JP2008199948A - Method for producing continuously fermented product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for eliminating the cleaning of fouling or biofilm which becomes a cause for clogging of a separation membrane in the continuous fermentation of microorganisms to use a membrane for separating the product. <P>SOLUTION: The method for producing a continuously fermented product comprises the supply of a solution containing 0.1-50 wt.% 4C polyol, especially erythritol to a separation membrane. The polyol-containing solution may be supplied to the primary side or to the secondary side of the separation membrane, or may be introduced by mixing it in a medium. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention improves the concentration of microorganisms or cultured cells involved in fermentation by recovering the product from the fermenter with a separation membrane while performing fermentation with microorganisms or cultured cells, and returning the unfiltered product to the fermentor. The present invention relates to a method for producing a continuous fermentation product characterized in that, in continuous fermentation for obtaining productivity, a solution containing a polyol having 4 carbon atoms is supplied to a separation membrane to wash or suppress fouling of the separation membrane.

  The end of the 20th century, when mass consumption and mass disposal are over, and in the 21st century, where the creation of an environmentally harmonious society is required, it is expected to promote the utilization of biomass resources, which are recyclable resources.

  Therefore, attention has been focused on the fermentation method, which is a material production method involving cultivation of microorganisms and cultured cells. Fermentation methods can be broadly classified into (1) batch fermentation methods (Batch fermentation methods) and fed-batch fermentation methods (Fed-Batch fermentation methods) and (2) continuous fermentation methods. The batch and fed-batch fermentation method of (1) is simple in terms of equipment, and has an advantage that culture is completed in a short time and there is little damage due to contamination with various bacteria. However, the product concentration in the culture solution increases with the passage of time, and the productivity and yield are reduced due to the influence of osmotic pressure or product inhibition. For this reason, it is difficult to stably maintain a high yield and high productivity over a long period of time. On the other hand, the continuous fermentation method (2) is characterized in that a high yield and high productivity can be maintained over a long period of time by avoiding accumulation of the target substance at a high concentration in the fermenter. Also in amino acid fermentation, the continuous culture method is disclosed about fermentation of L-glutamic acid (patent document 1) and L-lysine (non-patent document 1). However, in these examples, since the raw material is continuously supplied to the culture solution and the culture solution containing microorganisms and cells is extracted, the microorganisms and cells in the culture solution are diluted. The improvement was limited.

  Therefore, in the continuous fermentation method, microorganisms and cultured cells are filtered through a separation membrane, and the product is recovered from the filtrate, and at the same time, the filtered microorganisms and cultured cells are retained or refluxed in the culture solution. A method for maintaining high microorganism and cell concentrations has been proposed. For example, when culturing lactic acid bacteria (Bifidobacteria), the sugar concentration of the medium is adjusted to 1 to 1.5% by weight, and the bacterial inhibitor produced in the medium by culture is placed in communication with the culture tank. A method of circulating a culture solution that has been removed through a membrane and removing the inhibitor to a culture tank, and replenishing the culture tank with a fresh amount of liquid corresponding to the portion removed through the filtration membrane. It has been proposed that it is necessary to increase the medium supply rate according to the growth of bacterial cells (Patent Document 2).

  However, the more the cells grow, the more easily the filter membrane is clogged. As a result, the amount of filtration is reduced and the supply of the medium is delayed. That is, as in this method, in order to realize a method of increasing the medium supply rate according to the growth of bacterial cells, the membrane area needs to be extremely wide. It is not a practical method. In Patent Document 3, as a method for avoiding clogging of the filtration membrane, in a method of continuously culturing yoghurt starter lactic acid bacteria, the yeast extract concentration in the medium is 0.5 to 2.0%, and the amount of the culture solution A method for culturing lactic acid bacteria at a high concentration characterized by maintaining the ratio of the amount of filtrate per hour (dilution ratio) to a constant value of 1.0 or more is disclosed. Therefore, it is not a technique that can essentially solve clogging of the filtration membrane because the applicable microorganisms are limited.

  In these methods, a porous separation membrane is generally used as the separation membrane. However, a decrease in filtration flow rate and filtration efficiency due to clogging of the membrane is a big problem, and this is a big spread of this method. It is an obstacle. As a method for suppressing clogging of microorganisms and cultured cells, several techniques relating to separation membrane cleaning and setting of filtration conditions have been proposed, but none of them is sufficient. For example, an incubator or a bioreactor in which a porous membrane tubule having a clogging prevention function, that is, a porous membrane tubule in which a filtrate extraction tube and an air supply tube that are switched with each other by a switching valve are connected is disposed Using a reactor, intermittently ventilate from the side of the porous separation membrane that is in contact with the culture solution (inside the porous membrane tubule) to remove clogging substances that deposit in the pores. Thus, while culturing, a method for efficiently recovering a liquid containing a product through the membrane without causing clogging of the porous separation membrane from the microorganism or cell culture solution (Patent Document 4) or culturing the microorganism A method of reducing the concentration of metabolites produced by culturing by changing the substrate with a back-washable filter built in the culture tank (Patent Document 5), passing the culture solution through a cylindrical filter Separating metabolites and bacteria Apparatus for carrying out the cultivation solution is allowed continuously cultured circulated to the culture tank containing bacteria (Patent Document 6) are known. However, even when the separation membrane is washed by these methods, fouling due to clogging gradually proceeds as the filtration time becomes longer, and finally an insoluble film called a biofilm that cannot be peeled off by ordinary washing is formed.

The formation process of this biofilm consists of the formation of a condition film, the attachment of bacterial cells to the condition film, the proliferation of the attached cells and the production of the associated extracellular polymer, and the growth of the biofilm as a community including other bacteria and microorganisms. (Non-patent Document 3). The biofilm formed in this way is “filled with a low density polymer matrix containing water channels that are interspersed with bacterial microcolonies confined within the extracellular polysaccharide matrix and water is relatively free to move. It has a non-uniform structure. However, no method for cleaning or suppressing fouling based on the biofilm formation process or the structure of the formed biofilm has been developed, and there are still technological innovations to solve the fouling problem of the separation membrane. It was desired.
JP-A-10-150996 Japanese Patent Publication No. 6-69367 JP 2001-21118A JP-A-6-98758 JP 58-47485 A Japanese Patent Laid-Open No. 62-138184 Toshihiko Hirao et. Al., Appl. Microbiol. Biotechnol., Applied Microvials and Microbiology, 32, 269-273 (1989) Takeshi Kobayashi, Chemical Engineer, 12, 49 (1988) Hisao Morisaki, Hiroyuki Oshima, Kenji Isobe, Biofilms-Its Generation Mechanism and Prevention Science-Science Forum (1998)

  An object of the present invention is to provide a method for washing or suppressing fouling of a separation membrane in continuous fermentation using the separation membrane in view of the above-described problems of the conventional technology.

The present invention for solving the above problems is achieved by the following configurations (1) to (5).
(1) In a method for producing a continuous fermentation product in which a product obtained by continuous fermentation is filtered through a separation membrane, a solution containing 0.1 to 50% by weight of a C4 polyol is supplied to the separation membrane. The manufacturing method of the continuous fermentation product characterized by having the process to do.
(2) The method for producing a continuous fermentation product according to (1), wherein a solution containing 0.1 to 10% by weight of a polyol having 4 carbon atoms is supplied from the primary side of the separation membrane.
(3) The method for producing a continuous fermentation product according to (2), wherein a polyol having 4 carbon atoms is introduced in a medium.
(4) The method for producing a continuous fermentation product according to (1), wherein a solution containing a polyol having a carbon number of 1 to 50% by weight is supplied from the secondary side of the separation membrane.
(5) The method for producing a continuous fermentation product according to any one of (1) to (4), wherein the polyol having 4 carbon atoms is erythritol.

  According to the present invention, in continuous fermentation using a separation membrane, fouling of the separation membrane is washed or suppressed by supplying a solution containing a polyol having 4 carbon atoms to the separation membrane, and continuous fermentation showing high productivity. A method of manufacturing a product is provided. The polyol having 4 carbon atoms is adsorbed on the surface of the separation membrane and the fouling substance to suppress the interaction between the fouling substance and the separation membrane, in particular, aggregation, thereby suppressing the progress of fouling, and is further adsorbed on the separation membrane. / And penetrates into the inside of the agglomerated fouling material to facilitate separation of the fouling material.

  In addition, the polyol having 4 carbon atoms increases the osmotic pressure outside the biofilm, thereby blocking the water channel in the biofilm, causing the internal structure to collapse and facilitating removal of the biofilm. Furthermore, since the polyol having 4 carbon atoms is not easily metabolized by microorganisms or cultured cells, fouling can be washed or suppressed without greatly changing the environment of the culture tank. Therefore, by supplying a solution containing a polyol having 4 carbon atoms to the separation membrane, it is possible to stably produce a continuous fermentation product for a long period of time.

  In the present invention, a solution containing a polyol having 4 carbon atoms is used for cleaning and suppressing fouling of a separation membrane that occurs when a product is produced by long-term continuous fermentation.

  In the present invention, continuous fermentation is performed in parallel with a series of operations for performing fermentation with microorganisms or cultured cells in the fermenter while collecting the fermentation raw material in the fermenter, and collecting the resulting fermentation product with a separation membrane. It is a method to do. Each operation condition is set to an optimum value in advance so that the production efficiency is maximized, but may be changed during operation for the purpose of maintenance of equipment and facilities, improvement of production efficiency, and the like. Each operation can be controlled independently. For example, while only the filtration operation is stopped for a certain period, the fermentation raw material can be added or fermented. Moreover, you may implement the addition of a fermentation raw material, and filtration with a separation membrane continuously or intermittently. In the continuous fermentation of the present invention, nutrients necessary for cell growth described later may be added to the raw material culture solution so that the cell growth is continuously performed. Therefore, the change of each operation condition and discontinuity are freely selected according to the fermentation raw material, microorganisms and cultured cells, fermentation apparatus, equipment, fermentation product, etc., and do not impair the mode of continuous fermentation. Absent.

  The polyol having 4 carbon atoms in the present invention is not particularly limited as long as it has 4 carbon atoms constituting the molecule and has a plurality of hydroxyl groups in the molecule. However, it is inconvenient if it interacts strongly with the microorganisms and culture cells that control fermentation, the fermentation products obtained, etc., and the continuous fermentation cannot be continued. It is good to decide.

  Among the polyols having 4 carbon atoms, erythritol is particularly preferably used because it is stable in a wide range of pH, has high solubility in water, and has a low viscosity after being dissolved. Here, when the solubility in water is high, the osmotic pressure outside the biofilm is easily increased, and the water channel blocking effect in the biofilm is high. And when the viscosity of a solution is low, since the filtration resistance in a separation membrane can be restrained low, filtration efficiency becomes high. Erythritol has three types of isomers, L-form, D-form and meso-form, and any of them is preferably used in the present invention, and these may be used alone or in a mixture.

  The polyol having 4 carbon atoms is preferably dissolved in a medium such as water to form a solution from the viewpoint of easy handling. By supplying such a solution containing a polyol having 4 carbon atoms to the separation membrane, fouling can be easily washed and suppressed.

  The solution containing a polyol having 4 carbon atoms exhibits a fouling cleaning or suppressing effect whether supplied from the primary side (raw water side) or the secondary side (permeation side) of the separation membrane. The higher the C4 polyol concentration in the solution, the higher the fouling washing or suppression effect, but the concentration decreases as the fermentation raw material in the fermenter aggregates and precipitates, and the fermentation rate tends to decrease. is there. For this reason, in order to express the effect of washing or suppressing fouling without reducing the fermentation rate, a solution containing 0.1 to 50% by weight of a C4 polyol is used.

  Here, when the solution containing the polyol having 4 carbon atoms is supplied from the primary side of the separation membrane, it can be carried out continuously, intermittently or at regular intervals. When supplying continuously over a long period of time, such as continuously supplying, the polyol having 4 carbon atoms stays in the vicinity of the separation membrane, and repeats adsorption / desorption with the separation membrane and the fouling material, so that the fouling material and the separation membrane interact with each other. In order to reduce the action, the progress of fouling of the separation membrane can be suppressed. In this case, since there is an effect of preventing the biofilm generated by the progress of fouling, the concentration of the polyol having 4 carbon atoms can be lowered as compared with the case of cleaning the biofilm. Moreover, since it mixes with the fermented liquor in a fermenter when supplying from a primary side, the density | concentration of the C4 polyol in the solution which reaches | attains a separation membrane falls compared with the time of system | strain introduction. When a solution containing a high-concentration C4 polyol is used at the time of charging the system, there is a concern that precipitation occurs in the fermentor, adsorbing with the fermentation raw material and inhibiting fermentation, etc. It is preferable to make the polyol having a carbon number as low as possible within the range where it appears. From this viewpoint, when a solution containing a polyol having 4 carbon atoms is supplied from the primary side of the separation membrane, the polyol having 4 carbon atoms is preferably 0.1% by weight or more and 10% by weight or less. Is preferably 0.1 wt% or more and 5 wt% or less. In order to enhance the fouling suppressing effect, the content is preferably 1% by weight or more and 5% by weight or less.

  As a method for supplying a solution containing a polyol having 4 carbon atoms to the primary side of the separation membrane, a method in which a polyol having 4 carbon atoms is mixed into a culture medium and introduced into a fermenter is preferable. The concentration of the polyol having 4 carbon atoms mixed in the medium may be adjusted in advance considering that it is diluted with another fermentation broth in the fermenter. In consideration of the above-mentioned concerns, it is preferable to prepare the medium so that the concentration of the polyol having 4 carbon atoms when finally supplied to the separation membrane is 0.1 wt% or more and 10 wt% or less.

  Further, when a solution containing a polyol having 4 carbon atoms is supplied from the secondary side of the separation membrane, it is difficult to carry out continuously, but it can be carried out intermittently or at regular intervals. In the case of supplying from the secondary side, removal or promotion of removal of the biofilm can be expected even by physical force by feeding and supplying a solution containing a polyol having 4 carbon atoms. Here, if the concentration of the polyol having 4 carbon atoms is increased, the supply time and frequency of the solution can be reduced, so that the load on the filtration step is small and the recovery rate can be increased. For this reason, when a solution containing a polyol having 4 carbon atoms is supplied from the secondary side of the separation membrane, the polyol having 4 carbon atoms is preferably 1% by weight or more and 50% by weight or less, preferably 5% by weight or more. More preferably, it is 50% by weight or less. In order to reduce the load on the filtration step, the content is more preferably 40% by weight or less, and further preferably 30% by weight or less.

  The fermentation raw material used in the present invention may be any material that promotes the growth of microorganisms and cultured cells and produces the desired continuous fermentation product, but includes a carbon source, a nitrogen source, inorganic salts, and, if necessary, an amino acid. Ordinary liquid medium containing organic micronutrients such as vitamins as appropriate is preferable. Examples of the carbon source include saccharides having 6 or 12 carbon atoms such as glucose, sucrose, fructose, galactose, and lactose, starch saccharified solution containing these saccharides as a main component, sweet potato molasses, sugar beet molasses, and organic acids such as acetic acid, ethanol Alcohols such as glycerin are also used. Nitrogen sources include ammonia gas, aqueous ammonia, ammonium salts, urea, nitrates, and other supplementary organic nitrogen sources such as oil cakes, soybean hydrolysates, casein degradation products, other amino acids, vitamins, Corn steep liquor, yeast or yeast extract, meat extract, peptides such as hepton, various fermented cells and hydrolysates thereof are used. As inorganic salts, phosphates, magnesium salts, calcium salts, iron salts, manganese salts, and the like can be appropriately added. In addition, when the microorganisms or fermented cells used in the present invention require specific nutrients for growth, the nutrients are added as preparations or natural products containing them. An antifoaming agent is also used as necessary. In the present invention, the culture liquid refers to a liquid obtained as a result of growth of microorganisms or cultured cells on the fermentation raw material, and the composition of the added fermentation raw material increases the productivity of the intended continuous fermentation product. Moreover, you may change suitably from the fermentation raw material composition at the time of a culture | cultivation start.

  In the present invention, the saccharide concentration in the culture solution is preferably maintained at 5 g / L or less. The reason is to minimize the loss of saccharide due to withdrawal of the culture solution. Microorganisms are usually cultured in the range of pH 4-8 and temperature 20-40 ° C. The pH of the culture solution is adjusted to a predetermined value within the above range with an inorganic or organic acid, an alkaline substance, urea, calcium carbonate, ammonia gas, or the like. If it is necessary to increase the oxygen supply rate, means such as adding oxygen to the air to keep the oxygen concentration at 21% or higher, pressurizing the culture, increasing the stirring rate, or increasing the aeration rate can be used.

  Continuous fermentation may be started after microbial concentration is increased by performing Batch culture or Fed-Batch culture in the early stage of fermentation of the present invention, or high concentration bacterial cells may be seeded and continuous fermentation may be performed at the start of culture. good. It is possible to supply the raw material culture solution and extract the fermentation product from an appropriate time. The concentration of microorganisms or cultured cells in the culture solution should be maintained at a high level so that the environment of the culture solution is not suitable for the growth of microorganisms or cultured cells and the rate of death does not increase. As an example, good production efficiency can be obtained by maintaining the dry weight at 5 g / L or more.

  The microorganisms and cultured cells used in the present invention are not particularly limited. For example, yeasts such as baker's yeast often used in the fermentation industry, bacteria such as Escherichia coli and coryneform bacteria, filamentous fungi, actinomycetes, animal cells, Examples include insect cells. The microorganisms and cells used may be those isolated from the natural environment, or may be those whose properties have been partially modified by mutation or genetic recombination.

  In the present invention, a polyol having 4 carbon atoms is used for cleaning or suppressing fouling of the separation membrane. For this reason, it is desirable that microorganisms and cultured cells are difficult to use polyols having 4 carbon atoms as a carbon source, and it is best not to use them at all. Furthermore, since it is inconvenient if microorganisms and cultured cells interact with a polyol having 4 carbon atoms to inhibit continuous fermentation, it is preferable to experimentally determine microorganisms and cultured cells to be used in advance.

  The continuous fermentation product in the present invention is not particularly limited as long as it is a substance produced by the microorganism or cell in the culture solution, but examples include substances that are mass-produced in the fermentation industry, such as alcohols, organic acids, amino acids, and nucleic acids. be able to. The present invention can also be applied to the production of substances such as enzymes, antibiotics, and recombinant proteins. For example, examples of the alcohol include ethanol and 1,4-butanediol, and examples of the organic acid include acetic acid, lactic acid, succinic acid, and malic acid.

  It is desirable that the separation membrane used in the present invention is less likely to be clogged by microorganisms and cultured cells used for fermentation, and that the filtration performance continues stably for a long period of time. For this reason, the separation membrane used in the present invention may be selected in consideration of the properties of the culture solution and the fermentation product, but those having a surface pore diameter of 0.01 μm or more and 1 μm or less are preferably used. When the porous resin layer is present on both surfaces of the porous membrane, it is sufficient that at least one of the porous resin layers satisfies this condition. When the surface pore diameter is within this range, it is possible to achieve both a high exclusion rate at which bacterial cells do not leak and a high water permeability, and it is difficult to clog, and the water permeability can be maintained for a long time. Also, if the average pore diameter is within this range, when animal cells, yeast, filamentous fungi, etc. are used, there is little clogging and stable continuous fermentation can be performed without leakage of the cells into the filtrate. is there.

  Here, when bacteria smaller than animal cells, yeast and filamentous fungi are used, the surface pore diameter is preferably 0.4 μm or less, and more preferably 0.2 μm or less. If the surface pore diameter is too small, the water permeability tends to decrease. Therefore, it is usually preferably 0.02 μm or more, and more preferably 0.04 μm or more. Here, the surface pore diameter is obtained by taking a photograph with a scanning electron microscope at a magnification of 30,000, measuring the diameters of arbitrary pores of 10 or more, preferably 20 or more, and averaging the numbers. . When the pores are not circular, a circle having an area equal to the area of the pores (equivalent circle) is obtained by an image processing device or the like, and the equivalent circle diameter is obtained by the method of setting the diameter of the pores.

  The material of the separation membrane used in the present invention is not particularly limited as long as separability and water permeability according to the quality of water to be treated and the use can be obtained, but from the viewpoint of separation performance such as blocking performance, water permeability and dirt resistance. Is preferably a porous film including a porous resin layer. In addition, woven fabrics and non-woven fabrics made of organic fibers such as cellulose fibers, cellulose triacetate fibers, polyester fibers, polypropylene fibers, and polyethylene fibers, and porous substrates and inorganic resin layers made of inorganic materials But it ’s okay. An organic polymer membrane can also be used, but the organic polymer membrane is a separation membrane basically composed of an organic polymer material, such as a nonwoven fabric of organic fibers or a porous organic group having a macropore structure. In many cases, a material and a porous resin layer having a pore diameter smaller than that of the porous organic base material are combined. However, the present invention is not limited to this film structure.

  Here, the material of the porous resin layer includes polyethylene resin, polypropylene resin, polyvinyl chloride resin, polyvinylidene fluoride resin, polysulfone resin, polyethersulfone resin, polyacrylonitrile resin, and cellulose resin. Cellulose triacetate resins can be exemplified, but a mixture of resins mainly composed of these resins may be used. Among these, polyvinyl chloride resin, polyvinylidene fluoride resin, polysulfone resin, polyethersulfone resin, and polyacrylonitrile resin, which are easy to form in solution and have excellent physical durability and chemical resistance, are available. preferable. In particular, a polyvinylidene fluoride resin or a resin containing the same as a main component is most preferable. Here, as the polyvinylidene fluoride-based resin, a homopolymer of vinylidene fluoride is preferably used. In addition to a homopolymer of vinylidene fluoride, a copolymer of a vinyl monomer copolymerizable with vinylidene fluoride is used. A polymer is also preferably used. Examples of such vinyl monomers include tetrafluoroethylene, hexafluoropropylene, and trichlorofluoroethylene.

  The separation membrane of the present invention may be a flat membrane or a hollow fiber membrane. In the case of a flat membrane, the thickness is appropriately selected depending on the application, but for example, it is selected in the range of 20 μm to 5000 μm, preferably 50 μm to 2000 μm. As described above, it may be formed of a porous substrate and a porous resin layer. At that time, either the porous resin layer permeates the porous base material or the porous resin layer does not permeate the porous base material, and it is selected according to the application. The thickness of the porous substrate is selected in the range of 50 μm to 3000 μm. In the case of a hollow fiber membrane, the inner diameter is selected in the range of 200 μm to 5000 μm, and the film thickness is selected in the range of 20 μm to 2000 μm. Moreover, the woven fabric and knitting which made the organic fiber or the inorganic fiber the cylinder shape may be included.

  Hereinafter, in order to describe the present invention in more detail, an example in which the present invention is applied to a continuous production process of pyruvic acid will be described. The apparatus shown in FIG. 1 was used, and among the yeast Torulopsis glabrata, Torulopsis glabrata strain P120-5a (FERM P-16745) was used as a microorganism for producing pyruvic acid.

  First, the above P120-5a strain was added mainly to 5 ml of pyruvic acid fermentation medium (glucose 100 g / L, ammonium sulfate 5 g / L, potassium dihydrogen phosphate 1 g / L, magnesium sulfate heptahydrate 0.5 g / L in a test tube. Ingredients) and cultured overnight with shaking. The obtained culture solution was inoculated into 100 ml of a fresh pyruvate fermentation medium, and cultured with shaking in a 500 ml Sakaguchi flask at 30 ° C. for 24 hours.

The obtained culture solution is inoculated into a 1.5 L pyruvic acid fermentation medium, added to the fermentation reaction tank 2, stirred at 800 rpm by the attached stirring means 6, adjustment of the aeration amount of the fermentation reaction tank 2, temperature adjustment And 48 hours of batch culture. As for the sterilization of the medium, the fermentation reaction tank 2 was sterilized by high-pressure steam sterilization (121 ° C., 15 minutes) only when the culture was started up. As the separation membrane of the membrane separation apparatus 10, a porous flat membrane mainly composed of polyvinylidene fluoride (PVDF) was used. The pH of the culture solution was adjusted to pH 5.5 by using pH sensor 3 and directly adding 4N NaOH aqueous solution to fermentation reaction tank 2. Thereafter, a pyruvic acid fermentation medium in which trace components such as vitamins and ammonium sulfate were removed was prepared in the medium storage tank 1. Sodium hydroxide was added thereto, and a pyruvic acid fermentation medium with a sodium hydroxide concentration of 5 g / L was prepared. This was continuously supplied to the fermentation reaction tank 2 at a flow rate of 4.5 L / day using the medium supply pump 7, and a trace amount component such as vitamin and ammonium sulfate sterilized separately were also supplied continuously. Continuous culture was performed while controlling the amount of the membrane permeate in the membrane separator 10 so that the amount of the fermentation solution in the fermentation reaction tank 2 was 1.5 L, and pyruvic acid was produced by continuous fermentation. The membrane area of the membrane separator 10 was 120 cm ² , and the membrane filtration flux was 0.375 m ³ / m ² · day. The transmembrane pressure difference gradually increased from the start of fermentation, and the membrane filtration operation could not be continued because the transmembrane pressure difference exceeded 5 kPa two days after the start of fermentation.

  Therefore, backwashing was performed by feeding 10 L of 30 wt% erythritol aqueous solution as a polyol 12 having 4 carbon atoms from the secondary side of the membrane separation apparatus 10 at 5 kPa using the adding means 4. Thereafter, as a result of restarting the membrane filtration operation, filtration could be started at a transmembrane pressure difference of 0.3 kPa. That is, it was found that fouling of the separation membrane can be washed and removed by backwashing with a solution containing erythritol.

Next, erythritol was added as a polyol 4 having 4 carbon atoms to the above-described medium using the second addition means 5, and the erythritol in the fermenter during the continuous fermentation was adjusted to 5% by weight. . Continuous fermentation was carried out in the same manner as described above except that this medium containing erythritol was used. The continuous fermentation for 5 days was carried out under the condition of a membrane filtration flux of 0.375 m ³ / m ² · day, but the transmembrane pressure difference remained stable at 0.3 to 0.5 kPa. That is, it has been found that fouling of the separation membrane can be suppressed by supplying a medium containing erythritol to the fermenter and thus the separation membrane.

  Finally, the same continuous fermentation was tried again using a medium to which erythritol was not added. However, after 2 days from the start of fermentation, the transmembrane pressure difference exceeded 5 kPa, and the membrane filtration operation could not be continued.

It is the apparatus schematic which shows one embodiment of the continuous culture apparatus by this invention.

Explanation of symbols

1: Medium storage tank 2: Fermentation reaction tank 3: pH sensor 4: Addition means 5: Second addition means 6: Stirring means 7: Medium supply pump 8: Medium supply pipe 9: Filtrate discharge pump 10: Membrane separator 11: Circulation pump 12: C4 polyol

Claims (5)

In the method for producing a continuous fermentation product in which a product obtained by continuous fermentation is filtered through a separation membrane, a step of supplying a solution containing 0.1 to 50% by weight of a C4 polyol to the separation membrane The manufacturing method of the continuous fermentation product characterized by having. The method for producing a continuous fermentation product according to claim 1, wherein a solution containing 0.1 to 10% by weight of a polyol having 4 carbon atoms is supplied from the primary side of the separation membrane. The method for producing a continuous fermentation product according to claim 2, wherein the polyol having 4 carbon atoms is introduced in a medium. The method for producing a continuous fermentation product according to claim 1, wherein a solution containing a polyol having a carbon number of 1 to 50% by weight is supplied from the secondary side of the separation membrane. The method for producing a continuous fermentation product according to any one of claims 1 to 4, wherein the polyol having 4 carbon atoms is erythritol.

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