Method for producing poly-γ-glutamate ion complex

Abstract

To provide a production method of a PGA ion complex capable of mass-producing a PGA ion complex in which an aggregate particle size is controlled to be 10 mm or less at a yield of 60% or more.SOLUTION: A production method of a PGA ion complex includes the steps of: preparing a PGA solution containing poly-γ-glutamic acid of a concentration of 0.01-20%; preparing a cation solution containing a quaternary ammonium ion compound of a concentration of 10-20%; adding the PGA solution to the cation solution, while the cation solution is stirred at 50-1,000 rpm to precipitate a water-insoluble material containing a PGA ion complex in a lower part of the liquid; separating the water-insoluble material; washing the separated water-insoluble material; and extracting the PGA ion complex from the washed water-insoluble material.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a poly-γ-glutamate ion complex. [Background technology]

[0002] Poly-γ-glutamic acid (hereinafter also referred to as "PGA") is known as the main component of the stringy texture of natto (fermented soybeans) and possesses both biodegradability and high water absorption properties. By utilizing these functions, various applications are expected in many fields such as food, cosmetics, and pharmaceuticals. As a PGA ion complex with promising new applications, an ion complex formed from poly-γ-glutamic acid and a quaternary ammonium ion compound has been proposed (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Patent No. 5279080 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] However, the method described in Patent Document 1 results in large clumps of PGA ion complex exceeding 10 mm in size, making it impossible to control the aggregate particle size to 10 mm or less. In addition to being unable to filter due to clogging, washing away unreacted materials and impurities such as salts is difficult. Furthermore, combined with its viscosity, recovery is difficult, and mass production of PGA ion complex has not yet been achieved.

[0005] Therefore, the present invention aims to provide a method for producing PGA ion complexes with aggregate particle sizes controlled to be 10 mm or less, and capable of mass production with a yield of 60% or more. [Means for solving the problem]

[0006] To achieve the above objectives, the inventors conducted extensive research and discovered that by controlling the stirring speed and injection speed during manufacturing, it is possible to mass-produce PGA ion complex with an aggregate particle size of 10 mm or less at a yield of 60% or more.

[0007] In other words, the method for producing the PGA ion complex of the present invention is characterized by comprising the steps of: preparing a PGA solution containing 0.01 to 20% poly-γ-glutamic acid; preparing a cation solution containing 10 to 20% quaternary ammonium ion compound; adding the PGA solution while stirring the cation solution at 50 to 1000 rpm to precipitate the water-insoluble material containing the PGA ion complex to the bottom of the liquid; separating the water-insoluble material; washing the separated water-insoluble material; and extracting the PGA ion complex from the water-insoluble material after washing. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a method for producing a PGA ion complex in which the aggregate particle size is controlled to be 10 mm or less, and which can be mass-produced with a yield of 60% or more. [Brief explanation of the drawing]

[0009] [Figure 1] Scanning electron microscope image of the PGA ion complex obtained in Example 1. [Modes for carrying out the invention]

[0010] The method for producing the PGA ion complex of the present invention will be described in detail below. In the method for producing the PGA ion complex of the present invention, a PGA solution containing poly-γ-glutamic acid and a cation solution containing a quaternary ammonium compound are used as raw material solutions.

[0011] The PGA solution can be prepared by dissolving PGA in water as a solvent. The concentration of the PGA solution is defined to be 0.01 to 20%. When the concentration of the PGA solution is less than 0.01%, the target water-insoluble material cannot be synthesized. On the other hand, when it exceeds 20%, the viscosity becomes high and synthesis is difficult. The concentration of the PGA solution is preferably 1 to 10%, and more preferably 2.5 to 7.5%.

[0012] The cation solution can be prepared by dissolving a quaternary ammonium ion compound in water as a solvent. The quaternary ammonium ion compound is, for example, a compound represented by the following formula (I) or formula (II).

[0013]

Chemical formula

[0014] In the formula, R 1 ~R 3 independently represent a C 1-2 alkyl group, and R 4 ~R 5 independently represent a C 12-20 alkyl group.

[0015] The C 1-2 alkyl group means a linear or branched aliphatic hydrocarbon having 1 to 2 carbon atoms, that is, methyl or ethyl. The C 12-20 alkyl group means a linear or branched aliphatic hydrocarbon having 12 to 20 carbon atoms. For example, linear C such as dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, icosyl, etc. 12-20Alkyl groups; branched-chain C such as isotetradecyl, isopentadecyl, isohexadecyl, isoheptadecyl, isooctadecyl, sec-tetradecyl, sec-pentadecyl, sec-hexadecyl, sec-heptadecyl, sec-octadecyl, t-tetradecyl, t-pentadecyl, t-hexadecyl, t-heptadecyl, t-octadecyl, neotetradecyl, neopentadecyl, neohexadecyl, neoheptadecyl, neooctadecyl, etc. 12-20 Alkyl groups can be exemplified. R 4 As, preferably C 15-20 is an alkyl group, more preferably C 16-20 is an alkyl group, and most preferably C 17-20 is an alkyl group. R 5 As, preferably C 13-20 is an alkyl group, more preferably C 14-19 is an alkyl group, and most preferably C 15-18 is an alkyl group.

[0016] Examples of the compound represented by formula (I) or formula (II) include octadecyltrimethylammonium, hexadecylpyridinium, etc.

[0017] The concentration of the quaternary ammonium ion compound in the cation solution is defined as 0.01 - 20%. When the concentration of the cation solution is less than 0.01%, the target water-insoluble material cannot be synthesized. On the other hand, when it exceeds 20%, the viscosity becomes high and it is difficult to prepare the solution. The concentration of the quaternary ammonium ion compound in the cation solution is preferably 1 - 18%, more preferably 10 - 15%.

[0018] A predetermined amount of PGA solution is added while stirring a predetermined amount of cation solution at 50 to 1000 rpm. A magnetic stirrer or a mechanical stirrer can be used to stir the solution, with a mechanical stirrer being preferred. If the stirring speed of the cation solution is less than 50 rpm, the PGA is likely to aggregate. On the other hand, if it exceeds 1000 rpm, the reaction will not proceed and no change will occur. The stirring speed is preferably 50 to 500 rpm, and more preferably 100 to 300 rpm. The stirring speed should be controlled according to the concentration and volume of the raw material liquid. Generally, it is desirable to use a slower stirring speed for lower concentrations of the raw material liquid and a faster stirring speed for higher concentrations. Furthermore, it is desirable to use a slower stirring speed for larger volumes.

[0019] To produce the desired PGA ion complex, it is preferable that the number of moles of the quaternary ammonium ion compound is 0.8 to 1.2 times the number of moles of glutamic acid constituting poly-γ-glutamic acid. Therefore, it is desirable to determine the volume of each solution according to the concentration of each solution so that this ratio is achieved. It is more preferable that the number of moles of the quaternary ammonium ion compound is 0.9 to 1.1 times the number of moles of glutamic acid, and it is most preferable that they are equimolar.

[0020] For example, if the concentration of the PGA solution is 0.01 to 20% and the concentration of the cation solution is 10 to 20%, the above ratio can be achieved by adding a volume of PGA solution equal to 0.8 to 1000 times the volume of the cation solution. The volume of the PGA solution is preferably 0.6 to 1.4 times the volume of the cation solution, and more preferably 0.8 to 1.2 times. Specifically, if the concentration of the cation solution is 15% and the concentration of the PGA solution is 5%, then 500 mL of PGA solution can be used for 500 mL of cation solution.

[0021] The PGA solution should be added to the cation solution over a period of at least one minute to ensure uniform mixing. Adding the PGA solution to the cation solution in this way helps to suppress excessive aggregation. Depending on the volume of PGA solution used, the time required for adding it to the cation solution is preferably at least two minutes, and more preferably at least three minutes. Considering the efficiency during manufacturing, a maximum of about 60 minutes is sufficient.

[0022] The slower the injection rate when adding the PGA solution to the cation solution, the greater the aggregation suppression effect. The specific injection rate will vary depending on the scale of the synthesis, so it should be set appropriately according to the concentration and volume of the raw material solution. For example, when adding 500 mL of 5% PGA solution to 500 mL of 15% cation solution, the injection rate of the PGA solution into the cation solution should be 1000 mL / min or less, preferably around 350-650 mL / min, and more preferably around 400-600 mL / min.

[0023] After adding the PGA solution to the cation solution to ensure uniform mixing, further stirring at 30-80°C causes the water-insoluble material containing the PGA ion complex to precipitate at the bottom of the liquid. At this point, the reaction system separates into a liquid portion and a precipitate, and no further changes occur. This indicates that the reaction has proceeded completely. The temperature can be adjusted by setting the temperature of a heater, such as the jacket of the stirring tank. Depending on the concentration of the raw materials, if the temperature is too low, the synthesis will take a long time. On the other hand, if the temperature is too high, the PGA will quickly aggregate. A stirring temperature of 50-70°C is preferable. The stirring time is not particularly limited and can be appropriately determined according to the capacity of the synthesis vessel, etc. Typically, the desired water-insoluble material is produced by stirring for about 1-60 minutes.

[0024] Water-insoluble materials containing PGA ion complexes are separated from the solvent and then washed. For example, water-insoluble materials can be separated by pressure filtration at approximately 0.05 to 0.15 MPa. Water-insoluble materials can also be separated from the solvent by centrifugation, suction filtration, etc. Considering the ease of washing during manufacturing, it is preferable to use pressure filtration. In the method of the present invention, by defining the raw material concentration and stirring speed within a predetermined range and appropriately controlling the injection speed, water-insoluble materials do not completely agglomerate and can be easily separated.

[0025] The obtained water-insoluble material can be washed by adding pure water and performing pressure filtration. For example, 0.5 to 1.5 L of pure water at 50 to 70°C is added, and pressure filtration is performed at 0.05 to 0.15 MPa. This operation is repeated 3 to 7 times, preferably 4 to 6 times, to wash the water-insoluble material. Alternatively, the water-insoluble material may be washed with acetone or the like.

[0026] The water-insoluble material after washing can also be dissolved in an organic solvent to extract the PGA ion complex. Examples of organic solvents include alcohols, such as methanol, ethanol, propanol, n-propyl alcohol, isopropyl alcohol, butyl alcohol, and pentanol. Alcohols may be used individually or in combination of two or more. The organic solvent used may contain approximately 10% water. For example, 0.5 to 1.5 L of denatured ethanol is added to a water-insoluble material and stirred for 6 to 10 hours. The resulting solution is then collected to obtain the desired PGA ion complex. Any remaining unreacted PGA can be separated by ethanol precipitation and filtration.

[0027] If necessary, the water-insoluble material after washing may be dried by vacuum drying or freeze-drying. Because the separation from solvents and impurities is improved by the method of the present invention, PGA ion complex can be produced with a yield of 60% or more relative to the PGA used as a raw material. A yield of 70% or more is more preferable.

[0028] The shape of the PGA ion complex produced by the method of the present invention can be confirmed by scanning electron microscopy (SEM). The PGA ion complex produced by the method of the present invention consists of aggregated particles having a minimum unit that is plate-shaped with no corners. SEM observation confirms that the size of the minimum unit is approximately 0.1 mm × 0.2 mm, and the aggregate particle size is 10 mm or less.

[0029] Thus, in this invention, by setting the concentration of the PGA solution as the raw material liquid to 0.01-20%, stirring the cation solution to which the PGA solution is added at a rate of 50-1000 rpm, and adding the PGA solution to the cation solution at an appropriate injection rate, it became possible to mass-produce a PGA ion complex with an aggregate particle size controlled to 10 mm or less, with a yield of 60% or more.

[0030] The raw materials used in the production of the PGA ion complex in the method of the present invention are easily degradable and safe compounds, thus reducing the environmental burden. The PGA ion complex produced by the method of the present invention using these raw materials has excellent antibacterial and antiviral properties, and therefore acts effectively against bacteria, molds, and viruses. Specifically, it can delay and suppress the growth of influenza viruses, novel coronaviruses, Bacillus subtilis, Escherichia coli, Staphylococcus aureus, black mold, blue mold, dermatophytes, and Aspergillus niger.

[0031] The PGA ion complex produced by the method of the present invention can be fixed to the surface of a substrate by common methods such as spray coating to form a coating layer. The resulting coating layer itself acts as an antibacterial agent, eliminating the need for a binder. Moreover, the coating layer has sufficient water resistance, chemical resistance, and heat resistance, and can maintain its antibacterial effect for a long period of time. [Examples]

[0032] Examples are given below to specifically describe the present invention, but the scope of the present invention should not be construed as being limited to the specific examples shown below.

[0033] <Production of PGA ion complex> The PGA ion complex is produced by the method of the present invention. The synthesis apparatus used is as follows. · Air motor stirrer for pressurization AG-05-A M -YW · Stirrer for synthesis Three-one motor BL600 · Filtration test machine TSU-90A (heated to 60 °C with jacket) · Stainless steel mesh filter (1000 mesh, 15 μm, diameter 90 mm)

[0034] (Example 1) As raw material solutions, a 5% PGA solution and a 15% cation solution were prepared. The PGA solution was prepared by dissolving polyglutamine in water as a solvent, and the cation solution was prepared by dissolving hexadecylpyridinium chloride (HDP) in water as a solvent. While stirring 500 mL of the cation solution at 200 rpm, 450 mL of the PGA solution was added over 1 minute. The ratio of the number of moles of glutamic acid to the number of moles of the quaternary ammonium ion compound was calculated to be 1:1.1. The resulting mixture was stirred at 60 °C for 5 minutes to form a water-insoluble material containing the PGA ion complex. The water-insoluble material was filtered off and recovered by pressure filtration at 0.1 MPa.

[0035] 1 L of pure water at 60 °C was added to the obtained water-insoluble material, and pressure filtration was performed at 0.1 MPa. This operation was repeated 5 times to wash the water-insoluble material. After washing, 1 L of denatured ethanol (Daishin Chemical Co., Ltd., P-7) was added to the water-insoluble material, and after stirring for 8 hours, the denatured ethanol solution of the water-insoluble material was recovered.

[0036] The concentration of water-insoluble material in the recovered solution was 9.0% (based on evaporation-to-dry weight). The mass of the PGA ion complex (PGA / HDP) in Example 1 was 72 g, and the yield relative to the raw material (97.5 g) was 74%. Furthermore, the aggregate particle size of the PGA ion complex in Example 1 was confirmed to be 10 mm or less by visual inspection using a dot gauge conforming to JIS P8202. Figure 1 shows an SEM image of the PGA ion complex from Example 1. It was confirmed that rounded particles were obtained after washing. The smallest unit size in the aggregated particles was 0.1 mm × 0.2 mm.

[0037] (Example 2) The PGA ion complex of Example 2 was prepared using the same method as in Example 1, except that the concentration of the PGA solution was changed to 0.5% and the concentration of the cation solution was changed to 1.5%. In Example 2, the ratio of the number of moles of glutamic acid to the number of moles of the quaternary ammonium ion compound was calculated to be 1:1.1. The yield relative to the raw materials was 72%. In addition, the aggregate particle size of the PGA ion complex of Example 2 was 5 mm or less.

[0038] (Example 3) The PGA ion complex of Example 3 was prepared using the same method as in Example 1, except that the PGA solution was added to the cation solution over a period of 60 minutes. The yield relative to the raw materials was 75%. Furthermore, the aggregate particle size of the PGA ion complex of Example 3 was 5 mm or less.

[0039] In the method described in Patent Document 1, a PGA ion complex with aggregate particle size of 10 mm or more was obtained with a yield of approximately 50%. Patent Document 1 does not specify the raw material concentration in detail and does not include a stirring step. Therefore, it is presumed that the particle size of the PGA ion complex cannot be controlled, making washing and filtration difficult.

[0040] <Effect of stirring speed on aggregate particle size> Next, we investigated the effect of stirring speed on the aggregate particle size of the PGA ion complex. As described above, a 15% cation solution and a 5% PGA solution were prepared as raw material solutions. In a 100 mL beaker, the cation solution was stirred at a predetermined rate while 20 mL of PGA solution was added over 1 minute, and the mixture was stirred for another minute. The ratio of moles of glutamic acid to moles of quaternary ammonium ion compound was calculated to be 1:1. From there, the PGA ion complex was manufactured using the same method as described above.

[0041] Furthermore, PGA ion complexes were manufactured in the same manner, except that the reaction temperature was changed to 35°C. The aggregate particle size (mm) of the obtained PGA ion complex was determined by visual inspection using a dot gauge conforming to JIS P8202. The results are summarized in Table 1 below.

[0042] [Table 1]

[0043] As shown in Table 1 above, the aggregate particle size tends to decrease as the stirring speed increases. Here, the effect of stirring speed was investigated by stirring in a 100 mL beaker, but the stirring speed should be set according to the concentration and volume. When scaling up, it is possible to use larger impellers, so it is presumed that the desired effect can be obtained even with slower stirring speeds.

[0044] <Effects of concentration and volume of raw material solution (PGA solution) on aggregate particle size> The effects of PGA solution concentration and volume on the aggregate particle size of PGA ion complexes were investigated. Four different concentrations of PGA solution were prepared: 10%, 5%, 2.5%, and 1%. Each PGA solution was added to 10 mL of 15% cation solution in an equirequisite amount in 100 mL of water, and the mixture was stirred with a glass rod for 1 minute. Thereafter, the PGA ion complex was prepared using the same method as described above. The aggregated particle size (mm) of the obtained PGA ion complex was determined visually by comparing it with a dot gauge conforming to JIS P8202. The results are summarized in Table 2 below together with the PGA concentration and the liquid volume. Table 2 also shows the ratio of the number of moles of glutamic acid to the number of moles of the quaternary ammonium ion compound (glutamic acid: quaternary ammonium ion compound).

[0045]

Table 2

[0046] It was shown that reducing the concentration of the PGA solution makes the particle size of the obtained PGA ion complex finer. Specifically, when the concentration of the PGA solution is 2.5% or less, the aggregated particle size is 1 mm or less.

[0047] <Antibacterial performance of PGA ion complex> The antibacterial performance of the PGA ion complex of Example 1 was examined. As substrates, filter paper (No. 5C), non-woven fabric (TCP-30), and polyethersulfone resin (EO45) were prepared. The PGA ion complex was prepared as an antibacterial agent in a 0.2 wt% ethanol solution. After immersing the substrate in the antibacterial agent for 5 seconds, it was dried at 35 °C for coating. This was washed by passing a liquid through it with ultrapure water (25 mL / cm 2 ) and samples were prepared by punching out three locations near the center to a diameter of 13 mm.

[0048] For the antibacterial test, S. Marcescens (NBRC12648) was prepared as the bacterial species (pre-culture was in Bacto Brain Heart Infusion, 30 °C, 24 hours). The 200-fold diluted bacterial solution was spread on a Tryptic Soy Broth plate medium (diameter 90 mm) at 0.1 mL (about 1 - 3×10 8 CFU / mL) to prepare the test medium.

[0049] Each sample was attached to a test medium and cultured at 30 °C for 24 hours to examine the antibacterial performance. As a result, it was confirmed that the PGA ion complex produced by the method of the present invention has excellent antibacterial performance. For comparison, the antibacterial performance was examined in the same manner except that a commercially available product of a quaternary ammonium-based 0.1 to 0.2 wt% was used as the antibacterial solution. As a result, although some growth inhibition was observed, the antibacterial performance was inferior to that of the PGA ion complex.

[0050] <Antiviral performance of PGA ion complex> The PGA ion complex produced by the method of the present invention can enhance the antiviral properties in plastics such as PET films and textile products. Specific examples will be shown below to explain this.

[0051] The PGA ion complex of Example 1 was dissolved in ethanol to prepare a coating solution with a concentration of 10%. As the test virus, Severe acute respiratory syndrome coronaviurs 2 (SARS-CoV-2) (NIID isolate; JPN / TY / WK-521 (distributed by the National Institute of Infectious Diseases)) was prepared.

[0052] In order to confirm the antiviral properties on the surface of the PET film, test samples were prepared by the following method. First, two 100 mm × 100 mm PET films were prepared, and one of the surfaces was coated. Specifically, 2 mL of the coating solution was applied by a spin coater, air-dried, and then cut into 50 mm × 50 mm to obtain a test sample. The PET film without coating was used as a control sample.

[0053] The antiviral properties were evaluated in accordance with ISO 21702, and the infection value was evaluated by the plaque measurement method. The antiviral properties were evaluated by the value (decrease value) obtained by subtracting the virus infection value (common logarithm value) 24 hours after the action from the virus infection value (common logarithm value) immediately after inoculation. If the decrease value is 2 or more, it is considered that the virus has decreased to 1 / 100 or less, and it has an effect. While the control sample showed a reduction rate of 0.7, the test paper coated with PGA ion complex showed a reduction value of 3.1 or higher, confirming the antiviral effect on the surface of the PET film.

[0054] To investigate the antiviral properties of textile products, test samples were prepared using the following method. First, two sheets of 150 mm diameter filter paper (GA-100) were prepared, and one of them was coated. The coating solution was diluted with ethanol to a concentration of 1%. The filter paper was impregnated with this coating solution, air-dried, and then cut into 0.4 g pieces to be used as test samples. Filter paper that was not impregnated with the coating solution was used as a control sample.

[0055] Antiviral activity was evaluated in accordance with JIS L1922, and infection values ​​were assessed using the plaque assay method. When the reduction rate of viral infection values ​​(common logarithmic values) was determined in the same manner as described above, the control sample showed a reduction of 0.8, while the test samples impregnated with the PGA ion complex showed a reduction of 2.3 or higher. Antiviral effects were also confirmed in fibrous materials such as filter paper.

[0056] <Use in air filters> Using the PGA ion complex produced by the method of the present invention, an antibacterial coating was applied to glass filter paper, and the change in air permeability was investigated. Specifically, coating solutions were prepared by dissolving PGA ion complex in ethanol at various concentrations. Glass filter paper (GC-50, 5 × 5 cm) was immersed in this solution for 5 seconds, and the sample was dried at 35°C. The air permeability (seconds / 300 mL) of the obtained sample was measured using a Garre densometer (1 cm diameter). The results are shown in Table 3 below.

[0057] [Table 3]

[0058] In glass filter paper treated with an antibacterial coating, there is no change in air permeability when the coating weight is 0.1 wt%. Even with a coating weight of 0.7 wt%, the increase in air permeability is only about 11%. Therefore, the PGA ion complex produced by the method of the present invention may be effectively used as a coating agent for applying antibacterial coatings to air filters and the like. The PGA ion complex produced by the method of the present invention is a resin itself. Therefore, it is presumed that the PGA ion complex also functions as a binder for fibers.

[0059] The method of the present invention makes it possible to mass-produce PGA ion complex with appropriate particle size, which can be effectively used in various fields such as public health, medical applications, and food preservation.

Claims

1. A step of preparing a PGA solution containing 0.01 to 20% poly-γ-glutamic acid, A step of preparing a cationic solution containing 0.01 to 20% of a quaternary ammonium ion compound, The process involves adding the PGA solution to the cation solution while stirring it at 50 to 1000 rpm using a stirrer equipped with a stirring blade, thereby allowing the water-insoluble material containing the PGA ion complex to settle at the bottom of the liquid. A step of separating the water-insoluble material, A step of washing the separated water-insoluble material, and Process for extracting PGA ion complex from water-insoluble material after washing. A method for producing a PGA ion complex, characterized by comprising the following:

2. A method for producing a PGA ion complex according to claim 1, characterized in that the addition time when adding the PGA solution while stirring the cation solution is 1 minute or more.

3. A method for producing a PGA ion complex according to claim 1 or 2, wherein the PGA solution is added to the cation solution in a ratio such that the number of moles of the quaternary ammonium ion compound is 0.8 to 1.2 times the number of moles of glutamic acid constituting the poly-γ-glutamic acid.

4. A method for producing a PGA ion complex according to claim 3, wherein the PGA solution is added to the cation solution in a ratio such that the ratio of the number of moles of glutamic acid constituting the poly-γ-glutamic acid to the number of moles of the quaternary ammonium ion compound is 1:

1.

5. The method for producing a PGA ion complex according to claim 3 or 4, wherein the volume of the PGA solution is 0.8 to 1000 times the volume of the cation solution.

6. The method for producing a PGA ion complex according to any one of claims 1 to 5, wherein the stirring is performed at 30 to 80°C.

7. A method for producing a PGA ion complex according to any one of claims 1 to 6, wherein the separation of the water-insoluble material is performed by pressure filtration, centrifugal separation, or suction filtration.

8. A method for producing a PGA ion complex according to any one of claims 1 to 7, wherein the washing of the water-insoluble material is performed by pressurized filtration using pure water.

9. The method for producing a PGA ion complex according to any one of claims 1 to 8, wherein the extraction is performed using an organic solvent.

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