A polycaprolactam efficient enzymolysis process based on hydrothermal pretreatment and multi-enzyme synergistic catalysis

Abstract

This invention relates to the field of polymer material chemistry and biological recycling technology, specifically to a highly efficient enzymatic hydrolysis process for polycaprolactam based on hydrothermal pretreatment and multi-enzyme synergistic catalysis. The highly efficient enzymatic hydrolysis process for polycaprolactam based on hydrothermal pretreatment and multi-enzyme synergistic catalysis provided by this invention includes hydrothermal pretreatment, primary enzymatic depolymerization, secondary enzymatic depolymerization, and product post-processing steps. By combining a two-step strategy of hydrothermal pretreatment and multi-enzyme synergistic hydrolysis, highly efficient depolymerization of PA6 is achieved, and the PA6 hydrolytic enzyme used can be recycled, greatly reducing degradation costs and providing a new approach for the monomer recovery and high-value utilization of PA6.

Description

Technical Field

[0001] This invention relates to the field of polymer material chemistry and biological recycling technology, specifically to a high-efficiency enzymatic hydrolysis process for polycaprolactam based on hydrothermal pretreatment and multi-enzyme synergistic catalysis. Background Technology

[0002] Polycaprolactam (PA6) is widely used in textiles, automobiles, and electronics due to its excellent mechanical properties, abrasion resistance, and chemical stability. However, its inherent chemical stability also makes it difficult to degrade in the natural environment after disposal, causing serious "white pollution" problems. Traditional PA6 disposal methods, such as landfill and incineration, pose environmental risks such as occupying land resources and generating harmful gases. PA6 recycling methods mainly include mechanical recycling, chemical recycling, and biological recycling. Although mechanical recycling is simple to operate, repeated recycling leads to material performance degradation, resulting in a "degradation cycle" and making it difficult to meet the requirements of high-performance materials. Chemical recycling can convert PA6 waste into valuable chemicals, such as monomers and oligomers, providing the possibility for the recycling of PA6. Chemical recycling methods are mainly based on hydrolysis, pyrolysis, alcoholysis, aminolysis, and glycolysis. However, all of these methods require harsh reaction conditions (such as strong acids or strong bases), which not only leads to high energy consumption and increased recycling costs but also generates new secondary environmental pollution problems. Bio-enzymatic hydrolysis, as an environmentally friendly, mild, and low-energy-consumption green technology, has shown great potential in the field of polymer degradation.

[0003] Current research has revealed that certain enzymes, such as proteases, keratinases, and amidases, can hydrolyze PA6. Based on their cleavage patterns, they can be categorized as NylA (breaking cyclic dimers to generate linear dimers), NylB (exo-cleaving of linear dimers and linear oligomers into monomers), and NylC (endo-cleaving of cyclic and linear oligomers into linear dimers). Amidases UMG-SP-2 and UMG-SP-1, acting as endonucleases (cleaving PA6 into soluble oligomers) and exonucleases (cleaving soluble oligomers into monomers), respectively, exhibit certain hydrolytic activity against PA6 oligomers and certain surfaces.

[0004] However, due to the high crystallinity and hydrophobicity of PA6, its macroscopic solid form makes it extremely difficult for enzymes to access, resulting in very low efficiency and a very long cycle for direct enzymatic hydrolysis, which seriously hinders the industrial application of this technology. Furthermore, no enzyme has yet been found capable of directly degrading PA6 into monomers in one step. Therefore, a multi-enzyme synergistic degradation approach is used during enzymatic hydrolysis. However, simultaneous degradation by multiple enzymes can lead to poor compatibility between enzymes, resulting in unsatisfactory hydrolysis effects. In addition, compared to mechanical and chemical recycling, the production cost of enzymes in enzyme degradation recycling is higher, thus requiring immobilization methods to achieve enzyme recovery and reuse. Summary of the Invention

[0005] In view of this, the present invention provides a high-efficiency enzymatic hydrolysis process for polycaprolactam based on hydrothermal pretreatment and multi-enzyme synergistic catalysis. This process innovatively combines hydrothermal pretreatment with a multi-enzyme system. The hydrothermal pretreatment significantly alters the physical morphology and chemical accessibility of PA6, creating conditions for subsequent enzymatic hydrolysis reactions, thereby achieving efficient and deep degradation of PA6. It is a high-efficiency, green, and controllable PA6 enzymatic hydrolysis process.

[0006] To address the above technical problems, this invention provides a highly efficient enzymatic hydrolysis process for polycaprolactam based on hydrothermal pretreatment and multi-enzyme synergistic catalysis, comprising the following steps:

[0007] Hydrothermal pretreatment: The polycaprolactam waste to be treated is washed and crushed, mixed with water and subjected to hydrothermal reaction. After the reaction is completed, it is cooled to room temperature to obtain a pretreated slurry containing caprolactam monomer, soluble oligomers and insoluble PA polymers with reduced crystallinity.

[0008] Primary enzymatic depolymerization: The pretreated slurry is mixed with a buffer solution with a pH of 6.5-9.5, a first hydrolytic enzyme is added, and primary enzymatic depolymerization is carried out at a temperature of 30-70℃ to obtain a primary depolymerization slurry containing aminocaproic acid monomer, caprolactam monomer and linear soluble oligomers.

[0009] Secondary enzymatic depolymerization: A second hydrolytic enzyme is added to the primary depolymerization slurry, and secondary enzymatic depolymerization is carried out at pH 6.5~9.5 and temperature 25~70℃ to obtain a secondary depolymerization slurry containing caprolactam monomer and aminocaproic acid monomer.

[0010] Product post-processing: The secondary depolymerization slurry is filtered, concentrated, fractionated under reduced pressure and recrystallized to obtain caprolactam monomer and aminocaproic acid monomer.

[0011] The enzymatic hydrolysis process provided by this invention first involves hydrothermal pretreatment of the waste material to be degraded. Under a high-temperature and high-pressure hydrothermal environment, water molecules penetrate and act on the molecular chains of PA6, effectively destroying its crystal structure, weakening intermolecular hydrogen bonds, and inducing partial hydrolysis and depolymerization. Ultimately, PA6 dissolves or swells to varying degrees in the aqueous solution, forming a pretreated slurry containing caprolactam monomers, soluble oligomers, and insoluble PA polymers with reduced crystallinity. This transforms the solid PA6 into a "pre-depolymerized" state, which is more susceptible to enzymatic attack. Then, a stepwise enzymatic hydrolysis method is used for catalytic depolymerization: the first hydrolytic enzyme opens the ring-shaped PA molecules, catalytically depolymerizing the cyclic soluble oligomers in the pretreated slurry into linear soluble oligomers (including linear dimers and linear soluble oligomers with more than one dimer); the second hydrolytic enzyme further degrades the linear soluble oligomers obtained from the first enzymatic depolymerization step into aminocaproic acid monomers, yielding a secondary depolymerization slurry containing caprolactam monomers and aminocaproic acid monomers. After filtration, concentration and recrystallization, caprolactam monomer and aminocaproic acid monomer were obtained.

[0012] In conjunction with the first aspect, in the hydrothermal pretreatment step, the mass ratio of the crushed polycaprolactam waste to water is 1:4~20; the hydrothermal reaction is carried out in a high-temperature and high-pressure reactor at a reaction temperature of 180~250℃ and a reaction time of 10~30h. These reaction conditions can ensure that the polycaprolactam waste achieves a better depolymerization effect.

[0013] Preferably, in the hydrothermal pretreatment step, the mass ratio of the pulverized polycaprolactam waste to water is 1:5~9; the hydrothermal reaction is carried out in a high-pressure reactor at a reaction temperature of 200~220℃ for 15~30h.

[0014] In conjunction with the first aspect, in the primary enzyme-catalyzed depolymerization step, the first hydrolase is a mixture of a ring-opening enzyme and an endonuclease, or at least one of them; in the secondary enzyme-catalyzed depolymerization step, the second hydrolase is an exonuclease.

[0015] Among them, the ring-opening enzyme and endonuclease can open the ring of PA6 and cleave the PA polymer into soluble oligomers, while the exonuclease can further cleave the soluble oligomers into monomers.

[0016] In conjunction with the first aspect, in a single enzymatic depolymerization step, the first hydrolytic enzyme is either a free enzyme or an immobilized enzyme;

[0017] When the first hydrolytic enzyme is an immobilized enzyme, the steps of the primary enzyme-catalyzed depolymerization step are as follows:

[0018] The pretreated slurry was mixed with a buffer solution with a pH of 6.5 to 9.5, and the immobilized enzyme of the first hydrolytic enzyme was added. The mixture was subjected to a single enzymatic depolymerization at a temperature of 30 to 70°C. Solid-liquid separation was performed to obtain a single depolymerization solution containing aminocaproic acid monomer, caprolactam monomer and linear soluble oligomer, as well as the immobilized enzyme containing the first hydrolytic enzyme and insoluble PA polymer with reduced crystallinity.

[0019] The immobilized enzyme is separated and then recycled for a single enzyme-catalyzed depolymerization step.

[0020] In conjunction with the first aspect, in the secondary enzyme-catalyzed depolymerization step, the second hydrolytic enzyme is either a free enzyme or an immobilized enzyme;

[0021] When the second hydrolytic enzyme is an immobilized enzyme, the steps of the secondary enzyme-catalyzed depolymerization step are as follows:

[0022] Immobilized enzyme of the second hydrolase was added to the primary depolymerization slurry, and secondary enzyme-catalyzed depolymerization was carried out at pH 6.5~9.5 and temperature 25~70℃. Solid-liquid separation was performed to obtain a secondary depolymerization solution containing caprolactam monomer and aminocaproic acid monomer and immobilized enzyme containing the second hydrolase.

[0023] The immobilized enzyme is cycled and used in the secondary enzyme-catalyzed depolymerization step.

[0024] In conjunction with the first aspect, the immobilized enzyme includes at least one of carrier covalently immobilized enzyme, carrier adsorption immobilized enzyme, cross-linked enzyme polymer immobilized enzyme, and cross-linked enzyme crystal immobilized enzyme.

[0025] Preferably, the immobilized enzyme is a porous cross-linked enzyme polymer or a cross-linked enzyme polymer.

[0026] Preferably, the porous cross-linked enzyme polymer can be prepared by the following method:

[0027] The enzyme was added to the starch paste at a mass ratio of 0.015 to 0.75:1 to obtain a mixed solution. After stirring evenly at 4–30°C, an organic solvent of 7–9 times its mass was added and stirred for 30 minutes to obtain a suspension of enzyme-starch co-precipitated aggregates. Glutaraldehyde was added to this suspension, adjusting the amount to a final mass percentage of 1.0%–5.0%. The mixture was then stirred at 4–30°C for 4–16 hours to allow the glutaraldehyde to cross-link with the amino groups on the enzyme molecules, forming a strong, insoluble enzyme-starch complex aggregate. After cross-linking was complete, the mixture was subjected to a reaction at 8000–10000 °C. Centrifuge at rpm for 1-5 minutes, discard the supernatant, and wash the complex aggregates 3-5 times with phosphate buffer to remove unreacted organic solvents and impurities such as glutaraldehyde. Redisperse the washed aggregates in phosphate buffer at pH 7.0, and add 1%-10% α-amylase solution, where the mass ratio of phosphate buffer to α-amylase solution is 15-20:1. Stir and react at room temperature for 12-24 hours. After the reaction is complete, centrifuge and wash the precipitate multiple times with phosphate buffer to obtain porous cross-linked enzyme aggregates with a porous internal structure, and store at 4℃ for later use.

[0028] Preferably, the starch paste used can be prepared according to the following method:

[0029] S1. Dissolve a certain amount of water-soluble starch in phosphate buffer solution to obtain a starch solution;

[0030] S2. Gelatinize the starch solution by heating it in a boiling water bath for 2-4 minutes.

[0031] S3. Cool the gelatinized starch solution to room temperature before use.

[0032] Gelatinization of starch solution can destroy the crystalline structure of starch, making it a homogeneous colloidal solution that is easier to mix with enzyme molecules.

[0033] Preferably, the starch is corn starch, tapioca starch, potato starch, or wheat starch.

[0034] Preferably, the organic solvent is selected from at least one of ethanol, methanol, acetone or polyethylene glycol.

[0035] Preferably, the mass ratio of the water-soluble starch to the phosphate buffer solution is 1:5~10.

[0036] Preferably, the method for preparing the cross-linked enzyme polymer is as follows:

[0037] Add organic solvent dropwise to the enzyme solution while stirring to mix evenly. After the addition is complete, let it stand at 2-6°C for 25-35 minutes to precipitate, and obtain a suspension containing insoluble enzyme polymers.

[0038] The suspension was subjected to solid-liquid separation, the solid phase was collected, washed and dispersed in phosphate buffer, glutaraldehyde was added to make the final mass percentage of glutaraldehyde 1.0%~5.0%, and the mixture was stirred at 4~30℃ for 4~16h. The solid phase particles were then separated and washed to obtain the cross-linked enzyme polymer.

[0039] Preferably, the organic solvent is selected from at least one of ethanol, methanol, acetone or polyethylene glycol.

[0040] Preferably, the ring-opening enzyme is selected from at least one of NylC, mutants of NylC, NylA, and mutants of NylA; the endonuclease includes at least one of NylC, mutants of NylC, and UMG-SP-2; and the exonuclease includes at least one of NylB, mutants of NylB, and UMG-SP-1.

[0041] Preferably, the first hydrolase is NylC. k -TS and NylA, the second hydrolase is NylB, wherein NylC k -TS and NylA have a mass ratio of 1:0.25~0.5; or, the first hydrolase is UMG-SP-2 and the second hydrolase is UMG-SP-1.

[0042] In conjunction with the first aspect, in the primary enzyme-catalyzed depolymerization step, the mass ratio of the pretreated slurry to the buffer solution is 1:0.8~1.2; the buffer solution is selected from at least one of phosphate buffer, tris(hydroxymethyl)aminomethane-hydrochloric acid buffer, and water; and the concentration of the buffer solution is 15~30 mM.

[0043] In conjunction with the first aspect, the polycaprolactam waste includes textile fabrics, engineering plastics, fiber products, or film and pipe products containing polycaprolactam.

[0044] In conjunction with the first aspect, the amount of the first hydrolase and the second hydrolase added is 0.25% to 2.5% of the dry weight of the pulverized polycaprolactam waste. This amount can ensure the enzymatic hydrolysis effect on polycaprolactam without increasing the cost due to excessive addition.

[0045] Preferably, the enzymatic hydrolysis process of the present invention can also be used to degrade other types of waste containing polycaprolactam.

[0046] Compared with existing technologies, the high-efficiency enzymatic hydrolysis process for polycaprolactam based on hydrothermal pretreatment and multi-enzyme synergistic catalysis provided by this invention has the following beneficial effects:

[0047] (1) The present invention adopts a breakthrough pretreatment: high temperature and high pressure hydrothermal pretreatment is adopted to realize the transformation of PA6 from "non-degradable solid" to "enzyme accessible state" in a non-invasive and green way, which is the premise and key to subsequent efficient enzymatic hydrolysis.

[0048] (2) The present invention adopts a synergistic enzymatic hydrolysis system: the innovative use of a multi-enzyme synergistic catalytic system, different enzymes produce synergistic effects on attack sites and substrate specificity, to achieve precise and efficient cleavage of the pretreated PA6 molecular chain, and significantly improve the monomer yield (over 97%).

[0049] (3) The present invention uses starch as a pore-forming agent, which can effectively obtain enzyme cross-linked aggregates with excellent enzyme activity efficiency and can be repeatedly recycled, thus greatly reducing the cost of enzyme use.

[0050] (4) The process adopted in this invention is green and efficient: the whole process uses water as the main medium, the reaction conditions are relatively mild, and there is no need to use a large amount of organic solvents or strong acids and bases. It is environmentally friendly, has low energy consumption, and meets the requirements of green chemistry and sustainable development.

[0051] (5) The degradation degree of the present invention is controllable: by adjusting the intensity of hydrothermal pretreatment (including reaction temperature, time and liquid-solid ratio, etc.) and enzymatic hydrolysis conditions (including enzyme ratio, enzymatic hydrolysis temperature and time, etc.), the composition (e.g., whether the product obtained is a monomer or an oligomer) and distribution of degradation products can be controlled to meet the needs of different downstream applications. Attached Figure Description

[0052] Figure 1 This is a flowchart of the enzymatic hydrolysis process according to an embodiment of the present invention. Detailed Implementation

[0053] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0054] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the meaning consistent with their meaning in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless specifically defined.

[0055] Currently, although studies have found that certain enzymes, such as proteases, keratinases, and amidases, can hydrolyze PA6, the current enzymatic hydrolysis efficiency is extremely low and the hydrolysis cycle is extremely long, making it difficult to achieve large-scale application and limiting the development of enzymatic hydrolysis in industrial applications. In view of this, this invention provides a highly efficient enzymatic hydrolysis process for polycaprolactam based on hydrothermal pretreatment and multi-enzyme synergistic catalysis. This process can effectively disrupt the physical structure of PA6, increase the enzyme's sensitivity to PA6, thereby achieving highly efficient enzymatic hydrolysis of PA6 and successfully utilizing enzymatic hydrolysis for large-scale biorecycling of PA6.

[0056] The enzymatic hydrolysis process provided by the present invention will be described below through specific embodiments.

[0057] Unless otherwise specified, the raw materials, reagents and equipment used in this invention are all conventional commercially available reagents and equipment.

[0058] The NylA sequence used in this invention (as shown in SEQ ID NO.1) is derived from Arthrobacter sp. K172, and the vector is pET28a, which was synthesized by Genewiz and expressed in Escherichia coli BL21(DE3).

[0059] The NylB-SCY sequence (as shown in SEQ ID NO.2) is derived from the NylB homolog of Arthrobacter sp. K172. It was modified by Gregg T. Beckham et al. of the National Renewable Energy Laboratory in the United States to obtain NylB-SCY (R187S / F264C / D370Y). The vector is pET28a, which was synthesized by Genewiz and expressed in Escherichia coli BL21(DE3).

[0060] NylC k The -TS sequence (as shown in SEQ ID NO.3) is derived from basophilic Kocuria sp. and modified by Gregg T. Beckham et al. of the National Renewable Energy Laboratory in the United States to obtain NylC. k The -TS (S111G / A137L) mutant, using the pET28a vector synthesized by Genewiz, was expressed in Escherichia coli BL21(DE3).

[0061] The sequence of UMG-SP-1 can be found in GenBank (OP972509). The vector is pET26b, synthesized by Genewiz, and expressed in Escherichia coli BL21(DE3).

[0062] The sequence of UMG-SP-2 can be found in GenBank (OP972510). The vector is pET26b, which was synthesized by Genewiz and expressed in Escherichia coli BL21(DE3).

[0063] Example 1

[0064] This embodiment provides a highly efficient enzymatic hydrolysis process for polycaprolactam based on hydrothermal pretreatment and multi-enzyme synergistic catalysis, the steps of which include:

[0065] Hydrothermal pretreatment: Waste PA6 material (a mixture of fishing nets and textiles) is washed, dried and crushed into particles or powder with a particle size of 0.1-2 mm. 5 g of crushed PA6 and deionized water are weighed and placed in a high-pressure reactor at a mass ratio of 1:7. Then, the mixture is transferred to a forced-air drying oven for hydrothermal pretreatment reaction at a reaction temperature of 220℃ for 30 h. After the reaction is completed, the mixture is cooled to room temperature to obtain a pretreated slurry containing caprolactam monomer, soluble oligomers and insoluble PA polymers with reduced crystallinity.

[0066] Preparation of PA6 hydrolase porous cross-linked enzyme polymer: NylC k -TS and NylA were added to a phosphate buffer solution at a mass ratio of 1:0.35 (to obtain an enzyme solution concentration of 8 mg / ml), and then added to corn starch paste, where the enzyme solution to corn starch paste mass ratio was 0.75:1. The mixture was stirred thoroughly at 25°C, and then 8 times the mass of the mixture was added to ethanol and stirred for 30 min to obtain NylC. k A suspension of TS / NylA-starch coprecipitate aggregates was prepared. Glutaraldehyde was added to the suspension, adjusting the amount to a final mass percentage concentration of 1.0%. The mixture was stirred at 25°C for 16 hours to allow glutaraldehyde to cross-link with the amino groups on the enzyme molecules, forming a robust, insoluble enzyme-starch complex aggregate. After cross-linking, the mixture was centrifuged at 8000 rpm for 5 minutes, and the supernatant was discarded. The precipitate was washed five times with phosphate buffer to remove unreacted ethanol and glutaraldehyde. The washed precipitate was redispersed in phosphate buffer at pH 7.0, and 5% α-amylase solution was added (phosphate buffer to α-amylase solution mass ratio 18:1). The mixture was stirred at room temperature for 18 hours. After the reaction, the precipitate was centrifuged and washed multiple times with phosphate buffer to obtain the porous cross-linked enzyme aggregate of the first hydrolase with a porous internal structure—NylC. k -TS / NylA porous cross-linked enzyme polymer, stored at 4℃.

[0067] Preparation of PA6 hydrolase cross-linked enzyme polymers: Under stirring or shaking conditions, 8 times the mass of ethanol was added dropwise to NylB-SCY enzyme solution (mass concentration of 8 mg / ml). After the addition was complete, the mixture was shaken and allowed to stand at 4℃ for 30 minutes to allow the enzyme molecules to precipitate from the solution, forming a suspension containing insoluble enzyme polymers. Glutaraldehyde was added to the suspension, and the amount of glutaraldehyde added was adjusted to a final mass percentage concentration of 1.0%. The mixture was stirred at 25℃ for 16 hours to allow the glutaraldehyde to cross-link with the amino groups on the enzyme molecules. After the cross-linking was completed, the supernatant was discarded after centrifugation, and the obtained NylB-SCY cross-linked enzyme polymer particles were collected. The particles were washed repeatedly with phosphate buffer to completely remove unreacted glutaraldehyde and stored at 4℃.

[0068] One-step enzymatic depolymerization: The entire pretreated slurry was used as substrate and mixed with a 15 mM potassium phosphate buffer solution (pH 7.0) at a 1:1 mass ratio. Then, 1% of the prepared NylC was added based on the dry weight of the PA6 material. k -TS / NylA porous cross-linked enzyme polymers were enzymatically hydrolyzed at 60°C with constant shaking for 24 hours. After hydrolysis, the reaction solution was centrifuged and filtered to obtain a primary depolymerization solution containing aminocaproic acid monomer, caprolactam monomer, and linear soluble oligomers. The resulting solid was NylC. k -TS / NylA porous cross-linked enzyme polymers are stored at 4°C and recycled.

[0069] Secondary enzymatic depolymerization: 1.8% of NylB-SCY cross-linking enzyme polymer based on the dry weight of PA6 material was added to the obtained primary depolymerization solution. Enzymatic hydrolysis was carried out for 24 hours under constant temperature shaking at 50℃. After the enzymatic hydrolysis was completed, centrifugation was performed to obtain a secondary depolymerization solution containing caprolactam monomer and aminocaproic acid monomer and NylB-SCY cross-linking enzyme polymer precipitate. The NylB-SCY cross-linking enzyme polymer precipitate was stored at 4℃ and recycled.

[0070] Product post-processing: The secondary depolymerization solution was concentrated by vacuum distillation, and then fractionated under vacuum. The product after vacuum fractionation was recrystallized in water and dried to obtain 0.0166 mol caprolactam monomer and 0.0266 mol aminocaproic acid monomer. The purity was tested to be >98% and the yield was 98.2%.

[0071] Monomer yield (%) = [(Amount of caprolactam actually obtained + Amount of aminocaproic acid actually obtained) / Amount of monomer theoretically obtained] × 100%, where the amount of monomer theoretically obtained is 0.044 mol.

[0072] The yields of the following examples and comparative examples were calculated according to the above formula.

[0073] Example 2

[0074] This embodiment provides a highly efficient enzymatic hydrolysis process for polycaprolactam based on hydrothermal pretreatment and multi-enzyme synergistic catalysis, the steps of which include:

[0075] Hydrothermal pretreatment: Waste PA6 material (a mixture of fishing nets, textiles and industrial waste) is cleaned, dried and crushed into particles or powder with a particle size of 0.2-3mm. 5g of crushed PA6 is weighed and placed in a high-pressure reactor with deionized water at a mass ratio of 1:9. Then it is transferred to a forced-air drying oven for hydrothermal pretreatment reaction at a reaction temperature of 220℃ for 30h. After the reaction is completed, it is cooled to room temperature to obtain a pretreated slurry containing caprolactam monomer, soluble oligomers and insoluble PA polymers with reduced crystallinity.

[0076] Preparation of porous cross-linked enzyme polymers of PA6 hydrolase: UMG-SP-2 was added to phosphate buffer solution (to obtain an enzyme concentration of 5 mg / ml), and then added to wheat starch paste, with an enzyme solution:wheat starch paste mass ratio of 0.65:1. The mixture was stirred at 25℃ until homogeneous, and then 7 times the mass of the mixture was added to acetone and stirred for 30 min to obtain a suspension of UMG-SP-2-starch coprecipitate aggregates. Glutaraldehyde was added to the suspension to adjust the final mass percentage concentration to 2.0%. The mixture was stirred at 25℃ for 16 h to allow glutaraldehyde to cross-link with the amino groups on the enzyme molecules, forming a robust, insoluble enzyme-starch complex aggregate. After cross-linking, the mixture was centrifuged at 8000 rpm for 5 min, the supernatant was discarded, and the precipitate was washed 5 times with phosphate buffer to remove unreacted acetone and glutaraldehyde impurities. The washed precipitate was redispersed at pH = 8% (w / w) α-amylase solution was added to 7.0% phosphate buffer, with a phosphate buffer to α-amylase solution mass ratio of 15:1. The mixture was stirred and reacted at room temperature for 24 h. After the reaction was completed, the mixture was centrifuged and the precipitate was washed multiple times with phosphate buffer to obtain PA6 hydrolase porous cross-linked enzyme polymer—UMG-SP-2 porous cross-linked enzyme polymer with a porous internal structure, which was stored at 4 °C.

[0077] Preparation of PA6 hydrolase cross-linked enzyme polymers: Under stirring or shaking conditions, 7 times the mass of acetone was added dropwise to UMG-SP-1 enzyme solution (mass concentration of 5 mg / ml). After the addition was complete, the mixture was shaken and allowed to stand at 4℃ for 30 minutes to allow the enzyme molecules to precipitate from the solution, forming a suspension containing insoluble enzyme polymers. Glutaraldehyde was added to the suspension, and the amount of glutaraldehyde added was adjusted to a final mass percentage concentration of 2.0%. The mixture was stirred at 25℃ for 10 hours to allow the glutaraldehyde to cross-link with the amino groups on the enzyme molecules. After the cross-linking was completed, the supernatant was discarded after centrifugation, and the obtained UMG-SP-1 cross-linked enzyme polymer particles were collected. The particles were washed repeatedly with phosphate buffer to completely remove unreacted glutaraldehyde and stored at 4℃.

[0078] Primary enzymatic depolymerization: The entire pretreated slurry was used as substrate and mixed with 30 mM potassium phosphate buffer (pH 7.0) at a 1:1 mass ratio. Then, 1% of the prepared UMG-SP-2 porous cross-linked enzyme polymer was added based on the dry weight of the PA6 material. Enzymatic hydrolysis was performed at 40°C with shaking for 24 hours. After hydrolysis, the reaction solution was centrifuged and filtered to obtain a primary depolymerization solution containing aminocaproic acid monomer, caprolactam monomer, and linear soluble oligomers. The resulting solid was the PA6 hydrolase porous cross-linked enzyme polymer, which was stored at 4°C and recycled.

[0079] Secondary enzymatic depolymerization: 1.2% of the dry weight of PA6 material UMG-SP-1 cross-linking enzyme polymer was added to the primary depolymerization solution. Enzymatic hydrolysis was carried out for 24 hours under constant temperature shaking at 25℃. After the enzymatic hydrolysis was completed, centrifugation was performed to obtain a secondary depolymerization solution containing caprolactam monomer and aminocaproic acid monomer and UMG-SP-1 cross-linking enzyme polymer precipitate. The UMG-SP-1 cross-linking enzyme polymer precipitate was stored at 4℃ and recycled.

[0080] Product post-processing: The secondary depolymerization solution was concentrated by vacuum distillation, and then fractionated under vacuum. The product after vacuum fractionation was recrystallized in water and dried to obtain 0.0186 mol of caprolactam monomer and 0.0251 mol of aminocaproic acid monomer. The purity was tested to be >98% and the yield was 99.3%.

[0081] Example 3

[0082] Hydrothermal pretreatment: Waste PA6 material (a mixture of fishing nets and textiles) is washed, dried and crushed into particles or powder with a particle size of 1-4 mm. 5 g of crushed PA6 and deionized water are weighed and placed in a high-pressure reactor at a mass ratio of 1:4. Then, the mixture is transferred to a forced-air drying oven for hydrothermal pretreatment reaction at a reaction temperature of 180℃ for 30 h. After the reaction is completed, the mixture is cooled to room temperature to obtain a pretreated slurry containing caprolactam monomer, soluble oligomers and insoluble PA polymers with reduced crystallinity.

[0083] Preparation of PA6 hydrolase porous cross-linked enzyme polymer: NylC k -TS and NylA were added to a phosphate buffer solution at a mass ratio of 1:0.5 (to obtain an enzyme solution concentration of 5 mg / ml), and then added to cassava starch paste, where the enzyme solution to cassava starch paste mass ratio was 0.015:1. The mixture was stirred thoroughly at 25°C, and then 9 times the mass of methanol (by weight of the mixture) was added and stirred for 30 min to obtain NylC. k A suspension of -TS / NylA-starch coprecipitate aggregates was prepared. Glutaraldehyde was added to the suspension, adjusting the amount to a final mass percentage concentration of 4.0%. The mixture was stirred at 20°C for 16 hours to allow glutaraldehyde to cross-link with the amino groups on the enzyme molecules, forming a robust, insoluble enzyme-starch complex aggregate. After cross-linking, the mixture was centrifuged at 10,000 rpm for 3 minutes, and the supernatant was discarded. The precipitate was washed three times with phosphate buffer to remove unreacted methanol and glutaraldehyde. The washed precipitate was redispersed in phosphate buffer at pH 7.0, and 10% α-amylase solution was added (phosphate buffer to α-amylase solution mass ratio 20:1). The mixture was stirred at room temperature for 12 hours. After the reaction, the precipitate was centrifuged and washed multiple times with phosphate buffer to obtain a porous cross-linked enzyme aggregate of PA6 hydrolase—NylC. k -TS / NylA porous cross-linked enzyme polymer, stored at 4℃.

[0084] Preparation of PA6 hydrolase cross-linked enzyme polymers: Under stirring or shaking conditions, methanol (9 times the mass of the enzyme solution) was added dropwise to NylB-SCY enzyme solution (10 mg / ml). After the addition was complete, the mixture was shaken and allowed to stand at 4°C for 30 minutes to allow the enzyme molecules to precipitate from the solution, forming a suspension containing insoluble enzyme polymers. Glutaraldehyde was added to the suspension, and the amount of glutaraldehyde added was adjusted to a final mass percentage concentration of 5.0%. The suspension was then stirred at 15°C for 13 hours to allow the glutaraldehyde to cross-link with the amino groups on the enzyme molecules. After the cross-linking was completed, the supernatant was discarded after centrifugation, and the obtained NylB-SCY cross-linked enzyme polymer particles were collected. The particles were washed repeatedly with phosphate buffer to completely remove unreacted glutaraldehyde and stored at 4°C.

[0085] One-step enzymatic depolymerization: The entire pretreated slurry was used as substrate and mixed with 18 mM potassium phosphate buffer (pH 7.5) at a mass ratio of 1:0.8. Then, 2.5% of the prepared NylC was added based on the dry weight of the PA6 material. k-TS / NylA porous cross-linked enzyme polymers were enzymatically hydrolyzed at 40°C with constant shaking for 70 hours. After hydrolysis, the reaction solution was centrifuged and filtered to obtain a primary depolymerization solution containing aminocaproic acid monomers, caprolactam monomers, and linear soluble oligomers. The resulting solid was PA6 hydrolase porous cross-linked enzyme polymer, which was stored at 4°C and recycled.

[0086] Secondary enzymatic depolymerization: 2.5% of NylB-SCY cross-linking enzyme polymer (based on dry weight of PA6 material) was added to the primary depolymerization solution. Enzymatic hydrolysis was carried out for 10 hours under constant temperature shaking at 60℃. After hydrolysis, centrifugation was performed to obtain a secondary depolymerization solution containing caprolactam monomer and aminocaproic acid monomer, and NylB-SCY cross-linking enzyme polymer precipitate. The NylB-SCY cross-linking enzyme polymer precipitate was stored at 4℃ and recycled.

[0087] Product post-processing: The secondary depolymerization solution was concentrated by vacuum distillation, and then fractionated under vacuum. The product after vacuum fractionation was recrystallized in water and dried to obtain 0.0147 mol caprolactam monomer and 0.0282 mol aminocaproic acid monomer. The purity was tested to be >98% and the yield was 97.5%.

[0088] Example 4

[0089] This embodiment provides a highly efficient enzymatic hydrolysis process for polycaprolactam based on hydrothermal pretreatment and multi-enzyme synergistic catalysis, the steps of which include:

[0090] Hydrothermal pretreatment: Waste PA6 material (a mixture of fishing nets and industrial waste) is cleaned, dried and crushed into particles or powder with a particle size of 3-5 mm. 5 g of crushed PA6 is weighed and placed in a high-pressure reactor with deionized water at a mass ratio of 1:18. Then it is transferred to a forced-air drying oven for hydrothermal pretreatment reaction at a reaction temperature of 250℃ for 12 h. After the reaction is completed, it is cooled to room temperature to obtain a pretreated slurry containing caprolactam monomer, soluble oligomers and insoluble PA polymers with reduced crystallinity.

[0091] Preparation of PA6 hydrolase porous cross-linked enzyme polymers: UMG-SP-2 was added to phosphate buffer solution (to obtain an enzyme concentration of 10 mg / ml), and then added to potato starch paste, with an enzyme solution:potassium starch paste mass ratio of 0.5:1. After stirring at 10℃, 8 times the mass of the mixture of polyethylene glycol was added and stirred for 30 min to obtain a suspension of UMG-SP-2-starch coprecipitate aggregates. Glutaraldehyde was added to the suspension to adjust the final mass percentage concentration to 3.5%. The mixture was stirred at 10℃ for 16 h to allow glutaraldehyde to cross-link with the amino groups on the enzyme molecules, forming a robust, insoluble enzyme-starch complex aggregate. After cross-linking, the mixture was centrifuged at 8000 rpm for 5 min, the supernatant was discarded, and the precipitate was washed 5 times with phosphate buffer to remove unreacted polyethylene glycol and glutaraldehyde impurities. The washed precipitate was redispersed at pH = 5% α-amylase solution was added to 7.5% phosphate buffer, with a mass ratio of 18:1 between phosphate buffer and α-amylase solution. The mixture was stirred at room temperature for 18 hours. After the reaction was completed, the mixture was centrifuged and the precipitate was washed multiple times with phosphate buffer to obtain PA6 hydrolase porous cross-linked enzyme polymer—UMG-SP-2 porous cross-linked enzyme polymer with a porous internal structure, which was stored at 4℃.

[0092] Preparation of PA6 hydrolase cross-linked enzyme polymers: Under stirring or shaking conditions, 8 times the mass of polyethylene glycol was added dropwise to UMG-SP-1 enzyme solution (mass concentration of 8 mg / ml). After the addition was complete, the mixture was shaken and allowed to stand at 4℃ for 30 minutes to allow the enzyme molecules to precipitate from the solution, forming a suspension containing insoluble enzyme polymers. Glutaraldehyde was added to the suspension, and the amount of glutaraldehyde added was adjusted to a final mass percentage concentration of 4.0%. The mixture was stirred at 10℃ for 16 hours to allow the glutaraldehyde to cross-link with the amino groups on the enzyme molecules. After the cross-linking was completed, the supernatant was discarded after centrifugation, and the obtained UMG-SP-1 cross-linked enzyme polymer particles were collected. The particles were washed repeatedly with phosphate buffer to completely remove unreacted glutaraldehyde and stored at 4℃.

[0093] Primary enzymatic depolymerization: The entire pretreated slurry was used as substrate and mixed with 20 mM potassium phosphate buffer (pH 8.0) at a mass ratio of 1:1.2. Then, 2% of the prepared UMG-SP-2 porous cross-linked enzyme polymer was added based on the dry weight of the PA6 material. Enzymatic hydrolysis was carried out at 68℃ with shaking for 10 hours. After hydrolysis, the reaction solution was centrifuged and filtered to obtain a primary depolymerization solution containing aminocaproic acid monomer, caprolactam monomer, and linear soluble oligomers. The resulting solid was the PA6 hydrolase porous cross-linked enzyme polymer, which was stored at 4℃ and recycled.

[0094] Secondary enzymatic depolymerization: 1.0% of the dry weight of PA6 material UMG-SP-1 cross-linking enzyme polymer was added to the primary depolymerization solution, and enzymatic hydrolysis was carried out at a constant temperature of 45℃ for 10 hours. After the enzymatic hydrolysis was completed, centrifugation was performed to obtain a secondary depolymerization solution containing caprolactam monomer and aminocaproic acid monomer and UMG-SP-1 cross-linking enzyme polymer precipitate. The UMG-SP-1 cross-linking enzyme polymer precipitate was stored at 4℃ and recycled.

[0095] Product post-processing: The secondary depolymerization solution was concentrated by vacuum distillation, and then fractionated under vacuum. The product after vacuum fractionation was recrystallized in water and dried to obtain 0.0153 mol caprolactam monomer and 0.0280 mol aminocaproic acid monomer. The purity was tested to be >98% and the yield was 98.4%.

[0096] Example 5

[0097] This embodiment provides a highly efficient enzymatic hydrolysis process for polycaprolactam based on hydrothermal pretreatment and multi-enzyme synergistic catalysis, the steps of which include:

[0098] Hydrothermal pretreatment: Waste PA6 material (a mixture of fishing nets, textiles and films) is cleaned, dried and crushed into particles or powder with a particle size of 1-4 mm. 5 g of crushed PA6 and deionized water are weighed and placed in a high-pressure reactor at a mass ratio of 1:4. Then it is transferred to a forced-air drying oven for hydrothermal pretreatment reaction at a reaction temperature of 180℃ for 30 h. After the reaction is completed, it is cooled to room temperature to obtain the pretreated slurry.

[0099] Primary enzymatic depolymerization: The entire pretreated slurry was used as substrate and mixed with 18 mM potassium phosphate buffer (pH 7.5) at a 1:1 mass ratio. Then, NylC obtained in the primary enzymatic depolymerization step of Example 1 was added at 2.5% of the dry weight of PA6 material. k -TS / NylA porous cross-linked enzyme polymers were enzymatically hydrolyzed at 40°C with constant shaking for 70 hours. After hydrolysis, the reaction solution was centrifuged and filtered to obtain a primary depolymerization solution containing aminocaproic acid monomers, caprolactam monomers, and linear soluble oligomers. The resulting solid was PA6 hydrolase porous cross-linked enzyme polymer, which could be stored at 4°C and recycled.

[0100] Secondary enzymatic depolymerization: 2.5% of the dry weight of PA6 material of the NylB-SCY cross-linked enzyme polymer obtained in the secondary enzymatic depolymerization step in Example 1 was added to the primary depolymerization solution. Enzymatic hydrolysis was carried out for 10 hours under constant temperature shaking at 60°C. After the enzymatic hydrolysis was completed, centrifugation was performed to obtain a secondary depolymerization solution containing caprolactam monomer and aminocaproic acid monomer and NylB-SCY cross-linked enzyme polymer precipitate. The NylB-SCY cross-linked enzyme polymer precipitate was stored at 4°C and recycled.

[0101] Product post-processing: The secondary depolymerization solution was concentrated by vacuum distillation, and then fractionated under vacuum. The product after vacuum fractionation was recrystallized in water and dried to obtain 0.0188 mol of caprolactam monomer and 0.0244 mol of aminocaproic acid monomer. The purity was tested to be >98% and the yield was 98.2%.

[0102] Comparative Example 1

[0103] This comparative example provides a highly efficient enzymatic hydrolysis process for polycaprolactam based on hydrothermal pretreatment and simultaneous catalysis by multiple enzymes. The steps are similar to those in Example 1, except that the primary enzyme-catalyzed depolymerization and the secondary enzyme-catalyzed depolymerization are combined into one step, namely:

[0104] Hydrothermal pretreatment: Same as the corresponding steps in Example 1.

[0105] Preparation of PA6 hydrolase porous cross-linked enzyme polymer: Same as the corresponding steps in Example 1.

[0106] Preparation of PA6 hydrolase cross-linked polymer: Same as the corresponding steps in Example 1.

[0107] Multi-enzyme catalyzed depolymerization: The entire pretreated slurry obtained from the hydrothermal pretreatment step was used as the substrate and mixed with a 15 mM potassium phosphate buffer solution (pH 7.0) at a 1:1 mass ratio. Then, NylC was added at 1% of the dry weight of the PA6 material. k -TS / NylA porous cross-linked enzyme polymer and NylB-SCY cross-linked enzyme polymer prepared by adding 1.8% of PA6 material by dry weight were subjected to enzymatic hydrolysis at 60℃ with shaking for 24 hours. After enzymatic hydrolysis, the reaction solution was centrifuged and filtered to obtain a depolymerization solution containing caprolactam monomer, aminocaproic acid monomer and linear soluble oligomer, as well as NylC k -TS / NylA porous cross-linking enzyme polymer and NylB-SCY cross-linking enzyme polymer precipitate, store the cross-linking enzyme polymer at 4℃ and recycle it.

[0108] Product post-processing: The secondary depolymerization solution was concentrated by vacuum distillation, and then fractionated under vacuum. The product after vacuum fractionation was recrystallized in water and dried to obtain 0.0106 mol of caprolactam monomer and 0.0104 mol of aminocaproic acid monomer. The purity was tested to be >70% and the yield was 47.7%.

[0109] Comparative Example 2

[0110] This comparative example provides a highly efficient enzymatic hydrolysis process for polycaprolactam based on hydrothermal pretreatment and simultaneous catalysis by multiple enzymes. The steps are similar to those in Example 2, except that the primary enzyme-catalyzed depolymerization and the secondary enzyme-catalyzed depolymerization are combined into one step, namely:

[0111] Hydrothermal pretreatment: Same as the corresponding steps in Example 2.

[0112] Preparation of PA6 hydrolase porous cross-linked enzyme polymer: Same as the corresponding steps in Example 2.

[0113] Preparation of PA6 hydrolase cross-linked polymer: Same as the corresponding steps in Example 2.

[0114] Enzymatic depolymerization: The entire pretreated slurry obtained from the hydrothermal pretreatment step was used as the substrate and mixed with a 15 mM potassium phosphate buffer (pH 7.0) at a 1:1 mass ratio. Then, 1% of the prepared UMG-SP-2 porous cross-linked enzyme polymer and 1.2% of the prepared UMG-SP-1 cross-linked enzyme polymer were added based on the dry weight of PA6 material. Enzymatic hydrolysis was carried out at 40℃ with shaking for 24 hours. After enzymatic hydrolysis, the reaction solution was centrifuged and filtered to obtain a depolymerization solution containing caprolactam monomer, aminocaproic acid monomer, and linear soluble oligomers, as well as UMG-SP-2 porous cross-linked enzyme polymer and UMG-SP-1 cross-linked enzyme polymer precipitates. These were stored at 4℃ and recycled.

[0115] Product post-processing: The secondary depolymerization solution was concentrated by vacuum distillation, and then fractionated under vacuum. The product after vacuum fractionation was recrystallized in water and dried to obtain 0.0114 mol of caprolactam monomer and 0.0126 mol of aminocaproic acid monomer. The purity was tested to be >65% and the yield was 54.5%.

[0116] As can be seen from Examples 1-2 and Comparative Examples 1-2, only by using a multi-enzyme stepwise synergistic catalytic degradation method can PA6 molecules be degraded into caprolactam monomers and aminocaproic acid monomers more thoroughly.

[0117] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A process for efficient enzymatic hydrolysis of polycaprolactam based on hydrothermal pretreatment and multi-enzyme synergistic catalysis, characterized by the steps of The method comprises the following steps: hydrothermal pretreatment: washing, crushing and mixing the polyamide-6 waste to be treated with water, and then performing a hydrothermal reaction, and cooling to room temperature after the reaction, to obtain a pretreated slurry containing caprolactam monomers, soluble oligomers and insoluble polyamide-6 high molecules with reduced crystallinity; first enzyme-catalyzed depolymerization: mixing the pretreated slurry with a buffer solution with a pH of 6.5-9.5, adding a first hydrolytic enzyme, and performing first enzyme-catalyzed depolymerization at a temperature of 30-70℃, to obtain a first depolymerization slurry containing amino caproic acid monomers, caprolactam monomers and linear soluble oligomers; second enzyme-catalyzed depolymerization: adding a second hydrolytic enzyme to the first depolymerization slurry, and performing second enzyme-catalyzed depolymerization at a pH of 6.5-9.5 and a temperature of 25-70℃, to obtain a second depolymerization slurry containing caprolactam monomers and amino caproic acid monomers; product post-treatment: filtering, concentrating, fractionating under reduced pressure and recrystallizing the second depolymerization slurry, to obtain caprolactam monomers and amino caproic acid monomers; wherein the hydrothermal reaction is performed in a high-temperature and high-pressure reaction device, the reaction temperature is 180-250℃, and the reaction time is 10-30h; in the first enzyme-catalyzed depolymerization step, the first hydrolytic enzyme is a mixture of ring-opening enzymes and endo-enzymes; and in the second enzyme-catalyzed depolymerization step, the second hydrolytic enzyme is an exo-enzyme.

2. The process for high efficient enzymatic hydrolysis of polycaprolactam based on hydrothermal pretreatment and multi-enzyme synergistic catalysis according to claim 1, characterized in that, In the hydrothermal pretreatment step, the mass ratio of the crushed polyamide-6 waste to water is 1:4-20.

3. The process for high efficient enzymatic hydrolysis of polycaprolactam based on hydrothermal pretreatment and multi-enzyme synergistic catalysis according to claim 1, characterized in that, In the first enzyme-catalyzed depolymerization step, the first hydrolytic enzyme is a free enzyme or an immobilized enzyme; when the first hydrolytic enzyme is an immobilized enzyme, the first enzyme-catalyzed depolymerization step comprises the following steps: mixing the pretreated slurry with a buffer solution with a pH of 6.5-9.5, adding the immobilized enzyme of the first hydrolytic enzyme, and performing first enzyme-catalyzed depolymerization at a temperature of 30-70℃, and then performing solid-liquid separation, to obtain a first depolymerization liquid containing amino caproic acid monomers, caprolactam monomers and linear soluble oligomers, and an immobilized enzyme containing the first hydrolytic enzyme and insoluble polyamide-6 high molecules with reduced crystallinity; wherein the immobilized enzyme is separated and recycled for use in the first enzyme-catalyzed depolymerization step.

4. The process for high efficient enzymatic hydrolysis of polycaprolactam based on hydrothermal pretreatment and multi-enzyme synergistic catalysis according to claim 3, characterized in that, In the second enzyme-catalyzed depolymerization step, the second hydrolytic enzyme is a free enzyme or an immobilized enzyme; when the second hydrolytic enzyme is an immobilized enzyme, the second enzyme-catalyzed depolymerization step comprises the following steps: adding the immobilized enzyme of the second hydrolytic enzyme to the first depolymerization slurry, and performing second enzyme-catalyzed depolymerization at a pH of 6.5-9.5 and a temperature of 25-70℃, and then performing solid-liquid separation, to obtain a second depolymerization liquid containing caprolactam monomers and amino caproic acid monomers, and an immobilized enzyme containing the second hydrolytic enzyme; wherein the immobilized enzyme is recycled for use in the second enzyme-catalyzed depolymerization step.

5. The process for high efficient enzymatic hydrolysis of polycaprolactam based on hydrothermal pretreatment and multi-enzyme synergistic catalysis according to claim 3 or 4, characterized in that, The immobilized enzyme comprises at least one of a carrier covalently immobilized enzyme, a carrier adsorbed immobilized enzyme, a cross-linked enzyme aggregate immobilized enzyme and a cross-linked enzyme crystal immobilized enzyme.

6. The process for high efficient enzymatic hydrolysis of polycaprolactam based on hydrothermal pretreatment and multi-enzyme synergistic catalysis according to claim 1, characterized in that, The ring-opening enzyme is at least one of NylC and NylA, and the endo-enzyme comprises at least one of NylC and UMG-SP-2; The exo-enzyme comprises at least one of NylB and UMG-SP-1.

7. The process for high efficient enzymatic hydrolysis of polycaprolactam based on hydrothermal pretreatment and multi-enzyme synergistic catalysis according to claim 6, characterized in that, The first hydrolytic enzyme is NylC k TS and NylA, and the second hydrolytic enzyme is NylB, wherein the mass ratio of the NylC k The mass ratio of TS and NylA is 1:0.25-0.5; or The first hydrolytic enzyme is UMG-SP-2, and the second hydrolytic enzyme is UMG-SP-1.

8. The process for high efficient enzymatic hydrolysis of polycaprolactam based on hydrothermal pretreatment and multi-enzyme synergistic catalysis according to claim 1, characterized in that, In the first enzymatic depolymerization step, the mass ratio of the pretreated slurry to the buffer is 1:0.8-1.

2. The buffer is at least one selected from a phosphate buffer, a tris-hydroxymethyl aminomethane-hydrochloric acid buffer, and water. The concentration of the buffer is 15-30 mM.

9. The process for high efficient enzymatic hydrolysis of polycaprolactam based on hydrothermal pretreatment and multi-enzyme synergistic catalysis according to claim 1, characterized in that, The polyhexamethylene adipamide waste includes a textile fabric, an engineering plastic, a fiber product, or a film tube product containing polyhexamethylene adipamide.

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