culture apparatus 1 is set within a suitable range since the optimum temperature for growth varies depending on the genus and species of bacteria. For hydrogen bacteria, the temperature is controlled within a range of 25 to 75°C, for example, and preferably within a range of 25 to 50°C. The temperature may also be controlled by utilizing thermal energy from waste heat from a factory.

[0065] Here, the inventors conducted comparative experiments between culturing bacteria by supplying inorganic gas bubbles into the inorganic culture solution 11 in which the carrier 41 was immersed (Experimental Examples 1 to 4) and culturing bacteria by supplying inorganic gas bubbles into the inorganic culture solution 11 without adding the carrier 41 (Comparative Example 1). Specifically, in Experimental Examples 1 to 4, as shown in FIG. 2, a container 21 was filled with an inorganic culture solution 11 (Na in water). 2 HPO 4 12H 2 O 0.56 vol%, KH 2 PO 4 0.06 vol%, MgSO 4 7H 2 O 0.01 vol%, CaCl 2 0.0005 vol%, NH 4 0.12 vol% Cl, FeCl 3 6H 2 O 0.0004 vol%, NiCl 2 6H 2 A container containing 0.009 vol % O was placed in the container, and the carrier 41 was immersed therein.

[0066] An aeration unit 31 was placed below the inorganic culture solution 11 contained in the container 21, and further, an agitator 71 was placed therein. At this time, the carrier 41 was placed in a mesh-like container 23 and held at a predetermined height in the inorganic culture solution 11, away from the bottom of the container 21, so as not to come into contact with the aeration unit 31 and the agitator 71 located below the inorganic culture solution 11 in the container 21. Furthermore, the carrier 41 held in the container 23 and the container 21 containing the inorganic culture solution 11 were placed in a sealed container 25. The container 21 used in this experiment was cylindrical, and the carrier 41 was approximately cylindrical with a height (vertical length) of about 50 mm. The amount of inorganic culture solution 11 was about 400 ml, and in the initial state where inorganic gas bubbles were not being sprayed from the aeration unit 31, the upper surface of the carrier 41 was located above the liquid level of the inorganic culture solution 11. However, when inorganic gas bubbles were being sprayed from the aeration unit 31, the bubbles were set to reach above the upper surface of the carrier 41.

[0067] Then, inorganic gas was filled into the sealed container 25, and the inorganic gas in the sealed container 25 was sucked in by a pump 32 arranged outside the sealed container 25 and sent to the aeration section 31 installed in the container 21 (flow rate: 10 L / min), thereby supplying inorganic gas bubbles from the aeration section 31 into the inorganic culture solution 11, and while stirring the inorganic culture solution 11 with a stirrer 71 (speed: 100 rpm), cultivation of the bacteria (0.4 g) inoculated into the inorganic culture solution 11 in which the carrier 41 was immersed was started (under temperature control of approximately 30°C).

[0068] In this experiment, hydrogen bacteria were used as bacteria that use inorganic gas containing an inorganic carbon source as a nutrient source. More specifically, aerobic hydrogen bacteria were used that use energy obtained by aerobically oxidizing hydrogen with oxygen. A mixed gas of carbon dioxide, hydrogen, and oxygen (CO) was used as the inorganic gas containing an inorganic carbon source. 2 :O 2 :H 2 =1:1:7) was supplied in the form of air bubbles into the inorganic culture solution 11. In this experiment, as described above, the inorganic gases carbon dioxide, hydrogen, and oxygen were filled in advance into the sealed container 25, and the inorganic gas filled in the sealed container 25 was sucked in by the pump 32 and sent to the aeration section 31, thereby supplying bubbles of a mixed gas of carbon dioxide, hydrogen, and oxygen into the inorganic culture solution 11. Then, before the start of the culture and on the third day after the start of the culture, the carbon dioxide (CO 2 The amount of carbon dioxide consumed during the three-day culture was calculated by measuring the amount of carbon dioxide consumed using a gauge.

[0069] At this time, the present inventors conducted experiments using a number of different carriers 41 . In Experimental Examples 1 and 2, a fiber assembly made of hydrophobic fibers of polyester resin (polyethylene terephthalate: PET) was used as the carrier 41, in Experimental Example 3, a fiber assembly made of hydrophobic fibers of polyvinylidene chloride resin (PVDC) was used as the carrier 41, and in Experimental Example 4, a fiber assembly made of hydrophobic fibers of polypropylene resin (PP) was used as the carrier 41.

[0070] The polyester resin of the carrier 41 used in Experimental Examples 1 and 2 has a critical surface tension γc of 43 mN / m, the polyvinylidene chloride resin of the carrier 41 used in Experimental Example 3 has a critical surface tension γc of 40 mN / m, and the polypropylene resin of the carrier 41 used in Experimental Example 4 has a critical surface tension γc of 29 mN / m. The polyester resin carrier 41 used in Experimental Example 1 had a porosity of 98.6%, the polyvinylidene chloride resin carrier 41 used in Experimental Example 3 had a porosity of 95.6%, and the polypropylene resin carrier 41 used in Experimental Example 4 had a porosity of 97.3%. In Experimental Example 2, the porosity of the polyester resin carrier 41 was set to 50.0%.

[0071] The carrier 41 made of a chemical fiber assembly used in Experimental Examples 1 to 4 is a three-dimensional network structure formed by three-dimensionally irregularly curving continuous filamentary chemical fibers and bonding and entangling them at various places, with spaces between the fibers, which are interconnected to provide a predetermined porosity. The carrier 41 made of a chemical fiber assembly, which has a three-dimensional network structure, has elasticity to such an extent that the spaces between the fibers are deformed by an external force, but the spaces are restored when the external force is released. Therefore, in Experimental Example 2, an experiment was conducted by applying an external force to the carrier 41 used in Experimental Example 1 to reduce the porosity.

[0072] On the other hand, in Comparative Example 1, the carrier 41 was not used, that is, the carrier 41 was not added to the inorganic culture solution 11, and the rest of the experiment was carried out under the same conditions as those of the above-mentioned Examples 1 to 4. Table 1 shows the results of the carbon dioxide consumption (fixed amount) when the hydrogen bacteria were cultured for three days in each of the experimental examples and comparative examples.

[0073] [Table 1]

[0074] As shown in Table 1, in Experimental Examples 1 to 4, in which the carrier 41, an assembly of chemical fibers, was immersed in the inorganic culture solution 11 to culture the hydrogen bacteria, the amount of carbon dioxide consumption was greater than in Comparative Example 1, in which the hydrogen bacteria were cultured without placing the carrier 41 in the inorganic culture solution 11. Thus, in Experimental Examples 1 to 4, in which the carrier 41, an assembly of chemical fibers, was immersed in the inorganic culture solution 11 to culture the hydrogen bacteria, the bacteria grew faster and in greater numbers (greater bacterial growth), and the culture efficiency of the hydrogen bacteria was improved, compared to Comparative Example 1, in which the carrier 41 was not placed in the inorganic culture solution 11 to culture the hydrogen bacteria.

[0075] In particular, Experimental Examples 1 and 3 had higher carbon dioxide consumption than Experimental Examples 2 and 4, and the carbon dioxide consumption was 35% or more higher than Comparative Example 1 in which the carrier 41 was not used. That is, in Experimental Examples 1 and 3 in which the carrier 41 having a large critical surface tension γc of the polymer of the constituent material was used, the carbon dioxide consumption was higher than in Experimental Example 4 in which the carrier 41 having a small critical surface tension γc of the polymer of the constituent material was used. This is believed to be because in Experimental Example 4, the critical surface tension of the polymer material constituting the carrier 41 was small, which resulted in poor wetting of the inorganic culture solution 11 to the carrier 41 and low adhesion of the bacteria in the inorganic culture solution 11 to the carrier 41. In contrast, in Experimental Examples 1 and 3, which used a carrier 41 made of a resin with a large critical surface tension, the inorganic culture solution 11 wetted the carrier 41 well, and many of the bacteria inoculated into the inorganic culture solution 11 attached to and settled on the carrier 41. This is believed to have increased the contact efficiency and contact area between the inorganic gas bubbles passing through the gaps between the fibers of the carrier 41 and the bacteria, improving the efficiency of carbon dioxide consumption.

[0076] Further, even though both were made of the same polyester resin, Experimental Example 1 in which the porosity of the carrier 41 was high consumed more carbon dioxide than Experimental Example 2 in which the porosity of the carrier 41 was low. This is believed to be because in Experimental Example 2, due to the low porosity of the carrier 41, the air bubbles remained in the pores of the carrier 41 for a long time, and the air bubbles merged with each other, making the proportion of air bubbles too large, reducing the adhesion rate of bacteria and reducing the contact efficiency and contact area between the inorganic gas bubbles and the bacteria. In contrast, in Experimental Examples 1 and 3, which used a carrier 41 with a high porosity, it is presumed that the merging of air bubbles in the pores of the carrier 41 was suppressed, more bacteria adhered to the carrier 41, and the contact efficiency and contact area between the inorganic gas bubbles and the bacteria were increased, thereby improving the efficiency of carbon dioxide consumption by the bacteria.

[0077] According to the experimental research of the present inventors, the critical surface tension γc of the polymer constituting the carrier 41 is preferably 12 mN / m or more and 60 mN / m or less, more preferably 15 mN / m or more and 60 mN / m or less, even more preferably 25 mN / m or more and 55 mN / m or less, and particularly preferably 28 mN / m or more and 50 mN / m or less. If it is within this range, the inorganic culture solution 11 wets the carrier 41 well, the bacteria in the inorganic culture solution 11 adhere to the carrier 41 and are easily fixed there, the contact efficiency between the inorganic gas bubbles and the bacteria is increased, and the bacterial culture efficiency can be further improved.

[0078] The porosity of the carrier 41 is preferably 35.0% or more and 99.5% or less, more preferably 40.0% or more and 99.5% or less, even more preferably 45.0% or more and 99.5% or less, and particularly preferably 50.0% or more and 99.0% or less. Within this range, the coalescence of bubbles in the voids of the carrier 41 is suppressed, the contact efficiency and contact area between the inorganic gas bubbles and the bacteria are increased, and the bacterial culture efficiency can be further improved.

[0079] As described above, the bacterial culture apparatus 1 of this embodiment comprises an inorganic culture solution 11 for bacteria that uses an inorganic gas containing an inorganic carbon source as a nutrient source, a bubble generating means 30 consisting of an aeration section 31 and a pump 32 that generate bubbles of the inorganic gas containing the inorganic carbon source in the inorganic culture solution 11, and a carrier 41 consisting of an aggregate of chemical fibers with gaps between the chemical fibers, which is immersed in the inorganic culture solution 11 and to which bacteria adhere.

[0080] Therefore, according to the bacterial culture apparatus 1 of this embodiment, bubbles of inorganic gas containing an inorganic carbon source are generated by the bubble generating means 30 in the inorganic culture solution 11 of bacteria that use inorganic gas containing an inorganic carbon source as a nutrient source, so that bacteria tend to aggregate at the inorganic gas bubble interface, and since the bacteria can immediately take up the inorganic gas dissolved in water from the inorganic gas bubble interface, the bacteria tend to grow. Furthermore, by immersing the carrier 41, which is made of an aggregate of chemical fibers and has gaps between the chemical fibers, in the inorganic culture solution 11, the inorganic gas bubbles pass through the gaps in the carrier 41 and are easily retained in the inorganic culture solution 11, and are also dispersed and miniaturized.Furthermore, bacteria adhere to the carrier 11 and are easily able to grow and diffuse there, thereby increasing the contact efficiency and contact area between the inorganic gas bubbles and the bacterial bodies and facilitating the growth of bacteria. In this way, the inorganic gas containing an inorganic carbon source can be efficiently provided to the bacteria by the air bubble generating means 30 and the carrier 41 made of an aggregate of chemical fibers. Therefore, the efficiency of culturing bacteria that utilize the inorganic gas containing an inorganic carbon source as a nutrient source can be improved.

[0081] Furthermore, in the bacteria culture apparatus 1 of this embodiment, when the chemical fiber of the carrier 41 is made of a hydrophobic resin, the bacteria adhering to the carrier 41 can be easily separated and collected from the carrier 41. Furthermore, if the critical surface tension γc of the polymer material constituting the carrier 41 is preferably 12 mN / m or more and 60 mN / m or less, more preferably 15 mN / m or more and 60 mN / m or less, even more preferably 25 mN / m or more and 55 mN / m or less, and particularly preferably 28 mN / m or more and 50 mN / m or less, then the inorganic culture solution 11 will have good wettability to the carrier 41, and the bacteria in the inorganic culture solution 11 will be able to adhere, settle and grow there, thereby enabling the bacteria to be cultured more efficiently. In addition, if the porosity of the carrier 41 is preferably 35.0% or more and 99.5% or less, more preferably 40.0% or more and 99.5% or less, even more preferably 45.0% or more and 99.5% or less, and particularly preferably 50.0% or more and 99.0% or less, then the coalescence of bubbles in the voids of the carrier 41 is suppressed, thereby increasing the contact efficiency and contact area between the inorganic gas bubbles and the bacterial cells, and allowing the bacteria to be cultured more efficiently.

[0082] According to the bacteria culture apparatus 1 of this embodiment, the carrier 41 is non-water absorbing, so that the bacteria do not absorb water and penetrate into the inside of the carrier 41. Therefore, the bacteria can be easily separated and collected from the carrier 41.

[0083] Furthermore, the description of the above embodiment can also be considered as an invention of a bacterial culture method in which a carrier 41 consisting of an aggregate of chemical fibers and having voids between the chemical fibers is immersed in inorganic culture solution 11 for bacteria that use inorganic gas containing an inorganic carbon source as a nutrient source, and bubbles of inorganic gas containing an inorganic carbon source are generated in the inorganic culture solution 11 to culture the bacteria.

[0084] According to the bacterial culture method of the above embodiment, bubbles of inorganic gas containing an inorganic carbon source are generated in inorganic culture solution 11 of bacteria that use inorganic gas containing an inorganic carbon source as a nutrient source, so that bacteria tend to aggregate at the inorganic gas bubble interface, and the bacteria can quickly take up the inorganic gas dissolved in water from the inorganic gas bubble interface, which makes it easier for the bacteria to grow. Furthermore, by immersing the carrier 41, which is made of an aggregate of chemical fibers and has gaps between the chemical fibers, in the inorganic culture solution 11, the inorganic gas bubbles pass through the gaps in the carrier 41 and are easily retained in the inorganic culture solution 11, and are also dispersed and miniaturized.Furthermore, bacteria adhere to the carrier 11 and are easily able to grow and diffuse there, thereby increasing the contact efficiency and contact area between the inorganic gas bubbles and the bacterial bodies and facilitating the growth of bacteria. Therefore, the efficiency of culturing bacteria that utilize the inorganic gas containing an inorganic carbon source as a nutrient source can be improved.

[0085] Furthermore, in the bacterial culture method of the above embodiment, after culturing the bacteria, the bacteria are separated from the inorganic culture solution 11 and the carrier 41, and the organic matter produced by the bacteria is recovered, so that the cultured bacteria can be recovered without waste and a large amount of the organic matter produced by the bacteria can be recovered.

[0086] In addition, when implementing the present invention, the configuration, components, blending, etc. of other parts of the bacteria culture apparatus 1 are not limited to those in the above embodiment. Furthermore, the numerical values ​​given in the embodiments of the present invention do not all indicate critical values, but rather indicate suitable values ​​suitable for implementation, and therefore, even if the numerical values ​​are slightly changed within the allowable range, this does not negate the implementation. [Explanation of symbols]

[0087] 1 Bacteria culture device 11 Inorganic culture solution 30 Bubble generating means 41 Carrier

Claims

1. an inorganic culture solution for bacteria that uses inorganic gas containing an inorganic carbon source as a nutrient source; a bubble generating means for generating bubbles of inorganic gas containing the inorganic carbon source in the inorganic culture solution; a carrier consisting of an aggregate of chemical fibers, having voids between the chemical fibers, and being immersed in the inorganic culture solution to which the bacteria adhere; A bacterial culture device comprising:

2. 2. The bacteria culture device according to claim 1, wherein the chemical fiber of the carrier is made of a hydrophobic resin.

3. 2. The bacteria culture device according to claim 1, wherein the carrier has a polymeric material having a critical surface tension of 12 mN / m or more and 60 mN / m or less.

4. 2. The bacteria culture apparatus according to claim 1, wherein the carrier has a porosity of 35.0% or more and 99.5% or less.

5. 2. The bacteria culture device according to claim 1, wherein the carrier is non-water-absorbent.

6. A method for culturing bacteria, comprising the steps of: immersing a carrier consisting of an aggregate of chemical fibers having voids between the chemical fibers in an inorganic culture solution for bacteria that use an inorganic gas containing an inorganic carbon source as a nutrient source; and culturing the bacteria by generating bubbles of the inorganic gas containing the inorganic carbon source in the inorganic culture solution.

7. 7. The method for culturing bacteria according to claim 6, further comprising the steps of: separating the bacteria from the inorganic culture medium and the carrier after culturing the bacteria; and recovering organic matter produced by the bacteria.

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