Preparation method of compound enzyme preparation for catalyzing plastic degradation

Abstract

The invention discloses a preparation method of a compound enzyme preparation for catalyzing plastic degradation, and belongs to the technical field of enzyme preparations, a double-shell microcapsule with an enzyme preparation as an inclusion, chitosan as a first layer and sodium alginate as an outermost layer is formed through two times of self-assembly, and foam carbon is obtained after phenolic resin foam carbonization. Then the foam carbon is modified through castor oil modified graphene oxide, the modified foam carbon has excellent specific surface area and porosity, more enzyme preparations can be loaded, more active sites are provided for enzyme, accumulation of degradation products can be avoided, forward proceeding of an enzymatic reaction is promoted, and the activity of the enzyme preparation is improved. Due to the great surface area and roughness, the double-shell slow-release microcapsules can be effectively adsorbed, and the microcapsules are prevented from falling off through a mechanical interlocking effect.

Description

Technical Field

[0001] This invention belongs to the field of enzyme preparation technology, specifically a method for preparing a composite enzyme preparation for catalyzing the degradation of plastics. Background Technology

[0002] Plastic degradation refers to the decrease in polymer molecular weight and the decline in the physical properties of polymer materials. Typical manifestations include: plastic becoming brittle, cracking, softening, hardening, and losing mechanical strength. The aging and deterioration of plastics are a form of degradation. However, it generally takes decades or even centuries for plastics to degrade to an environmentally harmless state and return to the natural cycle. The degradation products must eventually be broken down into carbon dioxide and water to be considered truly degraded. Eco-friendly plastic bags are a general term for various biodegradable plastic bags made from polymers such as starch, PLA, and PBAT. Currently, starch-based biodegradable plastic bags are widely used. Compared to traditional plastic bags, eco-friendly plastic bags have the advantage of a shorter complete degradation time and less environmental impact. However, the complete degradation of eco-friendly plastic bags still requires a long time, and the degradation time is closely related to the composition of the eco-friendly bag. Naturally degrading eco-friendly plastic bags still have a significant environmental impact. Therefore, how to rapidly degrade eco-friendly plastic bags and minimize plastic bag pollution has become an urgent problem to solve.

[0003] Chinese patent announcement CN115197927B discloses a composite enzyme preparation for degrading bio-based plastics and its application. In this scheme, the composite enzyme preparation for degrading bio-based plastics includes glutaminase and sucrose fatty acid ester, which can destroy the hydrophobicity of the garbage bag surface. Alkaline protease, alkaline lipase, fungal amylase, and sodium citrate can synergistically destroy the internal structure. Attapulgite can adsorb the hydrolyzed substrate, making the reaction faster and more thorough. However, in this scheme, the attapulgite is mainly composed of nanorod-like structures with low specific surface area, and the linear channels are easily blocked by enzyme molecules or degradation products. Summary of the Invention

[0004] The purpose of this invention is to provide a composite enzyme preparation for catalyzing the degradation of plastics and its preparation method. The method involves carbonizing phenolic resin foam to obtain foamed carbon, and then modifying the foamed carbon with graphene oxide modified by castor oil. The modified foamed carbon has excellent specific surface area and porosity, which can support more enzyme preparations, provide more active sites for enzymes, help avoid the accumulation of degradation products, and promote the forward progress of enzymatic reactions.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A method for preparing a composite enzyme preparation for catalyzing the degradation of plastics includes the following steps:

[0007] Step 1: Add graphene oxide and formaldehyde solution to the reaction vessel and ultrasonically disperse for 40-50 min. Then add castor oil polyether polyol and sulfuric acid solution with a concentration of 1 mol / L as catalyst. Stir for 1-2 h at 70-80℃ and 400-500 r / min to obtain castor oil / graphene oxide dispersion.

[0008] Step 2: Add castor oil / graphene oxide dispersion and foamed carbon at a ratio of 200-300 mL: 30-40 g to a reaction vessel, stir at 70-80℃ and 400-500 r / min for 1-2 h, filter, wash, and vacuum dry to obtain castor oil / graphene oxide modified foamed carbon; mix castor oil / graphene oxide modified foamed carbon, modified titanium dioxide powder, and double-shell sustained-release microcapsules to obtain a composite enzyme preparation for catalyzing the degradation of plastics.

[0009] Furthermore, in step one, the ratio of graphene oxide, formaldehyde solution, castor oil polyether polyol, and sulfuric acid solution is 50-60g: 300-400mL: 30-40g: 1-2mL.

[0010] Furthermore, in step two, the mass ratio of castor oil / graphene oxide modified foamed carbon, modified titanium dioxide powder, and double-shell sustained-release microcapsules is 30-32:12-14:32-35.

[0011] Furthermore, the foamed carbon in step two is prepared through the following steps:

[0012] Phenolic resin foam is placed in a tube furnace and heated to 300-400℃ at 5-6℃ / min under nitrogen protection, and held for 1-2 hours. Then it is heated to 800-900℃ at 6-7℃ / min and held for 1-2 hours to convert nitrogen into carbon dioxide. After activation for 2-3 hours, carbon dioxide is converted back into nitrogen and the mixture is naturally cooled to room temperature to obtain foamed carbon.

[0013] Furthermore, phenolic resin foam is prepared through the following steps:

[0014] A 20-30% (w / w) formaldehyde solution, ammonium dihydrogen phosphate, and phenol are added to a reaction vessel and stirred for 1-2 hours at 55-60℃ and 500-600 rpm. Then, a 1% (w / w) NaOH solution is added, and the reaction continues for 1-2 hours. The mixture is then heated under reflux at 95-98℃ for 1-2 hours. The product is cooled to 60-70℃, and the pH is adjusted to neutral with HCl. The product is then dehydrated by vacuum distillation at a vacuum of 0.092-0.095 MPa. Tween 80, n-pentane, concentrated sulfuric acid, and deionized water are added to the product, and the mixture is stirred for 30-40 minutes. The mixture is then quickly removed and placed in a mold. The mixture is foamed and cured at 60-80℃ for 24-26 hours to obtain phenolic resin foam.

[0015] Furthermore, the ratio of formaldehyde solution, ammonium dihydrogen phosphate, phenol, NaOH solution, Tween 80, n-pentane, concentrated sulfuric acid, and deionized water is 200-250mL: 12-14g: 80-90g: 10-11mL: 1-2mL: 40-50mL: 4-5mL: 5-6mL.

[0016] Furthermore, the double-shell sustained-release microcapsules in step two are prepared through the following steps:

[0017] A 2 mg / mL chitosan solution and a 0.5 mol / L potassium chloride solution were added to a reaction vessel and stirred at 35-40℃ and 500-600 rpm for 30-40 min. The pH was adjusted to 5.5-6, and then the enzyme preparation was added. The mixture was stirred for 1-2 h and centrifuged at 1000-1200 rpm for 5-6 min to obtain a mixed solution. The mixed solution and a 1% glutaraldehyde solution were added to a 2 mg / mL potassium alginate solution and stirred at 35-40℃ and 500-600 rpm for 30-40 min. The mixture was filtered, and the filter cake was washed 2-4 times with deionized water and anhydrous ethanol, respectively. The mixture was then vacuum dried at 60-80℃ for 1-2 h to obtain double-shell sustained-release microcapsules.

[0018] Furthermore, the enzyme preparation is any one of glutaminase, alkaline lipase, alkaline protease, or fungal amylase.

[0019] Furthermore, the ratio of chitosan solution, potassium chloride solution, and enzyme preparation is 120-140 mL: 120-140 mL: 20-40 g.

[0020] Furthermore, the ratio of the mixed solution, glutaraldehyde solution, and potassium alginate solution is 80-90 mL: 1-2 mL: 120-140 mL.

[0021] Furthermore, the modified titanium dioxide powder in step two is prepared through the following steps:

[0022] Nano-titanium dioxide powder, 5-hydroxyisophthalic acid, and deionized water were added to a reaction vessel. Sodium hexadecyl sulfate was dissolved in a 70-75 wt% ethanol solution and then added to the reaction vessel. The mixture was stirred at 120-130℃ and 400-500 r / min for 1-2 h. Ferric chloride was added to the reaction vessel, and the reaction was continued with stirring for 4-5 h. The mixture was then filtered, and the filter cake was washed 2-4 times with deionized water and anhydrous ethanol, respectively. The mixture was then vacuum dried to obtain modified titanium dioxide powder with a particle size of 20-30 nm.

[0023] Furthermore, the ratio of nano-titanium dioxide powder, 5-hydroxyisophthalic acid, deionized water, sodium hexadecyl sulfate, and ethanol solution is 70-80g: 30-40g: 700-800mL: 1-2g: 120-140mL.

[0024] The beneficial effects of this invention are:

[0025] 1. The present invention provides a composite enzyme preparation for catalyzing the degradation of plastics, which has excellent degradation ability, long-term stable degradation ability, and is not easily affected by the environment.

[0026] 2. The double-shell sustained-release microcapsules of the present invention form a double-shell microcapsule with an enzyme preparation as the inclusion material, chitosan as the first layer, and sodium alginate as the outermost layer through two self-assemblies. The two-layer coating can effectively protect the enzyme preparation and ensure its stable function, avoiding enzyme preparation failure in harsh scenarios and extreme environments.

[0027] 3. The castor oil / graphene oxide modified foamed carbon of the present invention, after modification with castor oil / graphene oxide, contains abundant hydroxyl groups and long-chain fatty acid structures in castor oil. These polar groups can combine with oxygen-containing functional groups on the surface of graphene oxide through esterification, which helps to uniformly disperse graphene oxide and reduce the performance degradation caused by nanoscale agglomeration. The modified foamed carbon has excellent specific surface area and porosity, which can load more enzyme preparations, provide more active sites for enzymes, help avoid the accumulation of catalytic products, promote the forward catalytic reaction, and the large surface area and roughness can effectively adsorb double-shell sustained-release microcapsules through mechanical... Mechanical interlocking prevents microcapsule detachment; traditional resin-based carbon foam generally has low strength and is prone to fracture or collapse under long-term stress or impact loads, causing the loaded double-shell slow-release microcapsules to detach. The two-dimensional layered structure of graphene oxide forms a "skeleton support" effect in the carbon foam matrix, which can effectively disperse stress and inhibit crack propagation through the interlayer slip mechanism. However, graphene oxide contains abundant oxygen-containing groups on its surface, which can enhance the interlayer forces, but excessive oxidation can lead to structural defects and local stress concentration, causing brittleness. In contrast, the long-chain flexible segments of castor oil polyether polyol can absorb energy through extension deformation, thereby achieving a balance between strength and toughness. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1: A method for preparing a composite enzyme preparation for catalyzing the degradation of plastics, comprising the following steps:

[0030] S1: 70g of nano titanium dioxide powder, 30g of 5-hydroxyisophthalic acid and 700mL of deionized water were added to a reaction vessel. 1g of sodium hexadecyl sulfate was dissolved in 120mL of 70wt% ethanol solution and then added to the reaction vessel. The mixture was stirred at 120℃ and 400r / min for 1h. Ferric chloride was added to the reaction vessel and the reaction was continued to be stirred for 4h. The mixture was then filtered. The filter cake was washed twice with deionized water and anhydrous ethanol, respectively, and then dried under vacuum to obtain modified titanium dioxide powder with a particle size of 20nm.

[0031] Furthermore, 5-hydroxyisophthalic acid coordinates with the metallic iron ions in ferric chloride to form a metal framework loaded on the surface of titanium dioxide powder, thus obtaining modified titanium dioxide powder.

[0032] S2: Add 120 mL of 2 mg / mL chitosan solution and 120 mL of 0.5 mol / L potassium chloride solution to the reaction vessel, stir for 30 min at 35 °C and 500 r / min, adjust the pH to 5.5, then add 20 g of alkaline lipase, continue stirring for 1 h, centrifuge at 1000 r / min for 5 min to obtain a mixed solution; add 80 mL of the mixed solution and 1 mL of 1% glutaraldehyde solution to 120 mL of 2 mg / mL potassium alginate solution, stir for 30 min at 35 °C and 500 r / min, filter, wash the filter cake twice with deionized water and anhydrous ethanol respectively, and vacuum dry at 60 °C for 1 h to obtain double-shell sustained-release microcapsules.

[0033] Under acidic conditions, the amino groups on the chitosan molecular chain are protonated and cross-linked with the negative ions on the surface of alkaline lipase through electrostatic interaction, completing the first assembly. Then, the carboxyl group of potassium alginate is electrostatically adsorbed with the amino groups on the surface of chitosan to form the second assembly, resulting in a microcapsule with an enzyme preparation as the encapsulating material and a double shell of chitosan and sodium alginate.

[0034] S3: Add 200 mL of 20% formaldehyde solution, 12 g of ammonium dihydrogen phosphate, and 80 g of phenol to a reaction vessel. Stir for 1 h at 55 °C and 500 r / min. Then add 10 mL of 1% NaOH solution and continue the reaction for 1 h. Heat under reflux at 95 °C for 1 h. Cool the product to 60 °C, adjust the pH to neutral with HCl, and dehydrate by vacuum distillation at 0.092 MPa. Add 1 mL of Tween 80, 40 mL of n-pentane, 4 mL of concentrated sulfuric acid, and 5 mL of deionized water to the product and continue stirring for 30 min. Quickly remove the mixture and place it in a mold. Foam and cure at 60 °C for 24 h to obtain phenolic resin foam.

[0035] Ammonium dihydrogen phosphate releases hydrogen ions, creating a weakly acidic environment that promotes the condensation reaction of phenol and formaldehyde. The ortho and para active sites of the hydroxyl groups of phenol undergo nucleophilic addition with the carbonyl groups of formaldehyde to generate hydroxymethylphenol intermediates. n-Pentane acts as a physical foaming agent, generating gas and expanding to form a closed-cell structure.

[0036] S4: Place phenolic resin foam in a tube furnace, heat it to 300°C at 5°C / min under nitrogen protection, hold it for 1 hour, heat it to 800°C at 6°C / min, hold it for 1 hour, convert nitrogen to carbon dioxide, activate it for 2 hours, then convert carbon dioxide back to nitrogen, and cool it naturally to room temperature to obtain foamed carbon.

[0037] The foam carbon obtained by carbonizing phenolic resin foam has abundant pores and can be used as a carrier for enzyme preparations.

[0038] S5: Add 50g of graphene oxide and 300mL of formaldehyde solution to the reactor and ultrasonically disperse for 40min. Then add 30g of castor oil polyether polyol and 1mL of sulfuric acid solution with a catalyst concentration of 1mol / L. Stir for 1h at 70℃ and 400r / min to obtain castor oil / graphene oxide dispersion.

[0039] Graphene oxide was ultrasonically treated with formaldehyde solution. The cavitation effect of ultrasound was used to peel off the graphene oxide sheets and improve dispersibility. After adding castor oil polyether polyol, under the condition of acid catalyst, the oxygen-containing functional groups on the surface of graphene oxide and the hydroxyl groups of castor oil polyether polyol underwent an esterification reaction to obtain a castor oil modified graphene oxide dispersion.

[0040] S6: Add 200 mL of castor oil / graphene oxide dispersion and 30 g of foamed carbon to a reaction vessel, stir for 1 h at 70 °C and 400 r / min, filter, wash the filter cake twice with deionized water and anhydrous ethanol respectively, and dry under vacuum at 60 °C for 1 h to obtain castor oil / graphene oxide modified foamed carbon; mix 30 g of castor oil / graphene oxide modified foamed carbon, 12 g of modified titanium dioxide powder and 32 g of double-shell sustained-release microcapsules to obtain a composite enzyme preparation for catalyzing the degradation of plastics.

[0041] The foamed carbon modified with castor oil / graphene oxide has excellent specific surface area and porosity, which can load more enzyme preparations, provide more active sites for enzymes, help avoid the accumulation of degradation products, and promote the forward progress of catalytic reactions.

[0042] The two-dimensional sheet structure of graphene oxide forms a "skeleton support" effect in the carbon foam matrix. Its high modulus properties can effectively disperse stress and inhibit crack propagation. The long-chain flexible molecules of castor oil polyether polyol compensate for brittleness through a toughening mechanism.

[0043] Example 2: A method for preparing a composite enzyme preparation for catalyzing the degradation of plastics, comprising the following steps:

[0044] S1: 75g of nano titanium dioxide powder, 35g of 5-hydroxyisophthalic acid and 750mL of deionized water were added to a reaction vessel. 1.5g of sodium hexadecyl sulfate was dissolved in 130mL of 72.5wt% ethanol solution and then added to the reaction vessel. The mixture was stirred at 125℃ and 450r / min for 1.5h. Ferric chloride was added to the reaction vessel and the reaction was continued to be stirred for 4.5h. The mixture was then filtered. The filter cake was washed three times with deionized water and three times with anhydrous ethanol, and then dried under vacuum to obtain modified titanium dioxide powder with a particle size of 25nm.

[0045] S2: Add 130 mL of 2 mg / mL chitosan solution and 135 mL of 0.5 mol / L potassium chloride solution to the reaction vessel, stir for 35 min at 37.5℃ and 550 r / min, adjust the pH to 5.75, then add 30 g of alkaline lipase, continue stirring for 1.5 h, centrifuge at 1100 r / min for 5.5 min to obtain a mixed solution; add 85 mL of the mixed solution and 1.5 mL of 1% glutaraldehyde solution to 130 mL of 2 mg / mL potassium alginate solution, stir for 35 min at 37.5℃ and 550 r / min, filter, wash the filter cake three times with deionized water and anhydrous ethanol respectively, and vacuum dry at 70℃ for 1.5 h to obtain double-shell sustained-release microcapsules.

[0046] S3: Add 230 mL of 25% formaldehyde solution, 13 g of ammonium dihydrogen phosphate, and 85 g of phenol to a reaction vessel. Stir for 1.5 h at 57.5 °C and 550 r / min. Then add 10.5 mL of 1.0% NaOH solution and continue the reaction for 1.5 h. Heat under reflux at 96.5 °C for 1.5 h. Cool the product to 65 °C, adjust the pH to neutral with HCl, and dehydrate by vacuum distillation at 0.0935 MPa. Add 1.5 mL of Tween 80, 45 mL of n-pentane, 4.5 mL of concentrated sulfuric acid, and 5.5 mL of deionized water to the product and continue stirring for 35 min. Quickly remove the mixture and place it in a mold. Foam and cure at 70 °C for 25 h to obtain phenolic resin foam.

[0047] S4: Place phenolic resin foam in a tube furnace, heat it to 350℃ at 5.5℃ / min under nitrogen protection, hold it at 1.5h, heat it to 850℃ at 6.5℃ / min, hold it at 1.5h, convert nitrogen to carbon dioxide, activate it for 2.5h, then convert carbon dioxide back to nitrogen, and cool it naturally to room temperature to obtain foamed carbon.

[0048] S5: Add 55g of graphene oxide and 350mL of formaldehyde solution to the reactor and ultrasonically disperse for 45min. Then add 35g of castor oil polyether polyol and 1.5mL of sulfuric acid solution with a catalyst concentration of 1mol / L. Stir for 1.5h at 75℃ and 450r / min to obtain castor oil / graphene oxide dispersion.

[0049] S6: Add 250 mL of castor oil / graphene oxide dispersion and 35 g of foamed carbon to a reaction vessel, stir for 1.5 h at 75 °C and 450 r / min, filter, wash the filter cake three times with deionized water and anhydrous ethanol respectively, and dry under vacuum at 70 °C for 1.5 h to obtain castor oil / graphene oxide modified foamed carbon; mix 31 g of castor oil / graphene oxide modified foamed carbon, 13 g of modified titanium dioxide powder, and 33.5 g of double-shell sustained-release microcapsules to obtain a composite enzyme preparation for catalyzing the degradation of plastics.

[0050] Example 3: A method for preparing a composite enzyme preparation for catalyzing the degradation of plastics, comprising the following steps:

[0051] S1: Add 80g of nano titanium dioxide powder, 40g of 5-hydroxyisophthalic acid and 800mL of deionized water to a reaction vessel. Dissolve 2g of sodium hexadecyl sulfate in 140mL of 75wt% ethanol solution and add it to the reaction vessel. Stir at 130℃ and 500r / min for 2h. Add ferric chloride to the reaction vessel and continue stirring for 5h. Filter the mixture and wash the filter cake four times with deionized water and anhydrous ethanol, respectively. Dry it under vacuum to obtain modified titanium dioxide powder with a particle size of 20-30nm.

[0052] S2: Add 140 mL of 2 mg / mL chitosan solution and 140 mL of 0.5 mol / L potassium chloride solution to the reactor. Stir for 40 min at 40 °C and 600 r / min. Adjust the pH to 6, then add 40 g of alkaline protease and continue stirring for 2 h. Centrifuge at 1200 r / min for 6 min to obtain a mixed solution. Add 90 mL of the mixed solution and 2 mL of 1% glutaraldehyde solution to 140 mL of 2 mg / mL potassium alginate solution. Stir for 40 min at 40 °C and 600 r / min. Filter the mixture and wash the filter cake four times with deionized water and anhydrous ethanol, respectively. Vacuum dry at 80 °C for 2 h to obtain double-shell sustained-release microcapsules.

[0053] S3: Add 250 mL of 30% formaldehyde solution, 14 g of ammonium dihydrogen phosphate, and 90 g of phenol to a reaction vessel. Stir for 2 h at 60 °C and 600 r / min. Then add 11 mL of 1.0% NaOH solution and continue the reaction for 2 h. Heat under reflux at 98 °C for 2 h. Cool the product to 70 °C, adjust the pH to neutral with HCl, and dehydrate by vacuum distillation at 0.095 MPa. Add 2 mL of Tween 80, 50 mL of n-pentane, 5 mL of concentrated sulfuric acid, and 6 mL of deionized water to the product and continue stirring for 40 min. Quickly remove the mixture and place it in a mold. Foam and cure at 80 °C for 26 h to obtain phenolic resin foam.

[0054] S4: Place phenolic resin foam in a tube furnace, heat it to 400℃ at 6℃ / min under nitrogen protection, hold it for 2 hours, heat it to 900℃ at 7℃ / min, hold it for 2 hours, convert nitrogen to carbon dioxide, activate it for 3 hours, then convert carbon dioxide back to nitrogen, and cool it naturally to room temperature to obtain foamed carbon.

[0055] S5: Add 60g of graphene oxide and 400mL of formaldehyde solution to the reactor and ultrasonically disperse for 50min. Then add 40g of castor oil polyether polyol and 2mL of sulfuric acid solution with a concentration of 1mol / L as catalyst. Stir for 2h at 80℃ and 500r / min to obtain castor oil / graphene oxide dispersion.

[0056] S6: Add 300 mL of castor oil / graphene oxide dispersion and 40 g of foamed carbon to a reaction vessel, stir for 2 h at 80 °C and 500 r / min, filter, wash the filter cake 4 times with deionized water and anhydrous ethanol respectively, and vacuum dry at 80 °C for 2 h to obtain castor oil / graphene oxide modified foamed carbon; stir and mix 32 g of castor oil / graphene oxide modified foamed carbon, 14 g of modified titanium dioxide powder and 35 g of double-shell sustained-release microcapsules to obtain a composite enzyme preparation for catalyzing the degradation of plastics.

[0057] Comparative Example 1: Referring to the Chinese Patent No. CN115197927B, "A Composite Enzyme Preparation for Degrading Bio-based Plastics and Its Application", attapulgite is described in paragraph 34 of the specification. Based on Example 3 of this invention, castor oil / graphene oxide modified foam carbon in step S6 is replaced with attapulgite, while the other steps remain unchanged, to prepare a composite enzyme preparation for catalyzing the degradation of plastics.

[0058] Comparative Example 2: Based on Example 3, without step S5, the castor oil / graphene oxide dispersion in step S6 was omitted, and the remaining steps remained unchanged, to prepare a composite enzyme preparation for catalyzing the degradation of plastics.

[0059] Comparative Example 3: Based on Example 3, without step S2, the double-shell sustained-release microcapsules in step S6 were replaced with alkaline protease, while the other steps remained unchanged, to prepare a composite enzyme preparation that catalyzes the degradation of plastics.

[0060] The performance of the composite enzyme preparations for catalytic plastic degradation obtained in Examples 1-3 and Comparative Examples 1-3 was tested. Water was added to the biodegradable plastic to be treated to obtain the reaction substrate. The mass ratio of biodegradable plastic to water was 1:10. Based on the reaction substrate, the composite enzyme preparation was added to the reaction substrate at an addition rate of 1 kg / t. After thorough mixing, the reaction was carried out at 25°C and 100 r / min for 24 h. Then, the reaction temperature was raised to 40°C, and the pH value was adjusted to 3.0 with citric acid for a further 24 h of reaction. All remaining residues were collected. In order to test the efficiency (%) of different composite enzyme preparations in catalytic plastic degradation at different pH values ​​and temperatures, and to measure the effect of environmental changes on the composite enzyme preparations, pH levels of 4, 7, 9, and 11, and temperature levels of 20°C, 30°C, 40°C, and 50°C were selected. Each set of examples and comparative examples was repeated 3 times. The results are shown in Table 1.

[0061] Table 1 Performance Test Table of Composite Enzyme Preparations for Plastic Degradation

[0062] As can be seen from Table 1, the composite enzyme preparations for catalyzing the degradation of plastics prepared in Examples 1-3 showed significantly higher degradation rates than the comparative examples. The degradation rate varied less under different pH values ​​and temperatures than the comparative examples, and even under relatively extreme pH conditions, they still exhibited good and stable degradation rates. This indicates that the composite enzyme preparations prepared in this invention have excellent degradation capabilities in catalyzing the degradation of plastics, long-term stable degradation capabilities, and are not easily affected by the environment.

[0063] In Comparative Example 1, castor oil / graphene oxide modified foamed carbon was replaced with attapulgite. The castor oil / graphene oxide modified phenolic resin-based foamed carbon formed three-dimensional interconnected channels through a foaming process, resulting in a significantly higher specific surface area than attapulgite. This porous structure not only provides more enzyme immobilization sites but also allows for efficient diffusion of macromolecular substrates. Furthermore, the abundant active groups on the surfaces of castor oil and graphene oxide can immobilize enzyme molecules through covalent bonds or physical adsorption. Compared to attapulgite's reliance on the physical adsorption of negative charges in its natural structure, this significantly improves the stability of the composite enzyme preparation.

[0064] In Comparative Example 2, the castor oil / graphene oxide dispersion was discarded. The foamed carbon modified with castor oil / graphene oxide contains abundant hydroxyl groups and long-chain fatty acid structures. These polar groups can combine with the oxygen-containing functional groups on the surface of graphene oxide through esterification reaction, which helps to uniformly disperse graphene oxide and reduce the performance degradation caused by nanoscale agglomeration. The two-dimensional sheet structure of graphene oxide forms a "skeleton support" effect in the foamed carbon matrix, which can effectively disperse stress through the interlayer slip mechanism. The long-chain flexible segments of castor oil polyether polyol can absorb energy through extension deformation, thereby achieving a balance between strength and toughness.

[0065] In Comparative Example 3, the double-shelled sustained-release microcapsules were replaced with alkaline protease. Through two self-assemblies, a double-shelled microcapsule was formed, with the enzyme preparation as the encapsulant, chitosan as the first layer, and sodium alginate as the outermost layer. The two-layer encapsulation can effectively protect the enzyme preparation and ensure its stable function, avoiding enzyme failure in harsh scenarios and extreme environments. Therefore, in the performance test, without the protection of the double-shelled microcapsules, the alkaline protease's ability to catalyze the degradation of plastics is easily reduced by fluctuations in pH and temperature.

[0066] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for preparing a composite enzyme preparation for catalyzing the degradation of plastics, characterized in that, Includes the following steps: Step 1: Add graphene oxide and formaldehyde solution to the reaction vessel and ultrasonically disperse for 40-50 min. Then add castor oil polyether polyol and sulfuric acid solution with a concentration of 1 mol / L. Stir at 70-80℃ and 400-500 r / min for 1-2 h to obtain castor oil / graphene oxide dispersion. Step 2: Add castor oil / graphene oxide dispersion and foamed carbon at a ratio of 200-300mL:30-40g to the reaction vessel, stir at 70-80℃ and 400-500r / min for 1-2h, filter, wash, and vacuum dry to obtain castor oil / graphene oxide modified foamed carbon. Castor oil / graphene oxide modified foamed carbon, modified titanium dioxide powder, and double-shell slow-release microcapsules were stirred and mixed to obtain a composite enzyme preparation for catalyzing the degradation of plastics.

2. The method for preparing a composite enzyme preparation for catalyzing the degradation of plastics according to claim 1, characterized in that, The ratio of graphene oxide, formaldehyde solution, castor oil polyether polyol and sulfuric acid solution used in step one is 50-60g: 300-400mL: 30-40g: 1-2mL.

3. The method for preparing a composite enzyme preparation for catalyzing the degradation of plastics according to claim 1, characterized in that, In step two, the mass ratio of castor oil / graphene oxide modified foamed carbon, modified titanium dioxide powder, and double-shell sustained-release microcapsules is 30-32:12-14:32-35.

4. The method for preparing a composite enzyme preparation for catalyzing the degradation of plastics according to claim 1, characterized in that, The foamed carbon described in step two is prepared through the following steps: Phenolic resin foam is placed in a tube furnace and heated to 300-400℃ at 5-6℃ / min under nitrogen protection, and held for 1-2 hours. Then it is heated to 800-900℃ at 6-7℃ / min and held for 1-2 hours to convert nitrogen into carbon dioxide. After activation for 2-3 hours, carbon dioxide is converted back into nitrogen and the mixture is naturally cooled to room temperature to obtain foamed carbon.

5. The method for preparing a composite enzyme preparation for catalyzing the degradation of plastics according to claim 4, characterized in that, The phenolic resin foam is prepared through the following steps: Add 20-30 wt% formaldehyde solution, ammonium dihydrogen phosphate, and phenol to a reaction vessel, stir at 55-60℃ and 500-600 r / min for 1-2 h, then add 1 wt% NaOH solution and continue the reaction for 1-2 h. Heat under reflux at 95-98℃ for 1-2 h, cool the product to 60-70℃, adjust the pH to neutral with HCl, and dehydrate by vacuum distillation under a vacuum of 0.092-0.095 MPa. Add Tween 80, n-pentane, concentrated sulfuric acid, and deionized water to the product, and continue stirring for 30-40 min. Quickly remove the mixture and place it in a mold, foam and cure at 60-80℃ for 24-26 h to obtain phenolic resin foam.

6. The method for preparing a composite enzyme preparation for catalyzing the degradation of plastics according to claim 5, characterized in that, The ratio of formaldehyde solution, ammonium dihydrogen phosphate, phenol, NaOH solution, Tween 80, n-pentane, concentrated sulfuric acid, and deionized water is 200-250mL: 12-14g: 80-90g: 10-11mL: 1-2mL: 40-50mL: 4-5mL: 5-6mL.

7. The method for preparing a composite enzyme preparation for catalyzing the degradation of plastics according to claim 1, characterized in that, The double-shell sustained-release microcapsules described in step two are prepared through the following steps: A 2 mg / mL chitosan solution and a 0.5 mol / L potassium chloride solution were added to a reaction vessel and stirred at 35-40℃ and 500-600 rpm for 30-40 min. The pH was adjusted to 5.5-6, and then the enzyme preparation was added. The mixture was stirred for 1-2 h and centrifuged at 1000-1200 rpm for 5-6 min to obtain a mixed solution. The mixed solution and a 1 wt% glutaraldehyde solution were added to a 2 mg / mL potassium alginate solution and stirred at 35-40℃ and 500-600 rpm for 30-40 min. The mixture was then filtered, washed, and vacuum dried to obtain double-shell sustained-release microcapsules. The enzyme preparation is any one of glutaminase, alkaline lipase, alkaline protease, or fungal amylase.

8. The method for preparing a composite enzyme preparation for catalyzing the degradation of plastics according to claim 7, characterized in that, The ratio of chitosan solution, potassium chloride solution and enzyme preparation is 120-140 mL: 120-140 mL: 20-40 g; the ratio of mixed solution, glutaraldehyde solution and potassium alginate solution is 80-90 mL: 1-2 mL: 120-140 mL.

9. The method for preparing a composite enzyme preparation for catalyzing the degradation of plastics according to claim 1, characterized in that, The modified titanium dioxide powder mentioned in step two is prepared through the following steps: Nano-titanium dioxide powder, 5-hydroxyisophthalic acid, and deionized water were added to a reaction vessel. Sodium hexadecyl sulfate was dissolved in 70-75 wt% ethanol solution and then added to the reaction vessel. The mixture was stirred at 120-130℃ and 400-500 r / min for 1-2 h. Ferric chloride was added to the reaction vessel, and the reaction was continued with stirring for 4-5 h. The mixture was then filtered, washed, and vacuum dried to obtain modified titanium dioxide powder with a particle size of 20-30 nm.

10. The method for preparing a composite enzyme preparation for catalyzing the degradation of plastics according to claim 9, characterized in that, The ratio of nano-titanium dioxide powder, 5-hydroxyisophthalic acid, deionized water, sodium hexadecyl sulfate, and ethanol solution is 70-80g: 30-40g: 700-800mL: 1-2g: 120-140mL.

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