Method for extracting and converting protein into polypeptide by using green solvent, extracted polypeptide and application

Abstract

The invention relates to the field of biochemistry and food engineering, in particular to a method for extracting protein from a green solvent and converting the protein into polypeptide, the extracted polypeptide and application of the extracted polypeptide, and the method comprises a protein raw material pretreatment process, a protein-to-polypeptide extraction and conversion process and a polypeptide purification process. A green solvent used in the extraction and conversion process from the protein to the polypeptide is a deep-eutectic solvent; according to the method, the green and environment-friendly deep-eutectic solvent is utilized, the protein is synchronously converted into the polypeptide in the protein extraction process, and one-pot conversion is realized, so that the subsequent degradation and purification steps are remarkably simplified, the overall process efficiency is greatly improved, and resource waste and environmental burden are reduced.

Description

Technical Field

[0001] The present invention relates to the fields of biochemistry and food engineering, and in particular to a method for extracting and converting proteins into polypeptides using a green solvent, the extracted polypeptides and their applications. Background Art

[0002] As an important bioactive substance, peptides are widely used in many fields such as food, medicine, and cosmetics. However, the commonly used peptide extraction methods currently rely mainly on enzymatic hydrolysis or acid-base hydrolysis technology. These methods are often accompanied by problems such as high energy consumption, serious environmental pollution, and high costs, which limit their further promotion and application. In addition, traditional peptide purification technology is complex and difficult to achieve in a one-pot process. It generally has shortcomings such as low efficiency, complex operation, and poor protein stability, which further increase the difficulty of the process and production costs. Summary of the Invention

[0003] In order to solve the above problems, the present invention provides a method for extracting and converting proteins into polypeptides using green solvents, the extracted polypeptides and their applications, which simultaneously realize the conversion of proteins into polypeptides during the protein extraction process, thereby significantly simplifying the subsequent degradation and purification steps, which not only greatly improves the overall process efficiency, but also reduces resource waste and environmental burden.

[0004] A method for extracting and converting proteins into polypeptides using a green solvent includes a pretreatment process of the protein raw material, an extraction and conversion process of the protein into polypeptides, and a purification process of the polypeptides; the green solvent used in the protein-to-polypeptide extraction and conversion process is a low eutectic solvent.

[0005] Furthermore, the solid-to-liquid ratio of the pretreated protein raw material and the deep eutectic solvent during the protein-to-peptide extraction and conversion process is 1:5-1:100, preferably 1:5-1:20, and more preferably 1:10.

[0006] Furthermore, the low eutectic solvent includes a hydrogen bond acceptor and a hydrogen bond donor, the hydrogen bond acceptor is choline chloride or betaine; the hydrogen bond donor includes one of lactic acid, urea, malic acid, triethanolamine, ethylene glycol, glycerol, propylene glycol, butylene glycol, hexylene glycol, levulinic acid, xylitol or tartaric acid.

[0007] Further, the deep eutectic solvent includes any one of choline chloride / lactic acid, choline chloride / urea, choline chloride / malic acid, choline chloride / triethanolamine, choline chloride / ethylene glycol, choline chloride / glycerol, choline chloride / propylene glycol, choline chloride / butylene glycol, choline chloride / hexanediol, choline chloride / levulinic acid, choline chloride / xylitol, choline chloride / tartaric acid, betaine / lactic acid, betaine / urea, betaine / malic acid, betaine / triethanolamine, betaine / ethylene glycol, betaine / glycerol, betaine / propylene glycol, betaine / butylene glycol, betaine / hexanediol, betaine / levulinic acid, betaine / xylitol and betaine / tartaric acid.

[0008] Furthermore, the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:1 to 1:10, preferably 1:1 to 1:5, and more preferably 1:2.

[0009] Furthermore, the pretreatment process of the protein raw material is a process of grinding the protein raw material to pass through a 20-200 mesh sieve, washing and drying to obtain the protein raw material powder; wherein the grinding method includes mechanical crushing or ball milling, and the drying time is 12-48 hours.

[0010] Furthermore, the protein raw material includes any one of soybeans, fish, fish skin, corn kernels and milk.

[0011] Furthermore, the extraction and conversion process of the protein into the polypeptide includes any one of stirring extraction, ultrasonic extraction, microwave extraction or high-pressure extraction.

[0012] Furthermore, the stirring rate of the stirring extraction is 50~200r / min, preferably 50~100r / min; the extraction temperature is 20~90℃, preferably 20~60℃, more preferably 55℃; the stirring time is 1~8h, preferably 1~5h, more preferably 2h.

[0013] Furthermore, the extraction temperature of the ultrasonic extraction is 20-80°C, preferably 20-60°C; the ultrasonic power is 100-5000 W, preferably 100-3000 W; and the extraction time is 0.5-10 h, preferably 1-3 h.

[0014] Furthermore, the microwave frequency of the microwave extraction is 1000-3000 MHz, preferably 1000-2000 MHz; the microwave power is 500-1000 W, preferably 500-800 W; and the extraction time is 5-30 min, preferably 5-20 min.

[0015] Furthermore, the temperature of the high-pressure extraction is 25-80° C., preferably 25-60° C.; the pressure is 50-200 MPa, preferably 50-100 MPa; and the time is 5-60 min, preferably 5-30 min.

[0016] Furthermore, the purification process of the polypeptide includes dialysis to remove impurities, and the molecular weight cut-off range is 500 Da to 10,000 Da.

[0017] Furthermore, the dialysis and impurity removal treatment uses a dialysis bag.

[0018] Furthermore, the impurity removal treatment can also be performed by membrane filtration using an ultrafiltration membrane, and the molecular weight cut-off of the ultrafiltration membrane is 1000~3000Da.

[0019] Furthermore, the polypeptide purification process further includes a drying treatment, and the drying treatment includes any one of freeze drying, vacuum drying, oven drying, supercritical drying, and spray drying.

[0020] Furthermore, the freeze drying uses a freeze drying box with a drying temperature of -10 to -30°C, a drying time of 36 to 48 hours, and a vacuum degree of -0.06 MPa.

[0021] Furthermore, the vacuum drying is carried out in a vacuum drying oven at a drying temperature of 30-90°C.

[0022] The time is 48~96h, and the vacuum degree is -0.08MPa.

[0023] Furthermore, the oven drying uses a normal pressure drying oven, the drying temperature is 30-90° C., and the drying time is 48-96 hours.

[0024] Furthermore, the supercritical drying is carried out by placing the wet sample in a supercritical fluid at a temperature of 40~100°C, a pressure of 100~400 bar, a collector temperature of -50~0°C, a CO2 flow rate of 1~5 L / min, and a drying time of 1~6 hours.

[0025] Furthermore, the inlet air temperature of the spray drying is 120~200℃, the outlet air temperature is 60~90℃, the feed flow rate is 10 ml / min~50 ml / min, the atomizing air pressure is 1.5 bar~3 bar, and the drying air flow rate is 300 m³ / h~600 m³ / h.

[0026] On the other hand, the present invention also provides a polypeptide obtained by extraction and transformation using the above method.

[0027] On the other hand, the present invention also provides the use of the polypeptide extracted and converted using the above method in biomedicine, cosmetics or food.

[0028] Compared with the prior art, the advantages of the present invention are:

[0029] The present invention provides a method for extracting and converting proteins into polypeptides. By utilizing a green and environmentally friendly low eutectic solvent, the conversion of proteins into polypeptides is simultaneously achieved during the protein extraction process, realizing a one-pot conversion, thereby significantly simplifying subsequent degradation and purification steps. This not only greatly improves the overall process efficiency, but also reduces resource waste and environmental burden. The obtained protein has a molecular weight of 500-10,000 Da, which is within the molecular weight range of polypeptides. Compared with the prior art, the preparation method of the present invention is novel, has fewer steps, is simple and quick, and significantly improves the extraction rate of polypeptides obtained by extraction and conversion using this method, which is superior to the extraction rate of traditional alkali extraction and acid precipitation. The method has important significance for product development in other fields such as the pharmaceutical field, the cosmetic field, and the food industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The results of protein extraction using the deep eutectic solvents of different compositions of the present invention are shown below;

[0031] Figure 2 This is a photo of the polypeptide product obtained in Example 1 of the present invention;

[0032] Figure 3 Circular dichroism spectrum of soy protein extracted using the deep eutectic solvent of Example 1 of the present invention;

[0033] Figure 4 This is the infrared spectrum of soybean protein extracted using the deep eutectic solvent of Example 1 of the present invention;

[0034] Figure 5 The figures are the test results of Example 1 and Comparative Example 1 on the biological activity of protein DPPH free radical. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0036] It should be noted that the various installation methods and technical terms mentioned in the present invention are technical terms that have long been clearly known in the relevant technical field and therefore will not be further explained. In addition, the same reference numerals are used for the same components, but this does not affect nor constitute an accurate understanding of the technical solution by those skilled in the art.

[0037] Example 1 This example provides a method for extracting and converting proteins into polypeptides using a green solvent, including a pretreatment process of the protein raw material, a process of extracting and converting the protein into polypeptides, and a process of purifying the polypeptides, including the following steps:

[0038] Step 1. Pretreatment process of protein raw materials:

[0039] A protein raw material (the protein raw material used in this example is soy protein) is mechanically pulverized, ground into powder, passed through a 40-mesh sieve, washed with pure water, and dried in an oven at 60°C for 12 hours to obtain soy powder (it can also be dried naturally at room temperature);

[0040] Step 2. Extraction and conversion of protein to peptide:

[0041] Accurately weigh 10 g of the soybean powder obtained in step 1, add 100 g of a deep eutectic solvent composed of choline chloride / propylene glycol in a molar ratio of 1:2 (the deep eutectic solvent used in this example is the optimal composition screened in the experimental example), place in a stirrer (this example uses a stirring extraction method for extraction and conversion reaction), set the stirring speed to 50 r / min, and react at 55°C for 2 hours to obtain a polypeptide extract (this step allows the deep eutectic solvent and soybean powder to fully dissolve, promoting the conversion of protein to polypeptides).

[0042] Step 3. Peptide purification process:

[0043] Dialysis treatment: The polypeptide extract obtained in step 2 is placed in a dialysis bag (the molecular weight cutoff of the dialysis bag in this embodiment is 1000 Da) and dialyzed with deionized water for 24 hours to remove small molecular impurities and unreacted components to obtain polypeptide dialysate;

[0044] Drying treatment: After the polypeptide dialysate is concentrated by rotary evaporation, freeze-drying is performed at a drying temperature of -20°C for 48 hours to obtain the polypeptide product, such as Figure 2 shown.

[0045] The polypeptide obtained in this example has an extraction rate of 16.5%, a molecular weight of 2000-3000 Da, and a purity of 85% (the purity is determined using the determination method of GB 5009.5-2025 "National Food Safety Standard - Determination of Protein in Food").

[0046] Example 2 The method provided in this example for extracting and converting proteins into polypeptides using green solvents is the same as that in Example 1, except that:

[0047] The protein raw material of this embodiment is fish protein.

[0048] In the protein-to-peptide extraction and conversion process of this example, the deep eutectic solvent consisted of betaine / malic acid in a molar ratio of 1:3; the extraction method was ultrasound-assisted extraction, with the ultrasonic power set at 300 W, the extraction temperature at 60° C., and the extraction time for 1.5 h to promote protein dissolution and conversion.

[0049] In the polypeptide purification process of this example, the molecular weight cutoff of the dialysis bag for dialysis and impurity removal treatment was 3000 Da, and the dialysis time was 36 h.

[0050] The polypeptide obtained in this example has an extraction rate of 8.7%, a molecular weight of 3000-5000 Da, and a purity of 87%.

[0051] Example 3 The method provided in this example for extracting and converting proteins into polypeptides using green solvents is the same as that in Example 1, except that:

[0052] The protein raw material in this embodiment is zein.

[0053] In this embodiment, during the pretreatment of the protein raw material, the powder was ground through a 60-mesh sieve;

[0054] In this example, during the extraction and conversion of proteins into peptides, the deep eutectic solvent consisted of choline chloride / glycerol in a molar ratio of 1:1. The extraction method was microwave-assisted extraction, with the microwave power set at 600 W, the extraction temperature at 40° C., and the extraction time for 30 min, to promote rapid conversion of the protein.

[0055] In the polypeptide purification process of this example, the molecular weight cutoff of the dialysis bag for dialysis and impurity removal treatment was 500 Da, and the dialysis time was 24 h. The drying treatment adopted vacuum drying at a temperature of 50° C. for 24 h.

[0056] The polypeptide obtained in this example had an extraction rate of 11.84%, a molecular weight of 1000-2500 Da, and a purity of 86.14%.

[0057] Example 4 The method provided in this example for extracting and converting proteins into polypeptides using green solvents is the same as that in Example 1, except that:

[0058] The protein raw material in this embodiment is milk protein.

[0059] In this embodiment, during the pretreatment of the protein raw material, the powder was ground through a 60-mesh sieve;

[0060] In this example, during the protein-to-peptide extraction and conversion process, the deep eutectic solvent consisted of choline chloride / urea at a molar ratio of 1:3. High-pressure-assisted extraction was used, with a pressure set at 100 MPa, an extraction temperature of 50°C, and a time of 1 hour to promote protein fragmentation and peptide formation.

[0061] In the polypeptide purification process of this example, the molecular weight cutoff of the dialysis bag for dialysis and impurity removal treatment was 2000 Da, and the dialysis time was 48 h. The drying treatment adopted spray drying, with an inlet air temperature of 150°C, an outlet air temperature of 80°C, a feed flow rate of 30 ml / min, an atomizing air pressure of 1.5 bar, and a drying air flow rate of 400 m3 / h.

[0062] The polypeptide obtained in this example has an extraction rate of 10.2%, a molecular weight of 2000-4000 Da, and a purity of 89%.

[0063] Example 5 The method provided in this example for extracting and converting proteins into polypeptides using green solvents is the same as that in Example 1, except that:

[0064] The protein raw material in this embodiment is zein.

[0065] In this embodiment, during the pretreatment process of the protein raw material, the powder was ground through a 200-mesh sieve;

[0066] In the protein to peptide extraction and conversion process of this example, the deep eutectic solvent consists of betaine / triethanolamine with a molar ratio of 1:2; the extraction method is stirring extraction, the stirring speed is set to 80 r / min, the extraction temperature is 60°C, and the extraction time is 4 hours.

[0067] In the polypeptide purification process of this example, the molecular weight cutoff of the dialysis bag for dialysis and impurity removal treatment was 1500 Da, and the dialysis time was 24 hours; the drying treatment adopted normal pressure drying at a temperature of 70° C. for 72 hours.

[0068] The polypeptide obtained in this example has an extraction rate of 8.9%, a molecular weight of 1500-3000 Da, and a purity of 86%.

[0069] Example 6 The method provided in this example for extracting and converting proteins into polypeptides using green solvents is the same as that in Example 1, except that:

[0070] The protein raw material of this embodiment is fish skin protein.

[0071] In this embodiment, the protein raw material is pretreated by ball milling and passed through a 20-mesh sieve;

[0072] In the extraction and conversion process of proteins into polypeptides in this example, the deep eutectic solvent consists of choline chloride / ethylene glycol with a molar ratio of 1:5; the extraction method is microwave-ultrasonic combined extraction, the microwave power is 500 W, the ultrasonic power is 200 W, the extraction temperature is 70° C., and the extraction time is 40 min.

[0073] In this example, during the peptide purification process, the dialysis bag used for dialysis impurity removal had a molecular weight cutoff of 5000 Da and the dialysis time was 36 hours. Supercritical drying was used for drying, with the dialysate placed in a supercritical fluid (CO2 in this example) at a pressure of 200 bar and a temperature of 40°C. The collector temperature was -25°C, and the CO2 flow rate was 2 L / min. The drying time was 3 hours.

[0074] The polypeptide obtained in this example has an extraction rate of 11.0%, a molecular weight of 5000-8000 Da, and a purity of 90%.

[0075] Example 7 The method provided in this example for extracting and converting proteins into polypeptides using green solvents is the same as that in Example 1, except that:

[0076] In this example, during the extraction and conversion process of proteins into polypeptides, 1000 g of a deep eutectic solvent was added to 10 g of the pretreated protein raw material powder. The deep eutectic solvent consisted of choline chloride / propylene glycol at a molar ratio of 1:1.

[0077] In the polypeptide purification process of this example, the molecular weight cutoff of the dialysis bag for dialysis and impurity removal treatment was 2500 Da, and the dialysis time was 24 h.

[0078] The polypeptide obtained in this example has an extraction rate of 12.30%, a molecular weight of 2500-4000 Da, and a purity of 80%.

[0079] Example 8 The method provided in this example for extracting and converting proteins into polypeptides using green solvents is the same as that in Example 1, except that:

[0080] In this example, during the extraction and conversion process of proteins into polypeptides, 50 g of a deep eutectic solvent was added to 10 g of the pretreated protein raw material powder. The deep eutectic solvent consisted of choline chloride / propylene glycol at a molar ratio of 1:10.

[0081] In the polypeptide purification process of this example, the molecular weight cutoff of the dialysis bag for dialysis and impurity removal treatment was 3500 Da, and the dialysis time was 24 h.

[0082] The polypeptide obtained in this example has an extraction rate of 15.77%, a molecular weight of 3500-5000 Da, and a purity of 84%.

[0083] Comparative Example 1

[0084] In this comparative example, an alkaline NaOH solution was used to extract polypeptides from proteins.

[0085] Experimental Example 1

[0086] In this experiment, choline chloride and betaine were used as hydrogen bond acceptors, and lactic acid, urea, malic acid, triethanolamine, ethylene glycol, glycerol, propylene glycol, butylene glycol, hexanediol, levulinic acid, xylitol and tartaric acid were used as hydrogen bond donors. The compositions of choline chloride / lactic acid, choline chloride / urea, choline chloride / malic acid, choline chloride / triethanolamine, choline chloride / ethylene glycol, choline chloride / glycerol, choline chloride / propylene glycol, choline chloride / butylene glycol, and choline chloride / hexanediol were obtained. , choline chloride / levulinic acid, choline chloride / xylitol, choline chloride / tartaric acid, betaine / lactic acid, betaine / urea, betaine / malic acid, betaine / triethanolamine, betaine / ethylene glycol, betaine / glycerol, betaine / propylene glycol, betaine / butylene glycol, betaine / hexanediol, betaine / levulinic acid, betaine / xylitol and betaine / tartaric acid low eutectic solvents were used to extract and convert soybean protein into polypeptides, and the extraction rates were between 5% and 18%. Among them, the extraction effect of choline chloride as a hydrogen bond acceptor was better, and the extraction rate was relatively high. The low eutectic solvents with different compositions of choline chloride as a hydrogen bond acceptor were analyzed, and their properties are shown in Table 1. The extraction rate of soybean protein is as follows Figure 1 As shown by Figure 1 It can be seen that the extraction effect of choline chloride-propylene glycol with a molar ratio of 1:2 is the best, and the extraction rate exceeds 16%.

[0087] Table 1 Composition, viscosity, pH, molar ratio and relative polarity of deep eutectic solvents

[0088] hydrogen bond acceptors hydrogen bond donor Deep eutectic solvents molar ratio Viscosity mPa.s Polarity kcal / mol DES1 Choline chloride lactic acid Choline chloride-lactic acid 1:2 185 48.71 DES2 Choline chloride urea Choline chloride-urea 1:2 201 49.25 DES3 Choline chloride Malic acid Choline chloride-malic acid 1:1 16500 47.96 DES4 Choline chloride glycerin Choline chloride-glycerol 1:2 276 49.50 DES5 Choline chloride Propylene glycol Choline chloride-propylene glycol 1:2 265 49.51

[0089] Test Case 1 Structural Analysis

[0090] (1) The soybean peptides extracted from DES in Example 1 were analyzed by circular dichroism spectroscopy. The testing process was as follows:

[0091] The protein sample was prepared into a 0.5 mg / mL solution in 20 mM phosphate buffer (pH 7.0) as the solvent. The sample was scanned at 25°C in the wavelength range of 190–260 nm using a Jasco J-815 circular dichroism spectrometer with a scan speed of 100 nm / min, a response time of 1 s, and an optical path length of 0.1 cm. The temperature was kept constant during the test, and an appropriate buffer was used to control the pH value.

[0092] The results are as follows Figure 3As shown in the figure, it can be seen that the secondary structure of the protein changes significantly under different pH conditions: in acidic environment (pH=3 and pH=5), the molecule is mainly composed of β-folded structure; while in neutral and alkaline environment (pH=7 and pH=9), the molecule gradually changes to be mainly composed of α-helical structure. This change is due to the pH value changing the hydrogen bond network and charge state inside the molecule, thereby affecting the stability of its secondary structure.

[0093] (2) The structure of the soybean peptide product extracted by DES in Example 1 was analyzed by infrared spectroscopy. The test process was as follows: the potassium bromide tablet method (1:100) was used with a wave number range of 4000 to 400 cm⁻¹ and 64 scans.

[0094] The results are as follows Figure 4 As shown in the figure, the typical protein amide I band (~1650 cm⁻¹), amide II band (~1550 cm⁻¹), and N–H stretching vibration peak (~3300 cm⁻¹) are displayed, indicating the presence of a complete peptide bond structure in the sample. The peak position and shape of the amide I band can be used to further analyze changes in the secondary structure of the protein. In addition, other absorption peaks also provide information about side chain groups, hydrogen bonding status, and potential modifications, providing strong support for protein structure and function research.

[0095] Test Example 2 Protein Antioxidant Biological Activity Test

[0096] This test example tested the antioxidant biological activities of Example 1 (protein extracted from DES5) and Comparative Example 1 (basic protein) using the DPPH free radical scavenging method. The test process is as follows:

[0097] Example 1 (DES protein) and Comparative Example 1 (basic protein) were prepared into solutions of different concentrations (5 mg / mL, 10 mg / mL, 20 mg / mL, 30 mg / mL, and 40 mg / mL), using deionized water as the solvent to ensure that the samples were fully dissolved. A DPPH free radical solution of a certain concentration (0.1–0.2 mM) was prepared using ethanol as the solvent. A certain amount of DPPH free radical solution was mixed with the protein samples of different concentrations to maintain a consistent final volume. After mixing, the mixture was allowed to stand in the dark at room temperature for 30 minutes to ensure sufficient reaction. The absorbance (A) of the mixture was measured at a wavelength of 517 nm using a UV-visible spectrophotometer. At the same time, a blank control group (containing only the DPPH free radical solution and ethanol, without the protein sample) was set up. The clearance rate was calculated using the following formula:

[0098] ;

[0099] Wherein, DPPH represents the DPPH scavenging rate, A1 is the absorbance of the sample and free radical system, A2 is the absorbance of the sample and ethanol / water system, and A3 is the absorbance of the ethanol / water and free radical system.

[0100] The results showed that both proteins possessed antioxidant capacity, with their activity increasing with increasing concentration. However, Example 1 (DES protein) exhibited significantly higher antioxidant activity than Comparative Example 1 (basic protein). In particular, at high concentrations, the DES protein achieved an 80% DPPH free radical scavenging rate, demonstrating enhanced antioxidant performance. This result also suggests that peptides extracted from proteins using DES have greater application value, particularly in antioxidant-related fields.

[0101] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention may be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the present invention is defined by the appended claims rather than the foregoing description. It is intended that all variations that fall within the meaning and range of equivalents of the claims be embraced within the present invention. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

[0102] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any minor modifications, equivalent replacements, and improvements made to the above embodiments based on the technical essence of the present invention shall be included in the scope of protection of the technical solution of the present invention.

Claims

1. A method for extracting and converting proteins into polypeptides using green solvents, characterized in that: The method comprises a pretreatment process of protein raw materials, a process of extracting and converting proteins into polypeptides, and a process of purifying polypeptides; the green solvent used in the process of extracting and converting proteins into polypeptides is a low eutectic solvent.

2. The method for extracting and converting proteins into polypeptides using green solvents according to claim 1, characterized in that: In the process of extracting and converting the protein into polypeptides, the solid-to-liquid ratio of the pretreated protein raw material and the deep eutectic solvent is 1:5 to 1:

100.

3. The method for extracting and converting proteins into polypeptides using green solvents according to claim 1, characterized in that: The deep eutectic solvent includes a hydrogen bond acceptor and a hydrogen bond donor, wherein the hydrogen bond acceptor is choline chloride or betaine; and the hydrogen bond donor includes one of lactic acid, urea, malic acid, triethanolamine, ethylene glycol, glycerol, propylene glycol, butylene glycol, hexylene glycol, levulinic acid, xylitol or tartaric acid.

4. The method for extracting and converting proteins into polypeptides using green solvents according to claim 2, characterized in that: The molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:1 to 1:

10.

5. The method of extracting and converting proteins into polypeptides using green solvents according to claim 1, characterized in that: The extraction and conversion process of the protein into the polypeptide includes any one of stirring extraction, ultrasonic extraction, microwave extraction or high-pressure extraction.

6. The method of extracting and converting proteins into polypeptides using green solvents according to claim 1, characterized in that: The polypeptide purification process includes dialysis to remove impurities, and the dialysis to remove impurities uses a dialysis bag with a molecular weight cut-off range of 500 Da to 10,000 Da.

7. The method for extracting and converting proteins into polypeptides using green solvents according to claim 6, characterized in that: The polypeptide purification process further includes a drying process, and the drying process includes any one of freeze drying, vacuum drying, oven drying, supercritical drying, and spray drying.

8. The method of extracting and converting proteins into polypeptides using green solvents according to claim 1, characterized in that: The protein raw material pretreatment process is a process of grinding the protein raw material to pass through a 20-200 mesh sieve, washing and drying to obtain protein raw material powder; wherein the grinding method includes mechanical crushing or ball milling, and the drying time is 12-48 hours.

9. A polypeptide extracted and transformed based on the method according to any one of claims 1 to 8.

10. Use of a polypeptide extracted and converted by the method according to any one of claims 1 to 8 in biomedicine, cosmetics or food.

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