Method for removing thalli in biomacromolecule fermentation liquor through dead end filtration

Abstract

The invention discloses a method for removing thalli in biomacromolecule fermentation liquor through dead-end filtration. The method comprises the four steps of fermentation liquor pretreatment, filter aid adding, dead-end filtration and filter washing. The method disclosed by the invention has the advantages of simplicity in operation, large treatment capacity of fermentation liquor, low loss rate of target product biomacromolecules and relatively low energy consumption.

Description

Technical Field

[0001] The invention relates to a method for removing bacteria in biological macromolecular fermentation liquid by dead-end filtration, belonging to the technical field of biochemical separation. Background Art

[0002] Biomacromolecules are polymers formed by connecting basic units in a certain order and manner through biological cells, and their molecular weight ranges from thousands to tens of millions. Biomacromolecules have a high degree of polymerization and many active sites that can react on the molecules, so they usually have special biological activities and excellent physical and chemical properties. For this reason, biomacromolecules have broad application prospects in various fields such as agriculture, food, chemical industry, pharmaceuticals, and clinical medicine.

[0003] For biomacromolecules, chemical synthesis usually means low molecular weight, complex reaction process, expensive synthesis cost and environmental pollution caused by the synthesis process. At present, people still choose microbial fermentation to prepare biomacromolecule products on a large scale.

[0004] The advantage of producing biomacromolecules by microbial fermentation is that the product polymerization degree and molecular weight are relatively high, and the biological activity is fully guaranteed. However, after the fermentation process is completed, in addition to the target product, there are also byproducts such as bacterial cells, pigment molecules, miscellaneous proteins and polysaccharides, and impurities such as residual small molecular organic matter and inorganic salts in the culture medium that need to be removed. Only after the fermentation broth is separated and purified can a product without impurities be obtained. The extraction process needs to pay attention to the purity and yield of the product.

[0005] The first step of product impurity removal is to remove the bacterial cells in the fermentation liquid. The essence of this process is solid-liquid separation. The methods commonly used in the sterilization of fermentation liquid at present mainly include centrifugation and filtration. Centrifugation is easy to operate. For example, CN113698503A uses centrifugation to remove the bacterial cells of plant lactobacillus. However, the centrifugal sterilization fermentation liquid has a small processing capacity and high energy consumption, so it is costly, which restricts its further application in the industrial production of biomacromolecules.

[0006] Filtration sterilization is a method of separation that utilizes the interception effect of the filter medium to retain substances with larger particle sizes in the fermentation broth on the surface of the medium, and substances with smaller particles pass through the medium to form a filtrate. Depending on the flow direction of the slurry, filtration can be divided into two categories: cross-flow filtration and dead-end filtration. At present, research on the use of cross-flow filtration to remove bacterial cells in fermentation broth has been reported in many literatures. The biggest drawback of cross-flow filtration sterilization is that the operation is complicated and the separation process is accompanied by product loss. In addition, the spiral membrane is expensive and not conducive to production.

[0007] Dead-end filtration is different from cross-flow filtration. When the filtration process occurs, the filter pulp flows vertically to the surface of the filter medium under pressure. As the filtration continues, more and more particles accumulate on the surface of the medium, causing the filtration flux to decrease. Therefore, dead-end filtration adopts intermittent operation and requires regular cleaning or replacement of the filter membrane.

[0008] Since the insoluble solids contained in the fermentation broth are mostly bacterial cells, which are larger in particles (relative to the target product biomacromolecules), have a certain viscosity, and are easy to settle after inactivation, the bacterial cells can easily gather on the surface of the filter membrane during filtration to form an additional layer of smooth and dense bacterial film, which blocks the membrane pores and causes a decrease in the filtrate flux. Therefore, it is necessary to add a certain amount of filter aid to the diluted fermentation broth before filtration to form a new filtration medium, namely filter cake, to prevent the bacterial cells from adhering to the surface of the filter membrane to block the membrane pores and reduce the flux.

[0009] Dead-end filtration is simple to operate and has low equipment cost. However, there are few studies on using dead-end filtration to remove bacterial cells in fermentation broth. Summary of the invention

[0010] In view of the shortcomings of the prior art, the problem solved by the present invention is to provide a method for removing microbial cells in biomacromolecule fermentation broth by dead-end filtration, while the yield is not lost during the extraction process. The method has the characteristics of simple operation, large fermentation broth processing capacity, high bacterial removal rate, small product loss, low energy consumption, and low cost; it overcomes the defects of the prior art of complex operation, small processing capacity, high product loss, high energy consumption, and high cost. In order to achieve the above purpose, the present invention provides a method for removing bacterial cells in fermentation broth by dead-end filtration, which is composed of the following steps: (1) After the fermentation is completed, the fermentation liquid is heated and then cooled to room temperature. Preferably, the heating process is carried out at 121°C for 20 minutes and then cooled to room temperature. The pH value of the fermentation liquid is adjusted to 3-10, preferably 6.0 to 7.2, using reagents such as HCl and NaOH. Centrifuge to determine the amount of bacteria in the fermentation liquid at this time (the amount of bacteria is calculated by measuring the dry weight of the precipitate obtained after centrifugation of the fermentation liquid). Add water to the fermentation liquid stock solution according to the amount of bacteria; until the dilution ratio (fermentation liquid stock solution: total volume) reaches a preset value of 1:2 to 1:2.5. This step is intended to reduce the viscosity of the fermentation liquid, which is more conducive to filtration.

[0011] (2) Adding filter aids: According to the bacterial volume data obtained in step (1), filter aids are added to the diluted fermentation broth. The purpose is to form an excellent filter cake layer, that is, a filter medium, by controlling the type and amount of filter aids, so as to increase the permeation flux of the filtrate and reduce the product loss. The added filter aids include organic filter aids and inorganic filter aids. The organic filter aids include activated carbon, cellulose, and polyacrylamide; the inorganic filter aids include diatomaceous earth, perlite, kaolin, aluminum hydroxide, iron oxide, and calcium carbonate; the filter aids are any one or a combination of at least two; preferably, the filter aid is perlite or diatomaceous earth, and the diatomaceous earth is preferably a mixture of 400 mesh red diatomaceous earth and 800 mesh white diatomaceous earth in a volume ratio of 1:1. The amount of filter aid added is 1-10% by mass: volume, preferably 3-5%.

[0012] (3) Dead-end filtration: After the diluted fermentation liquid is fully mixed with the added filter aid, it is passed through a filter press at a filtration pressure of 0.05-0.8 MPa. The dead-end filtration sterilization is continued for 60-90 minutes under constant pressure. After the operating conditions are set correctly, the constant pressure dead-end filtration sterilization is performed to obtain the fermentation liquid with the bacterial cells removed. The driving force of dead-end filtration is positive pressure or negative pressure. The pressure range used is preferably 0.2-0.4 MPa.

[0013] (4) Filtration: After the dead-end filtration is completed, a filtration solvent is added to the filter residue to perform filtration. The filtration solvent is water adjusted to a pH of 6.0 to 7.2, and the reagents used are HCl and NaOH; the amount of the filtration solvent used is 1-5 times the volume of the filter assembly chamber. The filter membrane is an organic membrane or an inorganic membrane, and the membrane assembly type is a flat plate or a hollow type; the organic membrane material used is polysulfone, polyethersulfone, polyvinylidene fluoride, polytetrafluoroethylene, polyacrylonitrile, polyethylene, polyester, nylon, polypropylene; the inorganic membrane is a ceramic membrane, a metal membrane or a metal and ceramic composite membrane; the ceramic membrane material used is alumina, cobalt oxide, silicon oxide, aluminum silicate, silicon carbide; the metal membrane used is Ag membrane, Ni membrane, Ti membrane and stainless steel membrane; preferably 750B twill polypropylene multifilament membrane or F6 satin polypropylene monofilament multifilament filter membrane. The filtration pressure during diafiltration is in the range of 0.05-0.8 MPa, preferably 0.2-0.4 MPa.

[0014] The fermentation liquid described in the technical solution of the present invention can be a fermentation liquid obtained by fermenting Bacillus or Aconitum for 3-6 days.

[0015] Preferably, the specific steps are: after the fermentation is completed, the fermentation liquid is heated to 121°C for 20 minutes, cooled to room temperature, and the pH of the fermentation liquid is adjusted to 6.0 to 7.2 after the fermentation liquid is cooled; then water is added to dilute the fermentation liquid until the fermentation liquid accounts for 40-50% (v / v) of the diluted liquid; 3-5% (w / v) of filter aid is added to the diluted fermentation liquid; the filter aid is selected from perlite or a mixture of 400 mesh white diatomaceous earth and 800 mesh red diatomaceous earth mixed in a volume ratio of 1:1; The fermentation liquid fully mixed with the filter aid is filtered through a filter press; the filter membrane is 750B twill polypropylene multifilament membrane or F6 satin polypropylene monofilament membrane; the filtration pressure is 0.2-0.4MPa; under this operating condition, dead-end filtration and sterilization are continuously performed for 60-90 minutes to obtain a clear liquid without bacterial cells; after the filtration is completed, water is added to the filter residue for washing, the filtration pressure is 0.2-0.4Mpa, and the filter residue is washed with 6.0 to 7.2 water to recover the target product retained by the medium during the filtration process.

[0016] Beneficial effects of the present invention: The present invention relates to a method for removing microbial cells in a biomacromolecule fermentation broth by dead-end filtration, which is the first time that a dead-end filtration operation is introduced to remove bacterial cells in a fermentation broth; a set of constant-pressure dead-end filtration separation systems is established according to the different amounts of bacterial cells in the fermentation broth, overcoming the defects of the prior art such as low fermentation broth processing volume, complex operation, high product loss rate, and high energy consumption, thereby significantly improving the yield and total amount of the target product biomacromolecules and reducing the production cost.

[0017] Compared with the existing process technology, the advantages of the method of the present invention are as follows: (1) The present invention first pre-treats the fermentation liquid before sterilization. By heating, enzymolysis and dilution, the bacterial cells in the fermentation liquid are inactivated, the free proteins are precipitated, the viscosity and the amount of bacteria per unit volume are reduced, which is conducive to the dead-end filtration sterilization; (2) The present invention adopts dead-end filtration technology to remove bacterial cells in the fermentation broth, which is simple to operate, has a low product loss rate, and has a better sterilization effect than cross-flow filtration; (3) The present invention adopts dead-end filtration technology to remove bacterial cells in the fermentation broth. The fermentation broth processing volume is large, the total amount of product obtained in the same time is large, the turbidity of the clear liquid is lower, and the sterilization effect is better than the centrifugation method; (4) The present invention adopts dead-end filtration technology to remove bacterial cells in the fermentation broth, which has low energy consumption and is superior to cross-flow filtration and centrifugation in terms of production cost; (5) The present invention further reduces the loss of the product during the extraction process by washing the filter residue after the filtration is completed to recover the intercepted target product. DETAILED DESCRIPTION

[0018] The present invention will be further described below in conjunction with the embodiments. In the following detailed description, only certain exemplary embodiments of the present invention are described by way of illustration. Needless to say, those of ordinary skill in the art will appreciate that the described embodiments may be modified in a variety of ways without departing from the spirit and scope of the present invention. Therefore, the description of the embodiments is illustrative in nature and is not intended to limit the scope of protection of the claims.

[0019] Example 1 Pretreatment to remove protein The polymalic acid (PMLA) fermentation broth produced by Melaninogenic Aureobasidium was heated after fermentation and kept at 121°C for 20 minutes. After heating, the fermentation broth was cooled to room temperature, and then the pH was adjusted to 6.0 by HCl and NaOH. The pullulan (Pullulan) fermentation broth produced by Budding Aureobasidium was heated after fermentation and kept at 121°C for 20 minutes. After heating, the fermentation broth was cooled to room temperature, and then the pH was adjusted to 6.0 by HCl and NaOH. The polyglutamic acid (PGA) fermentation broth produced by Bacillus licheniformis was heated after fermentation and kept at 121°C for 20 minutes. After heating, the fermentation broth was cooled to room temperature, and then the pH was adjusted to 7.2 by HCl and NaOH. The pretreatment effect of the fermentation broth is shown in the following table:

[0020] Example 2: Centrifugal sterilization after dilution of fermentation broth Take the same batch of PMLA fermentation liquid as in Example 1 and treated in the same way (hereinafter the same), dilute with water until the dilution ratio (fermentation liquid stock liquid: total volume) is 1:2. The diluted fermentation liquid is heated at 10800 rpm Down Centrifuge for 10 minutes. Excluding the operating gap, 6 centrifugal sterilizations can be performed within 60 minutes. Take the Pullulan fermentation broth (the same below) of the same batch and treated in the same way as in Example 1, add water to dilute the fermentation broth, and the dilution multiple (fermentation broth stock solution: total volume) is 1:1. The diluted fermentation broth is centrifuged at 10,000 rpm for 15 minutes. The operating gap is not included in the extraction time, and 4 centrifugal sterilizations can be performed within 60 minutes. Take the PGA fermentation broth (the same below) of the same batch and treated in Example 1, do not dilute with water, and centrifuge at 15,000 rpm for 20 minutes. The operating gap is not included in the extraction time, and 3 centrifugal sterilizations can be performed within 60 minutes. The effects of sterilization by centrifugation of three different fermentation broths are shown in the following table:

[0021] Example 3 Cross-flow filtration after dilution of fermentation broth Take PMLA fermentation broth, dilute it with water until the dilution ratio (fermentation broth stock: total volume) is 1:2, and the diluted fermentation broth is cross-flow filtered through a 300kDa ceramic membrane at a pressure of 0.2MPa for 60 minutes. Take Pullulan fermentation broth, dilute it with water until the dilution ratio (fermentation broth stock: total volume) is 1:2, and the diluted fermentation broth is cross-flow filtered through a 300kDa ceramic membrane at a pressure of 0.2MPa for 60 minutes. Take PGA fermentation broth, dilute it with water until the dilution ratio (fermentation broth stock: total volume) is 1:2, and the diluted fermentation broth is cross-flow filtered through a 0.2μm PVDF membrane at a pressure of 0.1MPa for 60 minutes. The effects of cross-flow filtration and sterilization of the three fermentation broths are shown in the following table:

[0022] Example 4 Dead-end filtration after dilution of fermentation broth (without filter aid) Take PMLA fermentation broth, add water to dilute until the dilution ratio (fermentation broth stock solution: total volume) is 1:2, no additional filter aids are added, dead-end filtration sterilization is performed at 0.2MPa, the filter membrane is 750A polypropylene filter membrane, and the filtration time is 60min. Take Pullulan fermentation broth, add water to dilute until the dilution ratio (stock solution: total volume) is 1:2, no additional filter aids are added, dead-end filtration sterilization is performed at 0.2MPa, the filter membrane is Z45138-PP polypropylene filter membrane, and the filtration time is 60min. Take PGA fermentation broth, add water to dilute until the dilution ratio (stock solution: total volume) is 1:2, no additional filter aids are added, dead-end filtration sterilization is performed at 0.2MPa, and the filter membrane is F6 polypropylene filter membrane. The sterilization effect of dead-end filtration sterilization for the three fermentation broths is shown in the following table:

[0023] Example 5 Dead-end filtration after dilution of fermentation broth (with filter aid) Take PMLA fermentation broth, dilute with water until the dilution ratio (stock solution: total volume) is 1:2.5, add 4% 100 mesh cellulose filter aid, and perform dead-end filtration sterilization under a pressure of 0.2MPa. The filter membrane is 750B polypropylene filter membrane, and the filtration time is 60min. Take Pullulan fermentation broth, dilute with water until the dilution ratio (stock solution: total volume) reaches 1:2, add 3% (w / v) polyacrylamide, and perform dead-end filtration sterilization under a pressure of 0.2MPa. The filter membrane is F6 polypropylene filter membrane, and the filtration time is 60min. Take PGA fermentation broth, dilute with water until the dilution ratio (stock solution: total volume) is 1:2, add 3% (w / v) 80 mesh rod-shaped kaolin, and perform dead-end filtration sterilization under a pressure of 0.2MPa. The filter membrane is F6 polypropylene filter membrane, and the filtration time is 60min. The effects of dead-end filtration and sterilization after optimizing the operating conditions of the three fermentation broths are shown in the following table:

[0024] Example 6 Dead-end filtration after dilution of fermentation broth Take PMLA fermentation broth, dilute it with water until the dilution ratio (stock solution: total volume) is 1:2.5, add 4% 100 mesh cellulose filter aid, and perform dead-end filtration sterilization at a pressure of 0.2MPa. The filter membrane is 621 polyester filter membrane, and the filtration time is 60min. Take Pullulan fermentation broth, dilute it with water until the dilution ratio (stock solution: total volume) reaches 1:2, add 3% (w / v) polyacrylamide, and perform dead-end filtration sterilization at a pressure of 0.2MPa. The filter membrane is F8 polypropylene filter membrane, and the filtration time is 60min. Take PGA fermentation broth, dilute it with water until the dilution ratio (stock solution: total volume) is 1:2, add 3% (w / v) 80 mesh rod-shaped kaolin, and perform dead-end filtration sterilization at a pressure of 0.2MPa. The filter membrane is 740 polypropylene filter membrane, and the filtration time is 60min. The effects of dead-end filtration and sterilization after optimizing the operating conditions of the three fermentation broths are shown in the following table:

[0025] Example 7 Dead-end filtration after dilution of fermentation broth Take PMLA fermentation broth, dilute it with water until the dilution ratio (stock solution: total volume) is 1:2.5, add 4% 100 mesh cellulose filter aid, and perform dead-end filtration sterilization at a pressure of -0.1MPa. The filter membrane is 750B polypropylene filter membrane, and the filtration time is 60min. Take Pullulan fermentation broth, dilute it with water until the dilution ratio (stock solution: total volume) reaches 1:2, add 3% (w / v) polyacrylamide, and perform dead-end filtration sterilization at a pressure of -0.1MPa. The filter membrane is F6 polypropylene filter membrane, and the filtration time is 60min. Take PGA fermentation broth, dilute it with water until the dilution ratio (stock solution: total volume) is 1:2, add 3% (w / v) 80 mesh rod-shaped kaolin, and perform dead-end filtration sterilization at a pressure of -0.1MPa. The filter membrane is F6 polypropylene filter membrane, and the filtration time is 60min. The effects of dead-end filtration and sterilization after optimizing the operating conditions of the three fermentation broths are shown in the following table:

[0026] Example 8 Dead-end filtration after dilution of fermentation broth Take PMLA fermentation broth, add water to dilute until the dilution ratio (stock solution: total volume) is 1:2.5, add 4% (w / v) 200 mesh perlite, and perform dead-end filtration sterilization at a pressure of 0.4MPa. The filter membrane is 750B polypropylene filter membrane, and the filtration time is 60min. Take Pullulan fermentation broth, add water to dilute until the dilution ratio (stock solution: total volume) reaches 1:2, add 3% (w / v) diatomaceous earth (400 mesh white diatomaceous earth and 800 mesh red diatomaceous earth are mixed in a volume ratio of 1:1), perform dead-end filtration sterilization at a pressure of 0.3MPa, and the filter membrane is F6 polypropylene filter membrane, and the filtration time is 60min. Take the PGA fermentation liquid, add water to dilute until the dilution multiple (stock liquid: total volume) is 1:2, add 3% (w / v) diatomaceous earth (400 mesh white diatomaceous earth and 800 mesh red diatomaceous earth are mixed in a volume ratio of 1:1), and perform dead-end filtration sterilization at a pressure of 0.2MPa. The filter membrane is F6 polypropylene filter membrane, and the filtration time is 60min. The effects of dead-end filtration sterilization after optimizing the operating conditions of the three fermentation liquids are shown in the following table:

[0027] Example 9 Filter residue washing Take the residue after the PMLA fermentation broth is filtered according to the conditions of Example 5, add water equivalent to 2 times the volume of the fermentation broth for filtration, and the operating pressure during filtration is the same as that of Example 5. Take the residue after the Pullulan fermentation broth is filtered according to the conditions of Example 5, add water equivalent to 4 times the volume of the fermentation broth for filtration, and the operating pressure is consistent with that of Example 5. Take the residue after the PGA fermentation broth is filtered according to the conditions of Example 5, add water equivalent to 3 times the volume of the fermentation broth for filtration, and the operating pressure during filtration is the same as that of Example 5. The filtration results are shown in the following table:

[0028] In summary, under the optimal operating conditions, the PMLA fermentation broth was sterilized by dead-end filtration, and the average permeate flux of the clear liquid was 82.5 L / m 2 h, the total amount of PMLA was 27.24 g, which was lower than the flux under the initial conditions (2.13 L / m 2 ·h) and the total amount of product (0.69g) were greatly improved; under the optimal conditions, the Pullulan fermentation broth was sterilized by dead-end filtration, and the average permeate flux of the clear liquid reached 91.50 L / m 2 h, the total amount of Pullulan was 75.17 g, which was significantly higher than the flux under the initial conditions (4.25 L / m 2 h) and the total amount of product (1.98 g) were significantly improved; under the optimal conditions, the PGA fermentation broth was sterilized by dead-end filtration, and the average permeate flux of the clear liquid was 38.07 L / m 2 h, the total amount of PGA was 14.16 g, which was comparable to the flux under initial conditions (8.50 L / m 2 ·h), the total amount of product (3.11g), was significantly improved.

[0029] The description of the present invention is given for the purpose of illustration and description, and is not intended to be exhaustive or to limit the invention to the disclosed form. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiments are selected and described in order to better illustrate the principles and practical applications of the present invention and to enable those of ordinary skill in the art to understand the present invention and thereby design various embodiments with various modifications suitable for particular uses.

Claims

1. A method for removing bacteria from a biomacromolecule fermentation broth by dead-end filtration, characterized in that: The method comprises four steps of fermentation liquid pretreatment, adding filter aid, dead-end filtration, and diafiltration, and the specific steps include: (1) Pretreatment: heating the fermentation liquid, cooling it to room temperature after heating, and adjusting the pH value of the fermentation liquid to 3-10; determining the amount of bacterial cells in the fermentation liquid by centrifugation, and diluting the fermentation liquid with water according to the amount of bacterial cells; (2) Add filter aid to the diluted fermentation broth, mix thoroughly, and filter through a filter press; (3) Dead-end filtration: The diluted fermentation broth is fully mixed with the added filter aid and then filtered through a filter press and a filter membrane. The filtration pressure is 0.05-0.8 MPa. Dead-end filtration and sterilization are performed continuously for 60-90 minutes under constant pressure to obtain a fermentation broth clear liquid with bacterial cells removed. (4) Filtration washing: After the dead-end filtration is completed, a filtration washing solvent is added to the filter residue to perform filtration washing on the filter residue. The filtration washing solvent is water. The pH of the filtration washing solvent is adjusted to 6.0 to 7.

2. The reagents used are HCl and NaOH. The amount of the filtration washing solvent used is 1 to 5 times the volume of the filter assembly chamber.

2. The method for removing bacteria from a biomacromolecule fermentation broth by dead-end filtration according to claim 1, characterized in that: The heating in step (1) needs to be performed at 121° C. for 20 min.

3. The method for removing bacteria from a biomacromolecule fermentation broth by dead-end filtration according to claim 1, characterized in that: In step (1), the pH of the fermentation liquid is adjusted to 6.0 to 7.2, and the reagents used are HCl and NaOH.

4. The method for removing bacteria from a biomacromolecule fermentation broth by dead-end filtration according to claim 1, characterized in that: Step (1) adding water to dilute the fermentation broth until the dilution ratio is 1:2 to 1:2.5 based on the fermentation broth stock volume: total volume.

5. The method for removing bacteria from a biomacromolecule fermentation broth by dead-end filtration according to claim 1, characterized in that: The filter aid added in step (2) includes organic filter aid and inorganic filter aid, wherein the organic filter aid includes activated carbon, Fiber Vitamin , polyacrylamide; the inorganic filter aids include diatomaceous earth, perlite, kaolin, kaolin, aluminum hydroxide, iron oxide, and calcium carbonate; the filter aids are any one or a combination of at least two.

6. The method for removing bacteria from a biomacromolecule fermentation broth by dead-end filtration according to claim 5, characterized in that: The filter aid is 200-mesh perlite or diatomaceous earth, and the diatomaceous earth is a mixture of 400-mesh red diatomaceous earth and 800-mesh white diatomaceous earth in a volume ratio of 1:

1.

7. The method for removing bacteria from a biomacromolecule fermentation broth by dead-end filtration according to claim 1, characterized in that: The amount of the filter aid added is 1-10% by mass: volume.

8. The method for removing bacteria from a biomacromolecule fermentation broth by dead-end filtration according to claim 1, characterized in that: The dead-end filtration in step (3) uses an organic membrane or an inorganic membrane as the filter membrane, and the membrane assembly type is a flat plate type or a hollow type; the organic membrane material is polysulfone, polyethersulfone, polyvinylidene fluoride, polytetrafluoroethylene, polyacrylonitrile, polyethylene, polyester, nylon, polypropylene; the inorganic membrane is a ceramic membrane, a metal membrane or a metal and ceramic composite membrane; the ceramic membrane material used is aluminum oxide, cobalt oxide, silicon oxide, aluminum silicate, silicon carbide; the metal membrane used is Ag membrane, Ni membrane, Ti membrane and stainless steel membrane.

9. The method for removing bacteria from a biomacromolecule fermentation broth by dead-end filtration according to claim 1, characterized in that: The driving force for the dead-end filtration in step (3) is positive pressure or negative pressure, and the pressure range used is 0.05-0.8Mpa.

10. The method for removing bacteria from biomacromolecule fermentation broth by dead-end filtration according to claim 1, characterized in that: The specific steps are as follows: after the fermentation is completed, the fermentation liquid is heated to 121°C for 20 minutes, cooled to room temperature, and the pH is adjusted to 6.0 to 7.2 after the fermentation liquid is cooled; then water is added to dilute the fermentation liquid until the original fermentation liquid accounts for 40-50% (v / v) of the diluted liquid; 3-5% (w / v) of filter aid is added to the diluted fermentation liquid; the filter aid is selected from perlite or a mixture of 400 mesh white diatomaceous earth and 800 mesh red diatomaceous earth mixed in a volume ratio of 1:1; The fermentation liquid fully mixed with the agent is filtered through a filter press; the filter membrane is 750B twill polypropylene multifilament membrane or F6 satin polypropylene monofilament membrane; the filtration pressure is 0.2-0.4MPa; under this operating condition, dead-end filtration and sterilization are continuously performed for 60-90 minutes to obtain a clear liquid without bacterial cells; after the filtration is completed, water is added to the filter residue for washing, the filtration pressure is 0.2-0.4Mpa, and the filter residue is washed with 6.0 to 7.2 water to recover the target product retained by the medium during the filtration process.

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