A method for stabilizing high internal phase water-in-oil emulsions by ionically cross-linking a phenylalanine-aspartic acid copolymer with polylysine

Abstract

The application discloses a method for preparing phenylalanine-aspartic acid copolymer / polylysine ion cross-linking stable high internal phase water-in-oil emulsion, and belongs to the field of peptide surfactants and surface physical chemistry. The preparation of the high internal phase water-in-oil emulsion is as follows: a phenylalanine-aspartic acid copolymer / polylysine aqueous solution is used as a water phase, mixed with an oil phase to obtain a mixed system, wherein the volume ratio of the oil phase to the water phase is 7-9:1-3; then the mixed system is homogenized, and after homogenization, the mixed system is heated at 60-90 DEG C for 2-6 hours, and then naturally cooled to obtain the phenylalanine-aspartic acid copolymer / polylysine ion cross-linking stable high internal phase water-in-oil emulsion; the high internal phase water-in-oil emulsion has good stability and can be stable for 6-24 months within the pH range of 1-11.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for stabilizing high internal phase water-in-oil emulsion by ionically cross-linking phenylalanine-aspartic acid copolymer and polylysine, belonging to the field of peptide surfactant and surface physical chemistry. BACKGROUND

[0002] High internal phase emulsion (HIPE) generally refers to an emulsion with a volume fraction of the internal phase greater than 74%. Due to the high volume of the non-continuous phase of the high internal phase emulsion, the internal droplet size of the emulsion is not uniform or deformed. Certain particle-stabilized Pickering high internal phase emulsions will undergo phase inversion as the volume of the internal phase increases, while surfactant molecule-stabilized high internal phase emulsions will continue to stabilize the emulsion or demulsify as the volume of the internal phase increases. Due to the low proportion of the continuous phase, high internal phase emulsions often have high viscosity, and are therefore also called gel emulsions.

[0003] The emulsifiers used to prepare high internal phase emulsions in the prior art include synthetic polymers or inorganic particles, but their application in the cosmetics, pharmaceutical and food industries is limited due to their biological toxicity. Therefore, the development of environmentally friendly biocompatible particles as effective stabilizers has received special attention in recent years. Protein and polysaccharide derivatives in nature can be used as emulsifiers for high internal phase emulsions, and protein particles generally stabilize oil-in-water (O / W) high internal phase emulsions. High internal phase emulsions have a larger non-continuous phase surface area than ordinary emulsions of the same volume, and this characteristic of high internal phase emulsions can be used to prepare porous materials, organic semiconductors, filtration membranes, tissue engineering scaffolds, food and drug delivery systems using high internal phase emulsions as templates.

[0004] Zou Yanan (Food Science and Technology, 2022, 47(7): 129-133.) studied the effect of mung bean protein peptides with different degrees of hydrolysis on the stability of oil-in-water emulsions at pH 7.0 for 10 minutes. The results showed that with the increase of the degree of hydrolysis, the emulsification activity, emulsion stability, Zeta potential and surface hydrophobicity of the emulsion showed a trend of first increasing and then decreasing. Wang Dan et al. (China Oil and Fat, 2024(003):049.) studied the stability of soybean peptide Pickering emulsion. Soybean peptide aggregates were used as raw materials to prepare SPN by ultrasonic method. SPI was introduced into the SPN system to construct a composite emulsifier. The effect of SPI on the interfacial activity of SPN and the emulsion stability under neutral pH conditions for 15 days was studied. Chinese patent CN202111548661.4 discloses that walnut meal is used as raw material, after defatting, alkali extraction and acid precipitation, trypsin limited enzyme hydrolysis is used, and finally walnut polypeptide is obtained by ultrafiltration separation and dextran gel G25 gel chromatography purification. The emulsification properties under neutral conditions were investigated. CN201811525882.8 discloses a chitosan casein phosphopeptide composite nanoparticle stabilized Pickering high internal phase emulsion and its preparation. The emulsion stability is more than six months at pH 4-6. However, the emulsion of the peptides reported in the prior art is usually short in stable period, or the emulsion has weak pH change resistance, and can only maintain the emulsion in a limited pH range. In addition, the preparation of peptides from protease hydrolysis requires strict control of reaction conditions to ensure that the composition of each batch of products is approximately the same. SUMMARY

[0005] [TECHNICAL PROBLEM]

[0006] The stabilizers for stabilizing the Pickering high internal phase emulsion in the prior art often have complex preparation process and unclear composition. Although they can maintain the stability of the Pickering emulsion to some extent, the stable period is short or the emulsion has weak pH change resistance, and can only maintain the emulsion in a limited pH range. In view of the defects and deficiencies of the prior art, the present application provides a method for stabilizing high internal phase oil-in-water emulsion by ion cross-linking of phenylalanine-aspartic acid copolymer and polylysine. The method forms ion cross-linking (as shown below Figure 1 ) by cross-linking the aspartic acid beta carboxyl group of phenylalanine-aspartic acid copolymer and the amino group of polylysine, stabilizes the oil-water interface, and prepares high internal phase oil-in-water emulsion stable for 6-24 months at pH=1-11.

[0007] [TECHNICAL SCHEME]

[0008] In order to achieve the above purpose, the following technical scheme is adopted:

[0009] A method for stabilizing high internal phase water-in-oil emulsion by ion cross-linking of phenylalanine-aspartic acid copolymer and polylysine, the method comprising the following steps:

[0010] (1) preparing an aqueous solution of phenylalanine-aspartic acid copolymer and polylysine as the water phase;

[0011] (2) mixing the oil phase and the water phase of step (1) to obtain a mixed system, wherein the volume ratio of the oil phase to the water phase is 7-9:1-3; then homogenizing the mixed system, and after homogenization, heating at 60-90 ℃ for 2-6 hours, and after natural cooling, obtaining the high internal phase water-in-oil emulsion stabilized by ion cross-linking of phenylalanine-aspartic acid copolymer and polylysine.

[0012] In an embodiment, the concentration of phenylalanine-aspartic acid copolymer in the water phase of step (1) is 0.5-6 g / L, and the concentration of lysine is 0.075-1 g / L.

[0013] In an embodiment, the pH value of the water phase of step (1) is 1-11.

[0014] In an embodiment, the molecular weight of the polylysine of step (1) is 30000 Da-300000 Da; preferably 30000 Da-70000 Da or 70000 Da-150000 Da or 150000 Da-300000 Da.

[0015] In an embodiment, the preparation process of phenylalanine-aspartic acid copolymer of step (1) is as follows: adding L-phenylalanine methyl ester hydrochloride and L-aspartic acid dimethyl ester hydrochloride into a sodium phosphate dibasic-citric acid buffer, adding a protease, stirring at 25-55 ℃ for 3-6 h, after the reaction is completed, centrifuging the reaction solution, washing the precipitate with 3-5 times the volume of deionized water and anhydrous ethanol three times, centrifuging and then freeze-drying to obtain a random copolymer; placing the obtained random copolymer into dichloromethane / methanol, adding NaOH, stirring at 25-65 ℃ for 0.5-2 h, after the reaction is completed, reducing pressure and rotary evaporation of the reaction compound to obtain the phenylalanine-aspartic acid copolymer.

[0016] In an embodiment, the mass-volume ratio of L-phenylalanine methyl ester hydrochloride and L-aspartic acid dimethyl ester hydrochloride to the sodium phosphate dibasic-citric acid buffer is 4.3-6.5:7.9-23.7:60-150; g:g:mL.

[0017] In an embodiment, the concentration of the sodium phosphate dibasic-citric acid buffer is 0.2-0.5 mol / L, and the pH is 6.5-9.0.

[0018] In an embodiment, the protease is any one of bromelain, papain, neutral protease, alkaline protease.

[0019] In an embodiment, the mass ratio of the protease, L-phenylalanine methyl ester hydrochloride and L-aspartic acid dimethyl ester hydrochloride is 0.5-2.5:4.3-6.5:7.9-23.7.

[0020] In an embodiment, the centrifugal condition is 5000-8000 rpm for 5-10 min.

[0021] In an embodiment, the volume ratio of the methane / methanol is 6:1-9:1.

[0022] In an embodiment, the mass ratio of the NaOH, L-phenylalanine methyl ester hydrochloride and L-aspartic acid dimethyl ester hydrochloride is 0.8-6:4.3-6.5:7.9-23.7.

[0023] In an embodiment, the oil phase in step (2) is any one of n-octane, squalane, camellia oil, coconut oil, soybean oil.

[0024] In an embodiment, the oil / water volume ratio in step (2) is 7.4:2.6 or 8:1 or 9:1.

[0025] In an embodiment, the homogenization condition in step (3) is 10000-15000 rpm for 2-5 min.

[0026] The application also provides a phenylalanine-aspartic acid copolymer and polylysine ionically cross-linked stable high internal phase water-in-oil emulsion prepared by the above method.

[0027] The application also provides the use of the phenylalanine-aspartic acid copolymer and polylysine ionically cross-linked stable high internal phase water-in-oil emulsion in cosmetics and pharmaceuticals.

[0028] Beneficial effects:

[0029] The application adopts the cross-linking of the centrifugal pairing of the aspartic acid β carboxyl of the phenylalanine-aspartic acid copolymer and the amino group of the polylysine to stabilize the oil-water interface and form a stable high internal water-in-oil emulsion. The phenylalanine-aspartic acid copolymer is synthesized by an enzyme catalysis method, which is simple in process and easy to obtain raw materials. The phenylalanine-aspartic acid copolymer and polylysine stable high internal phase water-in-oil emulsion prepared has high stability and can be stable for 6-24 months within the pH=1-11 range. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1Schematic diagram of ion cross-linking between the beta carboxyl group of aspartic acid and the amino group of polylysine in the present application;

[0031] Figure 2 Stability figure of high internal phase water-in-oil emulsion stabilized by ion cross-linking between phenylalanine-aspartic acid copolymer prepared in Example 1 and polylysine; wherein the number on the bottle cap represents the pH value;

[0032] Figure 3 Stability figure of high internal phase water-in-oil emulsion stabilized by ion cross-linking between phenylalanine-aspartic acid copolymer prepared in Example 2 and polylysine; wherein the number on the bottle cap represents the pH value;

[0033] Figure 4 Stability figure of high internal phase water-in-oil emulsion stabilized by ion cross-linking between phenylalanine-aspartic acid copolymer prepared in Example 3 and polylysine; wherein the number on the bottle cap represents the pH value;

[0034] Figure 5 Stability figure of high internal phase water-in-oil emulsion stabilized by alanine-aspartic acid copolymer prepared in Comparative Example 1; wherein the number on the bottle cap represents the pH value.

[0035] Figure 6 Stability figure of high internal phase water-in-oil emulsion stabilized by alanine-aspartic acid copolymer prepared in Comparative Example 2; wherein the number on the bottle cap represents the pH value. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application. The following specific embodiments further describe the present application.

[0037] The raw materials involved in the present application are as follows:

[0038] Papain with an enzyme activity of 300 U / mg was purchased from Shanghai Titan Science and Technology Co., Ltd., product model 013632032.

[0039] Papain with an enzyme activity of 800000 U / g was purchased from Shanghai Titan Science and Technology Co., Ltd., product model 011344050.

[0040] Alkaline protease with an enzyme activity of 200 U / mg was purchased from Beijing Boao Sun Biotechnology Co., Ltd., product model D13102.

[0041] Example 1

[0042] The method for catalyzing synthesis of phenylalanine-aspartic acid copolymer by protease specifically includes the following steps:

[0043] (1) 4.3 g of L-phenylalanine methyl ester hydrochloride and 7.9 g of L-aspartic acid dimethyl ester hydrochloride were added into 60 mL of sodium phosphate dibasic-citric acid buffer (0.2 mol / L, pH=6.5), 0.5 g of bromelain was added, and the reaction was stirred (1000 rpm) at 25°C for 3 h. After the reaction was completed, the reaction mixture was centrifuged (6 min, 8000 rpm), the precipitate was washed with 3 times the volume of deionized water and anhydrous ethanol, centrifuged (6 min, 8000 rpm), and then freeze-dried to obtain a random copolymer;

[0044] (2) The obtained random copolymer was placed in 40 ml of dichloromethane / methanol (volume ratio of 6:1), 0.8 g of NaOH was added, and the reaction was stirred (1000 rpm) at 25°C for 0.5 h. After the reaction was completed, the reaction product was rotary evaporated under reduced pressure to obtain a phenylalanine-aspartic acid copolymer.

[0045] A method for ionically cross-linking a phenylalanine-aspartic acid copolymer with polylysine to stabilize a high internal phase water-in-oil emulsion, specifically including the following steps:

[0046] (1) A water solution (aqueous phase) of a phenylalanine-aspartic acid copolymer and polylysine was prepared in a 10 mL column-shaped sample bottle. The concentration of the phenylalanine-aspartic acid copolymer in the water solution was 0.5 g / L, and the concentration of the polylysine (molecular weight range: 30000~70000 Da, Beijing Baileijibioscience Technology Co., Ltd.) was 0.075 g / L. The pH of the water solution was adjusted to 1~11 using 0.1 mol / L of HCl or 0.1 mol / L of NaOH aqueous solution;

[0047] (2) The n-octane was mixed with the water phase of step (1) to obtain a mixed system, with the total volume of the oil and water phases being 7 mL and the volume ratio of the oil and water phases being 7.4:2.6. The mixed system was mechanically emulsified on an ULTRA-TURRAX T18 basic homogenizer (Germany IKA) at a rotation speed of 10000 rpm for 2 min. The homogenized mixed system was heated at 60°C for 2 h, and then naturally cooled to obtain a high internal phase water-in-oil emulsion of a phenylalanine-aspartic acid copolymer and polylysine ionically cross-linked.

[0048] The high internal phase water-in-oil emulsion prepared in this example was stable for 6 months within the pH=1~11 range of the water phase, as shown in Figure 2 .

[0049] Example 2

[0050] The method for catalyzing synthesis of phenylalanine-aspartic acid copolymer by protease specifically comprises the following steps:

[0051] (1) 6.5 g of L-phenylalanine methyl ester hydrochloride and 23.7 g of L-aspartic acid dimethyl ester hydrochloride were added into 150 mL of sodium phosphate dibasic-citric acid buffer (0.5 mol / L, pH=9.0), 2.5 g of papain was added, and the mixture was stirred (1000 rpm) at 55°C for 6 h. After the reaction, the reaction mixture was centrifuged (6 min, 8000 rpm), the precipitate was washed with 5 times the volume of deionized water and anhydrous ethanol for three times, centrifuged (6 min, 8000 rpm) and freeze-dried to obtain a random copolymer;

[0052] (2) The obtained random copolymer was placed into 100 ml of dichloromethane / methanol (volume ratio of 9:1), 6 g of NaOH was added, and the mixture was stirred (1000 rpm) at 65°C for 0.5 h. After the reaction, the reaction product was rotary evaporated under reduced pressure to obtain a phenylalanine-aspartic acid copolymer.

[0053] A method for stabilizing high internal phase water-in-oil emulsion by ion cross-linking of phenylalanine-aspartic acid copolymer and polylysine, specifically comprising the following steps:

[0054] (1) An aqueous solution (water phase) of phenylalanine-aspartic acid copolymer and polylysine was prepared in a 10 mL column-shaped sample bottle, the concentration of phenylalanine-aspartic acid copolymer in the aqueous solution was 6 g / L, and the concentration of polylysine (molecular weight range: 150000~300000 Da, Beijing Baishuiji Life Science and Technology Co., Ltd.) was 1 g / L. The pH of the aqueous phase was adjusted to 1~11 with 0.1 mol / L of HCl or 0.1 mol / L of NaOH aqueous solution;

[0055] (2) The squalane was removed and mixed with the aqueous phase of step (1) to obtain a mixed system with a total volume of 7 mL and an oil / water volume ratio of 9:1. The mixed system was mechanically emulsified on an ULTRA-TURRAX T18 basic homogenizer (Germany IKA) at a speed of 15000 rpm for 5 min. The homogenized mixture was heated at 90°C for 2 h, and then naturally cooled to obtain a high internal phase water-in-oil emulsion stabilized by ion cross-linking of phenylalanine-aspartic acid copolymer and polylysine.

[0056] The high internal phase water-in-oil emulsion prepared in this example was stable for 24 months within the pH range of 1~11 of the aqueous phase, as shown in Figure 3 .

[0057] Example 3

[0058] The method for catalyzing synthesis of phenylalanine-aspartic acid copolymer by protease specifically comprises the following steps:

[0059] (1) 5 g of L-phenylalanine methyl ester hydrochloride and 15 g of L-aspartic acid dimethyl ester hydrochloride are added into 100 mL of sodium phosphate-citric acid buffer (0.3 mol / L, pH=8.0), 1 g of alkaline protease is added, and the reaction is stirred (1000 rpm) at 35°C for 4 h. After the reaction is completed, the reaction mixture is centrifuged (6 min, 8000 rpm), the precipitate is washed with 4 times the volume of deionized water and anhydrous ethanol for three times, centrifuged (6 min, 8000 rpm) and freeze-dried to obtain a random copolymer;

[0060] (2) The obtained random copolymer is placed into 80 mL of dichloromethane / methanol (volume ratio of 8:1), 5 g of NaOH is added, and the reaction is stirred (1000 rpm) at 35°C for 2 h. After the reaction is completed, the reaction product is rotary evaporated under reduced pressure to obtain a phenylalanine-aspartic acid copolymer.

[0061] A method for stabilizing a high internal phase water-in-oil emulsion by ion cross-linking of a phenylalanine-aspartic acid copolymer and polylysine, comprising the following steps:

[0062] (1) A water solution (aqueous phase) of the phenylalanine-aspartic acid copolymer and polylysine is prepared in a 10 mL column-shaped sample bottle. The concentration of the phenylalanine-aspartic acid copolymer in the water solution is 3 g / L, the concentration of the polylysine (molecular weight range: 70000-150000 Da, Beijing Baishuiji Life Science and Technology Co., Ltd.) is 0.8 g / L, and the pH of the aqueous phase is adjusted to 1-11 by using 0.1 mol / L of HCl or 0.1 mol / L of NaOH aqueous solution;

[0063] (2) Coconut oil is mixed with the aqueous phase of step (1) to obtain a mixed system, with the total volume of the oil and water phases being 7 mL and the volume ratio of the oil and water phases being 8:1. The mixed system is mechanically emulsified on an ULTRA-TURRAX T18 basic homogenizer (Germany IKA) at a rotation speed of 12000 rpm for 3 min. The homogenized mixed system is heated at 70°C for 4 h, and a high internal phase water-in-oil emulsion stabilized by ion cross-linking of the phenylalanine-aspartic acid copolymer and the polylysine is obtained after natural cooling.

[0064] The high internal phase water-in-oil emulsion prepared in this example is stable for 12 months within the pH range of 1-11 of the aqueous phase, as shown in Figure 4 .

[0065] Comparative Example 1

[0066] A method for preparing a high internal phase emulsion stabilized by phenylalanine-aspartic acid copolymer, comprising the following steps:

[0067] (1) 4.3 g of L-phenylalanine methyl ester hydrochloride and 7.9 g of L-aspartic acid dimethyl ester hydrochloride were added to 60 mL of a sodium phosphate dibasic-citric acid buffer (0.2 mol / L, pH = 6.5), 0.5 g of bromelain was added, and the mixture was stirred (1000 rpm) at 25 °C for 3 h. After the reaction was completed, the reaction mixture was centrifuged (6 min, 8000 rpm), the precipitate was washed with 3 times the volume of deionized water and anhydrous ethanol, and then centrifuged (6 min, 8000 rpm) and freeze-dried to obtain a random copolymer;

[0068] (2) The obtained random copolymer was placed in 40 mL of dichloromethane / methanol (volume ratio 6:1), 0.8 g of NaOH was added, and the mixture was stirred (1000 rpm) at 25 °C for 0.5 h. After the reaction was completed, the reaction product was rotary evaporated under reduced pressure to obtain a phenylalanine-aspartic acid copolymer;

[0069] (3) A water solution (aqueous phase) of the phenylalanine-aspartic acid copolymer was prepared in a 10 mL column-shaped sample bottle. The concentration of the phenylalanine-aspartic acid copolymer in the water solution was 0.5 g / L, and the pH of the water solution was adjusted to 1-11 using 0.1 mol / L HCl or 0.1 mol / L NaOH aqueous solution;

[0070] (4) The n-octane was mixed with the water phase prepared in step (1) to obtain a mixed system, and the total volume of the oil and water phases was 7 mL, and the volume ratio of the oil and water phases was 7.4:2.6. The mixed system was mechanically emulsified on an ULTRA-TURRAX T18 basic homogenizer (Germany IKA) at a rotation speed of 10000 rpm for 2 min to obtain a high internal phase emulsion stabilized by the phenylalanine-aspartic acid copolymer.

[0071] The high internal phase emulsion prepared in this comparative example was separated after 15 days at a pH of 1-11 in the aqueous phase, and the emulsion had obvious instability, as shown in Figure 5 .

[0072] Comparative Example 2

[0073] A method for preparing a high internal phase emulsion stabilized by phenylalanine-aspartic acid copolymer, comprising the following steps:

[0074] (1) In 150 mL of Na2HPO4-citric acid buffer (0.5 mol / L, pH=9.0), 6.5 g of L-phenylalanine methyl ester hydrochloride and 23.7 g of L-aspartic acid dimethyl ester hydrochloride were added, 2.5 g of papain was added, and the reaction was stirred (1000 rpm) at 55 ℃ for 6 h. After the reaction was completed, the reaction mixture was centrifuged (6 min, 8000 rpm), the precipitate was washed with 5 times the volume of deionized water and anhydrous ethanol three times, centrifuged (6 min, 8000 rpm) and freeze-dried to obtain a random copolymer;

[0075] (2) The obtained random copolymer was placed in 100 ml of dichloromethane / methanol (volume ratio 9:1), 6 g of NaOH was added, and the reaction was stirred (1000 rpm) at 65 ℃ for 0.5 h. After the reaction was completed, the reaction product was rotary evaporated under reduced pressure to obtain a phenylalanine-aspartic acid copolymer.

[0076] (3) A water solution (aqueous phase) of the phenylalanine-aspartic acid copolymer was prepared in a 10 mL columnar sample bottle, and the concentration of the phenylalanine-aspartic acid copolymer in the water solution was 6 g / L. The pH of the aqueous phase was adjusted to 1-11 with 0.1 mol / L of HCl or 0.1 mol / L of NaOH aqueous solution.

[0077] (4) The squalane was mixed with the aqueous phase of step (1) to obtain a mixed system with a total volume of 7 mL and an oil-water volume ratio of 9:1. The mixed system was mechanically emulsified on an ULTRA-TURRAX T18 basic homogenizer (Germany IKA) at a speed of 15000 rpm for 5 min to obtain a high internal phase water-in-oil emulsion stabilized by the phenylalanine-aspartic acid copolymer.

[0078] The high internal phase water-in-oil emulsion prepared in the present comparative example showed separation after 15 days at a pH of 1-11 in the aqueous phase, and the emulsion had obvious instability, as shown in Figure 6 .

[0079] The examples provided above are not intended to limit the scope covered by the present application, and the described steps are not intended to limit the execution order. Those skilled in the art can make obvious improvements to the present application in combination with existing common knowledge, which also falls within the protection scope defined by the claims of the present application.

Claims

1. A method for the stabilization of high internal phase water-in-oil emulsions by ionically crosslinking phenylalanine-aspartic acid copolymers with polylysine, characterized in that, The method comprises the following steps: (1) preparing a water solution of phenylalanine-aspartic acid copolymer and polylysine as the water phase; the concentration of phenylalanine-aspartic acid copolymer in the water phase is 0.5-6 g / L, and the concentration of polylysine is 0.075-1 g / L; (2) mixing the oil phase and the water phase of step (1) to obtain a mixed system, wherein the volume ratio of the oil phase to the water phase is 7-9:1-3; then homogenizing the mixed system, heating the homogenized system at 60-90 ℃ for 2-6 hours, and naturally cooling to obtain a high internal phase water-in-oil emulsion of phenylalanine-aspartic acid copolymer and polylysine ionically crosslinked and stabilized.

2. The method of claim 1, wherein, The pH value of the water phase of step (1) is 1-12.

3. The method of claim 1, wherein, The molecular weight of the polylysine of step (1) is 30000 Da-300000 Da.

4. The method of claim 1, wherein, The preparation process of the phenylalanine-aspartic acid copolymer of step (1) is as follows: adding L-phenylalanine methyl ester hydrochloride and L-aspartic acid dimethyl ester hydrochloride into a sodium phosphate dibasic-citric acid buffer, adding a protease, stirring at 25-55 ℃ for 3-6 hours, centrifuging the reaction solution after the reaction, washing the precipitate with 3-5 times the volume of deionized water and anhydrous ethanol for 3 times, centrifuging and freeze-drying to obtain a random copolymer; placing the obtained random copolymer into dichloromethane / methanol, adding NaOH, stirring at 25-65 ℃ for 0.5-2 hours, and obtaining the phenylalanine-aspartic acid copolymer by rotary evaporation under reduced pressure after the reaction.

5. The method of claim 4, wherein, The mass-volume ratio of L-phenylalanine methyl ester hydrochloride and L-aspartic acid dimethyl ester hydrochloride to the sodium phosphate dibasic-citric acid buffer is 4.3-6.5:7.9-23.7:60-150; g:g:mL.

6. The method of claim 4, wherein, The protease is any one of neutral protease and alkaline protease.

7. The method of claim 4, wherein, The protease is any one of bromelain and papain.

8. The method of claim 1, wherein, The oil phase of step (2) is any one of n-octane, squalane, camellia oil, coconut oil, and soybean oil.

9. The high internal phase water-in-oil emulsion obtained by the method of any one of claims 1-8.

10. The high internal phase water-in-oil emulsion of claim 9 for use in cosmetics and pharmaceuticals.

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