A method for synthesizing n-acyl amino acid surfactants

Abstract

The application belongs to the technical field of surfactant synthesis, and specifically provides a method for synthesizing N-acyl amino acid surfactant, which comprises the following steps: S1, preparing a Fe3O4@UiO-66-NH2 magnetic MOF carrier; S2, preparing the magnetic MOF immobilized lipase by using the Fe3O4@UiO-66-NH2 magnetic MOF carrier and the lipase; S3, adding fatty acids and amino acids in a molar ratio of 1:1 to 1:3 into an aqueous phase or a phosphate buffer solution, adding the magnetic MOF immobilized lipase into the above solution to perform a reaction, separating and recovering the magnetic MOF immobilized lipase in the reaction liquid by using an external magnetic field after the reaction is completed, and obtaining the N-acyl amino acid surfactant through post-treatment of the reaction liquid; the method solves the problems of high cost of the existing N-acyl amino acid surfactant industrialized production and synthesis process, and difficulty in efficient recovery and reuse of the catalyst; the preparation method is simple and the conditions are mild, the use of high temperature and high pressure and organic solvents is avoided, the method meets the green chemistry concept, raw materials are easy to obtain, the cost is low, and the method is easy to industrialize.

Description

Technical Field

[0001] This invention belongs to the field of surfactant synthesis technology, specifically relating to a method for synthesizing N-acyl amino acid surfactants. Background Technology

[0002] N-acyl amino acid surfactants, a class of green surfactants composed of fatty acids and amino acids linked by amide bonds, have become the preferred raw materials for high-end personal care products and mild medical cleaning agents due to their excellent surface activity, mild and non-irritating properties, and good biodegradability. However, their industrial production has long faced the dual bottlenecks of synthesis process and catalyst recovery, and existing technologies struggle to achieve a balance between efficient synthesis and environmental friendliness.

[0003] Currently, industrial production mainly employs the Shorton-Baumann condensation method, which uses fatty acyl chlorides and amino acids as raw materials under alkaline conditions. However, fatty acyl chlorides are easily hydrolyzed in water, generating byproducts that not only reduce product yield but also lead to complex product composition. The reaction process generates large amounts of saline wastewater, resulting in a heavy environmental burden. Furthermore, the reaction conditions are harsh, with poor adaptability to heat-sensitive amino acids, limiting the expansion of product varieties. While enzyme-catalyzed synthesis can achieve highly selective reactions under mild conditions and has advantages such as fewer side reactions and environmental friendliness, existing immobilized enzyme carriers mostly rely on physical adsorption, leading to easy detachment and inactivation of enzyme molecules. After the reaction, catalyst recovery requires filtration or centrifugation, which is cumbersome and has limited recovery rates, especially in viscous product systems where separation is more difficult. The limited number of catalyst reuse batches results in high production costs, making it difficult to compete economically with chemical methods. In recent years, metal-organic frameworks (MOFs) have shown potential in the field of enzyme immobilization due to their ultra-high specific surface area and tunable pore structure, which can effectively improve the enzyme loading and stability. However, MOF materials usually exist in the form of nano or micron-sized powders, and high-speed centrifugation is required to separate them from the reaction system, which is not conducive to large-scale application.

[0004] Chinese patent document CN120097858A discloses a method for preparing an N-acyl amino acid surfactant, belonging to the field of surfactant technology. This document uses alkylamides and fatty acids as raw materials, and nano-Cu as a catalyst, reacting at 200–350°C for 3–5 hours. After the reaction, the nano-Cu is removed by filtration, the filtrate is allowed to stand and separate into layers, and the lower layer is collected to obtain the N-acyl amino acid surfactant. The alkylamide is a C6–C18 alkylamide; the fatty acid is a C6–C22 fatty acid. This document does not solve the long-standing problems of high synthesis process costs and difficulty in efficiently recovering and reusing the catalyst in industrial production. Summary of the Invention

[0005] The present invention provides a method for synthesizing N-acyl amino acid surfactants, aiming to overcome the problems of high cost and difficulty in efficient recovery and reuse of catalysts in the industrial production synthesis process of N-acyl amino acid surfactants in the prior art.

[0006] Therefore, the present invention provides a method for synthesizing N-acyl amino acid surfactants, comprising the following steps: S1. Preparation of Fe3O4@UiO-66-NH2 magnetic MOF support; S2. The Fe3O4@UiO-66-NH2 magnetic MOF support and lipase were used to prepare magnetic MOF immobilized lipase. S3. Add fatty acids and amino acids in a molar ratio of 1:1 to 1:3 to an aqueous phase or phosphate buffer solution. Add magnetic MOF-immobilized lipase to the above solution to carry out the reaction. After the reaction is completed, the magnetic MOF-immobilized lipase in the reaction solution is separated and recovered by an external magnetic field. The reaction solution is then post-treated to obtain an N-acyl amino acid surfactant.

[0007] Preferably, step S1 includes the following steps: preparing Fe3O4 magnetic nanoparticles, coating the surface of Fe3O4 magnetic nanoparticles with a silica layer to obtain Fe3O4@SiO2, dispersing Fe3O4@SiO2 in an N,N-dimethylformamide solution containing a zirconium source and 2-aminoterephthalic acid, and growing a UiO-66-NH2 shell in situ on the surface of the magnetic core by a solvothermal reaction to obtain the Fe3O4@UiO-66-NH2 magnetic MOF support.

[0008] Preferably, step S2 includes the following steps: dispersing the Fe3O4@UiO-66-NH2 magnetic MOF support in a glutaraldehyde solution for activation treatment, thereby introducing active aldehyde groups onto the surface of the Fe3O4@UiO-66-NH2 magnetic MOF support; adding the activated Fe3O4@UiO-66-NH2 magnetic MOF support to a phosphate buffer containing lipase; and immobilizing the lipase on the surface of the Fe3O4@UiO-66-NH2 magnetic MOF support by covalent bonding. After immobilization, the magnetic MOF immobilized lipase is obtained by separation, recovery, and washing using an external magnetic field.

[0009] Preferably, in step S1, the particle size of Fe3O4@SiO2 is 100–300 nm; and the thickness of the UiO-66-NH2 shell is 30–80 nm.

[0010] Preferably, in step S2, the mass ratio of Fe3O4@UiO-66-NH2 magnetic MOF carrier to lipase is 5:1-20:1.

[0011] Preferably, the activation treatment of dispersing the Fe3O4@UiO-66-NH2 magnetic MOF support in glutaraldehyde solution in step S2 includes: dispersing the Fe3O4@UiO-66-NH2 magnetic MOF support in phosphate buffer, adding the phosphate buffer containing the Fe3O4@UiO-66-NH2 magnetic MOF support to the glutaraldehyde aqueous solution, and activating by shaking at 25-50°C for 1-3 hours.

[0012] Preferably, the fatty acids in step S3 are C8-C9. 18 Saturated or unsaturated fatty acids.

[0013] Preferably, C8~C 18 The saturated or unsaturated fatty acids are one or more of the following: caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, oleic acid, and linoleic acid.

[0014] Preferably, the amino acid in step S3 is one or more of glycine, alanine, glutamic acid, sarcosine, and proline.

[0015] Preferably, the post-treatment in step S3 includes adjusting the pH of the reaction solution to 2-3 with acid to precipitate the product, followed by filtration, washing, and drying to obtain N-acyl amino acid surfactant powder.

[0016] The beneficial effects of this invention are: 1. This invention provides a method for synthesizing N-acyl amino acid surfactants. The method involves preparing a Fe3O4@UiO-66-NH2 magnetic MOF support, and then using the Fe3O4@UiO-66-NH2 magnetic MOF support and lipase to prepare a magnetic MOF-immobilized lipase. Fatty acids and amino acids are added to an aqueous phase or a phosphate buffer solution. The magnetic MOF-immobilized lipase is then added to the solution to initiate the reaction. After the reaction, the magnetic MOF-immobilized lipase in the reaction solution is separated and recovered using an external magnetic field. The reaction solution is then post-treated to obtain the N-acyl amino acid surfactant. This method achieves efficient synthesis and catalyst recovery of N-acyl amino acid surfactants with only gentle water bath shaking and external magnetic separation. The preparation method is simple and mild, avoiding high temperature, high pressure, and the use of organic solvents, conforming to the concept of green chemistry. The raw materials are readily available, the cost is low, and it is easy to industrialize.

[0017] 2. This invention provides a method for synthesizing N-acyl amino acid surfactants. The Fe3O4@UiO-66-NH2 magnetic MOF support not only provides a high loading capacity and stable microenvironment for lipases through the high specific surface area and abundant amino groups of the UiO-66-NH2 shell, but also endows the composite material with rapid magnetic response capability through the superparamagnetic properties of Fe3O4 magnetic nanoparticles. After the reaction, the catalyst can be efficiently separated and recovered by applying an external magnetic field, avoiding the cumbersome process of traditional filtration or centrifugation. The UiO-66-NH2 shell in the Fe3O4@UiO-66-NH2 magnetic MOF support has good hydrothermal and chemical stability, and its structure remains intact during repeated use. The support itself can be recycled for a long time, further reducing production costs.

[0018] 3. The present invention provides a method for synthesizing N-acyl amino acid surfactants. A Fe3O4@UiO-66-NH2 magnetic MOF support is dispersed in a glutaraldehyde solution for activation. A lipase is immobilized on the support surface using a glutaraldehyde covalent bonding method. A strong covalent bond is formed between the lipase and the Fe3O4@UiO-66-NH2 magnetic MOF support, significantly improving the stability and anti-detachment ability of the lipase. This overcomes the defects of easy enzyme inactivation and detachment in traditional physical adsorption methods. The catalyst has excellent reusability, the enzyme catalytic reaction has high selectivity, the amidation reaction of fatty acids and amino acids proceeds specifically, no byproducts are generated, the product purity is high, post-processing is simple, and the product yield can reach over 95%. Attached Figure Description

[0019] The present invention will now be described in further detail with reference to the accompanying drawings.

[0020] Figure 1 This is a flowchart of the method for synthesizing N-acyl amino acid surfactants according to the present invention; Figure 2 These are data graphs showing the foam stability and emulsification separation time of Examples 1, 2, 3, and 4 of the present invention; Figure 3 This is the hysteresis loop diagram of Embodiment 3 of the present invention; Figure 4 These are the catalyst recovery yield measurement charts for Examples 1, 2, 3, and 4 of this invention. Detailed Implementation

[0021] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0022] A method for synthesizing N-acyl amino acid surfactants includes the following steps: S1. Preparation of Fe3O4@UiO-66-NH2 magnetic MOF support; S2. The Fe3O4@UiO-66-NH2 magnetic MOF support and lipase were used to prepare magnetic MOF immobilized lipase. S3. Add fatty acids and amino acids in a molar ratio of 1:1 to 1:3 to an aqueous phase or phosphate buffer solution. Add magnetic MOF-immobilized lipase to the above solution to carry out the reaction. After the reaction is completed, the magnetic MOF-immobilized lipase in the reaction solution is separated and recovered by an external magnetic field. The reaction solution is then post-treated to obtain an N-acyl amino acid surfactant.

[0023] Specifically, this invention achieves efficient synthesis and catalyst recovery of N-acyl amino acid surfactants using only gentle water bath oscillation and external magnetic separation. The preparation method is simple and mild, avoiding the use of high temperature, high pressure, and organic solvents, which aligns with green chemistry principles. The raw materials are readily available, the cost is low, and it is easy to industrialize. The magnetic MOF-immobilized lipase can be reused more than 10 times, and the product yield remains above 85% of the first use even on the 10th use.

[0024] Preferably, step S1 includes the following steps: preparing Fe3O4 magnetic nanoparticles, coating the surface of Fe3O4 magnetic nanoparticles with a silica layer to obtain Fe3O4@SiO2, dispersing Fe3O4@SiO2 in an N,N-dimethylformamide solution containing a zirconium source and 2-aminoterephthalic acid, and growing a UiO-66-NH2 shell in situ on the surface of the magnetic core by a solvothermal reaction to obtain the Fe3O4@UiO-66-NH2 magnetic MOF support.

[0025] Specifically, the Fe3O4@UiO-66-NH2 magnetic MOF support of this invention not only provides a high loading capacity and stable microenvironment for lipases through the high specific surface area and abundant amino groups of the UiO-66-NH2 shell, but also allows the amino groups to serve as covalently immobilized reaction sites. Utilizing this characteristic, the Fe3O4@UiO-66-NH2 magnetic MOF support is prepared. Furthermore, the superparamagnetic properties of Fe3O4 magnetic nanoparticles endow the composite material with rapid magnetic response capabilities. After the reaction, the catalyst can be efficiently separated and recovered by applying an external magnetic field, avoiding the cumbersome process of traditional filtration or centrifugation. The UiO-66-NH2 shell in the Fe3O4@UiO-66-NH2 magnetic MOF support exhibits good hydrothermal and chemical stability, maintaining structural integrity during repeated use. The support itself can be recycled for a long time, further reducing production costs.

[0026] Preferably, step S2 includes the following steps: dispersing the Fe3O4@UiO-66-NH2 magnetic MOF support in a glutaraldehyde solution for activation treatment, thereby introducing active aldehyde groups onto the surface of the Fe3O4@UiO-66-NH2 magnetic MOF support; adding the activated Fe3O4@UiO-66-NH2 magnetic MOF support to a phosphate buffer containing lipase; and immobilizing the lipase on the surface of the Fe3O4@UiO-66-NH2 magnetic MOF support by covalent bonding. After immobilization, the magnetic MOF immobilized lipase is obtained by separation, recovery, and washing using an external magnetic field.

[0027] Preferably, the Fe3O4@UiO-66-NH2 magnetic MOF support is dispersed in glutaraldehyde solution for activation treatment, thereby introducing active aldehyde groups onto the surface of the Fe3O4@UiO-66-NH2 magnetic MOF support. After washing, it is added to phosphate buffer containing lipase and immobilized by shaking at 4-25°C for 4-12 hours. The lipase is then immobilized on the surface of the Fe3O4@UiO-66-NH2 magnetic MOF support by covalent bonding. After immobilization, the magnetic MOF immobilized lipase is obtained by separation, recovery, and washing using an external magnetic field.

[0028] Specifically, the Fe3O4@UiO-66-NH2 magnetic MOF support was dispersed in a glutaraldehyde solution for activation. Lipase was then immobilized on the support surface using a glutaraldehyde covalent bonding method. A strong covalent bond was formed between the lipase and the Fe3O4@UiO-66-NH2 magnetic MOF support, significantly improving the stability and resistance to detachment of the lipase. This method overcomes the shortcomings of traditional physical adsorption methods, such as easy enzyme inactivation and detachment. The catalyst exhibits excellent reusability, the enzyme catalytic reaction has high selectivity, the amidation reaction of fatty acids and amino acids proceeds specifically without byproduct formation, the product has high purity, and the post-processing is simple, with a product yield exceeding 95%.

[0029] Preferably, after the immobilization is completed, the washing solution is tested using the Bradford method until no protein is detected, to ensure the removal of unbound free lipase.

[0030] The BCA method is used to determine the protein concentration difference in the lipase solution before and after immobilization, and to calculate the lipase loading accordingly. The Bradford method is used to detect the free protein content in the washing or reaction solution to determine whether unbound free lipase has been washed away and whether enzyme leakage has occurred during the cyclic reaction. Although the two methods differ in their detection targets and evaluation purposes, both are used to evaluate the effectiveness of lipase immobilization.

[0031] Preferably, in step S1, the particle size of Fe3O4@SiO2 is 100-300 nm; the thickness of the UiO-66-NH2 shell is 30-80 nm; in order to obtain good magnetic responsiveness and sufficient enzyme loading space.

[0032] Preferably, in step S2, the mass ratio of Fe3O4@UiO-66-NH2 magnetic MOF carrier to lipase is 5:1-20:1 to obtain optimal enzyme loading and catalytic activity.

[0033] Preferably, the activation treatment of dispersing the Fe3O4@UiO-66-NH2 magnetic MOF support in glutaraldehyde solution in step S2 includes: dispersing the Fe3O4@UiO-66-NH2 magnetic MOF support in phosphate buffer, adding the phosphate buffer containing the Fe3O4@UiO-66-NH2 magnetic MOF support to the glutaraldehyde aqueous solution, and activating by shaking at 25-50°C for 1-3 hours.

[0034] Specifically, using phosphate buffer as the reaction system can stabilize the pH of the system and protect the Fe3O4@UiO-66-NH2 magnetic MOF framework and surface amino activity. The Fe3O4@UiO-66-NH2 magnetic MOF support is rich in amino sites, which, when activated with dialdehyde glutaraldehyde, can form stable covalent binding sites through Schiff base reaction, resulting in high activation efficiency. A mild temperature of 25-50℃ combined with shaking reaction for 1-3 hours can ensure sufficient activation and uniform reaction without causing structural damage or magnetic attenuation of the Fe3O4@UiO-66-NH2 magnetic MOF support. Furthermore, the material has magnetic separation characteristics, making subsequent separation operations simple. The overall process conditions are mild, the binding is strong, and the practicality is high.

[0035] Preferably, the fatty acids in step S3 are C8-C9. 18 Saturated or unsaturated fatty acids.

[0036] Specifically, C8~C 18 Saturated and unsaturated fatty acids have advantages such as compatible physicochemical properties, adjustable functions, and wide range of applications. They also have moderate carbon chain length and a balance of fluidity, solubility, and stability.

[0037] Preferably, C8~C 18 The saturated or unsaturated fatty acids are one or more of the following: caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, oleic acid, and linoleic acid.

[0038] Preferably, the amino acid in step S3 is one or more of glycine, alanine, glutamic acid, sarcosine, and proline.

[0039] Preferably, the post-treatment in step S3 includes adjusting the pH of the reaction solution to 2-3 with acid to precipitate the product, followed by filtration, washing, and drying to obtain N-acyl amino acid surfactant powder.

[0040] Specifically, in step S3, fatty acids and amino acids in a molar ratio of 1:1 to 1:3 are added to an aqueous phase or a phosphate buffer solution. Magnetic MOF-immobilized lipase is then added to the solution for reaction. The amount of magnetic MOF-immobilized lipase is 1 to 10 wt% of the total mass of fatty acids and amino acids. The reaction system is placed in a water bath shaker at 20 to 60°C and shaken at 100 to 200 rpm for 2 to 8 hours. During the reaction, the lipase catalyzes the amidation reaction between fatty acids and amino acids to generate N-acyl amino acid surfactants. After the reaction is completed, the reaction vessel is placed in an external magnetic field. The magnetic MOF-immobilized lipase rapidly accumulates on the container wall or bottom. The reaction solution can be poured out to achieve efficient separation of the catalyst. The separated magnetic MOF-immobilized lipase can be directly added to the next batch of reaction after washing. The reaction solution is then post-treated by acidification, extraction, crystallization, or freeze-drying to obtain high-purity N-acyl amino acid surfactant powder.

[0041] In this invention, the product yield is calculated as the percentage of the actual mass of the N-acyl amino acid surfactant obtained by separation and drying to the theoretical mass of the product; the product purity is determined by HPLC area normalization method; the magnetic separation recovery rate is calculated as the percentage of the dry weight of the immobilized enzyme recovered by magnetic separation after each batch of reaction to the dry weight of the immobilized enzyme added; the enzyme leakage rate is calculated as the percentage of the amount of free protein in the reaction solution and washing solution to the amount of protein initially loaded on the immobilized lipase.

[0042] Preferably, the lipase is selected from one of the following: lipase derived from Thermomyces lanuginosus, lipase B derived from Candida antarctica, or lipase derived from Rhizomucor miehei.

[0043] Example 1: like Figure 1 As shown, a method for synthesizing N-acyl amino acid surfactants includes the following steps: S1. Preparation of Fe3O4@UiO-66-NH2 magnetic MOF support; including the following steps: preparing Fe3O4 magnetic nanoparticles, coating the surface of Fe3O4 magnetic nanoparticles with a silica layer to obtain Fe3O4@SiO2, dispersing Fe3O4@SiO2 in an N,N-dimethylformamide solution containing a zirconium source and 2-aminoterephthalic acid, and growing a UiO-66-NH2 shell in situ on the surface of the magnetic core through a solvothermal reaction to obtain the Fe3O4@UiO-66-NH2 magnetic MOF support; Specifically, the solvothermal method for preparing Fe3O4 magnetic nanoparticles includes the following steps: First, 1.35g FeCl3·6H2O, 3.85g sodium acetate, and 40mL ethylene glycol are added to a 100mL reaction vessel (e.g., a beaker). Then, the reaction vessel is placed on a magnetic stirrer and stirred at 300rpm for 30min to completely dissolve the solids (FeCl3·6H2O and sodium acetate) to form a yellow transparent solution. The stirred solution in the reaction vessel is transferred to a 100mL stainless steel high-pressure reactor lined with polytetrafluoroethylene, sealed, and placed in an oven at 200℃ for 8h. After the reaction, the mixture is allowed to cool naturally to room temperature. The black precipitate in the reaction vessel is separated using an external magnetic field. The black precipitate is washed three times each with deionized water and anhydrous ethanol. After each wash, the supernatant is removed by magnetic separation. The washed precipitate is placed in a vacuum drying oven and dried at 60℃ for 12h to obtain Fe3O4 magnetic nanoparticles with a yield of 96.5%.

[0044] The preparation of Fe3O4@SiO2 includes the following steps: 0.5g of the prepared Fe3O4 magnetic nanoparticles are dispersed in 100mL of anhydrous ethanol and sonicated for 30min to ensure uniform dispersion of the Fe3O4 magnetic nanoparticles in the anhydrous ethanol. The dispersion is then transferred to a 250mL reaction vessel (three-necked flask) and placed in a heat-collecting magnetic stirrer. 10mL of deionized water and 5mL of ammonia (25%) are added, and the mixture is stirred at 200rpm for 10min at room temperature. Then, 1.0mL of tetraethyl orthosilicate (TEOS) is added dropwise to the mixture in the reaction vessel, with the addition time controlled at 15min. After the addition is complete, the mixture is stirred and reacted at room temperature for 6h. After the reaction is complete, the product is separated using an external magnetic field. The separated product is washed three times each with deionized water and anhydrous ethanol, and then vacuum dried at 60℃ for 12h to obtain Fe3O4@SiO2 core-shell structured nanoparticles with a yield of 98.2%.

[0045] The preparation of the Fe3O4@UiO-66-NH2 magnetic MOF support includes the following steps: 0.2g of the above-prepared Fe3O4@SiO2 is dispersed in 30mL of N,N-dimethylformamide (DMF), and ultrasonically treated for 20min to ensure that Fe3O4@SiO2 is uniformly dispersed in N,N-dimethylformamide (DMF). The dispersion is then transferred to a 100mL high-pressure reactor lined with polytetrafluoroethylene, and 0.125g of ZrCl4 and 0. 0.96 g of 2-aminoterephthalic acid and 0.5 mL of acetic acid were sealed and placed in an oven at 120 °C for 24 h. After the reaction, the mixture was allowed to cool naturally to room temperature. The product was separated using an external magnetic field and washed three times each with DMF and anhydrous methanol. After each washing, the supernatant was removed, and the washed product was placed in a vacuum drying oven and dried at 80 °C for 12 h to obtain the Fe3O4@UiO-66-NH2 magnetic MOF support with a yield of 94.7%. Transmission electron microscopy showed that the Fe3O4 core particle size was approximately 200 nm, and the UiO-66-NH2 shell thickness was approximately 50 nm.

[0046] S2. The Fe3O4@UiO-66-NH2 magnetic MOF carrier and lipase are prepared into magnetic MOF immobilized lipase; including the following steps: the Fe3O4@UiO-66-NH2 magnetic MOF carrier is dispersed in glutaraldehyde solution for activation treatment, so that active aldehyde groups are introduced on the surface of the Fe3O4@UiO-66-NH2 magnetic MOF carrier; the activated Fe3O4@UiO-66-NH2 magnetic MOF carrier is added to phosphate buffer containing lipase; the lipase is immobilized on the surface of Fe3O4@UiO-66-NH2 magnetic MOF carrier by covalent bonding; after immobilization, the magnetic MOF immobilized lipase is obtained by separation and recovery by an external magnetic field and washing. Specifically, the Fe3O4@UiO-66-NH2 magnetic MOF support was dispersed in a glutaraldehyde solution for activation, including the following steps: 0.1 g of the prepared Fe3O4@UiO-66-NH2 magnetic MOF support was dispersed in 10 mL of phosphate buffer (the phosphate buffer concentration was 0.1 mol / L, pH 7.0), sonicated for 5 min, and 2.5 mL of 25% glutaraldehyde aqueous solution was added to the dispersion. The mixture was then activated by shaking at 150 rpm in a 25℃ water bath for 2 h. After activation, the Fe3O4@UiO-66-NH2 magnetic MOF support was separated by an external magnetic field, and washed three times with phosphate buffer to remove excess glutaraldehyde, yielding the activated Fe3O4@UiO-66-NH2 magnetic MOF support for later use. 100 mg of the activated Fe3O4@UiO-66-NH2 magnetic MOF carrier was redispersed in 10 mL of phosphate buffer (0.1 mol / L, pH 7.0) to obtain a carrier dispersion. 20 mg of lipase B from Candida antarctica was dissolved in 5 mL of phosphate buffer to prepare a lipase solution. The lipase solution was added to the carrier dispersion, and the mixture was immobilized for 12 h at 120 rpm in a 4°C water bath. After immobilization, the immobilized enzyme was separated using an external magnetic field and washed three times with phosphate buffer until no protein was detected in the supernatant. The washed immobilized enzyme was collected and stored at 4°C for later use. The lipase loading was determined to be 102.7 mg / g carrier by the BCA method (diquinoline carboxylic acid protein quantification method).

[0047] S3. Lauric acid and sarcosine in a molar ratio of 1:1 were added to a phosphate buffer solution. Magnetic MOF immobilized lipase was added to the above solution to carry out the reaction. The amount of magnetic MOF immobilized lipase was 5 wt% of the total mass of fatty acids and amino acids. The reaction system was placed in a 40°C water bath shaker and shaken at 150 rpm for 6 hours. After the reaction was completed, the magnetic MOF immobilized lipase in the reaction solution was separated and recovered by an external magnetic field. The reaction solution was then post-treated to obtain N-lauroyl sarcosine surfactant.

[0048] Example 2: A method for synthesizing N-acyl amino acid surfactants includes the following steps: S1. Preparation of Fe3O4@UiO-66-NH2 magnetic MOF support; including the following steps: preparing Fe3O4 magnetic nanoparticles, coating the surface of Fe3O4 magnetic nanoparticles with a silica layer to obtain Fe3O4@SiO2, dispersing Fe3O4@SiO2 in an N,N-dimethylformamide solution containing a zirconium source and 2-aminoterephthalic acid, and growing a UiO-66-NH2 shell in situ on the surface of the magnetic core through a solvothermal reaction to obtain the Fe3O4@UiO-66-NH2 magnetic MOF support; Specifically, the solvothermal method for preparing Fe3O4 magnetic nanoparticles includes the following steps: First, 0.68g FeCl3·6H2O, 1.93g sodium acetate, and 40mL ethylene glycol are added to a 100mL reaction vessel (e.g., a beaker). Then, the reaction vessel is placed on a magnetic stirrer and stirred at 350rpm for 25min to completely dissolve the solids (FeCl3·6H2O and sodium acetate) to form a yellow transparent solution. The stirred solution in the reaction vessel is transferred to a 100mL stainless steel high-pressure reactor lined with polytetrafluoroethylene, sealed, and placed in an oven at 180℃ for 6h. After the reaction, the mixture is allowed to cool naturally to room temperature. The black precipitate in the reaction vessel is separated using an external magnetic field. The black precipitate is washed three times each with deionized water and anhydrous ethanol. After each wash, the supernatant is removed by magnetic separation. The washed precipitate is placed in a vacuum drying oven and dried at 60℃ for 10h to obtain Fe3O4 magnetic nanoparticles with a yield of 95.8%.

[0049] The preparation of Fe3O4@SiO2 includes the following steps: 0.4g of the prepared Fe3O4 magnetic nanoparticles are dispersed in 80mL of anhydrous ethanol and sonicated for 25min to ensure uniform dispersion of the Fe3O4 magnetic nanoparticles in the anhydrous ethanol. The dispersion is then transferred to a 250mL reaction vessel (three-necked flask) and placed in a heat-collecting magnetic stirrer. 8mL of deionized water and 4mL of ammonia (25%) are added, and the mixture is stirred at 180rpm for 10min at room temperature. Then, 0.6mL of tetraethyl orthosilicate (TEOS) is added dropwise to the mixture in the reaction vessel, with the addition time controlled at 10min. After the addition is complete, the mixture is stirred and reacted for 5h at room temperature. After the reaction is complete, the product is separated using an external magnetic field. The separated product is washed three times each with deionized water and anhydrous ethanol, and then vacuum dried at 60℃ for 10h to obtain Fe3O4@SiO2 core-shell structured nanoparticles with a yield of 97.6%.

[0050] The preparation of the Fe3O4@UiO-66-NH2 magnetic MOF support includes the following steps: 0.15g of the above-prepared Fe3O4@SiO2 is dispersed in 25mL of N,N-dimethylformamide (DMF), and ultrasonically treated for 15min to ensure uniform dispersion of Fe3O4@SiO2 in N,N-dimethylformamide (DMF). The dispersion is then transferred to a 100mL high-pressure reactor lined with polytetrafluoroethylene, and 0.100g of ZrCl4 and 0. 0.77 g of 2-aminoterephthalic acid and 0.4 mL of acetic acid were sealed and placed in an oven at 110 °C for 18 h. After the reaction, the mixture was allowed to cool naturally to room temperature. The product was separated using an external magnetic field and washed three times each with DMF and anhydrous methanol. After each washing, the supernatant was removed, and the washed product was placed in a vacuum drying oven and dried at 70 °C for 10 h to obtain the Fe3O4@UiO-66-NH2 magnetic MOF support with a yield of 93.9%. Transmission electron microscopy showed that the Fe3O4 core particle size was approximately 100 nm, and the UiO-66-NH2 shell thickness was approximately 30 nm.

[0051] S2. The Fe3O4@UiO-66-NH2 magnetic MOF carrier and lipase are prepared into magnetic MOF immobilized lipase; including the following steps: the Fe3O4@UiO-66-NH2 magnetic MOF carrier is dispersed in glutaraldehyde solution for activation treatment, so that active aldehyde groups are introduced on the surface of the Fe3O4@UiO-66-NH2 magnetic MOF carrier; the activated Fe3O4@UiO-66-NH2 magnetic MOF carrier is added to phosphate buffer containing lipase; the lipase is immobilized on the surface of Fe3O4@UiO-66-NH2 magnetic MOF carrier by covalent bonding; after immobilization, the magnetic MOF immobilized lipase is obtained by separation and recovery by an external magnetic field and washing. Specifically, the Fe3O4@UiO-66-NH2 magnetic MOF support was dispersed in a glutaraldehyde solution for activation, including the following steps: 0.4 g of the prepared Fe3O4@UiO-66-NH2 magnetic MOF support was dispersed in 10 mL of phosphate buffer (the phosphate buffer concentration was 0.1 mol / L, pH 7.0), sonicated for 5 min, and 2.5 mL of 25% glutaraldehyde aqueous solution was added to the dispersion. The mixture was then activated by shaking at 150 rpm in a 30℃ water bath for 2 h. After activation, the Fe3O4@UiO-66-NH2 magnetic MOF support was separated by an external magnetic field, and washed three times with phosphate buffer to remove excess glutaraldehyde, yielding the activated Fe3O4@UiO-66-NH2 magnetic MOF support for later use. 400 mg of the activated Fe3O4@UiO-66-NH2 magnetic MOF carrier was redispersed in 10 mL of phosphate buffer (0.1 mol / L, pH 7.0) to obtain a carrier dispersion. 20 mg of lipase from *Thermomyces lanuginosus* was dissolved in 5 mL of phosphate buffer to prepare a lipase solution. The lipase solution was added to the carrier dispersion, and the mixture was immobilized for 10 h at 130 rpm in a 10°C water bath. After immobilization, the immobilized enzyme was separated using an external magnetic field and washed three times with phosphate buffer until no protein was detected in the supernatant. The washed immobilized enzyme was collected and stored at 4°C for later use. The lipase loading was determined to be 42.6 mg / g carrier by the BCA method.

[0052] S3. Add octanoic acid and glycine in a molar ratio of 1:3 to the aqueous phase. Add magnetic MOF immobilized lipase to the above solution to carry out the reaction. The amount of magnetic MOF immobilized lipase is 1 wt% of the total mass of fatty acids and amino acids. Place the reaction system in a 20°C water bath shaker and shake at 100 rpm for 2 hours. After the reaction is completed, the magnetic MOF immobilized lipase in the reaction solution is separated and recovered by an external magnetic field. The reaction solution is then post-treated to obtain N-octanoylglycine surfactant.

[0053] Example 3: A method for synthesizing N-acyl amino acid surfactants includes the following steps: S1. Preparation of Fe3O4@UiO-66-NH2 magnetic MOF support; including the following steps: preparing Fe3O4 magnetic nanoparticles, coating the surface of Fe3O4 magnetic nanoparticles with a silica layer to obtain Fe3O4@SiO2, dispersing Fe3O4@SiO2 in an N,N-dimethylformamide solution containing a zirconium source and 2-aminoterephthalic acid, and growing a UiO-66-NH2 shell in situ on the surface of the magnetic core through a solvothermal reaction to obtain the Fe3O4@UiO-66-NH2 magnetic MOF support; Specifically, the solvothermal method for preparing Fe3O4 magnetic nanoparticles includes the following steps: First, 1.60 g FeCl3·6H2O, 4.50 g sodium acetate, and 45 mL ethylene glycol are added to a 100 mL reaction vessel (e.g., a beaker). Then, the reaction vessel is placed on a magnetic stirrer and stirred at 320 rpm for 35 min to completely dissolve the solids (FeCl3·6H2O and sodium acetate) to form a yellow transparent solution. The stirred solution in the reaction vessel is transferred to a 100 mL stainless steel high-pressure reactor lined with polytetrafluoroethylene, sealed, and placed in an oven. The temperature is raised to 200 °C and the reaction is carried out for 10 h. After the reaction is completed, the mixture is naturally cooled to room temperature. The black precipitate in the reaction vessel is separated using an external magnetic field. The black precipitate is washed three times each with deionized water and anhydrous ethanol. After each washing, the supernatant is removed by magnetic separation. The washed precipitate is placed in a vacuum drying oven and dried at 60 °C for 12 h to obtain Fe3O4 magnetic nanoparticles with a yield of 96.1%.

[0054] The preparation of Fe3O4@SiO2 includes the following steps: 0.5g of the prepared Fe3O4 magnetic nanoparticles are dispersed in 110mL of anhydrous ethanol and sonicated for 30min to ensure uniform dispersion of the Fe3O4 magnetic nanoparticles in the anhydrous ethanol. The dispersion is then transferred to a 250mL reaction vessel (three-necked flask) and placed in a heat-collecting magnetic stirrer. 12mL of deionized water and 5.5mL of ammonia (25%) are added, and the mixture is stirred at 200rpm for 10min at room temperature. Then, 1.0mL of tetraethyl orthosilicate (TEOS) is added dropwise to the mixture in the reaction vessel over a period of 20min. After the addition is complete, the mixture is stirred and reacted for another 7h at room temperature. After the reaction is complete, the product is separated using an external magnetic field. The product is washed three times each with deionized water and anhydrous ethanol, and then vacuum dried at 60℃ for 12h to obtain Fe3O4@SiO2 core-shell structured nanoparticles with a yield of 97.9%.

[0055] The preparation of the Fe3O4@UiO-66-NH2 magnetic MOF support includes the following steps: 0.2g of the above-prepared Fe3O4@SiO2 is dispersed in 30mL of N,N-dimethylformamide (DMF), and ultrasonically treated for 20min to ensure that Fe3O4@SiO2 is uniformly dispersed in N,N-dimethylformamide (DMF). The dispersion is then transferred to a 100mL high-pressure reactor lined with polytetrafluoroethylene, and 0.140g of ZrCl4 and 0. 108 g of 2-aminoterephthalic acid and 0.6 mL of acetic acid were sealed and placed in an oven at 125 °C for 22 h. After the reaction, the mixture was allowed to cool naturally to room temperature. The product was separated using an external magnetic field and washed three times each with DMF and anhydrous methanol. After each washing, the supernatant was removed, and the washed product was placed in a vacuum drying oven and dried at 80 °C for 12 h to obtain the Fe3O4@UiO-66-NH2 magnetic MOF support with a yield of 94.5%. Transmission electron microscopy showed that the Fe3O4 core particle size was approximately 200 nm, and the UiO-66-NH2 shell thickness was approximately 50 nm.

[0056] S2. The Fe3O4@UiO-66-NH2 magnetic MOF carrier and lipase are prepared into magnetic MOF immobilized lipase; including the following steps: the Fe3O4@UiO-66-NH2 magnetic MOF carrier is dispersed in glutaraldehyde solution for activation treatment, so that active aldehyde groups are introduced on the surface of the Fe3O4@UiO-66-NH2 magnetic MOF carrier; the activated Fe3O4@UiO-66-NH2 magnetic MOF carrier is added to phosphate buffer containing lipase; the lipase is immobilized on the surface of Fe3O4@UiO-66-NH2 magnetic MOF carrier by covalent bonding; after immobilization, the magnetic MOF immobilized lipase is obtained by separation and recovery by an external magnetic field and washing. Specifically, the Fe3O4@UiO-66-NH2 magnetic MOF support was dispersed in a glutaraldehyde solution for activation, including the following steps: 0.2g of the prepared Fe3O4@UiO-66-NH2 magnetic MOF support was dispersed in 10mL of phosphate buffer (the phosphate buffer concentration was 0.1mol / L, pH 7.0), sonicated for 5min, and 2.5mL of 25% glutaraldehyde aqueous solution was added to the dispersion. The mixture was then activated by shaking at 150rpm in a 40℃ water bath for 2h. After activation, the Fe3O4@UiO-66-NH2 magnetic MOF support was separated by an external magnetic field, and washed three times with phosphate buffer to remove excess glutaraldehyde, yielding the activated Fe3O4@UiO-66-NH2 magnetic MOF support for later use. 200 mg of the activated Fe3O4@UiO-66-NH2 magnetic MOF carrier was redispersed in 10 mL of phosphate buffer (0.1 mol / L, pH 7.0) to obtain a carrier dispersion. 20 mg of lipase from Rhizomucor miehei was dissolved in 5 mL of phosphate buffer to prepare a lipase solution. The lipase solution was added to the carrier dispersion, and the mixture was immobilized for 8 h at 140 rpm in a 15°C water bath. After immobilization, the immobilized enzyme was separated using an external magnetic field and washed three times with phosphate buffer until no protein was detected in the supernatant. The washed immobilized enzyme was collected and stored at 4°C for later use. The lipase loading was determined to be 88.6 mg / g carrier by the BCA method.

[0057] S3. Lauric acid and sarcosine in a molar ratio of 1:2 were added to a phosphate buffer solution. Magnetic MOF immobilized lipase was added to the above solution to carry out the reaction. The amount of magnetic MOF immobilized lipase was 5 wt% of the total mass of fatty acids and amino acids. The reaction system was placed in a 40°C water bath shaker and shaken at 150 rpm for 6 hours. After the reaction was completed, the magnetic MOF immobilized lipase in the reaction solution was separated and recovered by an external magnetic field. The reaction solution was then post-treated to obtain N-lauroyl sarcosine surfactant.

[0058] Example 4: A method for synthesizing N-acyl amino acid surfactants includes the following steps: S1. Preparation of Fe3O4@UiO-66-NH2 magnetic MOF support; including the following steps: preparing Fe3O4 magnetic nanoparticles, coating the surface of Fe3O4 magnetic nanoparticles with a silica layer to obtain Fe3O4@SiO2, dispersing Fe3O4@SiO2 in an N,N-dimethylformamide solution containing a zirconium source and 2-aminoterephthalic acid, and growing a UiO-66-NH2 shell in situ on the surface of the magnetic core through a solvothermal reaction to obtain the Fe3O4@UiO-66-NH2 magnetic MOF support; Specifically, the solvothermal method for preparing Fe3O4 magnetic nanoparticles includes the following steps: First, 2.03g FeCl3·6H2O, 5.77g sodium acetate, and 50mL ethylene glycol are added to a 100mL reaction vessel (e.g., a beaker). Then, the reaction vessel is placed on a magnetic stirrer and stirred at 300rpm for 40min to completely dissolve the solids (FeCl3·6H2O and sodium acetate) to form a yellow transparent solution. The stirred solution in the reaction vessel is transferred to a 100mL stainless steel high-pressure reactor lined with polytetrafluoroethylene, sealed, and placed in an oven at 220℃ for 10h. After the reaction, the mixture is allowed to cool naturally to room temperature. The black precipitate in the reaction vessel is separated using an external magnetic field. The black precipitate is washed three times each with deionized water and anhydrous ethanol. After each wash, the supernatant is removed by magnetic separation. The washed precipitate is placed in a vacuum drying oven and dried at 60℃ for 14h to obtain Fe3O4 magnetic nanoparticles with a yield of 95.2%.

[0059] The preparation of Fe3O4@SiO2 includes the following steps: 0.6g of the prepared Fe3O4 magnetic nanoparticles are dispersed in 120mL of anhydrous ethanol and sonicated for 35min to ensure uniform dispersion of the Fe3O4 magnetic nanoparticles in the anhydrous ethanol. The dispersion is then transferred to a 250mL reaction vessel (three-necked flask) and placed in a heat-collecting magnetic stirrer. 15mL of deionized water and 6mL of ammonia (25%) are added, and the mixture is stirred at 220rpm for 10min at room temperature. Then, 1.5mL of tetraethyl orthosilicate (TEOS) is added dropwise to the mixture in the reaction vessel, with the addition time controlled at 25min. After the addition is complete, the mixture is stirred and reacted at room temperature for 8h. After the reaction is complete, the product is separated using an external magnetic field. The separated product is washed three times each with deionized water and anhydrous ethanol, and then vacuum dried at 60℃ for 14h to obtain Fe3O4@SiO2 core-shell structured nanoparticles with a yield of 97.1%.

[0060] The preparation of the Fe3O4@UiO-66-NH2 magnetic MOF support includes the following steps: 0.25g of the above-prepared Fe3O4@SiO2 is dispersed in 40mL of N,N-dimethylformamide (DMF), and ultrasonically treated for 25min to ensure that Fe3O4@SiO2 is uniformly dispersed in N,N-dimethylformamide (DMF). The dispersion is then transferred to a 100mL high-pressure reactor lined with polytetrafluoroethylene, and 0.170g of ZrCl4 and 0. 130 g of 2-aminoterephthalic acid and 0.8 mL of acetic acid were sealed and placed in an oven at 130 °C for 24 h. After the reaction, the mixture was allowed to cool naturally to room temperature. The product was separated using an external magnetic field and washed three times each with DMF and anhydrous methanol. After each washing, the supernatant was removed. The washed product was then placed in a vacuum drying oven and dried at 80 °C for 14 h to obtain the Fe3O4@UiO-66-NH2 magnetic MOF support with a yield of 93.4%. Transmission electron microscopy characterization showed that the Fe3O4 core particle size was approximately 300 nm and the UiO-66-NH2 shell thickness was approximately 80 nm.

[0061] S2. The Fe3O4@UiO-66-NH2 magnetic MOF carrier and lipase are prepared into magnetic MOF immobilized lipase; including the following steps: the Fe3O4@UiO-66-NH2 magnetic MOF carrier is dispersed in glutaraldehyde solution for activation treatment, so that active aldehyde groups are introduced on the surface of the Fe3O4@UiO-66-NH2 magnetic MOF carrier; the activated Fe3O4@UiO-66-NH2 magnetic MOF carrier is added to phosphate buffer containing lipase; the lipase is immobilized on the surface of Fe3O4@UiO-66-NH2 magnetic MOF carrier by covalent bonding; after immobilization, the magnetic MOF immobilized lipase is obtained by separation and recovery by an external magnetic field and washing. Specifically, the Fe3O4@UiO-66-NH2 magnetic MOF support was dispersed in a glutaraldehyde solution for activation, including the following steps: 0.3g of the prepared Fe3O4@UiO-66-NH2 magnetic MOF support was dispersed in 10mL of phosphate buffer (the phosphate buffer concentration was 0.1mol / L, pH 7.0), sonicated for 5min, and 2.5mL of 25% glutaraldehyde aqueous solution was added to the dispersion. The mixture was then activated by shaking at 150rpm in a 50℃ water bath for 2h. After activation, the Fe3O4@UiO-66-NH2 magnetic MOF support was separated by an external magnetic field, and washed three times with phosphate buffer to remove excess glutaraldehyde, yielding the activated Fe3O4@UiO-66-NH2 magnetic MOF support for later use. 300 mg of the activated Fe3O4@UiO-66-NH2 magnetic MOF carrier was redispersed in 10 mL of phosphate buffer (0.1 mol / L, pH 7.0) to obtain a carrier dispersion. 20 mg of lipase B from Candida antarctica was dissolved in 5 mL of phosphate buffer to prepare a lipase solution. The lipase solution was added to the carrier dispersion, and the mixture was immobilized for 4 h at 160 rpm in a 25°C water bath. After immobilization, the immobilized enzyme was separated using an external magnetic field and washed three times with phosphate buffer until no protein was detected in the supernatant. The washed immobilized enzyme was collected and stored at 4°C for later use. The lipase loading was determined to be 55.2 mg / g carrier by the BCA method.

[0062] S3. Add palmitic acid and alanine in a molar ratio of 1:1 to a phosphate buffer solution. Add magnetic MOF immobilized lipase to the above solution to carry out the reaction. The amount of magnetic MOF immobilized lipase is 10 wt% of the total mass of fatty acids and amino acids. Place the reaction system in a 60℃ water bath shaker and shake at 200 rpm for 8 hours. After the reaction is completed, the magnetic MOF immobilized lipase in the reaction solution is separated and recovered by an external magnetic field. The reaction solution is then post-treated to obtain N-palmitoylalanine surfactant.

[0063] Comparative Example 1: Except for replacing the magnetic MOF-immobilized lipase with free Candida antarctica lipase B of equal activity, the remaining steps were the same as in Example 1. After the reaction, the catalyst could not be recovered by applying an external magnetic field, the product yield was 78.4%, and the HPLC purity was 91.2%. The second batch of reaction required the addition of free lipase again.

[0064] Comparative Example 2: Except for using a non-magnetic UiO-66-NH2 carrier to immobilize the lipase and centrifugation instead of magnetic separation, the remaining steps were the same as in Example 1. The product yield was 90.5%, the HPLC purity was 94.6%, the centrifugation recovery rate was 82.7%, and after 10 reuses, the product yield decreased to 63.5% of the initial yield.

[0065] Comparative Example 3: Except for the use of Fe3O4@UiO-66-NH2 magnetic MOF carrier for physical adsorption of lipase and the absence of glutaraldehyde activation treatment, the remaining steps were the same as in Example 1. The product yield was 86.8%, the HPLC purity was 93.4%, the magnetic separation recovery rate was 94.2%, the enzyme leakage rate was 8.9%, and after 10 reuses, the product yield decreased to 58.7% of the initial yield.

[0066] Performance Evaluation

[0067] Foam stabilization performance test method: Prepare a surfactant solution with a mass fraction of 1% using deionized water. Take 20 mL of the solution into a 100 mL stoppered graduated cylinder, sonicate for 30 min, and then shake vigorously 20 times. Record the initial foam height (H1, cm) and the foam height (H2, cm) after standing for 5 min. The larger this value, the better its foam stabilization performance.

[0068] Emulsification performance test method: Prepare a surfactant solution with a mass fraction of 1% using deionized water. Take 10 mL of the solution into a 100 mL stoppered graduated cylinder, add 10 mL of kerosene, shake vigorously 50 times, and let stand. Record the time it takes for 5 mL of aqueous phase to separate (separation time). Repeat the test three times and take the average value. The longer the separation time, the stronger its emulsification ability.

[0069] Product yield and purity testing methods: After acidification precipitation, filtration, washing and drying, the product mass was weighed and the product yield was calculated according to the theoretical yield. The dried product was dissolved in a methanol-water mixed solvent, filtered through a 0.22 μm filter membrane and then analyzed by HPLC. The product purity was calculated using the area normalization method. Each sample was measured in triplicate and the average value was taken.

[0070] Hysteresis loop test: The hysteresis loop of the sample was measured at room temperature using a vibrating sample magnetometer. The test magnetic field range was -20000 Oe to 20000 Oe. Taking the Fe3O4@UiO-66-NH2 magnetic MOF support prepared in Example 3 as an example, the test results are as follows: Figure 3 As shown.

[0071] Enzyme leakage rate test method: After each batch of reaction is completed and magnetic separation is finished, the reaction solution and washing solution are collected, and the content of free protein is determined by the Bradford method. The enzyme leakage rate is calculated based on the initial protein loading of the immobilized lipase. When the protein content in the washing solution is lower than the detection limit, it is determined that the unbound free lipase has been basically washed away.

[0072] Catalyst yield test: The magnetic MOF immobilized lipases prepared in Examples 1-4 were repeatedly tested according to the corresponding fatty acid, amino acid, molar ratio, catalyst dosage, reaction temperature, oscillation speed, and reaction time in S3 of each example. After each batch of reaction, the reaction vessel was placed next to a NdFeB permanent magnet for 3 minutes to allow the magnetic MOF immobilized lipase to accumulate on the vessel wall or bottom. The reaction solution was then poured out for product yield determination. The recovered immobilized enzyme was washed with phosphate buffer and directly added to the next batch of reaction, for a total of 10 batches. The product yields of the first, fifth, and tenth reactions were recorded, and the yield retention rate of the tenth product yield relative to the first product yield was calculated. After every 5 batches of reaction, the recovered immobilized enzyme was vacuum dried to constant weight, weighed, and the catalyst mass retention rate was calculated. The test results are shown below. Figure 4 As shown.

[0073] Test results showed that the initial product yields of Examples 1-4 were 95.8%, 92.6%, 96.1%, and 94.3%, respectively, with HPLC purities of 97.6%, 95.4%, 98.2%, and 96.7%, respectively; the magnetic separation recoveries after 3 min of separation under an external magnetic field were 98.1%, 95.8%, 98.4%, and 96.5%, respectively. After 10 consecutive cycles, the product yields of Examples 1-4 were 82.5%, 79.8%, 85.6%, and 81.5%, respectively, with corresponding yield retention rates of 86.1%, 86.2%, 89.1%, and 86.4%, respectively; the enzyme leakage rates in the reaction solution were 0.9%, 1.6%, 0.8%, and 1.2%, respectively. Compared with the comparative examples, this invention improves product yield, product purity, and catalyst reusability stability through the synergistic effect of high loading of the UiO-66-NH2 shell, covalent fixation of glutaraldehyde, and magnetic response separation of Fe3O4.

[0074] As verified by the examples, the product yield of the obtained N-acyl amino acid surfactant was 92.6-96.1%, and the HPLC purity was 95.4-98.2%. After separation by an external magnetic field for 3 min, the recovery rate of magnetic MOF immobilized lipase was 95.8-98.4%. After 10 consecutive cycles, the product yield still maintained 86.2-89.1% of the initial yield, and the enzyme leakage rate in the reaction solution was 0.8-1.6%.

[0075] The above examples are merely illustrative of the present invention and do not constitute a limitation on the scope of protection of the present invention. All designs that are the same as or similar to the present invention are within the scope of protection of the present invention.

Claims

1. A method for synthesizing N-acyl amino acid surfactants, characterized in that: Includes the following steps: S1. Preparation of Fe3O4@UiO-66-NH2 magnetic MOF support; S2. The Fe3O4@UiO-66-NH2 magnetic MOF support and lipase were used to prepare magnetic MOF immobilized lipase. S3. Add fatty acids and amino acids in a molar ratio of 1:1 to 1:3 to an aqueous phase or phosphate buffer solution. Add magnetic MOF-immobilized lipase to the above solution to carry out the reaction. After the reaction is completed, the magnetic MOF-immobilized lipase in the reaction solution is separated and recovered by an external magnetic field. The reaction solution is then post-treated to obtain an N-acyl amino acid surfactant.

2. The method for synthesizing N-acyl amino acid surfactants as described in claim 1, characterized in that: Step S1 includes the following steps: preparing Fe3O4 magnetic nanoparticles, coating the surface of Fe3O4 magnetic nanoparticles with a silica layer to obtain Fe3O4@SiO2, dispersing Fe3O4@SiO2 in an N,N-dimethylformamide solution containing a zirconium source and 2-aminoterephthalic acid, and growing a UiO-66-NH2 shell in situ on the surface of the magnetic core through a solvothermal reaction to obtain the Fe3O4@UiO-66-NH2 magnetic MOF support.

3. The method for synthesizing N-acyl amino acid surfactants as described in claim 1, characterized in that: Step S2 includes the following steps: dispersing the Fe3O4@UiO-66-NH2 magnetic MOF support in glutaraldehyde solution for activation treatment, thereby introducing active aldehyde groups onto the surface of the Fe3O4@UiO-66-NH2 magnetic MOF support; adding the activated Fe3O4@UiO-66-NH2 magnetic MOF support to phosphate buffer containing lipase; and immobilizing the lipase on the surface of the Fe3O4@UiO-66-NH2 magnetic MOF support by covalent bonding. After immobilization, the magnetic MOF immobilized lipase is obtained by separation and recovery by an external magnetic field and washing.

4. The method for synthesizing N-acyl amino acid surfactants as described in claim 2, characterized in that: In step S1, the particle size of Fe3O4@SiO2 is 100-300 nm; the thickness of the UiO-66-NH2 shell is 30-80 nm.

5. The method for synthesizing N-acyl amino acid surfactants as described in claim 3, characterized in that: In step S2, the mass ratio of Fe3O4@UiO-66-NH2 magnetic MOF carrier to lipase is 5:1-20:

1.

6. The method for synthesizing N-acyl amino acid surfactants as described in claim 3, characterized in that: The activation process of dispersing the Fe3O4@UiO-66-NH2 magnetic MOF support in glutaraldehyde solution in step S2 includes: dispersing the Fe3O4@UiO-66-NH2 magnetic MOF support in phosphate buffer, adding the phosphate buffer containing the Fe3O4@UiO-66-NH2 magnetic MOF support to the glutaraldehyde aqueous solution, and activating by shaking at 25-50°C for 1-3 hours.

7. The method for synthesizing N-acyl amino acid surfactants as described in claim 1, characterized in that: The fatty acids in step S3 are C8-C6. 18 Saturated or unsaturated fatty acids.

8. The method for synthesizing N-acyl amino acid surfactants as described in claim 7, characterized in that: The C8~C 18 The saturated or unsaturated fatty acids are one or more of the following: caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, oleic acid, and linoleic acid.

9. The method for synthesizing N-acyl amino acid surfactants as described in claim 1, characterized in that: The amino acid in step S3 is one or more of glycine, alanine, glutamic acid, sarcosine, and proline.

10. The method for synthesizing N-acyl amino acid surfactants as described in claim 1, characterized in that: The post-treatment in step S3 includes adjusting the pH of the reaction solution to 2-3 with acid to precipitate the product, followed by filtration, washing, and drying to obtain N-acyl amino acid surfactant powder.

Images