Culturing device

Abstract

This culturing device for culturing microorganisms or cells in which a raw material gas is used for proliferation or production of an organic substance comprises: a culture tank for storing a culture solution for culturing microorganisms or cells; a raw material gas supply part for supplying the raw material gas to the culture tank; and a plurality of circulation paths for extracting the culture solution in the culture tank through an extraction port and returning the extracted culture solution to the culture tank as a circulation flow through a return port positioned below the extraction port in the vertical direction. The circulation paths include at least one first circulation path for returning the circulation flow through a first return port and at least one second circulation path for returning the circulation flow through a second return port provided above the first return port in the vertical direction. An addition part for adding the raw material gas is disposed in at least one among the first circulation path and the second circulation path.

Description

Culture device

[0001] The technology disclosed herein relates to a culture device.

[0002] To reduce greenhouse gas emissions, research into phasing out petroleum-based raw materials is flourishing worldwide. As part of this research, technologies are being developed to utilize carbon sources other than petroleum as raw materials in the manufacturing of chemical and bio-products. For example, microorganisms that utilize carbon sources other than petroleum as raw materials for growth or the production of organic substances are known. One example of such microorganisms is hydrogen-oxidizing bacteria. Hydrogen-oxidizing bacteria grow by taking in gases containing carbon dioxide, hydrogen, and oxygen as raw materials, and by modifying the genes of hydrogen-oxidizing bacteria, they can efficiently produce organic substances such as alcohol and amino acids. Hydrogen-oxidizing bacteria are a general term for chemosynthetic bacteria that use the energy generated by the oxidation of hydrogen to convert the carbon contained in carbon dioxide into organic substances and incorporate them into the bacteria. Hydrogen-oxidizing bacteria are also attracting attention because they can effectively utilize carbon dioxide, which is emitted as a greenhouse gas, as carbon dioxide is used as a raw material for growth or the production of organic substances.

[0003] Microorganisms such as hydrogen bacteria are cultured using a culture apparatus having a culture tank. Japanese Patent Publication No. 2024-074193 describes a culture apparatus for culturing microorganisms. Raw material gas consumed by the microorganisms is supplied to the culture tank containing the culture medium. Inside the culture tank, the raw material gas dissolves in the culture medium, and as the dissolved culture medium spreads throughout the entire culture tank, the mixing of the raw material gas into the culture medium progresses.

[0004] The culture apparatus described in Japanese Patent Publication No. 2024-074193 comprises a stirring tank having stirring blades for containing a liquid for culturing microorganisms and stirring the contained liquid, and a liquid circulation pipe for returning the liquid removed from the stirring tank back into the tank. The culture apparatus described in Japanese Patent Publication No. 2024-074193 reduces the energy required for gas-liquid mixing by providing a liquid circulation pipe.

[0005] As described in Japanese Patent Publication No. 2024-074193, the mixing of raw material gas into the culture medium is facilitated by providing a liquid circulation pipe, but simply providing a liquid circulation pipe sometimes resulted in insufficient mixing.

[0006] The technology disclosed herein provides a culture apparatus that can improve the mixability of raw material gases compared to conventional methods.

[0007] To achieve the above objective, the culture apparatus of this disclosure is a culture apparatus for culturing microorganisms or cells that utilize a raw material gas for growth or production of organic matter, comprising: a culture tank containing a culture medium for culturing microorganisms or cells; a raw material gas supply unit for supplying a raw material gas to the culture tank; and a plurality of circulation paths for taking the culture medium from the culture tank through an outlet and returning the taken culture medium as a circulating flow to the culture tank through a return port located vertically below the outlet, wherein the circulation path includes at least one first circulation path that returns the circulating flow from a first return port and at least one second circulation path that returns the circulating flow from a second return port located vertically above the first return port, and an additive unit for adding a raw material gas is provided in at least one of the first circulation path and the second circulation path.

[0008] If H1 is the height from the bottom of the culture tank to the surface of the culture medium, and H2 is the height of the second return port, then H2 may satisfy the following condition: 0.3 × H1 ≤ H2 ≤ 0.7 × H1 ...Equation (1)

[0009] There may be multiple second circulation pathways.

[0010] Additives may be placed in all of the second circulation pathways.

[0011] Additives may be placed in both the first and second circulation pathways.

[0012] The concentration of microorganisms or cells in the culture vessel may be measured, and the flow rate of the circulating fluid in the circulation pathway may be adjusted according to the measured concentration of the culture.

[0013] If Db is a pre-set reference concentration for the culture, Qbd is a pre-set reference flow rate for the circulating flow relative to the reference concentration, DX is the measured value of the culture concentration, and Q is the flow rate of the circulating flow, then Q may be adjusted to satisfy the following condition in equation (2): 0.2 × DX / Db × Qbd ≤ Q ≤ 5 × DX / Db × Qbd ... Equation (2)

[0014] The flow rate of the circulating flow through the circulation path may be adjusted according to the amount of raw material gas supplied into the culture tank.

[0015] If Sb is a predetermined standard supply amount for the raw material gas, Qbs is a predetermined standard flow rate of the circulating flow according to the standard supply amount, S is the supply amount, and Q is the flow rate of the circulating flow, then Q may be adjusted to satisfy the following condition in equation (3): 0.2 × S / Sb × Qbs ≤ Q ≤ 5 × S / Sb × Qbs ...Equation (3)

[0016] The additive section may include a bubble atomizing device that atomizes the bubbles in the raw material gas.

[0017] The average volume and bubble diameter of bubbles after passing through the bubble refinement device may be between 10 μm and 1 mm.

[0018] A static mixer may also be used as the bubble miniaturization device.

[0019] A stirring device is not required inside the culture tank.

[0020] When reusing a mixed gas in the space above the liquid surface of the culture medium within a culture tank as a raw material gas, the mixed gas may be added to at least one of multiple circulation paths.

[0021] The mixed gas may be added in a state where the proportion of components with a relatively fast dissolution rate among the components of the source gas is higher than the proportion of components in the source gas contained in the culture medium in the culture vessel.

[0022] The culture vessel may be equipped with a composition ratio control mechanism that measures the composition ratio of the mixed gas in the space above the liquid surface of the culture medium and supplies adjusting gas to the space according to the measured composition ratio of the mixed gas, thereby maintaining the composition ratio of the mixed gas in the space at a preset target value outside the explosion range.

[0023] When carbon dioxide is contained in the raw material gas, the adjustment gas may be carbon dioxide.

[0024] The microorganism is a hydrogen-oxidizing bacterium, and the raw material gas contains hydrogen, and may further contain oxygen and carbon dioxide as other components.

[0025] According to the technology of the present disclosure, the mixing performance of the raw material gas can be improved as compared with conventional techniques.

[0026] These drawings are diagrams illustrating the functions of the culture apparatus. They are: a diagram illustrating the overall configuration of the culture apparatus, a diagram illustrating a configuration for supplying raw material gas component by component, a diagram illustrating the configuration of a circulation path, a diagram illustrating a comparative example, a diagram illustrating the operational effects of the culture apparatus of the present disclosure, a graph showing verification results of mixing time, a diagram illustrating the relationship between the concentration of hydrogen-oxidizing bacteria and the consumption amount of raw material gas, a diagram illustrating the relationship between the concentration of hydrogen-oxidizing bacteria and a target mixing time, a diagram illustrating the acceleration effect by bubbles, a diagram illustrating an embodiment of adding mixed gas to a circulation path, a diagram illustrating an example of a second embodiment, a diagram illustrating another example of the second embodiment, a diagram illustrating a third embodiment, a diagram illustrating a composition ratio control mechanism, and a diagram illustrating an example of composition ratio control of mixed gas.

[0027] [First Embodiment] As shown in FIG. 1, a culture apparatus 10 according to the first embodiment of the technology of the present disclosure cultures hydrogen-oxidizing bacteria, which are microorganisms, as an example of a culture object. Raw materials for growing hydrogen-oxidizing bacteria include hydrogen (H ２ ), oxygen (O ２ ), and carbon dioxide (CO ２ ), as well as inorganic components such as ammonium sulfate. Hydrogen is an example of a flammable gas. The culture apparatus 10 grows hydrogen-oxidizing bacteria in a culture solution by supplying a raw material gas into the culture solution. Furthermore, in the culture solution, hydrogen-oxidizing bacteria efficiently produce organic substances such as alcohols and amino acids by modifying the genes of the hydrogen-oxidizing bacteria. Organic substances are extracted by purifying the culture solution. The extracted organic substances are used, for example, in the production of chemical products or biological products. In addition, hydrogen-oxidizing bacteria are separated from the culture solution, and the use of the separated hydrogen-oxidizing bacteria, for example, as feed, food, fuel, and the like, is under consideration.

[0028] As shown in FIG. 2, the culture apparatus 10 includes a culture tank 11, a raw material gas tank 12, a culture solution tank 13, an adjustment gas tank 14, a culture product tank 15, and a processor 17. The culture tank 11 accommodates a culture solution 18. Examples of the hydrogen-oxidizing bacteria 21 include bacteria such as those of the genus *Hydrogenophilus* described in Japanese Patent No. 6528295. In this case, as described in Japanese Patent No. 6528295, the culture solution 18 is, for example, ammonium sulfate ((NH ４ ) ２ SO ４ ), potassium dihydrogen phosphate (KH ２ PO ４ ), dipotassium hydrogen phosphate (K ２ HPO ４ ), and an aqueous solution obtained by dissolving sodium chloride (NaCl) and the like in water. The culture tank 11 is an example of the "culture tank" according to the technology of the present disclosure. Note that, instead of or in addition to the raw material gas tank 12, a gas generator that generates the raw material gas 26 may be provided.

[0029] Supply paths 12A, 13A, 14A, and 15A respectively connected to the raw material gas tank 12, the culture solution tank 13, the adjustment gas tank 14, and the culture product tank 15 are connected to the culture tank 11. Each of the supply paths 12A, 13A, 14A, and 15A is composed of piping, valves, and the like. Further, a pump 22 and a flow meter 23 for measuring the flow rate of the fluid flowing through each supply path are arranged in each of the supply paths 12A, 13A, 14A, and 15A.

[0030] In the first embodiment, the supply passage 12A of the raw material gas tank 12 is connected to the culture tank 11 via a culture medium circulation path (hereinafter simply referred to as the circulation path) 54 that circulates the culture medium 18. The raw material gas 26 is supplied from the supply passage 12A to the culture medium 18 in the circulation path 54, and the culture medium 18 is supplied to the culture tank 11 by flowing into the culture tank 11 via the circulation path 54. The circulation path 54 is a flow path through which the culture medium 18 flows and is composed of piping. In Figure 2, only one circulation path 54 is shown to avoid complexity in the drawing, but in reality, multiple circulation paths 54 are provided. This will be described later (see Figures 4 and 14, etc.). In the following, the culture medium 18 flowing through the circulation path 54 and the culture medium 18 circulating in the culture tank 11 through the circulation path 54 may be referred to as the circulating flow.

[0031] The culture medium tank 13 contains the culture medium 18. The culture medium 18 is supplied from the culture medium tank 13 to the culture vessel 11 through the supply path 13A by driving the pump 22 located on the supply path 13A. The timing and amount of the culture medium 18 supply are controlled by the processor 17, which controls the operation of the pump 22.

[0032] The culture tank 15 contains hydrogen-oxidizing bacteria 21, which is an example of a culture. The hydrogen-oxidizing bacteria 21 are supplied from the culture tank 15 to the culture vessel 11 through the supply channel 15A by driving the pump 22 on the supply channel 15A. The timing and amount of supply of the hydrogen-oxidizing bacteria 21 are controlled by the processor 17 that controls the operation of the pump 22.

[0033] The raw material gas tank 12 contains the raw material gas 26. As mentioned above, the raw material gas 26 is, for example, hydrogen (H ２ ), oxygen (O ２ ) and carbon dioxide (CO2) ２ The raw material gas 26 is a gas containing various components such as ). The raw material gas 26 is supplied from the raw material gas tank 12 to the culture tank 11 through the supply path 12A by driving the pump 22 on the supply path 12A. The timing and amount of supply of the raw material gas 26 are controlled by the processor 17 which controls the driving of the pump 22.

[0034] The downstream end of the supply channel 12A is connected to the circulation path 54. More specifically, the circulation path 54 is provided with an additive section 71 for adding the raw material gas 26. The additive section 71 adds the raw material gas 26 to the circulating flow of the culture medium 18 in the circulation path 54. The downstream end of the supply channel 12A constitutes a part of the additive section 71. The additive section 71 will be described later (see Figure 3).

[0035] The circulation path 54 is provided on the outer surface of the culture tank 11. The circulation path 54 takes the culture medium 18 out of the culture tank 11 through an outlet 54A provided on the culture tank 11, and then returns the taken culture medium 18 to the culture tank 11 as a circulating flow through a return port 54B on the culture tank 11. This circulates the culture medium 18 inside the culture tank 11 to the outside. In the circulation path 54, the return port 54B is positioned vertically below the outlet 54A. A pump 22 is also provided in the circulation path 54. The pump 22 is a pump that generates pressure to circulate the culture medium 18 through the circulation path 54. The culture medium 18 inside the culture tank 11 is drawn into the circulation path 54 from the upper outlet 54A and flows out into the culture tank 11 from the lower return port 54B. This generates a vertically rising circulating flow inside the culture tank 11.

[0036] The raw material gas 26 is added to the circulating flow of the culture medium 18 in the circulation path 54 and flows into the culture tank 11 from the return port 54B. A portion of the added raw material gas 26 dissolves in the culture medium 18. The dissolved raw material gas 26 is taken up by the hydrogen-oxidizing bacteria 21 and consumed for the growth of the hydrogen-oxidizing bacteria 21 or for the production of organic matter 29. The organic matter 29 is, for example, alcohol or amino acids. The raw material gas 26 that does not dissolve in the culture medium 18 is released into the space 11A located above the liquid surface 18A of the culture medium 18. The space 11A is filled with a mixed gas 31, which is the raw material gas 26 released without dissolving in the culture medium 18.

[0037] The adjustment gas tank 14 contains adjustment gas 33. The adjustment gas 33 is supplied from the adjustment gas tank 14 to the space 11A of the culture tank 11 through the supply path 14A by driving the pump 22 on the supply path 14A. The timing and amount of adjustment gas 33 supplied are controlled by the processor 17 which controls the driving of the pump 22. The mixed gas 31 in space 11A contains hydrogen and oxygen, which are components of the raw material gas 26. Hydrogen is a flammable gas. The adjustment gas 33 is used to maintain the composition ratio of the mixed gas 31 in space 11A at a preset target value outside the explosion range. Composition ratio control will be described later (see Figure 14).

[0038] Furthermore, the mixed gas 31 contains components of the raw material gas 26. Therefore, a portion of the mixed gas 31 can be returned to the culture tank 11 via the gas circulation path 39 and reused as the raw material gas 26. The gas circulation path 39 is connected to the supply path 12A of the raw material gas 26. The mixed gas 31 that is reused as the raw material gas 26 is also supplied to the culture tank 11 via the additive section 71 provided in the circulation path 54. The mixed gas 31 that is not reused is discharged. Although not shown in the diagram, when discharging the mixed gas 31 that is not reused, the mixed gas 31 is diluted with an inert gas such as carbon dioxide before being released into the atmosphere.

[0039] A discharge channel 36 for extracting the mixed gas 31 is connected to the culture tank 11, and a pump 22 and a three-way valve 38 are provided in the discharge channel 36. The pump 22 generates pressure for discharging and circulating the mixed gas 31. The three-way valve 38 switches between a state in which the discharge channel 36 is connected to the gas circulation path 39 and a state in which the connection between the discharge channel 36 and the gas circulation path 39 is closed. The three-way valve 38 switches between sending the mixed gas 31 to the gas circulation path 39 or exhausting it to the outside. In addition, a composition ratio measuring unit 16 is provided in the discharge channel 36 for measuring the composition ratio of the mixed gas 31. The composition ratio measuring unit 16 is used for controlling the composition ratio of the mixed gas 31, which will be described later.

[0040] (Supply of raw material gas by component) Also, in Figure 2, for convenience in order to reduce the complexity of the drawing, the supply path 12A for the raw material gas 26 and the gas circulation path 39 for the mixed gas 31 are shown as a single path. However, in reality, as shown in Figure 3, the supply path 12A and the gas circulation path 39 are hydrogen (H ２ ), oxygen (O ２ ) and carbon dioxide (CO2) ２ Each component is separated, allowing for the individual supply of multiple components. A pump 22 and a flow meter 23 are provided in each component supply path 12A and gas circulation path 39.

[0041] (Removal of impurities from raw material gas) The connecting member 40 connects the supply passage 12A and the gas circulation passage 39. This integrates the supply passage 12A and the gas circulation passage 39 into a single integrated pipe 12B for each component. An impurity removal mechanism 51 is located upstream of the circulation passage 54 in the integrated pipe 12B. The impurity removal mechanism 51 removes impurities from the raw material gas 26 supplied to the culture tank 11. The impurities include sulfur oxides or nitrogen oxides (NO and NO). ２ This includes (etc.). The impurity removal mechanism 51 is a mechanism that utilizes one of the following methods for separating impurities from the raw material gas 26: membrane separation, cryogenic separation, physical adsorption, and chemical absorption.

[0042] The integrated piping 12B for each component is connected to the circulation path 54, and a nozzle at one end of the integrated piping 12B is positioned within the circulation path 54. From the nozzle of the integrated piping 12B for each component, hydrogen (H ２ ), oxygen (O ２ ) and carbon dioxide (CO2) ２ Each of these components is added to the circulating flow of the culture medium 18 through the circulation pathway 54.

[0043] The additive section 71 consists of a nozzle in the integrated piping 12B and a static mixer 82. Bubbles of raw material gas 26 are ejected from the nozzle in the integrated piping 12B, and the static mixer 82 refines these bubbles into smaller particles. The smaller the bubble diameter of the raw material gas 26, the larger the surface area per unit volume, thus improving its solubility in the culture medium 18. As is well known, the static mixer 82 is a static gas-liquid mixer without a drive unit. The static mixer 82 may, for example, have a structure with fine through-holes or a screw-shaped structure. Such a structure acts as an obstacle to the fluid, generating a shear force in the fluid and thereby reducing the bubble diameter. Figure 3 shows how the bubble diameter of the raw material gas 26 before passing through the static mixer 82 is reduced after passing through the static mixer 82. The static mixer 82 is an example of a "bubble refinement device" according to the technology of this disclosure.

[0044] The performance of the static mixer 82 is such that, for example, the average volume bubble diameter of the bubbles after passing through it is between 10 μm and 1 mm. Preferably, it is around 100 μm to 200 μm. As is well known, the average volume bubble diameter is the average bubble diameter based on the volume of each bubble when there is a distribution in the bubble diameter. The significance of miniaturizing bubbles is to increase the solubility of the raw material gas 26 and increase the consumption rate consumed by the hydrogen-oxidizing bacteria 21. Experiments have shown that, depending on the type of culture such as hydrogen-oxidizing bacteria 21, miniaturizing to around 100 μm to 200 μm is effective in obtaining the target consumption rate. As for bubble miniaturization devices, there are devices that miniaturize bubbles to the nano-order, such as nanobubble generators, but the higher the bubble miniaturization performance, the more energy is consumed to drive the bubble miniaturization device. When the culture is hydrogen-oxidizing bacteria 21, it is preferable to use a bubble miniaturization device that consumes less energy than a nanobubble generator. Since the static mixer 82 does not have a drive unit, it is suitable in terms of suppressing energy consumption.

[0045] (Separation of components contained in the mixed gas) Furthermore, since the mixed gas 31 is a mixture of hydrogen, oxygen, carbon dioxide, and other components, the gas circulation path 39 is provided with a component separation mechanism 52 for separating the components contained in the mixed gas 31. The component separation mechanism 52 separates the components contained in the mixed gas 31, and each separated component is supplied to the respective gas circulation path 39 provided for each component. The component separation mechanism 52 is a mechanism that utilizes one of the following methods for separating each component from the mixed gas 31: membrane separation, cryogenic separation, physical adsorption, and chemical absorption.

[0046] In this way, when supplying raw material gas 26 to the culture tank 11, hydrogen (H ２ ), oxygen (O ２ ) and carbon dioxide (CO2) ２ By supplying each component individually, such as hydrogen and oxygen, there are advantages in terms of culture efficiency and safety. The advantage in culture efficiency is that it is easy to adjust the composition of the raw material gas 26 supplied to the culture tank 11 to an appropriate level from the standpoint of culture efficiency. The advantages in terms of safety are as follows: The three elements of an explosion are flammable gas, oxygen, and an ignition source, but before supplying the raw material gas 26 to the culture tank 11, it is possible to separate and handle hydrogen and oxygen, which are flammable gases among the three elements of an explosion, thereby further reducing the risk of explosion.

[0047] Furthermore, the component separation mechanism 52 may separate other components of the mixed gas 31, such as nitrogen and methane, in addition to hydrogen, oxygen, and carbon dioxide. Since nitrogen and methane have the effect of reducing the solubility of the raw material gas 26 in the culture medium 18, separating them when reusing the mixed gas 31 can improve the solubility of the raw material gas 26.

[0048] (Recovery of Culture Medium) As shown in Figure 2, a culture medium recovery path 56 is connected to the culture tank 11. One end of the culture medium recovery path 56 is connected to a recovery medium outlet 56A provided in the culture tank 11, and the other end is connected to a culture medium recovery mechanism 55. The culture medium recovery path 56 removes a portion of the culture medium 18 from the culture tank 11 as a recovery liquid. The culture medium recovery mechanism 55 recovers the culture medium 18 containing organic substances 29 from the culture medium 18 removed from the culture tank 11 through the culture medium recovery path 56. The culture medium recovery mechanism 55 has a recovery liquid tank for containing the recovered culture medium 18, a separation mechanism for separating the target for purification from the recovery liquid, etc. The recovery liquid is transferred to a purification device (not shown), and organic substances 29 are extracted from the recovery liquid. Alternatively, the remaining culture medium 18 after recovery by the culture medium recovery mechanism 55, which contains hydrogen-oxidizing bacteria 21, may be returned to the culture tank 11. Furthermore, when purifying the proliferated hydrogen-oxidizing bacteria 21, they are recovered, for example, by a method different from that used for the organic substance 29.

[0049] (Temperature control, sensing of various information) In addition, the culture tank 11 is equipped with a thermometer 46, a temperature controller 47, a pressure gauge 48, a dissolved gas concentration measuring unit 49, and a bacterial cell density measuring unit 50. The thermometer 46 measures the temperature T in the culture medium 18. The temperature controller 47 heats or cools the culture medium 18 in the culture tank 11. The pressure gauge 48 measures the pressure PS in the space 11A. The dissolved gas concentration measuring unit 49 measures the dissolved gas concentration Dr of the raw material gas 26 dissolved in the culture medium 18.

[0050] The culture medium 18 is maintained at a target temperature suitable for culturing hydrogen-oxidizing bacteria 21. The target temperature is, for example, between 40°C and 95°C. The target temperature is set for each microorganism. If the hydrogen-oxidizing bacteria 21 are of the genus Hydrogenophilus, it is more preferably around 50°C. In addition to heating the culture medium 18 to reach the target temperature, cooling may also be necessary. This is because the microorganisms being cultured may generate heat during growth, causing the culture medium 18 to exceed the target temperature. Based on the temperature T measured by the thermometer 46, the processor 17 controls the operation of the temperature controller 47 so that the temperature T of the culture medium 18 is maintained at the target temperature.

[0051] Furthermore, the processor 17 controls the pressure of the mixed gas 31 in the space 11A based on the pressure PS measured by the pressure gauge 48. By setting the pressure PS of the mixed gas 31 to a target pressure, the solubility of the raw material gas 26 in the culture medium 18 is improved. In this way, the processor 17 ensures proper solubility in the culture medium 18 by controlling the pressure of the mixed gas 31. This improves the cultivation efficiency of the hydrogen-oxidizing bacteria 21. The pressure PS of the mixed gas 31 is adjusted for at least one of the following: the supply amount of raw material gas 26, the discharge amount of the mixed gas 31, and the supply amount of the adjustment gas 33. The processor 17 adjusts the supply or discharge amount of these gases by controlling the drive of each pump 22.

[0052] More specifically, the dissolved gas concentration measuring unit 49 measures the concentration of each component (hydrogen, oxygen, and carbon dioxide) contained in the raw material gas 26 dissolved in the culture medium 18. As an example, the dissolved gas concentration measuring unit 49 measures the dissolved hydrogen concentration (Dr(H) ２ A dissolved hydrogen meter (for example, Kyoei Electronics Research Institute: model number KM2100DH) measures the dissolved oxygen concentration (Dr(O)). ２ A dissolved oxygen meter (for example, a METTLER TOLEDO InPro6860i) measures the dissolved carbon dioxide concentration (Dr(CO)), and the dissolved carbon dioxide concentration (Dr(CO)) is measured by a dissolved oxygen meter (for example, a METTLER TOLEDO InPro6860i METTLER TOLEDO InPro6860i, and the dissolved carbon dioxide concentration (Dr(CO)) is measured by a METTLER TOLEDO InPro6860i, and the dissolved carbon dioxide concentration (Dr(CO)) is measured by a METTLER TOLEDO InPro6860i, and the dissolved carbon dioxide concentration (Dr(CO)) is measured by a METTLER TOLEDO InPro6860i, and the dissolved carbon dioxide concentration is measured by a METTLER TOLEDO ２ The system consists of a dissolved carbon dioxide meter (for example, a METTLER TOLEDO InPro5000i) that measures the dissolved gas concentration. The dissolved gas concentration measuring unit 49 outputs the measured value to the processor 17.

[0053] As shown in Figure 3, the raw material gas tanks 12 contain the raw material gas 26 according to its component (hydrogen, oxygen, carbon dioxide). In addition, supply lines 12A and pumps 22 are provided for each component.

[0054] The processor 17 obtains the measured dissolved gas concentration for each component from the dissolved gas concentration measuring unit 49, compares the dissolved gas concentration for each component with the target value, and supplies the deficient component of the raw material gas 26 to the culture tank 11. Through controlling the supply amount of each component of the raw material gas 26 in this way, the processor 17 can maintain the dissolved gas concentration of the raw material gas 26 in the culture medium 18 at an appropriate value.

[0055] The bacterial cell density measurement unit 50 is an example of a density measurement unit that measures the density of the culture present in the culture medium 18 in the culture tank 11. The bacterial cell density measurement unit 50 is composed of a total cell density sensor (for example, a Hamilton Dencytee RS485). In this example, the culture is hydrogen-oxidizing bacteria 21, so the bacterial cell density measurement unit 50 measures the bacterial cell density X, which is the density of hydrogen-oxidizing bacteria 21 in the culture medium 18. The bacterial cell density X is the mass or number of bacterial cells (hydrogen-oxidizing bacteria 21 in this example) contained per unit volume of culture medium 18. The bacterial cell density X has a positive correlation with the amount of raw material gas 26 consumed by the hydrogen-oxidizing bacteria 21. By measuring the bacterial cell density X, it is possible to calculate the amount of raw material gas 26 consumed by the hydrogen-oxidizing bacteria 21, or to use it for process checks to verify whether the amount of raw material gas 26 consumed is appropriate for the amount of hydrogen-oxidizing bacteria 21.

[0056] The water level gauge 66 measures the water level of the culture medium 18 in the culture tank 11, that is, the height of the liquid surface 18A. The amount of culture medium 18 present in the culture tank 11 can be determined by the water level of the culture medium 18 measured by the water level gauge 66. The water level gauge 66 is used for process checks to determine whether the amount of culture medium 18 is appropriate, and for calculating the necessary amount of replenishment of culture medium 18.

[0057] Furthermore, the culture tank 11 is provided with an explosion vent 67. The explosion vent 67 is designed to safely release the pressure inside the culture tank 11 and minimize damage in the event of an explosion, by being destroyed before other parts of the culture tank 11. The vicinity of the explosion vent 67 is selected to be a location where significant damage will not occur even if the pressure is released, or a location where measures have been taken to prevent the damage from spreading.

[0058] The processor 17 is composed of, for example, a CPU (Central Processing Unit) and RAM (Random Access Memory), and controls each part of the culture apparatus 10 as described above. The memory 17A is a non-volatile memory, such as flash memory, that stores various setting information. The memory 17A stores the operating program. The operating program is a program that causes the processor 17 to execute processes to control the culture apparatus 10.

[0059] (Configuration of the circulation pathway) As shown in Figure 4, in the culture apparatus 10, the circulation pathway 54 is composed of two pathways, for example, a first circulation pathway 541 and a second circulation pathway 542. The first circulation pathway 541 has a first outlet 541A and a first return outlet 541B, which serve as the outlet 54A and return outlet 54B. The culture medium 18 in the culture tank 11 is taken out of the culture tank 11 from the first outlet 541A and returned to the culture tank 11 as a circulating flow from the first return outlet 541B. The second circulation pathway 542 has a second outlet 542A and a second return outlet 542B, which serve as the outlet 54A and return outlet 54B. The culture medium 18 in the culture tank 11 is taken out of the culture tank 11 from the second outlet 542A and returned to the culture tank 11 as a circulating flow from the second return outlet 542B.

[0060] For example, the first outlet 541A of the first circulation path 541 and the second outlet 542A of the second circulation path 542 are at approximately the same vertical height and are both located near the liquid surface 18A of the culture medium 18. In contrast, the first return outlet 541B of the first circulation path 541 and the second return outlet 542B of the second circulation path 542 are at different vertical heights, with the second return outlet 542B being located vertically higher than the first return outlet 541B.

[0061] As an example, the first return port 541B is located near the bottom of the culture tank 11, while the second return port 542B is located approximately midway between the bottom of the culture tank 11 and the liquid surface 18A of the culture medium 18. More specifically, if H1 is the height from the bottom of the culture tank 11 to the liquid surface 18A, and H2 is the height of the second return port 542B, then it is preferable that H2 satisfies the following condition: Here, the height of the liquid surface 18A is, for example, the average height or maximum height when the culture apparatus 10 is in operation. Also, H2 is the center position of the opening of the second return port 542B. That is, the second return port 542B is located within a range of approximately 3 / 10 to 7 / 10 of H1. 0.3 × H1 ≤ H2 ≤ 0.7 × H1 ... Equation (1)

[0062] Furthermore, the first circulation path 541 and the second circulation path 542 are each provided with a pump 22 and an additive unit 71. The pump 22 is located near the first outlet 541A and the second outlet 542A, respectively, and the additive unit 71 is located near the first return port 541B and the second return port 542B, respectively. As a result, a circulating flow to which the raw material gas 26 has been added flows into the culture tank 11 from the first return port 541B and the second return port 542B, respectively.

[0063] The arrows indicated by the symbol CF schematically show the flow direction of the circulating flow within the culture tank 11. As shown in Figure 4, the circulating flow generated by the second circulation path 542 is added to the circulating flow generated by the first circulation path 541. This promotes agitation of the culture medium 18 within the culture tank 11 and improves the mixing of the raw material gas 26.

[0064] Here, mixing the raw material gas 26 into the culture medium 18 means that the raw material gas 26 dissolved in the culture medium 18 is distributed throughout the entire culture tank 11. Hydrogen-oxidizing bacteria 21 maintain their metabolism by consuming the raw material gas 26. If uneven concentrations of the raw material gas 26 occur within the culture tank 11, the hydrogen-oxidizing bacteria 21 in areas with low gas concentrations may lack the raw material gas 26, potentially preventing them from maintaining their metabolism. Therefore, mixing of the raw material gas 26 is performed to suppress uneven concentrations of the raw material gas 26 contained in the culture medium 18 within the culture tank 11. As shown in Figure 4, in the culture apparatus 10, mixing of the raw material gas 26 is performed by generating a circulating flow within the culture tank 11 through external circulation of the culture medium 18 via two circulation paths 54, the first circulation path 541 and the second circulation path 542.

[0065] This configuration yields the following effects. Figure 5 shows a comparative example culture apparatus 100 in which only the first circulation path 541 is provided. In the culture apparatus 100, the culture medium 18 from the culture tank 11 is taken out from the first outlet 541A near the liquid surface 18A, and the circulating flow is returned to the culture tank 11 from the first return outlet 541B near the bottom of the culture tank 11. As a result, a circulating flow as shown by the arrow CF is generated in the culture tank 11, but depending on the height of the culture tank 11, a low-concentration region LDA may occur near the middle of the culture tank 11. The low-concentration region LDA is a region in which the concentration of the raw material gas 26 is relatively low compared to the surroundings, and mixing proceeds slowly.

[0066] Furthermore, the curve C1 shown in Figure 5 schematically illustrates the concentration distribution of the raw material gas 26 in the height direction of the culture tank 11 of the culture apparatus 100. In the graph of curve C1, the horizontal axis is the height of the culture tank 11, and the vertical axis is the concentration of the raw material gas 26 (indicated by DG). Since the additive section 71 is provided near the first return port 541B located near the bottom of the culture tank 11, a circulating flow with a high concentration of raw material gas 26 flows into the culture tank 11 from the first return port 541B. For this reason, as shown in curve C1, the concentration of raw material gas 26 is high near the bottom of the culture tank 11. Then, as it approaches the liquid surface 18A, the concentration of raw material gas 26 decreases. This is because, inside the culture tank 11, the circulating flow of the culture medium 18 becomes an upward flow toward the liquid surface 18A, causing the hydrogen-oxidizing bacteria 21 to also rise. In this process, the consumption of raw material gas 26 by the hydrogen-oxidizing bacteria 21 progresses, so the concentration of raw material gas 26 decreases as it approaches the liquid surface 18A.

[0067] Figure 6 shows curves C1 and C2 schematically illustrating the circulation flow and the concentration distribution of the raw material gas 26 in the culture apparatus 10 of this disclosure, in comparison with the comparative example culture apparatus 100 in Figure 5. The culture apparatus 10 has a second circulation path 542 in addition to the first circulation path 541. The second return port 542B of the second circulation path 542 is located near the middle of the culture tank 11 in the height direction, so the circulation flow flows into the area near the middle of the culture tank 11. This inflow of circulation flow stirs the culture medium 18 near the middle of the culture tank 11, making it less likely for the low concentration region LDA shown in Figure 5 to occur in the culture apparatus 10.

[0068] Furthermore, since an additive section 71 is also provided near the second return port 542B, the concentration of the raw material gas 26 flowing in from the second return port 542B is also high. Thus, in the culture apparatus 10, a circulating flow with a high concentration of raw material gas 26 flows into the culture tank 11 from both the first return port 541B near the bottom of the culture tank 11 and the second return port 542B in the middle. Therefore, as conceptually shown in the graph in Figure 6, in the culture apparatus 10, the concentration distribution of curve C1 generated by the circulating flow from the first return port 541B and the concentration distribution of curve C2 generated by the circulating flow from the second return port 542B overlap, and the drop in the concentration of raw material gas 26 from the middle of the culture tank 11 to near the liquid surface 18A is suppressed.

[0069] Both the effect of the second circulation pathway 542 making it less likely for low-concentration regions (LDA) to occur, and the effect of suppressing the decrease in the concentration of the raw material gas 26 from the middle of the culture tank 11 to the liquid surface 18A, contribute to improving the mixability of the raw material gas 26.

[0070] Of course, even in the comparative example culture apparatus 100 shown in Figure 5, mixing will proceed if circulation is continued, but there is a concern that the mixing time required for the raw material gas 26 to mix will become too long. As mentioned above, if areas with low gas concentration of raw material gas 26 occur, the hydrogen-oxidizing bacteria 21 present in those areas will lack sufficient raw material gas 26, and may not be able to maintain their metabolism. Therefore, the mixing time is extremely important in order to quickly eliminate concentration variations.

[0071] An experiment was conducted to verify the superiority of the mixing time of the culture apparatus 10 of this disclosure over the comparative example culture apparatus 100 shown in Figure 5. Figure 7 shows the experimental results. The experiment was carried out using the decolorization reaction method described below. In both the comparative example culture apparatus 100 and the culture apparatus 10 of this disclosure (hereinafter referred to as the example), the culture tank 11 is cylindrical with a circular cross-section, and its dimensions are an inner diameter of 500 mm, a depth of 2 m, and a volume of 400 L. A culture tank made of polyvinyl chloride was used as the culture tank 11. The heights from the bottom surface of the culture tank 11 of the outlet 541A and return port 541B of the first circulation path 541, and the heights from the bottom surface of the culture tank 11 of the outlet 542A and return port 542B of the second circulation path 542 are as shown in Table 1 below. The heights were measured at the center position of all openings. Since the comparative example does not have a second circulation path, naturally, the heights of the second outlet and second return port are not shown in Table 1.

[0072]

[0073] The experimental procedure involved first adding 300 L of water to each culture apparatus in the comparative example and the example, and dissolving starch to a concentration of 0.7 g / L. Then, iodine was added to a concentration of 0.05 mmol / L. The liquid level 18A was 1.53 m. After confirming that the coloring was uniform, a sodium thiosulfate aqueous solution was added all at once from the liquid level 18A to a concentration of 0.13 mmol / L. The pumps 22 in the first circulation path 541 and the second circulation path 542 were set to a pressure of 250 L / min. Mixing was defined as starting at the point of adding sodium thiosulfate and completing at the point when the entire culture vessel became colorless. The mixing time from the start to the completion of mixing was measured for both the comparative example and the example.

[0074] In Figure 7, the horizontal axis represents mixing time, and the vertical axis represents mixing ratio. The solid line graph represents the example, and the dashed line graph represents the comparative example. As shown in Table 1, the mixing time TM0 for the comparative example was 35 seconds, and the mixing time TM1 for the example was 25 seconds. The mixing ratio was calculated by analyzing the change in the brightness value of the solution using a conventional method. That is, before adding the sodium thiosulfate aqueous solution, the whole solution was dark and the brightness value was low. After adding the sodium thiosulfate aqueous solution, as mixing progressed, the solution became transparent and the brightness value increased. The point at which the brightness value became the same as when the whole solution was transparent was defined as 100% mixing progress, and the point at which the mixing progress rate reached 100% was considered the completion of mixing. As shown in Figure 7 and Table 1, the culture apparatus 10 of this disclosure (example in Table 1) had a shorter mixing time than the culture apparatus 100 of the comparative example, and it could be evaluated that the mixing performance was improved.

[0075] As shown in Figure 8, the higher the concentration DX of hydrogen-oxidizing bacteria 21, the greater the consumption CG of raw material gas 26. The concentration DX of hydrogen-oxidizing bacteria 21 is equivalent to, for example, the bacterial density X mentioned above. Therefore, the higher the concentration DX of hydrogen-oxidizing bacteria 21, the faster the rate of consumption of raw material gas 26, and the faster the rate at which unevenness in the concentration of raw material gas 26 occurs in the culture tank 11. For this reason, it is necessary to shorten the mixing time of the raw material gas 26 in accordance with the rate of consumption of the raw material gas 26. As mentioned above, if there is a localized shortage of raw material gas 26, there is a risk that the hydrogen-oxidizing bacteria 21 will not be able to maintain their metabolism and will die.

[0076] Therefore, in the culture apparatus 10, the target mixing time TMT is set according to the concentration DX of the hydrogen-oxidizing bacteria 21, and the flow rate of the circulating flow is set so that the target mixing time TMT can be achieved. The higher the concentration DX of the hydrogen-oxidizing bacteria 21, the faster the rate of consumption of the raw material gas 26, so as shown in Figure 9, the higher the concentration DX of the hydrogen-oxidizing bacteria 21, the shorter the target mixing time TMT is set. Of course, hydrogen-oxidizing bacteria 21 are used as an example of the culture material, but if the type of culture material changes, the rate of consumption of the raw material gas will naturally change, and therefore the required target mixing time TMT will also change.

[0077] Furthermore, the effects of adding the raw material gas 26 to the circulating flow by the additive unit 71 in the first circulation path 541 and the second circulation path 542 are as follows.

[0078] As shown in Figure 10, a circulating flow to which the raw material gas 26 has been added flows into the culture tank 11 from the first return port 541B and the second return port 542B. When the raw material gas 26 is not dissolved, it floats up in the culture tank 11 as bubbles. When bubbles float up in the culture medium 18, the culture medium 18 surrounding the bubbles is also accelerated by the bubbles. The circulating flow that flows into the culture tank 11 from the first return port 541B and the second return port 542B contains many bubbles due to the addition of the raw material gas 26 in the addition unit 71. The circulating flow that flows into the culture tank 11 becomes an upward flow within the culture tank 11, but the acceleration effect of the bubbles increases the upward speed of the circulating flow. As a result, it is expected that the mixing properties of the raw material gas 26 will be further improved.

[0079] As described above, the culture apparatus 10 of this disclosure includes a plurality of circulation paths 54 that take the culture medium 18 from the culture tank 11 through an outlet 54A and return the taken culture medium 18 as a circulating flow to the culture tank 11 through a return outlet 54B located vertically below the outlet 54A. The circulation paths 54 include a first circulation path 541 that returns the circulating flow from a first return outlet 541B and a second circulation path 542 that returns the circulating flow from a second return outlet 542B located vertically above the first return outlet 541B. An additive section 71 for adding raw material gas 26 is provided in at least one of the first circulation path 541 and the second circulation path 542.

[0080] This improves the mixing of the raw material gas 26 with the culture medium 18 in the culture tank 11 compared to the conventional method. Specifically, because the second return port 542B allows the circulating flow to enter above the first return port 541B, the agitation of the culture medium 18 in the culture tank 11 is improved compared to the case where only the first return port 541B is used. This improves the mixing of the raw material gas 26. Furthermore, because the raw material gas 26 is added in the circulation path by the addition unit 71, a circulating flow containing a relatively large number of bubbles can be introduced into the culture tank 11. As a result, the upward speed of the circulating flow increases due to the accelerating effect of the bubbles, further improving the mixing of the raw material gas 26.

[0081] Concentration variations in the raw material gas 26 within the culture vessel 11 are more likely to occur as the capacity of the culture vessel 11 increases. Therefore, the technology of this disclosure is particularly effective when the capacity of the culture vessel 11 is large. The capacity of the culture vessel 11 is not particularly limited, but for example, a lower limit of about 30 L is preferred. A lower limit of 50 L or more is even more preferred. Examples of relatively small capacities of culture vessel 11 that are 30 L or more include 30 L, 40 L, 50 L, 60 L, 70 L, 80 L, 90 L, 100 L, 300 L, and 500 L. Examples of relatively large capacities include 1000 L, 2000 L, 5000 L, 10,000 L, 20,000 L, 50,000 L, 100,000 L, 200,000 L, and 500,000 L. The preferred capacity range is from 30 L to 500,000 L.

[0082] Furthermore, in the above embodiment, when the height from the bottom of the culture tank 11 to the liquid surface 18A of the culture medium 18 is H1, and the height of the second return port 542B is H2, H2 satisfies the conditions of formula (1) above. As shown in Figure 5, a low-concentration region LDA may occur in the middle section of the culture tank 11. By setting H2 to a height that satisfies the conditions of formula (1), the occurrence of a low-concentration region LDA is easily suppressed. Therefore, the effect of improving mixing properties is greater compared to when H2 does not satisfy the conditions of formula (1) above.

[0083] Furthermore, it is more preferable that H2 satisfies the conditions of the following formula (1-2), and even more preferable that it satisfies the conditions of the following formula (1-3): 0.4 × H1 ≤ H2 ≤ 0.6 × H1 ... Formula (1-2) 0.45 × H1 ≤ H2 ≤ 0.55 × H1 ... Formula (1-3) In other words, by bringing the second return port 542B closer to the middle section of the culture tank 11 where the low-concentration region LDA is generated, the mixing can be further improved.

[0084] Furthermore, in the above embodiment, the additive unit 71 is located in both the first circulation path 541 and the second circulation path 542. Compared to the case where it is located in either one, a greater acceleration effect on the circulation flow shown in Figure 10 can be expected, thus further improving the mixability of the raw material gas 26.

[0085] Furthermore, in the above embodiment, the additive section 71 includes a static mixer 82 (an example of a bubble refiner) that refines the bubbles of the raw material gas. By refining the bubbles, the solubility of the raw material gas 26 is improved. As a result, unevenness in the concentration of the raw material gas 26 is suppressed, and the mixing performance is improved.

[0086] Furthermore, in the above embodiment, the average volume and bubble diameter of the bubbles after passing through the bubble refinement device, such as the static mixer 82, is 10 μm or more and 1 mm or less. Therefore, performance such as that of a nanobubble generator is unnecessary, and energy consumption can be suppressed compared to the case in which a nanobubble generator is provided. In addition, since the static mixer 82 is used as the bubble refinement device, it is advantageous in terms of energy saving compared to bubble refinement devices that require a drive unit. Therefore, it is possible to improve the mixability of the raw material gas 26 while achieving energy savings.

[0087] In addition, a device other than the static mixer 82 may be used as the bubble atomization device. There are various types of bubble atomization devices, including microporous types such as spargers made of porous material, swirling flow type which generates bubbles by high-speed swirling flow, and ejector type (also called Venturi type) which generates bubbles by rapid pressure changes in the gas-liquid flow path. Furthermore, the additive section 71 may be configured by combining these bubble atomization devices. For example, a sparger may be provided at one end of the integrated piping 12B. In this case, the additive section 71 will consist of a sparger and a static mixer 82.

[0088] Furthermore, in the above embodiment, no stirring device for stirring the culture medium 18 is provided in the culture tank 11. The stirring device is, for example, a device having rotating stirring blades that cause the culture medium 18 to flow. By causing the culture medium 18 to flow with the stirring blades, the raw material gas 26 can be mixed with the culture medium 18. In the culture apparatus 10 of this disclosure, the culture medium 18 is stirred by providing a first circulation path 541 and a second circulation path 542 as circulation paths 54 for circulating the culture medium 18 to the outside. For this reason, the stirring device in the culture tank 11 can be omitted. Of course, a stirring device has driving energy. For this reason, the culture apparatus 10 of this disclosure can achieve energy savings by omitting the stirring device.

[0089] Furthermore, a stirring device may be provided in the culture tank 11. Although the energy-saving effect will be reduced, the combination of the first circulation path 541 and the second circulation path 542 with the stirring device can further improve the mixing of the raw material gas 26.

[0090] Furthermore, in the above embodiment, as shown in Figure 2, by providing a gas circulation path 39, the mixed gas 31 in the space 11A above the liquid surface 18A of the culture medium 18 in the culture tank 11 is reused as raw material gas 26. More specifically, in the above embodiment, as shown in Figure 2, the gas circulation path 39 is connected to the supply path 12A of the raw material gas 26, and as shown in Figure 3, the supply path 12A and the gas circulation path 39 are integrated into an integrated pipe 12B. The mixed gas 31 is then reused by being added to the circulating flow in the first circulation path 541 and the second circulation path 542 through the integrated pipe 12B. This improves the utilization efficiency of the raw material gas 26.

[0091] As shown in Figure 11, the supply path 12A may be connected to the first circulation path 541, and the gas circulation path 39 may be directly connected to the second circulation path 542 without going through the supply path 12A. In this case, the raw material gas 26 from the raw material gas tank 12 will not be added to the second circulation path 542, and only the mixed gas 31 will be added. Of course, the gas circulation path 39 may be directly connected to the first circulation path 541 instead of the second circulation path 542.

[0092] [Second Embodiment] The second embodiment shown in Figures 12 and 13 is a configuration in which the flow rate of the circulating flow is adjusted by controlling the pumps 22 of the first circulation path 541 and the second circulation path 542. The only difference from the first embodiment is the configuration for adjusting the flow rate of the circulating flow; all other configurations are the same.

[0093] The culture apparatus 10 shown in Figure 12 measures the concentration DX of hydrogen-oxidizing bacteria 21 in the culture tank 11 and adjusts the flow rate of the circulating flow through the circulation pathway 54, which includes the first circulation pathway 541 and the second circulation pathway 542, according to the measured value of the concentration DX. The concentration DX of hydrogen-oxidizing bacteria 21 is an example of the "culture concentration" according to the technology of this disclosure. As described above, the concentration DX of hydrogen-oxidizing bacteria 21 is equivalent to the cell density X, so the cell density X obtained from the cell density measurement unit 50 is used as the concentration DX. The processor 17 obtains the cell density X from the cell density measurement unit 50 and controls the driving force of the pump 22 according to the obtained cell density X. This adjusts the flow rate Q of the circulating flow. The flow rate Q is the flow rate per unit time of the circulating flow of culture medium 18 that flows through the first circulation pathway 541 and the second circulation pathway 542 and flows into the culture tank 11.

[0094] The higher the concentration DX of the hydrogen-oxidizing bacteria 21 culture, the greater the consumption CG of the raw material gas 26 (see Figure 8), and the more likely it is that unevenness in the concentration of the raw material gas 26 will occur. In this case, it is necessary to increase the flow rate Q of the circulating flow to improve the fluidity of the culture medium 18 in the culture tank 11, thereby eliminating the unevenness in concentration in a short time, that is, shortening the mixing time of the raw material gas 26. Conversely, if the concentration DX is low, unevenness in the concentration of the raw material gas 26 is less likely to occur, so the mixing time can be somewhat longer.

[0095] Therefore, as shown in the graph in Figure 12, the processor 17 controls the flow rate Q of the circulating flow to increase as the concentration DX increases, and to decrease the flow rate Q when the concentration DX is low. If the flow rate Q of the circulating flow were always kept high regardless of the concentration DX, the mixing time of the raw material gas 26 would be shortened, but the more the flow rate Q increases, the more energy the pump 22 consumes. For this reason, in the example shown in Figure 12, the processor 17 uses the concentration DX as an indicator of the concentration unevenness of the raw material gas 26 and adjusts the flow rate Q to match the concentration DX. This makes it possible to improve the mixability of the raw material gas 26 while suppressing unnecessary energy consumption.

[0096] The processor 17 adjusts the flow rate Q to satisfy the conditions of equation (2) below. Here, Db is a preset reference concentration with respect to the culture concentration (for example, the concentration DX of hydrogen-oxidizing bacteria 21), and Qbd is a preset reference flow rate of the circulating flow with respect to the reference concentration Db. Db and Qbd are set to establish a relationship between the concentration DX and the corresponding optimal flow rate Q, for example, if Db is 10 g / L, the optimal Qbd is 10 L / min. In equation (2), if it falls below the lower limit with a coefficient of 0.2, the mixing quality is likely to deteriorate, and if it exceeds the upper limit with a coefficient of 5, the energy consumption will be excessive. For this reason, it is preferable that Q satisfies the conditions of equation (2). 0.2 × DX / Db × Qbd ≤ Q ≤ 5 × DX / Db × Qbd ... Equation (2)

[0097] Furthermore, as shown in Figure 13, the flow rate Q of the circulating flow through the circulation path 54, including the first circulation path 541 and the second circulation path 542, may be adjusted according to the supply amount S of the raw material gas 26 supplied into the culture tank 11.

[0098] As explained in the example shown in Figure 12, the higher the concentration DX of the hydrogen-oxidizing bacteria 21 culture, the greater the consumption CG of the raw material gas 26 (see also Figure 8), and the more likely it is that unevenness in the concentration of the raw material gas 26 will occur. In the example shown in Figure 12, the concentration DX is used as an indicator of unevenness in the concentration of the raw material gas 26, and the flow rate Q is adjusted according to the concentration DX. This improves the mixing properties of the raw material gas 26 while suppressing unnecessary energy consumption. In contrast, in the example shown in Figure 13, for the same purpose, the supply amount S of the raw material gas 26 is used as an indicator of unevenness in the concentration of the raw material gas 26, and the flow rate Q is adjusted according to the supply amount S.

[0099] As described above, the culture apparatus 10 controls the consumption amount CG of the raw material gas 26 according to the supply amount S of the raw material gas 26. Therefore, a large supply amount S of the raw material gas 26 can be considered to mean a large consumption amount CG of the raw material gas 26. And a large consumption amount CG of the raw material gas 26 can be estimated to mean a high concentration DX.

[0100] As shown in the graph in Figure 13, the processor 17 controls the flow rate Q of the circulating flow to increase as the supply amount S (considered to be the consumption amount CG) of the raw material gas 26 increases. The processor 17 obtains the supply amount S from the flow meter 23. By adjusting the flow rate Q to match the supply amount S of the raw material gas 26 in this way, the same effect as in the example shown in Figure 12 can be obtained, namely, the effect of improving the mixability of the raw material gas 26 while suppressing unnecessary energy consumption.

[0101] Specifically, the processor 17 adjusts the flow rate Q to satisfy the conditions of equation (3) below. Here, Sb is a preset standard supply amount for the raw material gas 26, and Qbs is a preset standard flow rate of the circulating flow according to the standard supply amount Sb. Sb and Qbs set the relationship between the supply amount S of the raw material gas 26 and the corresponding optimal flow rate Q. In equation (3), if Q falls below the lower limit with a coefficient of 0.2, the mixing quality is likely to deteriorate, and if it exceeds the upper limit with a coefficient of 5, the energy consumption will be excessive. For this reason, it is preferable that Q satisfies the conditions of equation (3). 0.2 × S / Sb × Qbs ≤ Q ≤ 5 × S / Sb × Qbs ...Equation (3)

[0102] [Third Embodiment] In addition, as shown in the third embodiment in Figure 14, there may be multiple second circulation pathways 542. The culture apparatus 10 shown in Figure 14 has one first return port 541B and three second return ports 542B located above the first return port 541B as return ports 54B. In Figure 14, the circulation pathway 54 on the left side has a common section between the first circulation pathway 541 and the second circulation pathway 542. That is, the circulation pathway 54 on the left side has a common first outlet 541A and a common second outlet 542A, and branches downstream, with one branch connecting to the first return port 541B and the other to the second return port 542B.

[0103] Furthermore, the circulation path 54 on the right is the second circulation path 542. This second circulation path 542 also has one second outlet 542A, but it branches downstream, and each branch has a second return outlet 542B. By providing multiple second circulation paths 542 having second return outlets 542B in this way, the mixing properties of the raw material gas 26 are further improved.

[0104] The experimental results shown in Figure 7 represent an example with a single second circulation pathway 542, but it is believed that mixing performance can be improved to the same or even better level by increasing the number of second circulation pathways 542.

[0105] Furthermore, in this example, additive units 71 are located in all three second circulation paths 542. The additive units 71 are located near the three second return ports 542B. In addition, an additive unit 71 is also located in the first circulation path 541. As a result, the circulating flow from the second return ports 542B will contain many bubbles, which can be expected to accelerate the circulating flow as shown in Figure 10, further improving the mixability of the raw material gas 26.

[0106] Note that the configuration of the culture apparatus 10 shown in Figure 14 is just one example, and for example, four or more second circulation pathways 542 may be provided. Also, it is not necessary to provide an additive unit 71 in all three second circulation pathways 542, nor is it necessary to provide an additive unit 71 in the first circulation pathway 541. The additive unit 71 only needs to be located in one of the multiple circulation pathways that make up the first circulation pathway 541 and the second circulation pathway 542.

[0107] Furthermore, in Figure 14, the gas circulation path 39 is connected to the addition section 71 of all three second circulation paths 542, and the mixed gas 31 is added. However, the gas circulation path 12A may be connected to one or more of the three second circulation paths 542, and the raw material gas 26 from the raw material gas tank 12 may be added. In this way, when there is a mix of paths among the multiple second circulation paths 542, where the gas circulation path 39 is connected to add the mixed gas 31 and paths where the supply path 12A is connected to add the raw material gas 26, the positional relationship of the second return ports 542B of each path should be as follows.

[0108] In other words, the second return port 542B of the second circulation path 542 connected to the supply path 12A is positioned lower than the second return port 542B of the second circulation path 542 connected to the gas circulation path 39. This makes the floating distance of the raw material gas 26 from the supply path 12A relatively longer, and ensures the time required for the relatively difficult-to-dissolve components of the raw material gas 26 to dissolve. Specifically, it is as follows: As will be described later, since the mixed gas 31 uses carbon dioxide as the adjusting gas 33, it has a higher proportion of carbon dioxide and a lower proportion of hydrogen compared to the raw material gas 26 in the raw material gas tank 12. Carbon dioxide dissolves relatively easily, and hydrogen dissolves relatively poorly. Since the raw material gas 26 from the supply path 12A has a higher proportion of hydrogen than the mixed gas 31, it takes longer to dissolve than the mixed gas 31. Therefore, by positioning the second return port 542B as described above, the floating distance of the raw material gas 26, which has a high proportion of hydrogen, becomes relatively longer, making it easier to ensure the time required for hydrogen to dissolve.

[0109] Furthermore, in the embodiment shown in Figure 14, there are multiple second return ports 542B, and it is preferable that the height H2 of at least one of these second return ports 542B satisfies the conditions of formula (1) above. It is even more preferable that the height H2 of all of the multiple second return ports 542B satisfy the conditions of formula (1) above. Furthermore, in the embodiment shown in Figure 14, it is even more preferable that the height H2 satisfies formula (1-2) or formula (1-3) above.

[0110] The total number of the first and second circulation routes is not particularly limited, but considering the manufacturing cost of the culture device 10 and the space required for piping installation, it is preferable to have around 2 to 10 routes. In addition, each circulation route may have multiple outlets or return ports. Figures 4 and 14 show a single circulation route with one outlet and one or two return ports. However, it is not limited to this, and there may be two or more outlets, or three or more return ports. Considering the manufacturing cost of the culture device 10 and the space required for piping installation, it is preferable to have an upper limit of around five outlets or return ports.

[0111] The cross-sectional shapes of the first and second circulation paths, as well as the respective outlets and return ports, are preferably circular, considering ease of piping manufacturing and flow resistance. However, the cross-sectional shape is not limited to a circle and may be polygonal.

[0112] (Control of the composition ratio of the mixed gas) In addition, in each of the above embodiments, the culture apparatus 10 may be equipped with a composition ratio control mechanism as shown in Figure 15. The composition ratio control mechanism measures the composition ratio of the mixed gas 31 in the space 11A located above the liquid surface 18A of the culture medium 18 in the culture tank 11, and supplies an adjustment gas 33 into the space 11A according to the measured composition ratio of the mixed gas 31, thereby maintaining the composition ratio of the mixed gas 31 in the space 11A at a preset target value outside the explosion range. Safety is further improved by providing such a composition ratio control mechanism.

[0113] As shown in Figure 15 as an example, the memory 17A of the processor 17 contains, as an example, a target value outside the explosion range used for composition ratio control, the target value of hydrogen concentration (TD(H) ２ )), target value of oxygen concentration (TD(O) ２ The following are stored: )) and water vapor concentration (not shown), target temperature, etc.

[0114] As described above, hydrogen is a flammable gas, and the adjusting gas 33 is used to maintain the composition ratio of the mixed gas 31 in space 11A at a preset target value outside the explosion range. In the mixed gas 31, hydrogen, which is a flammable gas, is mixed with oxygen. In this case, an explosion may occur depending on the composition ratio of the mixed gas 31. The composition ratio of the mixed gas at which an explosion occurs is called the explosion range. As described above, the memory 17A of the processor 17 contains the target value of hydrogen concentration (TD(H)) as the target value outside the explosion range. ２ )), target value of oxygen concentration (TD(O) ２ The following are set: )) and water vapor concentration, etc. The target value for the outside of the explosion range varies depending on the components of the mixed gas 31. In the case of a mixed gas 31 containing hydrogen and oxygen, as in this example, the target value for the outside of the explosion range is generally less than 5% oxygen concentration or less than 4% hydrogen concentration in the mixed gas 31.

[0115] Furthermore, the applicant has experimentally verified that if the water vapor concentration is 7% or higher, the composition ratio of the mixed gas can be kept outside the explosive range even if the oxygen concentration is 5% or higher. Therefore, in this example, the target value for being outside the explosive range is set as follows: if the water vapor concentration is 7% or higher and 90% or lower, the oxygen concentration is set to be in the range of 5% or higher and 9% or lower.

[0116] The experiment was conducted using the following method. A stainless steel chamber with an inner diameter of 200 mm, a depth of 200 mm, and a volume of 6 L was used as the explosive vessel. Hydrogen, oxygen, carbon dioxide, and water vapor were filled into the explosive vessel (water vapor was added by pouring water into the explosive vessel and evacuating it to the saturation vapor pressure at the internal temperature of the vessel to vaporize the water. Hydrogen, oxygen, and carbon dioxide were added from gas cylinders through gas introduction piping installed in the explosive vessel). After homogenizing the gases by rotating a stirring fan inside the explosive vessel, an attempt was made to ignite the gases using a thin wire detonator installed in the explosive vessel. Ignition or failure was determined based on the presence or absence of pressure increase and the presence or absence of negative pressure inside the explosive vessel due to water generation. The pressure was measured using a pressure sensor (Kyowa Electric Industry, PHS-B-10MP) placed on the upper valve of the gas discharge piping installed in the explosive vessel.

[0117] Table 2 shows experimental results regarding whether or not ignition occurs depending on the gas concentration of the gas mixture. Both Example 1 and Comparative Example 1 in Table 2 are examples where the water vapor concentration is 0%, and the concentrations other than oxygen are almost the same. In Example 1, where ignition did not occur, the oxygen concentration was 4%, which is less than 5%, while in Comparative Example 1, where ignition occurred, the oxygen concentration was 9%, which is above 5%. From Example 1 and Comparative Example 1, the experimental results show that, as is generally known, ignition does not occur when the water vapor concentration is 0% and the oxygen concentration is less than 5%.

[0118] Furthermore, Examples 2, 3, and Comparative Example 2 all involve water vapor concentrations of 7% or higher, with only the oxygen concentration differing significantly. Examples 2 and 3 had an oxygen concentration of 9%, while Comparative Example 2 had an oxygen concentration of 16%, exceeding 9%. These experimental results indicate that when the water vapor concentration is 7% or higher, ignition does not occur even if the oxygen concentration is 5% or higher, as long as it is 9% or lower.

[0119]

[0120] Although Table 2 does not include experimental results for hydrogen concentrations below 4%, it is known that if the hydrogen concentration is below 4%, the mixed gas will not ignite even if the water vapor concentration is 0%, instead of setting the oxygen concentration below 5%. Therefore, as a target value outside the explosion range, instead of setting the oxygen concentration of the mixed gas 31 to below 5%, the hydrogen concentration of the mixed gas 31 may be set to below 4%.

[0121] The adjusting gas 33 is, for example, an inert gas. More specifically, in this example, carbon dioxide (CO2). ２ ) is used. By supplying the adjusting gas 33 to the space 11A, the oxygen concentration or hydrogen concentration decreases, and the composition ratio of the mixed gas 31 is maintained at a target value outside the explosion range. Note that any gas other than an inert gas can be used as the adjusting gas 33. For example, hydrogen, which is a flammable gas, can be used as the adjusting gas 33 to reduce the oxygen concentration of the mixed gas 31 to less than 5%, or any other gas can be used to maintain the composition ratio of the mixed gas 31 at a target value outside the explosion range. Thus, any gas can be used as the adjusting gas 33, but as mentioned above, when the mixed gas 31 is reused, it is preferable to use the components of the raw material gas 26 as the adjusting gas 33.

[0122] As shown in Figure 15, the composition ratio measuring unit 16 is located on the discharge channel 36 that discharges the mixed gas 31 from the space 11A of the culture tank 11. The composition ratio measuring unit 16 measures, for example, the hydrogen concentration (D(H) ２ A gas analyzer (for example, Horiba, Ltd. model TCA-51d) measures oxygen concentration (D(O)). ２ A gas analyzer (for example, Horiba, Ltd. model VA-5113) measures carbon dioxide concentration (D(CO)). ２The system consists of a gas analyzer (for example, Horiba, Ltd. model VA-5113) that measures the concentration of each component of the mixed gas 31 and the total flow rate (Qout(total)) of the mixed gas 31 (for example, Emerson, model CMFS007M). This allows the composition ratio measuring unit 16 to measure the concentration of each component of the mixed gas 31 and the total flow rate (Qout(total)). The composition ratio measuring unit 16 outputs each measured value as a measurement signal to the processor 17.

[0123] The processor 17 determines the amount of adjusting gas 33 to be supplied, for example, based on the total flow rate and measured oxygen concentration of the mixed gas 31, so that the oxygen concentration of the mixed gas 31 is maintained below a preset upper limit. The processor 17 then controls the pump 22 to supply the determined amount of adjusting gas 33 from the adjusting gas tank 14 to the space 11A. This reduces the amount of carbon dioxide supplied to the space 11A (Qin(CO)). ２ )) increases, and the relative oxygen concentration (D(O) ２ )) decreases, and the composition ratio of the mixed gas 31 in space 11A falls to a preset target value (TD(O) outside the explosion range. ２ The hydrogen concentration (D(H)) is maintained by increasing the supply amount of the adjusting gas 33. ２ )) will also decrease, so the hydrogen concentration will also decrease, and the target value outside the explosion range (TD(H) ２ It is possible to maintain the following. The processor 17, the adjustment gas tank 14, and the pump 22 on the supply line 14A are examples of the "composition ratio control mechanism" according to the technology of this disclosure.

[0124] Furthermore, since both the culture medium 18 and the space 11A are located within the culture vessel 11, maintaining the temperature T of the culture medium 18 at the target temperature allows the temperature in space 11A to be maintained at approximately the same temperature. As described later, the composition ratio of the mixed gas 31 in space 11A is maintained at a predetermined target value outside the explosion range. The target value includes the water vapor concentration of the mixed gas 31. By controlling the temperature of the culture medium 18 to 40°C or higher, the temperature of the mixed gas 31 can be raised to 40°C or higher. This makes it possible to adjust the water vapor concentration of the mixed gas 31 to 7% or higher.

[0125] Note that in Figure 15, the circulation pathway 54 and other components have been omitted to reduce the complexity of the drawing; however, the culture apparatus 10 shown in Figure 15 actually has the aforementioned circulation pathway 54.

[0126] Furthermore, in the example shown in Figure 15, carbon dioxide is used as the adjusting gas 33, and as a result, the control shown in Figure 16 can be achieved. As shown in Figure 16, the processor 17 controls the composition ratio of the mixed gas 31 added to the first circulation path 541 and the second circulation path 542 so that the ratio of the component with a relatively fast dissolution rate among the components of the raw material gas 26 is higher than the ratio of the component in the raw material gas 26 contained in the culture medium 18 in the culture tank 11. Carbon dioxide has a relatively fast dissolution rate among the components of the raw material gas 26. When carbon dioxide dissolves quickly, the volume of bubbles of the other components of the added mixed gas 31 decreases, and the specific surface area of ​​the bubbles as a whole increases. As a result, bubbles of the other components also dissolve more easily. By making the mixed gas 31 added to the circulation flow contain a large amount of carbon dioxide in this way, the solubility of the raw material gas 26 in the circulation flow is improved. As a result, the mixability of the raw material gas 26 can be further improved.

[0127] It is also possible to perform only the control shown in Figure 16 without performing the control shown in Figure 15. Of course, if the proportion of carbon dioxide increases, safety will improve as a result. In addition, substances other than carbon dioxide may be used as components with a relatively fast dissolution rate.

[0128] In the embodiments described above, hydrogen-oxidizing bacteria 21 were used as an example of a microorganism, but the technology of this disclosure can also be applied to microorganisms or cells other than hydrogen-oxidizing bacteria 21. Examples of microorganisms may include acetic acid-producing bacteria such as Clostridium autoethanogenum, and methane-utilizing bacteria such as Methylococcus capsulatus. In the case of acetic acid-producing bacteria, the component of the raw material gas 26 is hydrogen (H), which is a flammable gas. ２ ), carbon monoxide (CO) and carbon dioxide (CO) ２ ) In the case of methane-utilizing bacteria, the component of the raw material gas 26 is methane (CH4), which is a combustible gas. ４) and air. Furthermore, a cell is a morphological and / or functional unit that constitutes a living organism, and the living organism from which the cell originates is not particularly limited, but may be an animal or a plant. Cells may be cell lines or genetically modified cells, and may also include artificial cells. Examples include CHO cells (Chinese hamster ovary cells), HEK293 cells (Human Embryonic Kidney cells 293), and Sf9 cells (Spodopterafrugiperda cells 9).

[0129] In each of the above embodiments, the configurations of the first circulation path 541 and the second circulation path 542 can be modified in various ways. Not only the number of each, but also the positions of the pump 22 and the additive unit 71 can be changed as appropriate.

[0130] Furthermore, the above embodiment discloses the following additional information.

[0131] [Addendum 1] A culture apparatus for culturing microorganisms or cells that utilize a raw material gas for growth or production of organic matter, comprising: a culture tank containing a culture medium for culturing microorganisms or cells; a raw material gas supply unit for supplying a raw material gas to the culture tank; and a plurality of circulation paths for taking the culture medium from the culture tank through an outlet and returning the taken culture medium as a circulating flow to the culture tank through a return port located vertically below the outlet, wherein the circulation path includes at least one first circulation path that returns the circulating flow from a first return port and at least one second circulation path that returns the circulating flow from a second return port located vertically above the first return port, and an additive unit for adding a raw material gas is provided in at least one of the first circulation path and the second circulation path. [Note 2] When H1 is the height from the bottom of the culture tank to the liquid surface of the culture medium and H2 is the height of the second return port, H2 satisfies the following condition: 0.3 × H1 ≤ H2 ≤ 0.7 × H1 ... Formula (1) Culture apparatus as described in Note 1. [Note 3] Culture apparatus as described in Note 1 or 2, wherein there are multiple second circulation pathways. [Note 4] Culture apparatus as described in Note 3, wherein additive units are provided in all of the second circulation pathways. [Note 5] Culture apparatus as described in any one of Notes 1 to 4, wherein additive units are provided in all of the first and second circulation pathways. [Note 6] Culture apparatus as described in any one of Notes 1 to 5, wherein the concentration of the culture of microorganisms or cells in the culture tank is measured, and the flow rate of the circulating flow through the circulation pathway is adjusted according to the measured value of the culture concentration. [Note 7] When Db is a pre-set standard concentration for the culture medium, Qbd is a pre-set standard flow rate of the circulating flow relative to the standard concentration, DX is the measured value of the culture medium concentration, and Q is the flow rate of the circulating flow, Q is adjusted to satisfy the following condition in equation (2): 0.2 × DX / Db × Qbd ≤ Q ≤ 5 × DX / Db × Qbd ... Equation (2) Culture apparatus as described in Note 6. [Note 8] Culture apparatus as described in any one of Notes 1 to 5, which adjusts the flow rate of the circulating flow through the circulation path according to the amount of raw material gas supplied into the culture tank.[Note 9] When the amount of raw material gas supplied is set in advance as a standard supply amount Sb, the standard flow rate of the circulating flow set in advance according to the standard supply amount Qbs, the supply amount S, and the flow rate of the circulating flow Q, Q is adjusted to satisfy the following condition of formula (3): 0.2 × S / Sb × Qbs ≤ Q ≤ 5 × S / Sb × Qbs ...Formula (3) The culture apparatus as described in Note 8. [Note 10] The culture apparatus as described in any one of Notes 1 to 9, wherein the addition section includes a bubble atomizer that atomizes the bubbles of the raw material gas. [Note 11] The culture apparatus as described in Note 10, wherein the average volume bubble diameter of the bubbles after passing through the bubble atomizer is 10 μm or more and 1 mm or less. [Note 12] The culture apparatus as described in Note 10 or 11, wherein the bubble atomizer is a static mixer. [Note 13] A culture apparatus according to any one of Notes 1 to 12, wherein no stirring device is provided in the culture tank. [Note 14] A culture apparatus according to any one of Notes 1 to 13, wherein, when the mixed gas in the space above the liquid surface of the culture medium in the culture tank is reused as a raw material gas, the mixed gas is added to at least one of a plurality of circulation paths. [Note 15] A culture apparatus according to Note 14, wherein the mixed gas is added in a state in which the ratio of components with a relatively fast dissolution rate among the components of the raw material gas is higher than the ratio of components in the raw material gas contained in the culture medium in the culture tank. [Note 16] A culture apparatus according to any one of Notes 1 to 15, comprising a composition ratio control mechanism that measures the composition ratio of the mixed gas in the space above the liquid surface of the culture medium in the culture tank and supplies adjusting gas into the space according to the measured composition ratio of the mixed gas to maintain the composition ratio of the mixed gas in the space at a preset target value outside the explosion range. [Note 17] The culture apparatus according to Note 16, wherein if the raw material gas contains carbon dioxide, the adjusting gas is carbon dioxide. [Note 18] The culture apparatus according to any one of Notes 1 to 17, wherein the microorganism is hydrogen-oxidizing bacteria, the raw material gas contains hydrogen, and other components include oxygen and carbon dioxide.

[0132] In the above embodiment, the processing performed by the processor 17 is performed on any computer. Furthermore, any computer may perform these processes using a processor as hardware, a program as software, or a combination thereof. In that case, the processor is configured to cooperate with the program to perform the various processes in this embodiment, and can function as a unit or means in this embodiment. Also, the execution order of the processes by the processor is not limited to the order described and may be changed as appropriate.

[0133] Any computer may be a general-purpose computer, a computer designed for a specific purpose, a workstation, or any other system capable of performing each process. A processor may consist of one or more pieces of hardware, and the type of hardware is not limited. For example, a processor may consist of programmable logic devices such as a CPU (Central Processing Unit), MPU (Micro Processing Unit), FPGA (Field Programmable Gate Array), dedicated circuits for performing specific processes such as an ASIC (Application Specific Integrated Circuit), a GPU (Graphic Processing Unit), or an NPU (Neural Processing Unit). Furthermore, the type of hardware may be a combination of different types of hardware. When multiple hardware components are configured to execute one or more processes of a processor, these components may reside in physically separate devices or in the same device. Furthermore, in any embodiment, the order of the processes performed by the processor is not limited to the order described above and may be changed as appropriate. The hardware components are composed of electrical circuits (circuits) and the like, which are combinations of circuit elements such as semiconductor elements.

[0134] Furthermore, the program may be firmware or software such as microcode. Alternatively, the program may be, for example, a group of program modules, each function of which may be implemented by a processor configured to perform its respective function. The program may be program code or multiple code segments stored on one or more non-temporary computer-readable media (e.g., storage media and other storage). The program may be divided and stored on multiple non-temporary computer-readable media located in physically separate devices. Program code or code segments may represent any combination of procedures, functions, subprograms, routines, subroutines, modules, software packages, classes, or instructions, data structures, or program statements. Program code or code segments may be connected to other code segments or hardware circuits by sending and receiving information, data, arguments, parameters, or memory contents.

[0135] The technology of this disclosure can be appropriately combined with the various embodiments and / or variations described above. Furthermore, it is understood that various configurations can be adopted without departing from the gist of the invention, and the invention is not limited to the embodiments described above. In addition, the technology of this disclosure extends to storage media for storing programs non-temporarily. The storage media are computer-readable non-temporarily storage media such as USB (Universal Serial Bus) memory, flexible disks, and CD-ROMs (Compact Disc Read Only Memory). Programs may also be provided online via a network such as the Internet. Furthermore, the technology of this disclosure extends to program products in addition to programs. Program products include all forms of products for providing programs. Like programs, program products may be stored and provided on computer-readable non-temporarily storage media, or they may be provided online.

[0136] The descriptions and illustrations presented above are detailed explanations of the technical aspects of this disclosure and are merely examples of the technical aspects. For example, the above descriptions of the structure, function, operation, and effect are examples of the structure, function, operation, and effect of the technical aspects of this disclosure. Therefore, it goes without saying that you may delete unnecessary parts, add new elements, or replace elements in the descriptions and illustrations presented above, as long as you do not deviate from the essence of the technical aspects of this disclosure. Furthermore, in order to avoid confusion and facilitate understanding of the technical aspects of this disclosure, explanations of common technical knowledge and the like that do not require special explanation to enable the implementation of the technical aspects of this disclosure have been omitted from the descriptions and illustrations presented above.

[0137] In this specification, "A and / or B" is synonymous with "at least one of A and B." That is, "A and / or B" means that it may be A alone, or B alone, or a combination of A and B. Furthermore, in this specification, the same concept as "A and / or B" applies when expressing three or more things linked by "and / or."

[0138] The disclosure of Japanese Patent Application No. 2025-057010, filed on 28 March 2025, is incorporated herein by reference in its entirety. Furthermore, all documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually indicated as being incorporated by reference.

Claims

1. A culture apparatus for culturing microorganisms or cells that utilize a raw material gas for growth or production of organic matter, comprising: a culture tank containing a culture medium for culturing the microorganisms or cells; a raw material gas supply unit for supplying the raw material gas to the culture tank; and a plurality of circulation paths for removing the culture medium from the culture tank through an outlet and returning the removed culture medium as a circulating flow to the culture tank through a return port located vertically below the outlet, wherein each circulation path includes at least one first circulation path for returning the circulating flow from a first return port and at least one second circulation path for returning the circulating flow from a second return port located vertically above the first return port, and an additive unit for adding the raw material gas is provided in at least one of the first and second circulation paths.

2. When the height from the bottom of the culture tank to the liquid surface of the culture medium is H1 and the height of the second return port is H2, H2 satisfies the following condition: 0.3 × H1 ≤ H2 ≤ 0.7 × H1 ... Formula (1) The culture apparatus according to claim 1.

3. The culture apparatus according to claim 1, wherein the second circulation pathway is a plurality of.

4. The culture apparatus according to claim 3, wherein the additive unit is arranged in all of the second circulation pathways.

5. The culture apparatus according to claim 1, wherein the additive unit is arranged in all of the first circulation pathway and the second circulation pathway.

6. The culture apparatus according to claim 1, wherein the concentration of the culture of microorganisms or cells in the culture tank is measured, and the flow rate of the circulating flow through the circulation path is adjusted according to the measured value of the culture concentration.

7. When Db is a preset standard concentration for the culture, Qbd is a preset standard flow rate of the circulating flow relative to the standard concentration, DX is a measured value of the culture concentration, and Q is the flow rate of the circulating flow, Q is adjusted to satisfy the following condition: 0.2 × DX / Db × Qbd ≤ Q ≤ 5 × DX / Db × Qbd ... Equation (2) The culture apparatus according to claim 6.

8. The culture apparatus according to claim 1, wherein the flow rate of the circulating flow through the circulation path is adjusted according to the amount of raw material gas supplied to the culture tank.

9. With respect to the supply amount of the raw material gas, if a preset standard supply amount is Sb, a preset standard flow rate of the circulating flow according to the standard supply amount is Qbs, the supply amount is S, and the flow rate of the circulating flow is Q, then Q is adjusted to satisfy the following condition of equation (3): 0.2 × S / Sb × Qbs ≤ Q ≤ 5 × S / Sb × Qbs ... Equation (3) The culture apparatus according to claim 8.

10. The culture apparatus according to claim 1, wherein the additive section includes a bubble refiner that refines the bubbles of the raw material gas.

11. The culture apparatus according to claim 10, wherein the average volume and bubble diameter of the bubbles after passing through the bubble micronization apparatus is 10 μm or more and 1 mm or less.

12. The culture apparatus according to claim 10, wherein the bubble micronization device is a static mixer.

13. The culture apparatus according to claim 1, wherein a stirring device is not provided in the culture tank.

14. The culture apparatus according to claim 1, wherein, when the mixed gas in the space above the liquid surface of the culture medium in the culture tank is reused as the raw material gas, the mixed gas is added to at least one of the plurality of circulation paths.

15. The culture apparatus according to claim 14, wherein the mixed gas is added in a state in which the proportion of the component with a relatively fast dissolution rate among the components of the raw material gas is higher than the proportion of the component in the raw material gas contained in the culture medium in the culture tank.

16. The culture apparatus according to claim 1, further comprising a composition ratio control mechanism that measures the composition ratio of the mixed gas in the space above the liquid surface of the culture medium in the culture tank, and supplies an adjusting gas into the space according to the measured composition ratio of the mixed gas, thereby maintaining the composition ratio of the mixed gas in the space at a preset target value outside the explosion range.

17. The culture apparatus according to claim 16, wherein if the raw material gas contains carbon dioxide, the adjusting gas is carbon dioxide.

18. The culture apparatus according to claim 1, wherein the microorganism is a hydrogen-oxidizing bacterium, and the raw material gas contains hydrogen and other components include oxygen and carbon dioxide.

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