Method and apparatus for producing chemical by continuous fermentation
阅读说明：本技术 基于连续发酵的化学品的制造方法及制造装置 (Method and apparatus for producing chemical by continuous fermentation ) 是由 志村芙美 金森智子 高木亮太 于 2018-06-29 设计创作，主要内容包括：本发明提供能够同时具有目标物质的生产率及过滤性的化学品的制造方法。在连通发酵槽和膜分离组件的配管上设置除去固体成分的机构，并且将在除去机构中所除去的固体成分添加于培养液。(The invention provides a method for producing a chemical product capable of achieving both the productivity and filterability of a target substance. A means for removing solid components is provided in a pipe connecting the fermentation tank and the membrane separation module, and the solid components removed by the removing means are added to the culture solution.)
1. A chemical production apparatus comprising:
a fermentation tank that contains a culture solution containing a raw material and a microorganism that produces methane from the raw material by fermentation;
an external pressure type membrane separation module for separating the microorganisms from the culture solution to obtain a filtrate and a concentrated solution;
a supply pipe for supplying the culture solution in the fermentation tank to the membrane separation module;
a return pipe for returning the concentrated liquid from the membrane separation module into the fermentation tank; and
a solid component removing mechanism provided in the supply pipe and configured to capture a part of the solid component in the culture solution,
the membrane separation module is provided with: a container; a separation membrane housed within the container; and a first opening provided in the container and through which a culture solution flowing into the container passes and a second opening through which a concentrated solution flowing out of the container passes,
the first opening and the second opening are disposed so as to be separated from each other in a longitudinal direction of the container,
at least one of the first opening and the second opening is provided on a side surface of the container,
the opening of the solid component removing means is 1/3 or less which is smaller in the major diameter of the first opening and the second opening provided in the side surface of the container.
2. The chemical production apparatus according to claim 1, wherein an opening of the solid component removal means is 0.1mm or more.
3. The chemical production apparatus according to claim 1 or 2, wherein an opening of the solid component removal means is 10mm or less.
4. The chemical production apparatus according to claim 3, wherein an opening of the solid component removal means is 2mm or less.
5. The chemical production apparatus according to any one of claims 1 to 4, further comprising:
and a solid component addition pipe for adding the solid component captured by the solid component removal means to the culture solution in the fermentation tank.
6. A method for producing a chemical by using the chemical production apparatus according to any one of claims 1 to 5,
the manufacturing method comprises the following steps: according to the linear velocity v [ m ] of the culture solution on the membrane surface in the membrane separation module in the longitudinal direction of the container3/m2/s]And the smaller of the major diameters of the first opening and the second opening provided in the side surface of the container A [ m ]]Satisfies v > 0.8(2gA (S-1))0.5In such a manner that the culture solution flows in the membrane separation module.
7. A method for producing a chemical by using the chemical production apparatus according to any one of claims 1 to 5,
the manufacturing method comprises the following steps: the solid matter captured by the solid matter removing means is directly added to the culture solution in the fermentation tank.
8. A method for producing a chemical by using the chemical production apparatus according to any one of claims 1 to 5,
the manufacturing method comprises the following steps: the solid component captured by the solid component removing means is added to the culture solution in the fermentation tank through the return pipe.
9. A method for producing a chemical, which comprises using the chemical production apparatus according to any one of claims 1 to 5 and further comprising a raw material supply pipe connected to the fermentation tank,
the manufacturing method comprises the following steps:
adding a fermentation raw material to the fermentation tank through the raw material supply pipe; and
and a step of adding the solid component captured by the solid component removal means to the culture solution in the fermentation tank through the raw material supply pipe.
Technical Field
The present invention relates to a method and an apparatus for producing chemicals by continuous fermentation.
Background
The continuous fermentation method is one of substance production methods accompanied by cell (hereinafter, in "cell", including "microorganism") culture.
In the continuous fermentation method, the amount of liquid in the fermentation tank can be always kept constant by supplying fresh medium to the fermentation tank and discharging the same amount of culture liquid to the outside of the fermentation tank. In the continuous fermentation method, in order to maintain the concentration of microorganisms in the fermentation tank, it has been proposed to separate the microorganisms from the discharged culture solution by a separation membrane, use the filtrate from which the microorganisms have been removed for purification of the target product, and return the separated microorganisms to the culture solution (see patent document 1).
On the other hand, in the continuous fermentation method, there are cases where: during the filtration operation, the flow channel and the pores of the membrane are clogged with the solid content in the culture solution, and the filtration capacity is reduced or the culture solution cannot be fed to the membrane module.
Patent document 2 discloses the following method: in methane fermentation, large solid components are removed from water to be treated in advance by a removing means such as a screen (screen) in order to remove solid components trapped in a reactor.
Disclosure of Invention
Problems to be solved by the invention
The purpose of the present invention is to provide a method for producing a chemical that can achieve both the productivity and filterability of a target substance.
Means for solving the problems
The present invention provides the following.
[ 1] A chemical production apparatus comprising:
a fermentation tank for containing a culture solution containing a raw material and a microorganism that produces methane by fermentation of the raw material;
an external pressure type membrane separation module for separating the microorganisms from the culture solution to obtain a filtrate and a concentrated solution;
a supply pipe for supplying the culture solution in the fermentation tank to the membrane separation module;
a return pipe for returning the concentrated solution from the membrane separation module into the fermentation tank; and
a solid component removing means provided in the supply pipe for capturing a part of the solid component in the culture solution,
the membrane separation module includes: a container; a separation membrane housed in the container; and a first opening provided in the container and through which a culture solution flowing into the container passes and a second opening through which a concentrated solution flowing out of the container passes,
the first opening and the second opening are disposed so as to be separated from each other in the longitudinal direction of the container,
at least one of the first opening and the second opening is provided on a side surface of the container,
the opening of the solid content removal means is 1/3 or less, which is the smaller of the major diameters of the first opening and the second opening provided in the side surface of the container.
[ 2] the chemical production apparatus according to [ 1], wherein an opening of the solid removing means is 0.1mm or more.
[ 3] the chemical production apparatus according to [ 1] or [ 2], wherein an opening of the solid component removing means is 10mm or less.
[ 4 ] the chemical production apparatus according to [ 3], wherein an opening of the solid removing means is 2mm or less.
[ 5 ] the chemical production apparatus according to any one of [ 1] to [ 4 ], further comprising:
and a solid component addition pipe for adding the solid component captured by the solid component removal means to the culture solution in the fermentation tank.
A method for producing a chemical using the chemical production apparatus according to any one of [ 1] to [ 5 ],
the manufacturing method comprises the following steps: according to the linear velocity v [ m ] of the culture medium on the membrane surface in the membrane separation module in the longitudinal direction of the container3/m2/s]And the smaller one A [ m ] of the major diameters of the first opening and the second opening provided in the side surface of the container]Satisfies v > 0.8(2gA (S-1))0.5In such a manner that the culture solution flows in the membrane separation module.
A method for producing a chemical using the chemical production apparatus according to any one of [ 1] to [ 5 ],
the manufacturing method comprises the following steps: the solid matter captured by the solid matter removing means is directly added to the culture solution in the fermentation tank.
A method for producing a chemical using the chemical production apparatus according to any one of [ 1] to [ 5 ],
the manufacturing method comprises the following steps: the solid component captured by the solid component removing means is added to the culture solution in the fermentation tank through the return pipe.
A method for producing a chemical using the apparatus for producing a chemical according to any one of [ 1] to [ 5 ] and further comprising a raw material supply pipe connected to the fermentation tank,
the manufacturing method comprises the following steps:
a step of adding a fermentation material to the fermentation tank through the material supply pipe; and
and a step of adding the solid component captured by the solid component removal means to the culture solution in the fermentation tank through the raw material supply pipe.
Effects of the invention
The solid content removing mechanism is provided between the fermentation tank and the membrane separation module, and the size of the opening of the mechanism is set with respect to the length of the opening at the bend of the flow path of the culture solution in the membrane separation module, thereby preventing the membrane separation module from being clogged with the solid content.
In the solid component removing mechanism, if the opening is excessively reduced, the mechanism itself for removing the solid component is frequently clogged. On the other hand, if the opening is increased, the solid component flows into the membrane separation module, and the flow path is blocked. In the present invention, by appropriately setting the size of the opening, it is possible to realize stable operation while suppressing clogging of either the mechanism for removing solid components or the membrane separation module.
Drawings
FIG. 1 is a schematic view showing a membrane separation continuous fermentation apparatus according to an embodiment of the present invention.
Fig. 2 is a cross-sectional view showing an example of an external pressure type membrane separation module.
Fig. 3 is a sectional view showing another example of the external pressure type membrane separation module.
FIG. 4 is a schematic view showing a membrane separation continuous fermentation apparatus according to a reference example.
Detailed Description
1. Continuous fermentation device
An example of the continuous fermentation apparatus will be described with reference to FIG. 1. FIG. 1 is a schematic side view of a continuous fermentation apparatus according to the present embodiment.
As shown in fig. 1, the continuous fermentation apparatus 100 includes a fermentation tank 1, a membrane separation module 2, and a pipe connecting the fermentation tank 1 and the membrane separation module 2. The fermentation tank 1 and the membrane separation module 2 are connected to form a circulation system.
1-1. fermentation tank
The fermentation tank 1 is configured to accommodate a culture solution therein. The culture solution will be described later.
Specifically, the fermentation tank 1 is made of a material having excellent pressure resistance and stain resistance. Various shapes such as a cylindrical shape and a polygonal cylindrical shape can be applied to the fermentation tank 1. When the fermentation tank 1 is cylindrical, the efficiency of stirring the culture solution becomes good.
The fermentation tank 1 is configured to be sterilized and sealed as necessary. The fermentation raw material and the like contained in the fermentation tank 1 are stirred by a stirring device 6 described later. The fermentation tank 1 is preferably cylindrical from the viewpoint of the efficiency of stirring the culture solution.
1-2. Membrane separation Module
The membrane separation module 2 is not limited to a specific configuration as long as it can separate microorganisms from the culture solution and can obtain a concentrated solution and a filtrate by filtering the culture solution. As shown in fig. 2, the membrane separation module 2 includes a container 103 and a large number of separation membranes 104 housed in the container.
In the present embodiment, the separation membrane 104 is a hollow fiber membrane. The module having the hollow fiber membranes is more capable of increasing the membrane area per unit volume of the module than the module having the flat membranes.
The separation membrane module 2 includes a plurality of separation membrane bundles 104A. The separation membrane bundle 104A includes a plurality of separation membranes 104.
The separation membrane may be any of an organic membrane and an inorganic membrane. The separation membrane may be any membrane that can be used for removing microorganisms from the culture solution or microorganisms. Examples of the separation membrane include membranes made of polyvinylidene fluoride, polysulfone, polyethersulfone, polytetrafluoroethylene, polyethylene, polypropylene, and ceramic. In particular, a separation membrane made of polyvinylidene fluoride, which is less likely to cause contamination due to fermentation liquid, is easy to clean, and has excellent durability against cleaning with gas, is preferable.
In order to efficiently separate microorganisms in the fermentation liquid, the separation membrane is preferably a porous membrane having pores with an average pore diameter of 0.001 μm or more and less than 10 μm.
The average pore diameter of the membrane was according to ASTM: f316-86 (alias: semi-dry method). It is to be noted that the average pore diameter of the minimum pore diameter layer of the membrane is determined by the semi-dry method.
The standard measurement conditions for measuring the average pore diameter by the semidry method are as follows.
The use of a liquid: ethanol
Measuring temperature: 25 deg.C
Pressure rise speed: 1 kPa/sec
The average pore diameter [ μm ] was determined by the following formula.
Average pore diameter [ μm ] (2860 × surface tension [ mN/m ])/half-dry air pressure [ Pa ]
The surface tension of ethanol at 25 ℃ is 21.97mN/m (edited by the Japan chemical society, revised edition of the Foundation of chemical society, pp. II-82, Takayama, 1984), and thus the standard measurement conditions of the present invention can be determined by the following formula.
Average pore diameter [ μm ] ═ 62834.2/(semi-dry air pressure [ Pa ])
The membrane separation module 2 is preferably of the external pressure type. In the external pressure type membrane separation module, the culture solution flows outside the hollow fiber membranes, and the filtrate flows inside the hollow fiber membranes (i.e., hollow portion). That is, during filtration, the liquid flows from the outside toward the inside of the hollow fiber membrane. The concentrate containing the unfiltered substance flows outside the hollow fiber membranes. In the internal pressure type, the flow of liquid at the time of filtration becomes opposite.
The outer diameter of the external pressure type hollow fiber membrane is preferably 0.5mm to 3 mm. By setting the outer diameter to 0.5mm or more, the resistance of the filtrate flowing through the hollow fiber membrane can be suppressed to a small value. Further, by setting the outer diameter to 3mm or less, it is possible to suppress the hollow fiber membrane from being broken by external pressure due to the fermentation liquid or gas.
The inner diameter of the internal pressure type hollow fiber membrane is preferably 0.5mm to 3 mm. By setting the inner diameter to 0.5mm or more, the resistance of the fermentation liquid flowing through the hollow fiber membrane can be suppressed to be small. Further, by setting the inner diameter to 3mm or less, the membrane surface area can be secured, and therefore, the increase of the membrane separation module can be suppressed.
The container 103 of the membrane separation module is made of a material having excellent pressure resistance, and may be in a shape capable of supplying the fermentation liquid to the primary side of the membrane, such as a cylindrical shape or a polygonal cylindrical shape. In consideration of the flow and handling properties of the fermentation liquid, the container is preferably cylindrical. The membrane separation module may be an immersion type membrane separation device in which the separation membrane is immersed in a water tank.
In fig. 2, the vessel 103 of the membrane separation module is cylindrical, and the hollow fiber membranes are arranged such that the longitudinal direction thereof is along the height direction of the vessel 103 (the longitudinal direction of the vessel).
In the present embodiment, the vessel 103 includes a vessel main body 103A, an upper cap 103B, and a lower cap 103C.
In the present embodiment, a bottom opening 105 is provided in the bottom of the lower cap 103C, and a side opening 106 is provided in the side surface of the container main body 103A.
The culture solution flows into the container 103 from the bottom opening 105 and is supplied between the separation membranes 104. The culture solution is separated into a concentrated solution and a filtrate by the separation membrane 104. The concentrated liquid passes between the separation membranes 104 (between the separation membranes 104) and is discharged from the side opening 106 to the outside of the container 103. The concentrated solution is returned to the fermentation tank 1 as described later. The filtrate passes through the inside of the separation membrane 104 and is discharged to the outside of the container 103 through an upper opening 107 provided in the upper cap 103B.
The vessel of the separation membrane module includes a first opening and a second opening. The first opening and the second opening are disposed so as to be separated from each other in the longitudinal direction of the container. At least one of the first opening and the second opening is provided in parallel with the longitudinal direction of the container (i.e., the longitudinal direction of the hollow fiber membrane). That is, the culture solution flowing into the container passes through the first opening, and the concentrated solution flowing out of the container passes through the second opening. Further, at least one of the flow direction of the culture solution flowing into the container from the first opening and the flow direction of the concentrated solution flowing out of the container from the second opening is perpendicular to the longitudinal direction of the container (i.e., the longitudinal direction of the hollow fiber membrane).
Here, in the container 103, the bottom opening 105 corresponds to a first opening, and the side opening 106 corresponds to a second opening. That is, in the present embodiment, the second opening is provided in the container side surface. The present invention is not limited to this, and only the first opening portion may be provided on the container side surface, or both the first opening portion and the second opening portion may be provided on the container side surface. For example, a first opening may be provided on a side surface of the container main body 103A or the lower cap 103C instead of the bottom opening 105.
By providing the first opening and the second opening so as to be separated from each other in the longitudinal direction of the container and housing the hollow fiber membranes in parallel with the longitudinal direction of the container, the culture solution and the concentrated solution flow from the first opening toward the second opening along the longitudinal direction of the container, that is, along the longitudinal direction of the hollow fiber membranes.
Further, at least one of the first opening and the second opening is provided on a side surface of the container in the longitudinal direction, whereby a bent portion is generated in a flow path of the culture solution or the concentrated solution flowing into the membrane separation module. Here, the bent portion is a portion where the flow of the culture medium changes at a right angle or an angle close to a right angle. The curved portion is one portion when one of the first opening portion and the second opening portion is provided on the longitudinal side surface of the container, and the curved portion is two portions when the two opening portions are provided on the longitudinal side surface of the container.
By having the bent portion, an opening portion for collecting the filtrate passing through the hollow portion of the hollow fiber membrane and a discharge opening portion for discharging the concentrate accumulated in the container are provided in the short-side direction, that is, in the radial direction of the hollow fiber membrane contained in the container. As described later, since the solid components in the culture solution or the concentrated solution are likely to be accumulated or accumulated in the bent portion, the relationship between the length of the opening and the size of the solid components affects the ease of clogging due to the solid components in the membrane separation module.
In the embodiment shown in fig. 3, the membrane separation module 2 includes a flow straightening member 111 in addition to the configuration of fig. 2. The rectifying member 111 is a member that rectifies the liquid in the membrane separation assembly. In the present embodiment, the rectifying member 111 is a cylindrical member, and is disposed in the vicinity of the upper end of the container main body 103A in the container 103. The rectifying member 111 has a plurality of rectifying holes 112 on a side surface (a surface parallel to the side surface of the container main body 103A). The rectifying member 111 is disposed so that the side opening 106 overlaps the rectifying hole 112.
In the present embodiment, the concentrated liquid passes between the separation membranes 104 (between the separation membranes 104), passes through the rectifying holes 112 of the rectifying member 111, and is discharged from the side opening 106 to the outside of the container 103.
That is, as in the present embodiment, when the membrane separation module includes the rectifying member 111 disposed in the container, the concentrated liquid passes through both the rectifying hole 112 and the side opening 106. Therefore, the smaller of the diameter of the rectifying hole 112 and the diameter of the side opening 106 substantially defines the diameter of the second opening. That is, the smaller of the longer diameter of the rectifying hole 112 and the longer diameter of the side opening 106 is the longer diameter of the second opening. When the membrane separation module includes the rectifying member, the rectifying hole of the rectifying member is often smaller than the opening of the container outside the rectifying hole, and therefore the major diameter of the rectifying hole is regarded as the major diameter of the 2 nd opening. That is, in the present embodiment, the major diameter of the rectifying hole 112 is regarded as the major diameter of the second opening portion.
1-3. circulation system
The continuous fermentation apparatus 100 includes a circulation system for circulating a culture solution between the fermentation tank 1 and the membrane separation module 2. Specifically, the continuous fermentation apparatus 100 includes: a supply pipe 23 which communicates the fermentation tank 1 and the primary side of the membrane separation module 2; and a return pipe 25 for returning the concentrated liquid that has not passed through the separation membrane of the membrane separation module 2 to the fermentation tank 1. The pipe 23 may be connected to any of the lower portion and the upper portion of the membrane separation module 2. Further, a circulation pump 24 is disposed in a pipe 23 for supplying the culture solution from the fermentation tank 1 to the membrane separation module 2. The circulation pump 24 is operated to feed the culture solution from the fermentation tank 1 to the membrane separation module 2.
1-4 solid component removing mechanism
The continuous fermentation apparatus 100 has a solid content removing mechanism 102 in the middle of a pipe 23 which communicates the fermentation tank 1 and the membrane separation module 2 and supplies the culture solution from the fermentation tank 1 to the membrane separation module 2.
The solid component removal means 102 can remove a part of the solid component from the culture solution by capturing a solid component larger than the microorganisms that can be separated by the membrane separation module 2.
Specifically, the solid component removing means has a filter material. The filter medium is a mesh, slit or porous filter. The filter material may be any filter material capable of separating coarse solid substances in a water flow, such as a filter mesh (filter), a sintered filter material, a mesh filter, a drum filter, a disc filter, a mesh filter, and a rod screen (bar screen), and is preferably a filter material that can be used in a closed system.
The size of the solid component separated by the solid matter removing means is determined by the opening of the filter material. The opening is a short diameter of the opening of the filter medium. In the case of a web formed of fibers crossed by the filter material, the interstices between the fibers are open. In the filter material having the slits, the slits are openings. If the filter material is porous, the pores are open.
The opening of the solid component removal means is preferably 1/3 or less, which is the smaller of the major diameter of the first opening and the major diameter of the second opening provided in the side surface of the container of the membrane separation module. The opening is more preferably 1/4 or 1/5 or less, which is smaller in the major axis of the opening. The opening preferably satisfies the condition of 1/3 being the major diameter of the first opening or the second opening, and is 0.1mm or more. The opening is preferably 10mm or less, more preferably 2mm or less.
As described above, a bent portion is generated in the flow path of the culture solution or the concentrated solution flowing into the membrane separation module. At the bend and its vicinity, the flow of the liquid becomes small, and therefore the solid component is likely to accumulate. By making the opening smaller than 1/3 in the major diameter of the first opening and the second opening, the accumulation of solid components on the flow path of the membrane separation module 2 can be suppressed. The reason is that the short diameter of the first opening or the second opening is not used, but the long diameter is used as a reference, but it is not clear that the reason is considered that: even if the diameter is larger than the short diameter, the solid component can pass through the first opening and the second opening by rotating as long as the diameter is 1/3 or less.
Further, by setting the opening to 0.1mm or more, clogging of the solid component removing mechanism itself can be suppressed, and the discharge frequency of the captured solid component can be reduced.
In the embodiment shown in fig. 2, only the side opening 106 is provided on the side surface of the container, and therefore the opening may be made equal to or smaller than 1/3, which is the major diameter of the side opening 106. When the first opening portion is present on the side surface of the container main body 103A or the lower cap 103C in place of the bottom opening portion 105, the opening may be formed so as to be smaller than 1/3, which is the smaller of the major diameter of the first opening portion and the major diameter of the side opening portion 106, which is the second opening portion.
In the embodiment shown in fig. 3, only the side opening 106 is provided on the side surface of the container, the rectifying member 111 is disposed in the container, and the concentrated solution passes through the rectifying hole 112 of the rectifying member and the side opening 106, and therefore the opening is not more than 1/3, which is the major diameter of the rectifying hole 112.
In the arrangement of the side opening 106 and the rectifying member 111, similarly to fig. 3, when a first opening is present on the side surface of the vessel main body 103A or the lower cap 103C instead of the bottom opening 105, the smaller of the major diameter of the rectifying hole 112 and the major diameter of the first opening is a criterion for setting the opening size of the solid component removing means.
In the case where the membrane separation module is cylindrical and includes the rectifying member having the rectifying hole with the side surface, the second opening portion is usually provided in the side surface of the container. In this case, the rectifying hole and the second opening portion are preferably overlapped, but may be shifted. On the other hand, in the case where the membrane separation module does not include the rectifying member, the second opening portion may be provided at an end portion (other portion than the side surface) of the container. If the second opening is provided at the end of the container and the first opening is provided at the side of the container, the major axis of the first opening is the standard of the opening of the solid component removing means.
The solid component removing means may be provided only one, or may be provided as a backup (backup) in the solid component discharge process.
1-5 solid component adding mechanism
In the example of fig. 1, the continuous fermentation apparatus 100 includes a solid content addition pipe 120 directly connecting the solid content removal means 102 and the fermentation tank 1.
The solid component addition pipe 120 is an example of a solid component addition means for adding the solid component captured by the solid component removal means 102 to the culture solution in the fermentation tank 1. The solid component adding means may be provided with a pump or the like, not shown. By adding the temporarily removed solid component to the culture solution, the soluble substance adsorbed to the solid component can also be returned to the culture solution, and therefore, the decrease in the concentration of the substance serving as a substrate for fermentation can be suppressed, and the productivity of the target substance can be maintained high.
The solid content adding means may be any means as long as it can finally add the solid content to the culture solution in the fermentation tank, and may be configured to pass through the return pipe 25 to add the solid content to the culture solution in the fermentation tank 1 or may be configured to pass through the pipe for supplying the raw material from the raw material tank 101 to the fermentation tank 1 if it is applied to the configuration of fig. 1 in addition to the direct addition to the fermentation tank.
1-6. other mechanisms
The continuous fermentation apparatus 100 includes a control device 28. The control device 28 can perform various calculations. The controller 28 controls the operations of the respective units in the continuous fermentation apparatus 100 based on the detection results of the various sensors, the input of the user, and various settings.
In the present embodiment, in addition to the above configuration, the continuous fermentation apparatus 100 further includes a temperature control unit 5, a stirring device 6, a pH control unit 7, a liquid level control unit 8, an air tank 91, and the like.
The temperature control unit 5 includes a temperature sensor and a temperature adjustment unit. The temperature sensor detects the temperature of the culture solution in the fermentation tank 1. The temperature adjustment portion is operated under the control of the control device 28 so that the detection result by the temperature sensor shows a certain range. By maintaining the temperature in the fermentation tank 1 constant in this manner, a temperature environment suitable for fermentation or growth of microorganisms is maintained. The temperature adjustment unit may have a function of one or both of heating and cooling.
The stirring device 6 stirs the culture solution in the fermentation tank 1 to maintain an appropriate fermentation environment.
The pH control unit 7 includes a pH sensor 71 and a neutralizer supply pump 13. The pH sensor 71 detects the pH of the culture solution in the fermentation tank 1. The neutralizer supply pump 13 is provided in a pipe connecting the neutralizer tank and the fermentation tank 1, and adds the neutralizer to the fermentation tank 1. The neutralizer supply pump 13 is operated so that the detection result of the pH sensor 71 indicates a predetermined range under the control of the control device 28. As the neutralizing agent, an acid and a base are used.
The liquid level control unit 8 includes a liquid level sensor 81 and a raw material supply pump 12. The raw material supply pump 12 is disposed in a pipe connecting the raw material tank 101 and the fermentation tank 1. Under the control of the control unit 28, when the detection result of the liquid level sensor 81 indicates that the liquid level of the culture solution in the fermentation tank 1 is lower than a predetermined lower limit, the raw material supply pump 12 is operated to supply the culture medium to the fermentation tank 1, and when the liquid level indicates that the liquid level reaches the upper limit, the operation of the raw material supply pump 12 is stopped. Thus, the amount of the culture medium in the fermentation tank 1 is appropriately secured.
The gas tank 91 is connected to the fermentation tank 1 via a discharge line 90. The gas generated in the fermentation tank 1 is discharged through a discharge line 90 and accumulated in a gas tank 91.
The continuous fermentation apparatus 100 further includes a pipe 26 connected to the membrane separation module 2 and discharging the filtrate (i.e., permeate) to the outside of the apparatus. The pipe 26 is provided with a filtrate pump 14, and a filtrate valve 15 is provided between the filtrate pump and the membrane separation module 2.
The continuous fermentation apparatus 100 is configured to perform back pressure cleaning of the membrane separation module 2. The back pressure cleaning is as follows: the separation membrane is cleaned by passing a cleaning liquid (hereinafter, sometimes referred to as "cleaning liquid") through the separation membrane from the secondary side to the primary side. The continuous fermentation apparatus 100 includes a cleaning liquid tank for storing a cleaning liquid, a cleaning pipe 27 for connecting the cleaning liquid tank to the secondary side of the membrane separation module 2, a cleaning pump 16 provided on the cleaning pipe 27, and a cleaning valve 17 provided between the cleaning pump 16 and the membrane separation module 2. The cleaning liquid is supplied to the membrane separation module 2 by the cleaning pump 16. The cleaning liquid may be a filtrate that has permeated through the separation membrane, or may be water supplied from the outside of the system. In addition, any chemical may be contained in the water.
The cleaning pipe 27 may be provided with a pressure gauge, a flow meter, and the like.
The differential pressure controller 9 can detect the Transmembrane Pressure Difference (TPD) of the membrane separation module 2. That is, a differential pressure between the primary side (the side to which the culture solution is supplied) and the secondary side (the side to which the filtrate is discharged) of the membrane separation module 2 is detected. The inter-membrane pressure difference becomes a propulsive force for filtration.
Further, the continuous fermentation apparatus 100 is configured to participate in scrubbing (scrubbing). Scrubbing is the following cleaning method: by supplying gas to the primary side of the membrane separation module 2, substances adhering to the surface of the separation membrane are removed from the surface of the separation membrane by utilizing the shaking of the liquid and gas generated when the gas passes through the inside of the membrane separation module 2.
In the continuous fermentation apparatus 100, in particular, gas is supplied to the membrane separation module 2 from at least one of the lower portion of the membrane separation module 2 and the pipe 23 that communicates the fermentation tank 1 and the membrane separation module 2. In particular, as a configuration participating in the scrubbing, a membrane separation module gas supply device, a gas supply port, and a mechanism capable of adjusting the supply rate of gas from a gas supply source are provided. The supplied gas or the gas generated by the metabolism of the microorganisms may be recovered and supplied again to the membrane separation module 2.
Specifically, the continuous fermentation apparatus 100 includes a gas supply control valve 18 and a gas supply device 19.
The gas supply device 19 is connected to the membrane separation module 2 via a pipe on the primary side of the membrane separation module 2, i.e., on the side where the culture solution is supplied.
The gas supply port is a portion for releasing gas into the culture solution. The gas supply port is preferably formed so as to generate bubbles capable of cleaning the surface of the film. The generated bubbles may be fine bubbles or coarse bubbles. The size of the bubbles is changed by changing the shape of the gas supply port according to conditions such as the type of the separation membrane and the amount of the dispersed gas. The gas supply port may be formed by providing an air discharge hole in a pipe made of vinyl chloride or stainless steel, and porous rubber, ceramics, an air diffuser pipe using a filter (membrane), or the like may be used. The size of the gas supply port may be set to a size that allows a predetermined amount of gas to be supplied and does not cause clogging due to the fermentation liquid.
As described above, in fig. 1, the gas supply port may be provided at the lower portion of the membrane separation module 2, and in the configuration in which the culture solution is supplied from the fermentation tank to the membrane separation module 2 by using the pump, the gas supply port may be provided between the fermentation tank and the pump, or between the pump and the membrane separation module 2.
2. Method for producing chemical
The production method of the present embodiment is a method for producing a chemical, which is methane, by continuous fermentation, and includes the following steps (a) to (e):
(a) a fermentation step of producing methane from a raw material by fermentation with a microorganism in a culture solution in a fermentation tank
(b) A filtration step of filtering the culture solution having undergone the fermentation step with the membrane separation module to obtain a filtrate and a concentrated solution
(c) A reflux step of refluxing the concentrated solution obtained in the filtration step from the membrane separation module into the fermentation tank through a reflux pipe
(d) A solid component capturing step of capturing the solid component in the culture solution by a solid component removing means provided in the supply pipe
(e) A solid content adding step of adding the solid content thus captured to the culture solution in the fermentation tank
Hereinafter, each step will be explained.
2-1. production Process of chemical (a)
[ microorganisms ]
In the present embodiment, the microorganism may be a mixture of a plurality of types as long as it contains a methanogenic bacterium that produces methane. The microorganism may include an acid-producing microorganism in addition to the methanogenic microorganism. The organic substances are decomposed into methane and carbon dioxide by the respective actions of the plurality of species. When a chemical other than methane is produced, a microorganism that produces the target chemical may be used.
[ raw materials ]
A fermentation raw material (hereinafter, simply referred to as "raw material") refers to a substance that produces a target chemical by fermentation. The raw material can be changed depending on the microorganism, culture conditions, target chemical, and the like. In the case where the chemical is methane, the raw materials are: high-concentration organic wastes such as feces, livestock feces, domestic garbage, food waste, activated sludge and the like; or sludge produced by the treatment of these substances, sludge obtained by subjecting these substances to pretreatment such as pulverization, hydrolysis, and preliminary removal of solid substances, and other treatments, liquid substances and solid substances containing organic substances.
The raw material used for the culture contains components that promote the growth of the microorganism and can produce a chemical that is a target fermentation product in a satisfactory manner.
In addition, organic micronutrients such as amino acids and vitamins may be added as necessary.
[ culture solution ]
The culture solution contains a raw material for chemicals and microorganisms cultured therein, and may contain chemicals produced as a result of the culture.
[ culture ]
In the continuous fermentation apparatus 100, continuous culture is performed by introducing a raw material into the fermentation tank 1 and withdrawing a culture solution from the fermentation tank 1.
Introduction of the raw material will be described. In FIG. 1, the raw material is introduced from the raw material tank 101 into the fermentation tank 1 by operating the raw material supply pump 12 during the culture.
During the culture execution, the introduction of the raw material may be continuously performed without stopping, or the introduction and stopping of the raw material may be switched depending on the situation. For example, as described above, the start and stop of the introduction of the raw material may be performed based on the detection result of the liquid level sensor 81, or may be performed at regular intervals based on the measurement result of a timer, not shown. It should be noted that not only the mode in which the introduction of the raw material is automatically performed but also the mode in which the introduction is manually performed is included in the technical scope of the present invention.
Next, the extraction of the culture medium will be described. In order to obtain efficient productivity, it is preferable to maintain the concentration of the microorganism in the culture solution at a high level in a range where the environment of the culture solution is not unsuitable for growth of the microorganism.
The continuous fermentation apparatus 100 can recover chemicals by withdrawing a culture solution by a circulation system, and can perform continuous culture while maintaining a high concentration of microorganisms. The details of the culture solution extraction using the circulation system will be described later.
The fermentation tank 1 may be connected to a flow path for extraction through which the culture medium can be extracted, in addition to the pipe 23 connected to the membrane separation module 2. In this case, not only the liquid portion of the culture medium but also the microorganisms can be extracted.
During the culture, a new suspension containing the microorganism may be introduced into the fermentation tank 1. The introduction of the microorganism may be performed manually or automatically
In the fermentation tank, the starting timing of the supply of the raw material and the extraction of the culture solution need not be the same. The supply of the raw material and the extraction of the culture medium may be continuous or intermittent.
Continuous culture operation is generally preferably conducted in a single fermentation tank in terms of management. However, the number of fermentation tanks is not limited as long as it is a continuous fermentation culture method in which a microorganism is allowed to grow and a product is produced. A plurality of fermentation tanks may be used for the reason of, for example, a small capacity of the fermentation tank. In this case, even when a plurality of fermentation tanks are connected in parallel or in series by pipes to perform continuous culture, high productivity can be obtained.
In the continuous fermentation apparatus 100 of FIG. 1, the culture solution in the fermentation tank 1 is stirred by the stirring device 6, and the conditions suitable for fermentation are maintained by the temperature control unit 5, the pH control unit 7, the liquid level control unit 8, and the like.
The culture of the microorganism is usually carried out at a pH of 3 to 10 inclusive and at a temperature which varies depending on the type of the methanogenic bacterium to be cultured, and may be carried out at 50 to 60 ℃ inclusive in the high-temperature methane fermentation, at 30 to 40 ℃ inclusive in the medium-temperature methane fermentation, or at 10 to 20 ℃ inclusive in the low-temperature methane fermentation. The pH of the culture medium can be adjusted to a predetermined range within the above range by using an inorganic or organic acid, an alkaline substance, urea, calcium hydroxide, calcium carbonate, ammonia gas, or the like. In the continuous fermentation apparatus 100, the pH is automatically controlled by the pH controller 7 under the control of the controller 28, and the temperature is automatically controlled by the temperature controller 5.
2-2 filtration step (b) of the culture solution
By the filtration step, chemicals can be continuously recovered from the culture solution, and the culture can be continued.
In the filtration step, the culture solution is supplied to the membrane separation module. Specifically, in fig. 1, the culture solution is pumped out of the fermentation tank 1 by the circulation pump 24 and supplied to the membrane separation module 2 through the pipe 23 (supply pipe). The culture solution is separated into a concentrated solution and a filtrate by the membrane separation module 2. The pump 24 of fig. 1 corresponds to a circulation pump.
As the filtration method, any of cross-flow filtration and total volume filtration can be used. However, in the continuous fermentation operation, the amount of contaminants such as microorganisms attached to the membrane is large, and therefore, in order to effectively remove the contaminants, cross-flow filtration is preferably performed. This is due to: by the cross-flow filtration, the dirt can be removed by the shearing force of the culture solution.
In order to suppress the power cost of the circulation pump, the circulation flow rate of the culture solution in the case of crossflow filtration is preferably low. However, if the flow rate is low, the rate at which the solid components flowing into the membrane separation module are accumulated in the membrane separation module becomes dominant, and the circulation path is clogged. For this reason, it is desirable to set a circulation flow rate at which the pump power is suppressed as much as possible and the operation can be stabilized.
The inventors of the present application have made intensive studiesAs a result of the study, a method of setting a circulation flow rate capable of suppressing clogging of a circulation path and performing stable operation has been found. That is, by setting the linear velocity v [ m ] of the membrane surface parallel to the longitudinal direction of the membrane separation module3/m2/s]And the smaller one A [ m ] of the major diameters of the first opening and the second opening provided in the side surface of the container in the membrane separation module]Stable operation can be achieved by satisfying the following formula 1.
v＞0.8(2gA(S-1))0.5(formula 1)
Further, the operation can be stabilized by satisfying the following expression 2 for the linear velocity v of the film surface.
v＞0.8(2.5gA(S-1))0.5(formula 2)
The process of deriving the above is as follows. As the equation relating to the stacking speed, the Durand equation shown below is known.
vd＝Fd(2gD(S-1))0.5
Deposition rate: v. ofd[m/s]、
Acceleration of gravity: g [ m/s2]
Pipe diameter: d [ m ]
Specific gravity of solid component: s
Fd: experimentally found coefficients
The circulation flow rate at which clogging of the circulation path in the membrane separation module does not occur is experimentally found with reference to the Durand formula. Before the experiment, it is expected that the most likely deposition of solid components in the membrane separation module is between membranes, which are narrow sections in the flow path through which the liquid containing the solid components (i.e., the culture solution and the concentrated solution) passes. Therefore, it is considered that the distance between the membranes is substituted into the tube diameter D in the Durand formula. Here, the distance between the films is specifically the distance between the film bundles (the width of the gap between the film bundles).
However, the inventors of the present application found that: surprisingly, the width of the gap between the membrane bundles is not the same as the tube diameter D, but the smaller one a of the major diameters of the first opening and the second opening provided in the side surface of the container in the membrane separation module.
This is believed to be due to: in the vicinity of an opening provided in a side surface of a container of a membrane separation module, a flow of a culture solution or a concentrated solution passing through the container is bent. In order to suppress the build-up in the membrane separation module, it is effective to: the circulation flow rate is set according to the length of the opening at the bent portion where the flow of the culture solution or the concentrated solution changes, and the opening of the solid component removing means is set relative to the length of the opening at the bent portion, thereby removing a part of the solid component in advance.
In particular, in methane fermentation for the production of methane, F in the Durand formula depends on the average particle size of the culture or concentrate flowing in the membrane separation moduledThe concentration of the activated sludge-treated wastewater and other fermentation liquids was determined characteristically in a manner different from that of the activated sludge-treated wastewater and other fermentation liquids, and experimentally found to be 0.8.
In combination with the above situation, a plurality of experiments were carried out, and as a result, it was found that: the circulation flow rate capable of stable operation in methane fermentation is in a range satisfying the formula (1).
By further combining scrubbing in cross-flow, higher cleaning efficiency can be achieved. As the gas used for scrubbing, compressed gas supplied from a gas bomb (gas bomb), a blower (blower), a compressor, or a pipe can be used. Further, the gas generated by the metabolism of the microorganism in the fermentation tank may be collected and supplied.
The execution conditions of the scrubbing, that is, the timing, frequency, time per scrubbing, and the like of the scrubbing are not particularly limited. The conditions for performing the scrubbing can be changed according to various conditions such as the inter-membrane differential pressure, the change in the inter-membrane differential pressure, the pressure in the fermentation tank, the type of gas to be supplied, the type of microorganism to be cultured, the type of chemical to be produced, and the type of raw material. For example, the scrubbing may be performed continuously, or may be performed every time a predetermined time has elapsed since the end of the previous scrubbing, or may be performed every time the supply amount of the culture solution to the membrane separation module 2, that is, the filtration amount or the inter-membrane differential pressure reaches a predetermined value. In order to determine the start and end of the scrubbing, the continuous fermentation apparatus 100 may be provided with a measuring device such as a timer, not shown.
The driving force for filtration can be obtained by siphoning using a liquid level difference (water head difference) between the fermentation tank 1 and the membrane separation module 2, or by using a pressure difference between membranes generated by a circulation pump. In addition, as a driving force for filtration, a suction pump may be provided on the filtrate side of the membrane separation module 2. In the configuration of fig. 1, the filter pump 14 corresponds to a suction pump. The pressure of the suction pump can be used to control the differential pressure between the membranes. Further, the inter-membrane differential pressure may be controlled by the pressure of the gas or liquid introduced into the primary side of the membrane separation module 2. The difference between the pressure on the primary side of the membrane separation module 2 and the pressure on the filtrate side can be detected as an inter-membrane differential pressure, and the pump control and the like can be performed based on the inter-membrane differential pressure.
In the configuration of fig. 1, the culture solution is supplied from the fermentation tank 1 to the membrane separation module 2 by the circulation pump 24. Further, the amount of culture solution supplied to the membrane separation module 2 can be appropriately adjusted by controlling the operation of the circulation pump 24 and the filtration pump 14 based on the inter-membrane differential pressure detected by the differential pressure control unit 9.
The filtration may be carried out continuously or intermittently. In the case of intermittently performing filtration, for example, filtration may be stopped for a predetermined time (for example, 0.1 to 10 minutes) every time filtration is continuously performed for 5 to 120 minutes. More preferably, the filtration is stopped for 0.25 to 3 minutes each time the filtration is continued for 5 to 60 minutes. The scrubbing can be carried out either during the stoppage of the filtration or during the filtration.
2-3 reflux step (c)
The microorganisms in the culture solution do not permeate the separation membrane, and therefore the concentration of the microorganisms can be increased in the concentrated solution (the solution that does not permeate the membrane) after passing through the membrane separation module 2. The concentrated solution is returned to the fermentation tank 1 through the return pipe 25, whereby the microorganisms are returned to the fermentation tank 1. On the other hand, the filtrate having passed through the separation membranes of the membrane separation module 2 is discharged to the outside of the apparatus through the pipe 26.
Thus, the microorganism concentration in the fermentation tank 1 is kept high, and the components including the metabolites and the removed moisture and new raw materials are supplied, so that the fermentation production is continued.
2-4 solid content capturing step (solid content removing step) (d)
The culture solution circulating from the fermentation tank 1 to the membrane separation module 2 passes through the solid component removal means, whereby the solid components larger than the opening thereof are captured by the solid component removal means, and deposits accumulated in the membrane separation module are reduced in the culture solution supplied to the membrane separation module. The solid removal means may be provided between the pipes communicating the fermentation tank 1 and the membrane separation module 2, and may be located upstream or downstream of the circulation pump.
2-5 step (e) of adding the discharged solid matter to the culture solution
The solid matter trapped by the solid matter removing means in the above 2-4 may be directly added to the fermentation tank as it is or in the form of a suspension, or may be added to the culture solution in the fermentation tank through at least one of a pipe for returning the concentrated solution from the membrane separation module to the fermentation tank and a pipe for connecting the raw material tank and the fermentation tank. Even if the solid component is added by any of these methods, the solid component is consequently added to the culture solution in the fermentation tank, and therefore "adding to the culture solution in the fermentation tank" also includes any of these methods. The addition may be performed automatically by the operation of the apparatus or manually.
Thus, the solid component is added to the culture solution without entering the membrane separation module 2, and is metabolized by the microorganisms and effectively utilized as a fermentation raw material.
The term "directly added to the fermentation tank" means that the raw material is added to the fermentation tank without passing through a piping, a raw material tank, or the like.
The solid component is discharged from the solid component removing means before being added to the culture solution. The solid component may be discharged together with the cleaning liquid by cleaning the solid component removing means with the cleaning liquid, or may be discharged by scraping the solid component from the solid component removing means. The solid component removing means may be provided with a cleaning means or a scraping means for discharging the solid component. When the opening is subjected to back pressure cleaning in the direction opposite to the direction in which the culture medium permeates, clogging of the removing means can be eliminated, and the cleaning liquid used in the back pressure cleaning becomes a suspension of solid components, so that addition to the culture medium is facilitated. In addition, these discharging operations may be performed manually, but are preferably performed automatically.
The timing of the discharge may be controlled by detecting a pressure difference between before and after the removal mechanism and discharging when the pressure difference reaches a predetermined pressure difference, or by a timer at predetermined time intervals.
2-6. others
The method for producing a chemical may further include a step of back pressure cleaning the separation membrane of the membrane separation module. In the configuration of fig. 1, the cleaning pipe 27 is connected to the secondary side of the membrane separation module 2, and therefore the cleaning liquid can be fed into the membrane separation module 2 by using the cleaning pump 16.
When the back pressure cleaning is performed, the filtration is stopped so that the cleaning liquid does not flow into the filtrate tank in which the filtrate is stored. That is, the filter valve 15 is closed, and the filter pump 14 is stopped. In this state, the back pressure cleaning is performed by opening the cleaning valve 17 and operating the cleaning pump 16.
When the back pressure cleaning is stopped, the cleaning valve 17 is closed and the cleaning pump 16 is stopped. In this state, the filtration is performed by opening the filter valve 15 and operating the filter pump 14.
These controls may be performed by the control device 28. The continuous fermentation apparatus 100 may be provided with a measuring device such as a timer, not shown, for determining the start time and the end time of the back pressure cleaning.
Examples of the cleaning liquid used for back pressure cleaning include liquids that do not adversely affect fermentation and can clean separation membranes, and examples thereof include: water, filtrate, fermentation medium, or a portion of a component added to the fermentation medium; or an aqueous solution of hydrochloric acid, sulfuric acid, nitric acid, sodium hydroxide, calcium hydroxide, sodium hypochlorite, or a mixed solution thereof.
3. Chemical product
The chemical obtained by the production method described in the present specification is a substance produced by a microorganism in a culture solution. Examples of the chemical include substances produced by metabolic reactions of microorganisms, such as alcohols, organic acids, diamines, amino acids, methane, hydrogen, and nucleic acids. The above-described production method can also be applied to the production of substances such as enzymes, antibiotics, and recombinant proteins.