Fermentation method and continuous fermentation method, and fermentation device and continuous fermentation device

Abstract

To provide a fermentation method and a fermentation device that allow efficient fermentation and achieve a further reduction in remaining raw materials.SOLUTION: The present invention provides a fermentation method, wherein, in a culture solution containing a raw material stored in fermentors 2a, 2b, 2c, the raw material is fermented (steps P1a, P1b, P1c) to yield a fermentation product, wherein a fermentation product mixed gas containing the fermentation product generated in the fermentors 2a, 2b, 2c is condensed (steps P2a, P2b, P2c) to obtain a mixture of a liquid component containing the fermentation product and a gas component, the mixture is separated (steps P3a, P3b, P3c) to obtain the liquid component and the gas component, and cavitation is generated in the culture solution stored in the fermentors 2a, 2b, 2c. The present invention also provides a fermentation device to which the fermentation method is applied.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a fermentation method, a continuous fermentation method, a fermentation apparatus, and a continuous fermentation apparatus. [Background technology]

[0002] Conventionally, industrial production of ethanol has been carried out by fermenting a culture solution containing sugar as a raw material, yeast, and water in a fermenter under anoxic conditions to decompose the sugar. To improve fermentation efficiency and increase the yield of ethanol, a continuous (multistage) fermentation method or continuous (multistage) fermentation apparatus is also known in which multiple fermenters that store culture solution are connected in series so that the culture solution is sequentially sent to the subsequent fermenter, and fermentation is carried out in each fermenter.

[0003] However, even in continuous fermentation methods or continuous fermentation apparatuses, a certain amount of unfermented raw material ultimately remains. Therefore, even in continuous fermentation methods or continuous fermentation apparatuses, there is a need to further improve the fermentation efficiency and the ethanol yield. Of course, there is also a need to further improve the fermentation efficiency and the ethanol yield in single-tank fermentation methods or fermentation apparatuses that are not multistage. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 51-91386 [Patent Document 2] Japanese Patent Publication No. 59-59195 Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, an object of the present invention is to provide a fermentation method and a continuous fermentation method, as well as a fermentation apparatus and a continuous fermentation apparatus, which can efficiently ferment and further reduce the amount of residual raw material. [Means for solving the problem]

[0006] The above object can be achieved by the present invention described below. [1] A fermentation product is produced by fermenting a raw material in a culture medium containing the raw material stored in a fermenter, condensing the fermentation product mixed gas containing the fermentation product produced in the fermenter to obtain a mixture of a liquid component and a gas component containing the fermentation product; A fermentation method comprising separating the mixture to obtain the liquid component and the gas component, A fermentation method comprising generating cavitation in the culture solution stored in the fermenter. [2] The fermentation method described in [1], wherein the occurrence of cavitation in the culture medium is intermittent. [3] The fermentation method according to [1], wherein the means for generating cavitation in the culture solution is an ultrasonic vibrator. [4] The fermentation method according to [1], wherein a carrier gas is supplied to the culture solution stored in the fermenter. [5] The fermentation method described in [4], wherein the gas component is used as part or all of the carrier gas. [6] The fermentation method according to [4], wherein the main component of the carrier gas is carbon dioxide. [7] The fermentation method according to [4], wherein the fermenter is kept under reduced pressure. [8] The fermentation method according to [7], wherein the pressure in the fermenter is 50 kPa or less. [9] The fermentation method according to [1], wherein the liquid component is concentrated to obtain a concentrate having a high concentration of the fermentation product.

[10] A plurality of fermenters for storing a culture solution containing a raw material are connected in series, and the culture solution is sequentially sent to the subsequent fermenter, and in each of the plurality of fermenters, the raw material is fermented in the culture solution to produce a fermentation product; condensing the fermentation product mixed gas containing the fermentation product produced in the plurality of fermenters to obtain a mixture of a liquid component and a gas component containing the fermentation product; A continuous fermentation method in which the mixture is separated to obtain the liquid component and the gas component, A continuous fermentation method, wherein cavitation is generated in the culture solution stored in some or all of the plurality of fermenters.

[11] The continuous fermentation method according to

[10] , wherein there are a plurality of fermenters in which cavitation occurs, and the cavitation conditions are different for each of the fermenters.

[12] A fermenter that stores a culture solution containing a raw material and ferments the raw material in the culture solution to produce a fermentation product; a condensation means for condensing the fermentation product mixed gas containing the fermentation product produced in the fermenter to obtain a mixture of a liquid component containing the fermentation product and a gas component; a separation means for separating the mixture to obtain the liquid component and the gas component; a cavitation generating means for generating cavitation in the culture solution stored in the fermenter; A fermentation apparatus comprising:

[13] The fermentation apparatus according to

[12] , wherein the cavitation generating means generates cavitation intermittently.

[14] The fermentation apparatus according to

[12] , wherein the cavitation generating means is an ultrasonic vibrator.

[15] The fermentation apparatus according to

[12] , further comprising a carrier gas supply means for supplying a carrier gas to the culture solution stored in the fermentation tank.

[16] The fermentation apparatus according to

[15] , wherein the gas component is used as part or all of the carrier gas supplied by the carrier gas supply means.

[17] The fermentation apparatus according to

[15] , wherein the main component of the carrier gas supplied by the carrier gas supply means is carbon dioxide.

[18] The fermentation apparatus according to

[12] , wherein the fermentation tank is under reduced pressure.

[19] The fermentation apparatus according to

[18] , wherein the pressure in the fermentation tank is 50 kPa or less.

[20] The fermentation apparatus according to

[12] , further comprising a concentration means for concentrating the liquid component separated by the separation means to obtain a concentrate having a high concentration of the fermentation product.

[21] A system for storing a culture solution containing a raw material, fermenting the raw material in the culture solution to produce a fermentation product, and connecting a plurality of fermenters in series so that the culture solution is sequentially sent to subsequent fermenters; a condensation means for condensing the fermentation product mixed gas containing the fermentation product produced in the plurality of fermenters to obtain a mixture of a liquid component containing the fermentation product and a gas component; a separation means for separating the mixture to obtain the liquid component and the gas component; a cavitation generating means for generating cavitation in the culture solution stored in some or all of the plurality of fermenters; A continuous fermentation apparatus comprising:

[22] A continuous fermentation apparatus according to

[21] , comprising a plurality of fermentation tanks each having a cavitation generating means, wherein the cavitation conditions in the cavitation generating means are different for each of the plurality of fermentation tanks. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a fermentation method and a continuous fermentation method, as well as a fermentation apparatus and a continuous fermentation apparatus, which are capable of efficiently fermenting and further reducing the amount of residual raw material. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing a continuous fermentation apparatus according to an embodiment of the present invention. [Figure 2] FIG. 1 is a flow chart showing steps of a continuous fermentation method according to an embodiment of the present invention. [Figure 3] FIG. 1 is a flow chart showing steps of a continuous fermentation method according to a first modified example which is an exemplary embodiment of the present invention. [Figure 4] FIG. 1 is a schematic diagram showing a continuous fermentation apparatus according to a second modified example, which is an exemplary embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, a continuous fermentation method and a continuous fermentation apparatus according to an embodiment of the present invention will be specifically described with reference to the drawings. Fig. 1 is a schematic diagram showing the configuration of a continuous fermentation apparatus 1 according to an embodiment. Fig. 2 is a flow diagram showing the steps of a continuous fermentation method according to an embodiment using the continuous fermentation apparatus 1. In Fig. 1, the movement of gas, liquid, etc. is represented by arrows. In Fig. 2, the movement of only gas that basically does not contain fermentation products is represented by dashed arrows, and the movement of liquid or gas that contains fermentation products is represented by solid arrows.

[0010] As shown in Figures 1 and 2, in this embodiment, three fermenters 2a, 2b, and 2c that store culture medium containing raw materials are connected in series. In this embodiment, "connected in series" refers to a state in which the stored culture medium is continuously connected so that it is sent sequentially to the subsequent fermenter, regardless of whether the arrangement is linear. Such multiple fermenters connected in series are usually called "continuous fermenters."

[0011] As shown in Fig. 1, in this embodiment, water containing yeast (hereinafter referred to as "yeast-containing water") is stored in a yeast tank 10, and the yeast-containing water is sent to a first fermenter 2a by a pump 22-2 through a pipe 20-4. Also, an aqueous solution containing raw materials such as sugar (hereinafter referred to as "raw material aqueous solution") is stored in a raw material tank 12, and the raw material aqueous solution is sent to the first fermenter 2a by a pump 22-1 through a pipe 20-5. The yeast-containing water and the raw material aqueous solution introduced into the first fermenter 2a are stirred and mixed by a stirrer 18a to form a culture solution containing the raw materials.

[0012] In the culture solution stored in the first fermenter 2a, the raw material is fermented by culturing cells through the activity of yeast bacteria, and a fermentation product, i.e., ethanol, is produced. The culture solution stored in the first fermenter 2a is adjusted to a temperature suitable for fermentation by a heater and a temperature regulator (not shown) (the same applies to the second fermenter 2b and the third fermenter 2c).

[0013] The yeast-containing water and the raw material aqueous solution are fed into the first fermenter 2a continuously or intermittently, and eventually exceed the storage capacity of the first fermenter 2a, causing it to overflow. The culture liquid that overflows the first fermenter 2a is sent to the second fermenter 2b through piping 20-1. Next, the culture liquid that overflows the second fermenter 2b is sent to the third fermenter 2c through piping 20-2 (the fermenters 2a, 2b, and 2c are connected in series).

[0014] In this embodiment, the three fermenters 2a, 2b, and 2c are each an independent sealed tank and are kept under reduced pressure. Alternatively, the three fermenters 2a, 2b, and 2c may form a single space, which may be sealed and kept under reduced pressure.

[0015] In the second fermenter 2b and the third fermenter 2c, which are downstream fermenters, the material is stirred by agitators 18b and 18c, as in the first fermenter 2a, and the raw material is fermented by the activity of yeast to produce a fermentation product. The culture medium that overflows from the third fermenter 2c is sent by pump 22-5 through piping 20-3 to a centrifuge or filter press (not shown). The yeast in the culture medium is separated by the centrifuge or filter press, and a portion is returned to the yeast tank 10 for reuse.

[0016] The bottoms of the first fermenter 2a, the second fermenter 2b, and the third fermenter 2c are provided with ultrasonic vibrators 8a, 8b, and 8c, respectively, as cavitation generating means. The ultrasonic vibrators 8a, 8b, and 8c vibrate the culture solution stored in the tanks, generating cavitation.

[0017] The first fermenter 2a, the second fermenter 2b, and the third fermenter 2c similarly undergo fermentation steps P1a, P1b, and P1c, condensation steps P2a, P2b, and P2c, and separation steps P3a, P3b, and P3c, respectively. The progress of these steps, centered on the first fermenter 2a, will be described below with reference to Figures 1 and 2.

[0018] In the first fermenter 2a, the fermentation product is produced in a state where it is contained in a fermentation product mixed gas together with the co-produced carbon dioxide and a carrier gas supplied as described below (fermentation step P1a). The fermentation product mixed gas produced in the first fermenter 2a rises above the liquid surface of the culture medium in the first fermenter 2a and is sent to a heat exchanger 4a, which serves as a condensing means, through a pipe 20-6a.

[0019] Cold water is sent to the heat exchanger 4a from the cold water tank 14 through a pipe 20-8a. Then, inside the heat exchanger 4a, heat exchange occurs between the fermentation product mixed gas and the cold water, and the fermentation product mixed gas loses heat to the cold water and is condensed, thereby obtaining a mixture of liquid components containing the fermentation product and gas components (condensation step P2a).

[0020] The chilled water after heat exchange is returned from the heat exchanger 4a through a pipe 20-9a by a pump 22-6a to the chilled water tank 14. It is then cooled again in the chilled water tank 14 and is used for the next heat exchange. Meanwhile, a mixture of liquid and gas components condensed by the heat exchange is sent through a pipe 20-7a to a separation tank 6a, which is a separation means.

[0021] Separation tank 6a is a tank connected to a recovery pipe 20-16a at its bottom. The liquid component of the mixture sent from heat exchanger 4a is stored in separation tank 6a, and the gas component is discharged from a pipe 20-10a connected to the top of separation tank 6a (separation step P3a).

[0022] The discharged gas component is mainly carbon dioxide (CO2) and may contain other impurities. On the other hand, the liquid component stored in separation tank 6a is a mixed solution of alcohol and water, which is a fermentation product, and is sent to the outside by pump 22-7a through pipe 20-16a and can be recovered from OUT-a.

[0023] The above explanation of the fermentation, condensation, and separation steps P1a, P2a, and P3a mainly performed in the first fermenter 2a also applies to the second fermenter 2b and the third fermenter 2c. That is, the fermentation, condensation, and separation steps mainly performed in the second fermenter 2b and the third fermenter 2c can be explained with reference to Figures 1 and 2 by changing the suffix of the reference numerals of the components and steps in the above explanation from "a" for the first fermenter 2a to "b" for the second fermenter 2b and "c" for the third fermenter 2c.

[0024] In the condensation steps P2b and P2c, which are mainly performed in the second fermentation tank 2b and the third fermentation tank 2c, the cold water after heat exchange is sent to the pipe 20-9a by the pumps 22-6b and 20-6c through the pipes 20-9b and 20-9c, where it is combined with the cold water in the pipe 20-9a and returned to the cold water tank 14.

[0025] In the first fermenter 2a, into which the yeast-containing water from the yeast tank 10 and the aqueous raw material solution from the raw material tank 12 are first introduced, the sugar content (raw material concentration) is high, and a large amount of the raw material is consumed by fermentation. Due to this consumption, the sugar content of the culture solution drops to a certain extent, and the culture solution overflows and is sent to the subsequent second fermenter 2b. In the second fermenter 2b, the raw material is similarly consumed by fermentation, and the sugar content of the culture solution drops further, and the culture solution overflows and is sent to the subsequent third fermenter 2c. In other words, the sugar content of the culture solution decreases as it progresses to the subsequent tanks. This is also true when the number of raw material tanks is not three as in this embodiment, but two or four or more tanks.

[0026] In this embodiment, carrier gas is supplied to the culture solution stored in all three fermenters 2a, 2b, and 2c. Specifically, carrier gas is supplied to the culture solution stored in the fermenters 2a, 2b, and 2c by pumps 22-3a, 22-3b, and 22-3c from pipes 20-14a, 20-14b, and 20-14c connected to the bottoms of the fermenters 2a, 2b, and 2c, respectively.

[0027] The carrier gas used for this purpose is gas components discharged from the separation tanks 6a, 6b, and 6c. The gas components discharged from pipes 20-10a, 20-10b, and 20-10c, which are connected to the tops of the separation tanks 6a, 6b, and 6c, respectively, are combined into pipe 20-12. By combining the gas components into one, the gas pressure within all tanks becomes the same. If an imbalance in the pressure within the tanks occurs, the gas pressure may unintentionally push the culture solution within one tank into another tank. Pipe 20-12 then branches into pipes 20-13 and 20-15, and one of the branched pipes, pipe 20-13, further branches into pipes 20-14a, 20-14b, and 20-14c, which are supplied to the culture solution from the bottom of the fermentation tanks 2a, 2b, and 2c, respectively, by pumps 22-3a, 22-3b, and 22-3c.

[0028] In this embodiment, the device configuration that contributes to supplying carrier gas to the culture solution stored in the fermenters 2a, 2b, and 2c corresponds to the “carrier gas supply means.” Specifically, the “carrier gas supply means” includes the pipes 20-10 to 20-14 (including cases where any of the symbols a, b, and c is added to the end of the names) and the pumps 22-3a, 22-3b, and 22-3c in Fig. 1, and also includes the configuration of the portion indicated by the dashed line in Fig. 2.

[0029] In addition, pipe 20-11, which is connected to pressure gauge 16, is connected to pipe 20-12 midway. If the pressure of the gas component in pipe 20-12 increases, the gas can be released to the outside of the system by pump 22-4 from pipe 20-15, which branches off from pipe 20-12. If the amount of gas discharged from separation tanks 6a, 6b, and 6c is too much to supply to the culture solution stored in fermentation tanks 2a, 2b, and 2c, or if the fermentation operation is stopped, the gas is passed through pipe 20-15 and stored by pump 22-4 outside the system, for example, in a storage tank (not shown), or sent to other facilities or devices that require gas.

[0030] In the culture medium stored in the fermentation tanks 2a, 2b, and 2c, yeast cells decompose the sugars in the raw material into carbon dioxide (CO2) and ethanol (C2H5OH) under anaerobic conditions. 12Taking O6 (glucose, etc.) as an example, the chemical reaction formula can be expressed as shown in Equation 1 below. C6H 12 O6→2CO2+2C2H5OH (Formula 1)

[0031] In the above equation (1), the higher the concentration (molar concentration) on the left side and the lower the concentration (molar concentration) on the right side, the faster the reaction rate. As the reaction progresses through fermentation, the amount of sugar in the system decreases (the concentration on the left side decreases), and the concentrations of carbon dioxide and ethanol increase (the concentrations on the right side increase), slowing the reaction rate. Therefore, the fermentation reaction rate can be increased by removing the carbon dioxide and ethanol produced by fermentation from the system as soon as possible after production (preferably immediately) to reduce the concentration (molar concentration) on the right side.

[0032] In this embodiment, as described above, ultrasonic vibrators (cavitation generating means) 8a, 8b, and 8c are provided in the three fermenters 2a, 2b, and 2c, respectively. The ultrasonic vibrators 8a, 8b, and 8c vibrate the culture solution stored in the tanks, generating cavitation, which generates carbon dioxide bubbles from the dissolved carbon dioxide. This means that carbon dioxide generated during alcoholic fermentation can be removed from the liquid phase (culture solution) early, keeping the carbon dioxide supersaturation in the culture solution low. Therefore, the carbon dioxide concentration on the right side of the above formula 1 can be kept low, accelerating the fermentation reaction.

[0033] The output conditions of the ultrasonic vibrators 8a, 8b, and 8c cannot be generalized because they depend on the tank capacity of the fermenters 2a, 2b, and 2c, the amount of overflow of the culture medium, the amount of carrier gas supplied, etc., and should be selected appropriately on a case-by-case basis.

[0034] If yeast cells are exposed to relatively strong cavitation such as the ultrasonic vibration in this embodiment for a long period of time, the yeast cells may be destroyed (killed). Therefore, it is preferable that cavitation be generated in the culture solution intermittently (in other words, it is preferable that the cavitation generating means generate cavitation intermittently).

[0035] The time conditions for cavitation cannot be generalized as they depend on the type and strength of the cavitation generating means, the type of yeast, the tank capacity, etc., but in the case of ultrasonic vibrations by ultrasonic vibrators 8a, 8b, and 8c, an example can be intermittent vibration in which the vibration is turned on for approximately 1 to 60 seconds, then stopped (off) for approximately 1 to 3600 seconds, and then vibrated again.

[0036] The cavitation conditions in the cavitation generating means may be different for each of the three fermenters 2a, 2b, and 2c. The "cavitation conditions" here refer to the output or time conditions of the cavitation generating means. In the case of ultrasonic vibrations using ultrasonic vibrators 8a, 8b, and 8c, the fermentation efficiency of the continuous fermentation method or the continuous fermentation apparatus as a whole can be improved by appropriately adjusting the output and total vibration time per unit time (ON time × ON count / unit time) for each fermenter.

[0037] In a continuous fermentation tank consisting of multiple tanks (n tanks in this explanation), not limited to the three tanks of this embodiment, the sugar concentration of the fermentation raw material decreases as the tank approaches the last tank (nth tank), making it difficult for the fermentation reaction to proceed. Therefore, the amount of carbon dioxide produced by fermentation decreases as the tank approaches the last tank (nth tank). Therefore, a specific approach to adjusting the cavitation conditions is to adjust them so that cavitation generation decreases from the first tank to the last tank (nth tank) (shorten the total vibration time per unit time).

[0038] In this embodiment, a carrier gas is supplied to the fermenter, whereby the alcohol produced by fermentation is taken up by the carrier gas and then quickly extracted from the system, forcibly transported and discharged outside the system, thereby promoting the fermentation reaction by reducing the ethanol concentration on the right side of the aforementioned formula 1. The supplied carrier gas also triggers the gasification of carbon dioxide produced by fermentation and dissolved in the culture solution in a supersaturated state, making it more likely to be discharged, thereby promoting the fermentation reaction by reducing the carbon dioxide concentration on the right side of the above formula 1.

[0039] In this embodiment, the carrier gas is supplied in the third fermenter 2c, which is the last stage, at the largest amount c, followed by the second fermenter 2b at the next largest amount b, and the first fermenter 2a, which is the first stage, at the smallest amount a (a <b<c)。

[0040] In this embodiment, as described above, cavitation is generated in the culture solution stored in the fermenters 2a, 2b, and 2c, thereby discharging carbon dioxide produced by fermentation from the liquid phase to the outside of the system, thereby promoting the fermentation reaction. Furthermore, in this embodiment, a carrier gas is supplied to the fermenters 2a, 2b, and 2c, thereby discharging ethanol produced by fermentation from the liquid phase to the outside of the system, thereby promoting the fermentation reaction. In other words, because both of the reaction products on the right side of the above-described formula 1 are discharged to the outside of the system, the fermentation efficiency is high and the amount of remaining raw material can be further reduced.

[0041] In this embodiment, the pressure inside the three fermenters 2a, 2b, and 2c is reduced. Maintaining a reduced pressure inside the tanks is preferable because it increases the ethanol transport rate per unit injected amount of carbon dioxide, thereby improving the ethanol transport efficiency. Specifically, the pressure inside the tanks is preferably 50 kPa or less, more preferably 30 kPa or less, and even more preferably 20 kPa or less. The lower limit of the pressure inside the tanks may be equal to or greater than the vapor pressure of water.

[0042] The mechanism by which the transport efficiency of ethanol increases by maintaining reduced pressure inside the tank is as follows. During fermentation steps P1a, P1b, and P1c, carbon dioxide gas is generated one after another through fermentation, and this gas is removed from fermentation tanks 2a, 2b, and 2c. As a result, the gas components initially present in the tanks are diluted by the carbon dioxide gas, and the gas phase inside fermentation tanks 2a, 2b, and 2c becomes filled only with carbon dioxide gas, ethanol vapor, and water vapor. Of these components, carbon dioxide gas has the lowest solubility in the culture solution, so the majority of the gas phase is filled with carbon dioxide gas.

[0043] The partial pressure of ethanol vapor depends only on the ethanol concentration and temperature in the liquid phase (culture solution), and the partial pressure of water vapor depends only on the water concentration and temperature in the liquid phase (culture solution). When the pressure inside fermenters 2a, 2b, and 2c is reduced, only the partial pressure of carbon dioxide in the gas phase (carbon dioxide + ethanol vapor (a value determined by the ethanol concentration and temperature regardless of whether the pressure is reduced) + water vapor (a value determined by the water concentration and temperature regardless of whether the pressure is reduced)) decreases. In other words, the proportion of ethanol vapor in the gas phase increases, and the transport efficiency of ethanol improves.

[0044] The carrier gas supplied to the fermenters 2a, 2b, and 2c preferably contains carbon dioxide (carbon dioxide gas) as its main component. By supplying carbon dioxide (carbon dioxide gas) as a carrier gas to the fermenters 2a, 2b, and 2c, the alcohol produced by fermentation can be quickly removed from the system and forcibly transported and discharged outside the system. Note that the "main component" here refers to the component with the highest partial pressure among the components contained in the gas. Furthermore, while it is chemically preferable to use an inert gas such as nitrogen or argon, carbon dioxide is economically preferable because it allows the gas generated within the process to be utilized.

[0045] As mentioned above, when the gas components discharged from the separation tanks 6a, 6b, and 6c are used as the supplied carrier gas, the main component is carbon dioxide (CO2). Furthermore, the alcohol partial pressure is relatively lower than other gases because of its low concentration. The sum of the carbon dioxide partial pressure and water vapor partial pressure is approximately equal to the total pressure in the system, which is controlled to a constant pressure by the pressure gauge 16 and pump 22-4, and the water vapor partial pressure is determined by the temperature of the fermentation liquid. Therefore, the carbon dioxide partial pressure and water vapor partial pressure are roughly determined by the pressure and temperature in the system.

[0046] The liquid components containing the fermentation product (ethanol) obtained from each fermenter 2a, 2b, 2c and stored in separation tanks 6a, 6b, 6c can be directly recovered from OUT-a, OUT-b, OUT-c, but because the alcohol concentration is low, it is preferable to concentrate them. Therefore, in this embodiment, the liquid components extracted from OUT-a, OUT-b, OUT-c are each concentrated as shown in Figure 2 to obtain concentrates with high ethanol concentrations (concentration steps P4a, P4b, P4c).

[0047] The concentration means (not shown in FIG. 1) for concentrating the liquid component is not particularly limited, and a conventionally known concentration method can be used. Applicable concentration methods include evaporation, membrane concentration, and freeze concentration. The concentrates concentrated by the concentration means in concentration steps P4a, P4b, and P4c are recovered as final products P5a, P5b, and P5c as ethanol with different concentrations.

[0048] The above-described embodiments merely show typical aspects of the present invention, and the present invention is not limited to these embodiments. For example, in the above-described embodiments, an ultrasonic vibrator is used as a means for generating cavitation, but the present invention is not limited to this. Other examples of means for generating cavitation include a stirrer, a high-speed mixer, a homogenizer, and a microbubble generator.

[0049] Furthermore, in the above embodiment, an example of a continuous fermentation tank having a three-tank configuration was described, but the present invention is not limited to this and can be applied without any problems to a continuous fermentation tank having a two-tank configuration or four or more tanks.

[0050] Furthermore, in the above embodiment, the condensation of the fermentation product mixed gas is described as an example in which the fermentation product mixed gas produced in the plurality of fermenters 2a, 2b, and 2c is separately condensed by three condensation means (heat exchangers 4a, 4b, and 4c) (condensation steps P2a, P2b, and P2c), but the present invention is not limited to this. That is, the fermentation product mixed gas produced in the plurality of fermenters (2a, 2b, and 2c) may be combined into one and condensed by one condensation step (condensation means) to obtain one condensate (a mixture of liquid components and gas components containing the fermentation product).

[0051] In this way, even when only one condensate (mixture) is obtained, or when multiple condensates (mixtures) are obtained separately using multiple condensation means, these multiple condensates (mixtures) may be combined into one and then separated in a single separation step (separation means) to obtain one liquid component and one gas component.

[0052] 3 is a flow chart showing the steps of a continuous fermentation method according to a first modified example, in which the fermentation product mixed gases produced in the fermenters are combined into one, and then condensed and separated in a condensation step (condensation means) and a separation step (separation means). In FIG. 3, the same components and steps as those in FIG. 2 are denoted by the same reference numerals, and detailed descriptions thereof will be omitted.

[0053] In this modification, the fermentation product mixed gases generated in the fermentation steps P1a, P1b, and P1c in the multiple fermenters (2a, 2b, and 2c) are combined and condensed by a single condensation means (condensation step P2). By the operation of condensation step P2, a single condensate (a mixture of liquid components and gas components containing the fermentation product) is obtained.

[0054] The condensate (mixture) 1 obtained in the condensation step P2 is separated by a separation means 1 (separation step P3). By the operation of separation step P3, a liquid component 1 and a gas component 1 are obtained. Thereafter, as in the above embodiment, the liquid component obtained in separation step P3 is subjected to the operation of concentration step P4, and the obtained gas component is supplied to a carrier gas supply means (the portion represented by the dashed line).

[0055] However, as in the above embodiment, it is preferable from the viewpoint of condensation efficiency to provide the same number of condensation means (heat exchangers 4a, 4b, 4c) as the number of fermentation tanks 2a, 2b, 2c, which separately condense the fermentation product mixed gases produced in each of the multiple fermentation tanks 2a, 2b, 2c.

[0056] Furthermore, as in the above embodiment, it is preferable from the viewpoint of separation efficiency to provide the same number of separation means (separation tanks 6a, 6b, 6c) as the number of fermenters 2a, 2b, 2c, which separate the mixtures obtained in the plurality of condensation means (heat exchangers 4a, 4b, 4c). Furthermore, since the ethanol recovered from each of the fermenters 2a, 2b, 2c has a different concentration, it is advantageous from the viewpoint of efficient recovery to have separate systems for the concentration steps P4a, P4b, P4c and the recovery steps P5a, P5b, P5c, as shown in Figure 2.

[0057] Furthermore, in the above embodiment, the culture medium overflowing from the fermenters 2a, 2b is sent to the subsequent fermenters 2b, 2c via the pipes 20-1, 20-2. However, connecting multiple fermenters in series is not limited to this configuration. For example, multiple fermenters of the same height can be lined up in a row and connected in series by joining the upper edges of adjacent fermenters without any gaps. A continuous fermentation apparatus in which a series of fermenters are connected and integrated in this way will be described below as a second modified example.

[0058] Fig. 4 is a schematic diagram showing the configuration of a continuous fermentation apparatus 1' according to a second modified example. However, unlike Fig. 1 in the above embodiment, Fig. 4 omits illustration of heat exchangers (condensation means) 4a, 4b, 4c, cold water tank 14, separation tanks (separation means) 6a, 6b, 6c, and peripheral components such as piping and pumps therearound.

[0059] Furthermore, in the continuous fermentation apparatus 1' according to the second modified example, the fermenter has five stages, namely, the first fermenter 2a' to the fifth fermenter 2e', which differs from the above embodiment in that the number of stages of fermenter is three. In Fig. 4, components that show configurations unique to this modified example are indicated by a prime "'" next to their reference numerals.

[0060] In this modified example, the components and steps having the same configuration as those in the above embodiment are denoted by the same reference numerals as in Fig. 1, and detailed descriptions thereof will be omitted. Furthermore, for the components in the fourth fermenter 2d' and the fifth fermenter 2e', the components having the same configuration as those in the first fermenter 2a to the third fermenter 2c in the above embodiment are denoted by the letter "d" in the reference numerals in Fig. 1, and by the letter "e" in the reference numerals in Fig. 1, and detailed descriptions thereof will be omitted.

[0061] In this modified example, five stages of fermenters 2a', 2b', 2c', 2d', and 2e' are integrated to form a single continuous fermenter 2'. In the continuous fermenter 2', the entire space above the integrated first to fifth fermenters 2a' to 2e' is closed off by side walls 28 that surround the four sides and a top plate 30 that covers the top.

[0062] Between the first fermenter 2a' and the second fermenter 2b', a liquid partition wall 24ab is provided closer to the first fermenter 2a', and a hanging partition wall 26ab is provided closer to the second fermenter 2b'. The liquid partition wall 24ab separates the yeast-containing water stored in the first fermenter 2a' and the second fermenter 2b'. When the yeast-containing water stored in the first fermenter 2a' exceeds the capacity of the first fermenter 2a', it can overflow beyond the upper end of the liquid partition wall 24ab.

[0063] The hanging partition wall 26ab hangs down vertically from the top plate 30 and is submerged in the yeast-containing water, and the lower end of the hanging partition wall 26ab is located above the bottom 32 of the continuous fermenter 2' (second fermenter 2b'). In the yeast-containing water, the hanging partition wall 26ab is disposed parallel to and opposite the liquid partition wall 24ab with a certain gap therebetween.

[0064] The spaces above the first fermenter 2a' and the second fermenter 2b' are separated by the hanging partition wall 26ab. On the other hand, in the yeast-containing water, the first fermenter 2a' side and the second fermenter 2b' side are not separated by the hanging partition wall 26ab, and the bottom 32 of the continuous fermenter 2' (second fermenter 2b') and the hanging partition wall 26ab are in communication with each other.

[0065] Therefore, the yeast-containing water that has overflowed from the first fermenter 2a' by exceeding the upper end of the liquid partition wall 24ab passes between the liquid partition wall 24ab and the hanging partition wall 26ab and between the lower end of the hanging partition wall 26ab and the bottom 32 of the continuous fermenter 2' (second fermenter 2b') and flows into the second fermenter 2b'. That is, the spaces between the liquid partition wall 24ab and the hanging partition wall 26ab and between the lower end of the hanging partition wall 26ab and the bottom of the continuous fermenter 2' (second fermenter 2b') form flow paths for the yeast-containing water that communicate between the two fermenters, similar to the piping 20-1 in Fig. 1.

[0066] Similar to the case between the first fermenter 2a' and the second fermenter 2b', a pair of liquid partition walls 24ab, 24bc, 24cd, 24de and a pair of hanging partition walls 26ab, 26bc, 26cd, 26de are provided between the second fermenter 2b' and the third fermenter 2c', between the third fermenter 2c' and the fourth fermenter 2d', and between the fourth fermenter 2d' and the fifth fermenter 2e'. The liquid partition walls 24ab, 24bc, 24cd, 24de have the same length (height) from the bottom 32 of the continuous fermenter 2'.

[0067] Therefore, the upper spaces between adjacent (consecutive) fermenters are separated by hanging partition walls 26ab, 26bc, 26cd, and 26de, respectively. That is, the upper spaces of the five fermenter stages 2a', 2b', 2c', 2d', and 2e' are each independently sealed and placed under reduced pressure.

[0068] Furthermore, between two adjacent (consecutive) fermenters, the stored yeast-containing water is partitioned by liquid partition walls 24ab, 24bc, 24cd, and 24de, allowing overflow of the stored yeast-containing water. That is, when yeast-containing water and raw material aqueous solution are introduced into the first fermenter 2a', the amount stored in each fermenter exceeds the capacity, and the amount overflows into the subsequent fermenter (five fermenter stages 2a', 2b', 2c', 2d', and 2e' are connected in series).

[0069] Even if the heights of the liquid partition walls 24ab, 24bc, 24cd, and 24de are the same, the liquid level in each fermenter exceeds the corresponding length (height), causing overflow, and the yeast-containing water that overflows the first fermenter 2a' will overflow into the subsequent fermenters. To prevent backflow of the yeast-containing water and ensure a smooth overflow, the entire continuous fermenter 2' may be installed at an angle so that the subsequent fermenters are lower, or the liquid partition walls 24ab, 24bc, 24cd, and 24de may be configured to be successively lower in the subsequent stages.

[0070] Other configurations of the second modified example described above are the same as those of the above embodiment. In addition to the method of overflow as in the above embodiment and the second modified example, the culture medium may be forcibly sent to the subsequent fermenter by a pump, and in this case, it can also be said that a plurality of fermenters are connected in series.

[0071] In the above embodiment, an example was described in which cavitation was generated in all of the multiple fermenters in the continuous fermenter, but the present invention is not limited to this, and it is also possible to have a configuration in which cavitation is generated in only some of the multiple fermenters. Even if only some of the fermenters generate cavitation, if there is a fermenter in which cavitation is generated, fermentation is promoted in that fermenter and the amount of residual raw material can be reduced.

[0072] Furthermore, in the above embodiment, an example of a continuous fermenter having multiple fermenters was described, but the present invention can be applied without problem not only to a continuous fermenter but also to a fermentation method and fermentation apparatus having only one tank (single tank). Even if there is only one fermenter, fermentation can be promoted by generating cavitation in the culture solution stored in the fermenter, and the amount of remaining raw material can be reduced.

[0073] In addition, those skilled in the art can implement various modifications of the present invention in accordance with conventionally known knowledge without departing from the gist of the present invention. As long as such modifications still comprise the fermentation method, continuous fermentation method, fermentation apparatus, or continuous fermentation apparatus configuration of the present invention, they are of course included in the scope of the present invention. [Explanation of symbols]

[0074] 2a, 2a′: first fermenter, 2b, 2b′: second fermenter, 2c, 2c′: third fermenter, 2d′: fourth fermenter, 2e′: fifth fermenter, 2′: continuous fermenter, 4a, 4b, 4c: heat exchanger (condensing means), 6a, 6b, 6c: Separation tank (separation means), 8a, 8b, 8c, 8a', 8b', 8c', 8d', 8e': ultrasonic vibrator (cavitation generating means), 10: Yeast tank, 12: Raw material tank, 14:Cold water tank, 16: Pressure gauge, 18a, 18b, 18c, 18a′, 18b′, 18c′, 18d′, 18e′: agitators, 20-1 to 20-16: Piping, 22-1~22-7: Pump, 24ab, 24bc, 24cd, 24de: Liquid partition wall, 26ab,26bc,26cd,26de: hanging partition wall, 28: side wall, 30: Top plate, 32: Bottom

Claims

1. a fermentation product is produced by fermenting a raw material in a culture solution containing the raw material stored in a fermenter, condensing the fermentation product mixed gas containing the fermentation product produced in the fermenter to obtain a mixture of a liquid component and a gas component containing the fermentation product; A fermentation method comprising separating the mixture to obtain the liquid component and the gas component, A fermentation method comprising generating cavitation in the culture solution stored in the fermenter.

2. 2. The fermentation method according to claim 1, wherein the generation of cavitation in the culture medium is intermittent.

3. 2. The fermentation method according to claim 1, wherein the means for generating cavitation in the culture solution is an ultrasonic vibrator.

4. The fermentation method according to claim 1 , wherein a carrier gas is supplied to the culture solution stored in the fermenter.

5. The fermentation method according to claim 4 , wherein the gas component is used as part or all of the carrier gas.

6. The fermentation method according to claim 4, wherein the main component of the carrier gas is carbon dioxide.

7. The fermentation method according to claim 4, wherein the fermenter is kept under reduced pressure.

8. The fermentation method according to claim 7, wherein the pressure in the fermenter is 50 kPa or less.

9. The fermentation method of claim 1 , wherein the liquid component is concentrated to obtain a concentrate having a high concentration of the fermentation product.

10. a plurality of fermenters each storing a culture solution containing a raw material are connected in series, and the culture solution is sequentially sent to a subsequent fermenter; and in each of the plurality of fermenters, the raw material is fermented in the culture solution to produce a fermentation product; condensing the fermentation product mixed gas containing the fermentation product produced in the plurality of fermenters to obtain a mixture of a liquid component and a gas component containing the fermentation product; A continuous fermentation method in which the mixture is separated to obtain the liquid component and the gas component, A continuous fermentation method, wherein cavitation is generated in the culture solution stored in some or all of the plurality of fermenters.

11. The continuous fermentation method according to claim 10, wherein there are a plurality of fermenters in which cavitation occurs, and the cavitation conditions are different for each of the fermenters.

12. a fermenter that stores a culture solution containing a raw material and ferments the raw material in the culture solution to produce a fermentation product; a condensing means for condensing the fermentation product mixed gas containing the fermentation product produced in the fermenter to obtain a mixture of a liquid component containing the fermentation product and a gas component; a separation means for separating the mixture to obtain the liquid component and the gas component; a cavitation generating means for generating cavitation in the culture solution stored in the fermenter; A fermentation apparatus comprising:

13. The fermentation apparatus according to claim 12, wherein the cavitation generating means generates cavitation intermittently.

14. 13. The fermentation apparatus according to claim 12, wherein the cavitation generating means is an ultrasonic vibrator.

15. The fermentation apparatus according to claim 12, further comprising a carrier gas supply means for supplying a carrier gas to the culture solution stored in the fermenter.

16. The fermentation apparatus according to claim 15, wherein the gas component is used as part or all of the carrier gas supplied by the carrier gas supply means.

17. 16. The fermentation apparatus according to claim 15, wherein the main component of the carrier gas supplied by the carrier gas supply means is carbon dioxide.

18. The fermentation apparatus of claim 12 wherein the fermenter is under reduced pressure.

19. 19. The fermentation apparatus of claim 18, wherein the pressure in the fermenter is 50 kPa or less.

20. The fermentation apparatus according to claim 12, further comprising a concentration means for concentrating the liquid component separated by the separation means to obtain a concentrate having a high concentration of the fermentation product.

21. a plurality of fermenters that store a culture solution containing a raw material, ferment the raw material in the culture solution to produce a fermentation product, and are connected in series so that the culture solution is sequentially sent to subsequent fermenters; a condensation means for condensing the fermentation product mixed gas containing the fermentation product produced in the plurality of fermenters to obtain a mixture of a liquid component containing the fermentation product and a gas component; a separation means for separating the mixture to obtain the liquid component and the gas component; a cavitation generating means for generating cavitation in the culture solution stored in some or all of the plurality of fermenters; A continuous fermentation apparatus comprising:

22. 22. The continuous fermentation apparatus according to claim 21, comprising a plurality of fermenters each having a cavitation generating means, wherein the conditions of cavitation in the cavitation generating means are different for each of the plurality of fermenters.

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