A method for preparing epsilon-polylysine hydrochloride using continuous ion exchange technique

Abstract

The application discloses a method for preparing epsilon-polylysine hydrochloride by using a continuous ion exchange technology and belongs to the technical field of industrial fermentation. The method for preparing epsilon-polylysine hydrochloride by using the continuous ion exchange technology is that epsilon-polylysine fermentation liquor is sequentially subjected to solid-liquid separation, ion exchange, nanofiltration membrane desalination, decolorization, concentration and drying to obtain epsilon-polylysine hydrochloride. The method can simplify a process, reduce generation of waste water, reduce acid and alkali consumption, improve a yield, make the yield be up to 75% or more, make the purity be not less than 95%, greatly reduce production cost and have great industrial application prospects.

Description

Technical Field

[0001] This invention relates to a method for preparing ε-polylysine hydrochloride using continuous ion exchange technology, belonging to the field of industrial fermentation technology. Background Technology

[0002] ε-Polylysine (ε-PL) is a homoamino acid polymer produced through microbial fermentation. Due to its unique structure, ε-PL possesses advantages such as a broad antibacterial spectrum, high thermal stability, wide pH tolerance, and easy biodegradability, making it widely used as a green and safe biological food preservative. Furthermore, due to the multi-cationic properties of ε-PL, it also has wide applications in pharmaceuticals, materials, and other fields, making it a novel industrial biotechnology product with enormous potential market value.

[0003] Currently, ε-PL is mainly obtained through submerged fermentation of microorganisms. It is a secondary metabolite secreted extracellularly by Streptomyces, filamentous fungi, or Bacillus species. After years of research, the fermentation level for ε-PL production has significantly improved, increasing from 20-30 g / L in the early stages to over 65 g / L currently. However, the corresponding cell mass has also increased significantly, with the dry weight increasing from 30 g / L to over 50 g / L. Therefore, the early low-concentration ε-PL extraction process is far from suitable for current fermentation levels, making the research on extraction processes suitable for high-concentration ε-PL urgent. At the same time, traditional extraction processes suffer from low extraction efficiency, high extraction costs, and large amounts of wastewater, which also limit their widespread application. Although there are many extraction processes for existing fermentation products, the separation methods and conditions required will differ depending on the product, material, and even the microbial species. Directly copying existing extraction processes cannot meet practical needs. For example, in the fermentation broth for producing γ-aminobutyric acid (GABA) from *Lactobacillus brevis* SC221, the yield is 30-90 g / L, while the cell mass is only 2-8 g / L. Patent CN106544372A can achieve an GABA extraction yield of ≥70% and a purity of ≥95%. For fermentation broths containing only 20-30 g / L ε-PL and a cell dry weight of 30 g / L, patents ZL200910152931.2 and ZL201110053004.2 can also achieve a yield of over 60% and a purity of over 95%. However, when the ε-PL yield is above 65 g / L and the cell dry weight is above 50 g / L, the above three methods struggle to achieve effective cell separation, ultimately resulting in an ε-PL yield below 55% and a purity of only around 60%. Meanwhile, in existing patent applications, the solution to high bacterial counts often involves large-scale dilution of the fermentation broth, leading to increased wastewater volume and dilution of the target product, thus increasing subsequent concentration costs. Furthermore, reported ε-PL extraction processes typically employ multiple ion exchange resins for separating the target product, often using anion, cation, and anion column combinations in intermittent operation. This process not only wastes significant amounts of acid and alkali but also results in low resin utilization and a substantial decrease in production intensity. Therefore, traditional ε-PL extraction processes suffer from drawbacks such as large wastewater volume, high acid and alkali consumption, low production intensity, and high production costs associated with high-concentration ε-PL fermentation broths. Consequently, there is an urgent need to develop a method for extracting ε-polylysine from fermentation broths with high bacterial concentrations and high ε-polylysine yields.

[0004] The extraction processes described in patents ZL200920069827.5, ZL200910152931.2, and ZL201110053004.2 can achieve a yield of 70-80% and a purity of 95-97% for fermentation broths with ε-PL fermentation levels below 40 g / L. However, for fermentation broths fermented by the inventors' team using Streptomyces simonii CGMCC No.10480 as the fermenting microorganism, which contain ε-PL ≥65 g / L and have a cell dry weight ≥50 g / L, effective product separation cannot be achieved, ultimately resulting in a yield below 55% and a purity of only about 60%. This shows that for the same product, the extraction process varies depending on the properties of the material. Furthermore, the extraction process cannot be copied from one product to another. For example, patent CN106544372A is relatively easy to separate bacteria with a cell count of only 2-8 g / L, so it can achieve an extraction yield of γ-aminobutyric acid of ≥70% and a purity of ≥95%. However, the extraction process reported therein is not applicable to the material characteristics (cell count above 50 g / L) in the inventor's patent application. Summary of the Invention

[0005] This invention addresses the shortcomings of existing fermentation processes that cannot meet the requirements of ε-polylysine yields of 65 g / L or higher and cell dry weights of 50 g / L or higher. It also addresses the problems of low extraction efficiency, high extraction costs, and large wastewater volumes associated with traditional extraction methods. This invention provides a novel method for extracting ε-polylysine hydrochloride from the fermentation broth under this new fermentation process.

[0006] The technical solution adopted in this invention is:

[0007] This invention provides a method for preparing ε-polylysine hydrochloride from fermentation broth using continuous ion exchange technology. The method includes: sequentially passing the ε-polylysine fermentation broth through solid-liquid separation, continuous ion exchange, nanofiltration membrane desalting, decolorization, concentration, and spray drying to obtain ε-polylysine hydrochloride.

[0008] In one implementation, the method includes the following steps:

[0009] (1) The ε-polylysine fermentation broth was subjected to solid-liquid separation to remove suspended solids such as bacterial cells and obtain a clear liquid;

[0010] (2) The clear liquid obtained in step (1) is then adsorbed and desorbed by a continuous ion exchange device to obtain the desorbed liquid;

[0011] (3) The eluent obtained in step (2) is desalted through a nanofiltration membrane to obtain a desalted solution;

[0012] (4) The desalination solution obtained in step (3) is decolorized with activated carbon to obtain a decolorized solution;

[0013] (5) The decolorized liquid obtained in step (4) is concentrated by evaporation to obtain a concentrated liquid;

[0014] (6) The concentrated solution obtained in step (5) is spray-dried to obtain ε-polylysine hydrochloride product.

[0015] In one embodiment, the solid-liquid separation employs any one or a combination of two of plate and frame filtration and ultrafiltration membrane filtration; from the perspective of saving investment and operating costs, plate and frame filtration is preferred.

[0016] In one embodiment, when using plate and frame filtration, the temperature is controlled at 25-40°C, preferably the original temperature of the fermentation broth. The pH does not need to be specially adjusted, and it is preferred to maintain the original pH of the fermentation broth at 3.8-4.2. Before filtration, diatomaceous earth is pre-coated, with the amount of diatomaceous earth pre-coated per square meter of filtration area being 0.35-1 kg. During filtration, the amount of diatomaceous earth added is 1.5-4% (m / v) of the fermentation broth.

[0017] In one embodiment, when using ultrafiltration membrane filtration, the ultrafiltration membrane is a tubular ultrafiltration membrane or a ceramic ultrafiltration membrane, with a molecular weight cutoff of 30-100 kDa, an operating temperature of 25-45°C, an operating pressure of 0.2-0.6 MPa, a membrane surface flow rate of 2-4 m / s, and a pH maintained at 3.8-4.5.

[0018] In one embodiment, the ion exchanger is a cation exchange resin, which includes strong acid type or weak acid type; the strong acid type cation exchange resin is a sodium type cation exchange resin, and the weak acid type cation exchange resin is a hydrogen type cation exchange resin; the continuous ion exchange device consists of 4 to 6 ion exchange columns connected in series, with the effluent from the previous exchange column connected to the influent from the next exchange column, and the ion exchange columns are controlled by valves; at any given time, 3 to 4 ion exchange columns are performing exchange adsorption, while the other 1 to 2 ion exchange columns are performing washing and elution. When the breakthrough concentration of the previous ion exchange column reaches 70-90% of the feed concentration (indicating that the adsorption capacity of the packing is saturated), the sample injection is stopped, and the valve switches to the washing and elution stage. At this time, the feed pipe switches to the next ion exchange column for sample loading and adsorption; while the eluted ion column switches to the adsorption stage, thus forming a sequential continuous ion exchange program, performing sample loading, washing, and elution operations in sequence.

[0019] In one embodiment, the resin packing height-to-diameter ratio of the ion exchange column is (4-6):1, the sample concentration on the ion exchange column is controlled at 20-45 g / L, the sample loading rate is controlled at 1-2 BV, the sample loading pH is 6.0-8.2, and 0.3-0.8 mol / L sodium hydroxide is used for ion exchange elution, with an elution rate of 1.5-3.5 BV.

[0020] In one embodiment, the nanofiltration membrane has a molecular weight cutoff of 600-1000 Da; during nanofiltration membrane desalination, concentrated hydrochloric acid is used to adjust the eluent to maintain the pH at 3.8-4.2, and the conductivity of the retentate is controlled to be below 4000 μs / cm before the nanofiltration membrane is used to concentrate the ε-polylysine to a concentration of 50 g / L or higher before stopping nanofiltration.

[0021] In one embodiment, the decolorization is performed by adding activated carbon, with the amount of activated carbon added being 0.5%-3% (m / v), the decolorization temperature being controlled at 55-70℃, the decolorization time being 30-90 min, and then filtration separation is carried out.

[0022] In one embodiment, the evaporation and concentration are carried out using a single-effect evaporator or a multi-effect evaporator under reduced pressure.

[0023] In one embodiment, the evaporation and concentration are carried out using double-effect vacuum evaporation, and the concentration is stopped when the concentration of ε-polylysine hydrochloride reaches 200-350 g / L.

[0024] In one embodiment, the spray drying is used to dry the concentrate to obtain the product ε-polylysine hydrochloride, and the drying method is preferably spray drying.

[0025] In one embodiment, the fermentation broth refers to a fermentation broth that produces ε-polylysine through microbial fermentation, wherein the ε-polylysine concentration is above 65 g / L and the cell concentration is above 50 g / L.

[0026] The present invention also claims protection for the use of the method in the production of products containing ε-polylysine hydrochloride.

[0027] Beneficial effects:

[0028] 1. This invention simplifies and optimizes each operation unit of the extraction process, resulting in a simple preparation method for ε-polylysine hydrochloride with a yield of over 75% and a purity of not less than 95%, which greatly reduces production costs.

[0029] 2. This invention improves the traditional solid-liquid separation process, reduces the dilution of the fermentation broth, and thus reduces the amount of wastewater generated;

[0030] 3. This invention uses single-stage cation continuous ion exchange technology to replace the traditional two-stage or even three-stage ion exchange process combining anions and cations. The acid and alkali consumption is less than 70% of that of the traditional process. By using continuous ion exchange technology, the sample concentration is increased, the amount of water used is reduced, and the resin utilization rate is increased by more than 50% compared with the intermittent process. This enables continuous operation, increases production intensity, and reduces production costs. Attached Figure Description

[0031] Figure 1 The chromatogram is for ε-polylysine hydrochloride standard.

[0032] Figure 2 The chromatogram is of the ε-polylysine hydrochloride product prepared in Example 1 of this invention.

[0033] Figure 3 This is a flowchart of the continuous ion exchange process in the preparation of ε-polylysine hydrochloride in Example 1 of the present invention.

[0034] Figure 4 This is a flowchart of the continuous ion exchange process in the preparation of ε-polylysine hydrochloride in Example 2 of the present invention. Detailed Implementation

[0035] The present invention will be further described below by way of embodiments:

[0036] The fermentation broth used in the examples was obtained by fermenting *Streptomyces leucosus* with preservation number CGMCC No. 10480, with an ε-PL ≥ 65 g / L and a cell dry weight ≥ 50 g / L.

[0037] The yield is calculated as follows: ε-PL yield = {(C1×V1)÷(C0×V0)}×100%, where C0 is the initial ε-PL concentration of the sample solution (g / L), V0 is the initial sample solution volume (L), C1 is the ε-PL concentration of the treated sample solution (g / L), and V1 is the treated sample solution volume (L).

[0038] The purity calculation method is as follows: ε-PL purity = {(C×V)÷m}×100%, where C is the ε-PL concentration of the sample redissolved in deionized water (g / L), V is the volume of the sample after redissolution (L), and m is the mass of the redissolved sample (g).

[0039] ε-PL determination method: The concentration of ε-PL was determined by HPLC (RSC Advances, 2020.10:29587-29593).

[0040] Example 1

[0041] (1) First, add a certain amount of diatomaceous earth to clean water. The amount of diatomaceous earth added should be controlled at 1 kg / m³. 2 To pre-coat the filter area, start the pump to deliver all the clean water and diatomaceous earth into the plate frame. Then add diatomaceous earth to the fermentation broth at 4% (m / v). The fermentation broth temperature is 30℃ and the pH is 4.0. After stirring evenly, pump the mixture into the plate frame for filtration. After filtration, wash the plate frame with an appropriate amount of clean water, then purge it with compressed air and collect the obtained filtrate.

[0042] (2) Adjust the pH of the membrane filtrate obtained in step (1) to 7.5 with 6N sodium hydroxide, and load the sample onto a continuous ion exchange column consisting of four weakly acidic cation exchange columns connected in series at a rate of 1.5 BV / h (e.g., Figure 3 As shown, the cation exchange column is packed with hydrogen-form weak acid cation exchange resin. Samples are loaded and adsorbed sequentially onto three exchange columns, and eluted onto one. When the effluent from the first exchange column shows a color development on a Dradorf detector, loading is stopped and the process switches to the second exchange column. At this point, the fourth exchange column is connected to the second and third exchange columns for adsorption. Meanwhile, the first exchange column is washed with water and then eluted with 0.8N sodium hydroxide at a rate controlled at 1.5 BV / h. After elution, the effluent is again connected to the third, fourth, and first exchange columns for adsorption, while the second column is washed and eluted. This cycle is repeated until all eluent is collected.

[0043] (3) Adjust the pH of the eluent obtained in step (2) with 6N hydrochloric acid and control it to 4.0. Then perform nanofiltration through a nanofiltration membrane with a molecular weight cutoff of 600 Da. The operating pressure is controlled at 1.2 MPa. During the desalting process, deionized water is added to maintain the volume of the eluent. The retentate is collected and circulated into the nanofiltration membrane until the conductivity of the retentate is 3500 μs / cm. Then stop adding deionized water and continue nanofiltration to concentrate until the concentration of ε-polylysine in the retentate is higher than 50 g / L.

[0044] (4) The nanofiltration retentate from step (3) is put into a decolorization tank. Activated carbon is added to the nanofiltration retentate at a ratio of 1.5% (m / v) and stirred evenly. The decolorization temperature is controlled at 60°C. After decolorization for 30 minutes, the solution is filtered to obtain the decolorized solution.

[0045] (5) The decolorizing solution from step (4) is introduced into a two-effect vacuum concentration system. The first-effect evaporation pressure is controlled at an absolute pressure of 50 kPa, and the second-effect evaporation pressure is controlled at 10 kPa. Evaporation and concentration are completed when the concentration of ε-polylysine reaches 300 g / L.

[0046] (6) The concentrate from step (5) was spray-dried to obtain the dried product ε-polylysine hydrochloride with a yield of 80.2% and a purity of 96.9%.

[0047] Example 2

[0048] (1) First, add a certain amount of diatomaceous earth to the clean water. The amount of diatomaceous earth added should be controlled at 0.65 kg / m³. 2To pre-coat the filter area, start the pump to deliver all the clean water and diatomaceous earth into the plate frame. Then add diatomaceous earth to the fermentation broth at 2.5% (m / v). The fermentation broth temperature is 25℃ and the pH is 4.1. After stirring evenly, pump the mixture into the plate frame for filtration. After filtration, wash the plate frame with an appropriate amount of clean water, then purge it with compressed air and collect the obtained filtrate.

[0049] (2) After adjusting the pH of the filtered solution obtained in step (1) to 6.5 with 0.6N sodium hydroxide, the solution is loaded onto a continuous ion exchange column consisting of six strongly acidic cation exchange columns connected in series at a rate of 1.0 BV / h (e.g., ...). Figure 4 As shown, the cation exchange column is packed with sodium-type strong acid ion exchange resin. Samples are loaded and adsorbed sequentially onto four exchange columns, followed by washing and elution onto two columns. Loading is stopped when the ε-polylysine concentration in the effluent from the first exchange column reaches 80% of the feed concentration, and the flow is switched to the second exchange column via a valve. At this point, the fifth exchange column is connected to columns 2, 3, and 4 for sample loading and adsorption. Meanwhile, column 1 is washed with water and then eluted with 0.6N sodium hydroxide at a rate controlled at 2 BV / h. After elution, the solution is again connected to columns 4, 5, and 6 for sample loading and adsorption, with column 2 undergoing elution and column 3 being washed. This cycle continues until all eluent is collected.

[0050] (3) Adjust the pH of the eluent obtained in step (2) to 4.0 with 6N hydrochloric acid, and then perform nanofiltration through a nanofiltration membrane with a molecular weight cutoff of 1000 Da. The operating pressure is controlled at 1.0 MPa. During the desalting process, deionized water is added to maintain the volume of the eluent. The retentate is collected and circulated into the nanofiltration membrane until the conductivity of the retentate is 2500 μs / cm. Then the addition of deionized water is stopped. Then nanofiltration is continued to concentrate until the concentration of ε-polylysine in the retentate is higher than 55 g / L.

[0051] (4) The nanofiltration retentate from step (3) is put into a decolorization tank. Activated carbon is added to the nanofiltration retentate at a ratio of 2.5% (m / v) and stirred evenly. The decolorization temperature is controlled at 70°C. After decolorization for 60 minutes, the solution is filtered to obtain the decolorized solution.

[0052] (5) The nanofiltration retentate collected in step (4) is introduced into a two-effect vacuum concentration system. The first effect evaporation pressure is controlled at an absolute pressure of 70 kPa, and the second effect evaporation pressure is controlled at 20 kPa. Evaporation and concentration are completed when the concentration of ε-polylysine is higher than 200 g / L.

[0053] (6) The concentrate was spray-dried to obtain the dried product ε-polylysine hydrochloride with a yield of 77.5% and a purity of 96.1%.

[0054] Example 3

[0055] (1) First, add a certain amount of diatomaceous earth to clean water. The amount of diatomaceous earth added should be controlled at 0.4 kg / m³. 2 For filtration, the pump is started to deliver all the water and diatomaceous earth into the plate frame for pre-coating. Then, 1.5% (m / v) diatomaceous earth is added to the fermentation broth. The fermentation broth temperature is 37℃, and the pH is 4.2. After stirring evenly, the mixture is pumped into the plate frame for filtration. After filtration, the plate frame is washed with an appropriate amount of water and then purged with compressed air. The resulting filtrate is collected. The filtrate is then passed through a ceramic membrane with a molecular weight cutoff of 100 kDa. The filtration pressure is controlled at 0.3 MPa, and the membrane surface velocity is 4 m / s. The filtrate and retentate are collected separately. The collected retentate continues to be filtered through the ceramic membrane. When the filtration speed decreases, water is added to the retentate, and filtration continues until the ε-polylysine concentration in the retentate is below 1 g / L. Filtration is then stopped.

[0056] (2) Adjust the pH of the filtrate collected in step (1) to 7.0 with 6N hydrochloric acid, and load the sample onto a continuous ion exchange column consisting of four strongly acidic cation exchange columns connected in series at a rate of 1.5 BV / h (e.g., Figure 3 As shown, the cation exchange column is packed with ammonium-type cation exchange resin. Samples are loaded and adsorbed sequentially onto three exchange columns, while one exchange column is used for elution. Loading is stopped when the ε-polylysine concentration in the effluent from the first exchange column reaches 70% of the feed concentration, and the process is switched to the second exchange column via a valve. At this point, the fourth exchange column is connected to the second and third exchange columns for adsorption. Meanwhile, the first exchange column is washed with water and then eluted with 0.4N sodium hydroxide at a rate controlled at 1.8 BV / h. After elution, the solution is again connected to the third, fourth, and first exchange columns for adsorption, while the second exchange column is washed and eluted. This cycle is repeated until all eluent is collected.

[0057] (3) Adjust the pH of the eluent obtained in step (2) to 3.8 with 6N hydrochloric acid, and then perform nanofiltration through a nanofiltration membrane with a molecular weight cutoff of 1000 Da. The operating pressure is controlled at 0.8 MPa. During the desalting process, deionized water is added to maintain the volume of the eluent. The retentate is collected and circulated into the nanofiltration membrane until the conductivity of the retentate is 1500 μs / cm. Then the addition of deionized water is stopped. Then nanofiltration is continued to concentrate until the concentration of ε-polylysine in the retentate is 52 g / L.

[0058] (4) The nanofiltration retentate from step (3) is put into a decolorization tank. Activated carbon is added to the nanofiltration retentate at a ratio of 1% (m / v) and stirred evenly. The decolorization temperature is controlled at 55°C. After decolorization for 90 minutes, the solution is filtered to obtain the decolorized solution.

[0059] (5) The decolorized liquid from step (4) is introduced into a two-effect vacuum concentration system. The first-effect evaporation pressure is controlled at an absolute pressure of 50 kPa, and the second-effect evaporation pressure is controlled at 10 kPa. Evaporation and concentration are completed when the concentration of ε-polylysine reaches 250 g / L.

[0060] (6) The concentrate from step (5) was spray-dried to obtain the dried product ε-polylysine hydrochloride with a yield of 75.2% and a purity of 97.2%.

[0061] Comparative Example 1:

[0062] The specific implementation method is the same as in Example 1, except that the continuous ion exchange in step (2) is changed to single-column interstitial ion exchange. The results show that the yield is 67.2%, the purity is 95.1%, the acid and alkali consumption increases by 90%, the resin utilization rate decreases by 60%, and the wastewater increases by 2.5 times.

[0063] Comparative Example 2:

[0064] The specific implementation method is the same as in Example 1, except that plate and frame filtration is not used, but ultrafiltration membrane filtration is used directly. Since ultrafiltration membrane filtration requires dilution of the fermentation broth, it can only achieve a yield of 78.5% and a purity of 95.5% after dilution by 8 times, which is equivalent to the effect of plate and frame filtration. The amount of wastewater generated is 8 times that of Example 1, the amount of acid and alkali consumed is 1.6 times that of Example 1, and the amount of steam consumed is 1.2 times that of Example 1.

[0065] Comparative Example 3:

[0066] The specific implementation method is the same as in Example 1, except that the order of step (1) and step (2) is reversed, that is, step (2) is performed first and then step (1). The result shows that the operation cannot be carried out, that is, it is almost impossible to obtain the product.

[0067] If steps (3) and (4) are swapped, the amount of activated carbon added increases by 2.2 times, the yield is only 62.2%, and the purity is 95.8%.

[0068] Comparative Example 4:

[0069] The specific implementation method is the same as in Example 1, except that the amount of diatomaceous earth pre-coated per square meter is adjusted to 0.2 kg. The results show that the yield is 70.1% and the purity is 95.2%.

[0070] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A method for preparing ε-polylysine hydrochloride, characterized in that, The method includes the following steps: (1) The undiluted ε-polylysine fermentation broth was directly subjected to solid-liquid separation to obtain a clear liquid; The fermentation broth is a fermentation broth containing ε-polylysine produced by microbial fermentation, with an ε-polylysine concentration ≥65g / L and a cell concentration ≥50g / L; The solid-liquid separation is performed using plate and frame filtration, with the temperature controlled at 25~40℃ and the pH at 3.8~4.5; before filtration, diatomaceous earth is pre-coated, with the amount of diatomaceous earth pre-coated per square meter of filtration area being 0.35~1kg; (2) The clear liquid obtained in step (1) is then adsorbed and desorbed by a continuous ion exchange device to obtain the desorbed liquid; The continuous ion exchange device consists of 4-6 cation exchange columns connected in series. The effluent from one exchange column is connected to the influent from the next exchange column, and the ion exchange columns are controlled by valves. At any given time, 3-4 ion exchange columns are performing exchange adsorption, while the other 1-2 columns are performing washing and elution. When the breakthrough concentration of the previous ion exchange column reaches 70-90% of the feed concentration, the sample injection stops, and the valve switches to the washing and elution stage. At this time, the feed tube switches to the next ion exchange column for sample loading and adsorption. The eluted ion column then switches back to the adsorption stage, thus forming a sequential continuous ion exchange program, performing sample loading, washing, and elution operations in sequence. (3) The eluent obtained in step (2) is desalted by passing it through a nanofiltration membrane to obtain a desalted solution; (4) The desalination solution obtained in step (3) is decolorized with activated carbon to obtain a decolorized solution; (5) The decolorized liquid obtained in step (4) is concentrated by evaporation to obtain a concentrated liquid; (6) The concentrate obtained in step (5) is spray-dried to obtain ε-polylysine hydrochloride product.

2. The method according to claim 1, characterized in that, The solid-liquid separation method described herein includes ultrafiltration membrane filtration after plate and frame filtration. When using ultrafiltration membrane filtration, the molecular weight cutoff of the ultrafiltration membrane is 30~100 kDa, the operating temperature is 25~45℃, the operating pressure is 0.2~0.6 MPa, the membrane surface flow rate is 2~4 m / s, and the pH is maintained at 3.8~4.

5.

3. The method according to claim 1, characterized in that, The packing material of the cation exchange column is a cation exchange resin, which is a strong acid type or a weak acid type cation exchange resin; the sample loading concentration of the ion exchange column is 20~45g / L, the sample loading rate is 1~2BV, and the sample loading pH is 6.0~8.2; 0.3~0.8mol / L sodium hydroxide is used for ion exchange elution, and the elution rate is 1.0BV or 1.5~3.5BV.

4. The method according to claim 1, characterized in that, The nanofiltration membrane has a molecular weight cutoff of 600-1000 Da. During nanofiltration desalination, the pH of the retentate is controlled at 3.8-4.2, and the conductivity of the retentate is controlled at less than 4000 μs / cm. Then, the nanofiltration membrane is used to concentrate the ε-polylysine until the concentration reaches ≥50 g / L, at which point nanofiltration is stopped.

5. The method according to claim 1, characterized in that, The decolorization process involves adding activated carbon, with the decolorization temperature controlled at 55-70℃ and the decolorization time at 30-90 minutes, followed by filtration and separation.

6. The method according to claim 1, characterized in that, The evaporation and concentration process continues until the concentration of ε-polylysine hydrochloride reaches ≥200 g / L, at which point the concentration is stopped.

7. The use of the method according to any one of claims 1 to 6 in the production of products containing ε-polylysine hydrochloride.

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