An enzyme composition for microplastic degradation and a preparation method and application thereof

Abstract

The application discloses an enzyme composition for microplastic degradation, a preparation method and application thereof. The enzyme composition comprises plastic degradation enzyme and emulsifier. The emulsifier is selected from a combination of one or more of lignosulfonate, sulfobetaine emulsifier, fatty alcohol polyoxyethylene ether sulfate and C12-C18 alkyl polyoxyethylene ether sulfate. The application also provides a plastic degradation method, which comprises the steps of mixing plastic and the aforementioned enzyme composition, and performing a degradation reaction. The enzyme composition can be used for microplastic degradation, and has improved degradation efficiency and degradation activity. It is expected to be used in the environmental governance of microplastics.

Description

Technical Field

[0001] This invention relates to an enzyme composition for the degradation of microplastics, its preparation method, and its application. Background Technology

[0002] Numerous plastic products are widely used in construction, electronics, textiles, and daily consumer goods, and enter the environment after use. Improperly disposed plastic materials gradually break down into microplastic particles smaller than 5 mm under natural weathering, mechanical abrasion, and photo-oxidation. These particles persist in water bodies, soil, and organisms, accumulating through the food chain and posing a potential risk to ecosystem stability and biological health. Studies show that microplastics are not only difficult to degrade naturally but also readily adsorb heavy metals, organic pollutants, and pathogenic microorganisms, further amplifying their environmental harmful effects. Therefore, microplastic pollution has become one of the globally significant environmental governance challenges.

[0003] Current treatment methods for microplastic pollution mainly include physical recycling, thermal treatment, and chemical degradation. Physical recycling is limited by the small particle size and high dispersion of microplastics, making separation and collection difficult. While thermal treatment and chemical methods can achieve material degradation, they generally suffer from high energy consumption, complex equipment requirements, and potential secondary pollution, making them difficult to apply in natural environment restoration and large-scale ecological governance scenarios. Therefore, developing environmentally friendly, low-energy-consumption, and mild microplastic degradation technologies has become an important research direction.

[0004] In recent years, microplastic degradation technologies centered on bio-enzyme catalysis have gradually attracted attention. This type of technology utilizes specific plastic-degrading enzymes to selectively break down polymer chains, transforming large plastic molecules into low-molecular-weight products or intermediates that can be further metabolized by microorganisms, thereby achieving the biotransformation and environmentally friendly treatment of plastics. Compared with traditional physicochemical methods, enzyme-catalyzed degradation has advantages such as mild reaction conditions, high selectivity, and good environmental compatibility of byproducts, and is considered a potential sustainable technological route to solve the problem of microplastic pollution.

[0005] However, existing bio-enzymatic degradation technologies still face multiple bottlenecks in practical applications. First, microplastics generally possess characteristics such as strong hydrophobicity, low surface energy, and high crystallinity, making it difficult for enzyme molecules to effectively contact the plastic surface in aqueous systems, resulting in low interfacial mass transfer efficiency and limiting the reaction rate. Second, some plastic-degrading enzymes lack stability in complex aqueous environments, easily undergoing conformational changes or activity decay, affecting sustained catalytic ability. Furthermore, microplastics are usually highly dispersed in environmental systems, lacking effective interfacial control methods, making it difficult to construct reaction microenvironments conducive to enzyme catalysis, further restricting the engineering application of enzyme degradation technology.

[0006] Therefore, how to improve mass transfer conditions, increase the effective contact frequency between microplastics and enzymes, and construct an efficient degradation reaction system suitable for complex environments while maintaining enzyme catalytic activity and structural stability has become a key technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide an improved enzyme composition. This enzyme composition can be used for microplastic degradation and has improved degradation efficiency and activity.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: An enzyme composition for plastic degradation, the enzyme composition comprising a plastic-degrading enzyme and an emulsifier; the emulsifier is selected from one or more combinations of lignin sulfonate, sulfobetaine emulsifier, fatty alcohol polyoxyethylene ether sulfate, and C12-C18 alkyl polyoxyethylene ether sulfate.

[0009] In some embodiments, the lignin sulfonate is selected from sodium lignin sulfonate and potassium lignin sulfonate.

[0010] In some embodiments, the sulfobetaine emulsifier is selected from hexadecyl sulfobetaine, octadecyl sulfobetaine, and dodecyl sulfobetaine.

[0011] In some embodiments, the fatty alcohol polyoxyethylene ether sulfate is selected from sodium fatty alcohol polyoxyethylene ether sulfate and potassium fatty alcohol polyoxyethylene ether sulfate.

[0012] In some embodiments, the C12-C18 alkyl polyoxyethylene ether sulfate is selected from sodium lauryl polyoxyethylene ether sulfate, sodium hexadecyl polyoxyethylene ether sulfate, and sodium octadecyl polyoxyethylene ether sulfate.

[0013] In some embodiments, the plastic-degrading enzyme is selected from one or a combination of several of keratinase, lipase, polyethylene terephthalate hydrolase, and carboxylesterase.

[0014] In some embodiments, the ratio of the enzyme activity of the plastic-degrading enzyme to the mass of the emulsifier is 100U:(2-10)mg. For example, it can be 100U:2mg, 100U:3mg, 100U:4mg, 100U:5mg, 100U:6mg, 100U:7mg, 100U:8mg, 100U:9mg, or 100U:10mg. Preferably, it is 100U:(4-6)mg.

[0015] In some embodiments, the enzyme composition further includes an oil phase; the oil phase is selected from one or a combination of several of paraffin oil, hexadecane, octadecane, dodecane, and silicone oil.

[0016] In some embodiments, the volume ratio of the oil phase to the mass ratio of the emulsifier is (10-50) μL:(2-10) mg. For example, it can be 10 μL:5 mg, 20 μL:5 mg, 30 μL:5 mg, 40 μL:5 mg, 50 μL:5 mg. Preferably, it is (10-50) μL:(4-6) mg.

[0017] In some embodiments, the oil phase contains nano-ferric oxide. Adding nano-ferric oxide to the oil phase facilitates the separation of the system after plastic degradation.

[0018] The present invention also provides a method for preparing the aforementioned enzyme composition for plastic degradation, the method comprising the step of mixing the plastic-degrading enzyme, an emulsifier, and optionally an oil phase.

[0019] The present invention also provides the use of the aforementioned enzyme composition for plastic degradation for degrading plastics.

[0020] The present invention also provides a method for degrading plastics, the method comprising the steps of mixing plastics and an enzyme composition and carrying out a degradation reaction; wherein the enzyme composition is the aforementioned enzyme composition for plastic degradation of the present invention.

[0021] In some embodiments, the plastic is selected from one or more combinations of polyethylene terephthalate, propylene terephthalate, and butylene terephthalate.

[0022] In some embodiments, the plastic exists in the form of an aqueous dispersion of nanoparticles. Smaller particle sizes of the plastic to be degraded facilitate contact with the enzyme, thereby improving the degradation effect.

[0023] In some embodiments, the method includes the following steps: preparing the plastic into an aqueous dispersion of nanoparticles, adding the enzyme composition to the aqueous dispersion of nanoparticles to obtain a reaction system, and subjecting the reaction system to a degradation reaction.

[0024] In some embodiments, the mass concentration of the plastic in the reaction system is 0.01-0.5 mg / mL, and the mass-volume concentration of the emulsifier is 2-10 mg / mL.

[0025] Preferably, in the reaction system, the mass concentration of the plastic is 0.05-0.2 mg / mL.

[0026] Preferably, in the reaction system, the mass-volume concentration of the emulsifier is 4-6 mg / mL.

[0027] In some embodiments, the degradation reaction is carried out at a temperature of 30-80°C for a time of 1-8 hours.

[0028] In some embodiments, the average particle size of the nanoparticles is 50-200 nm, preferably 100-150 nm.

[0029] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art: (1) The enzyme composition of the present invention can synergistically regulate the interfacial behavior of the degrading enzyme and the microplastic to be degraded, stabilize enzyme activity and enhance the degradation process of microplastics (plastics with small particle size, such as micron or nanometer particle size), thereby improving degradation efficiency and degradation activity, significantly promoting the degradation of microplastics, and making the bio-enzyme degradation technology a promising application in the environmental remediation of microplastics.

[0030] (2) The enzyme composition of the present invention uses an emulsifier with good environmental compatibility as the core component, avoiding the use of highly toxic organic solvents or strong corrosive chemical additives. While maintaining the stability of the system, it reduces the potential load on water bodies, soil and ecosystems. It is suitable for microplastic treatment applications under open environmental conditions and is conducive to achieving a green, safe and sustainable plastic pollution control path.

[0031] (3) The specific emulsifier in the enzyme composition of the present invention has excellent interface regulation ability, which can stably disperse plastic degradation enzyme and hydrophobic microplastic particles in the aqueous system, inhibit microplastic aggregation and sedimentation, and at the same time build a stable interface microenvironment between enzyme molecules and plastic surface, enhance the effective contact area and interaction strength between the two, thereby providing favorable mass transfer and adsorption conditions for subsequent catalytic reactions, and ultimately improving the microplastic degradation efficiency.

[0032] (4) The enzyme composition of this application constructs a composite interface structure that is conducive to enzyme catalysis through the synergistic effect of emulsifier, plastic degrading enzyme and optional oil phase component. It can simultaneously improve substrate accessibility, enzyme conformational stability and reaction kinetic conditions, thereby improving the degradation rate and conversion efficiency of microplastics as a whole. This helps to overcome the engineering bottleneck of low reaction efficiency and insufficient stability in traditional microplastic enzyme degradation systems. Attached Figure Description

[0033] Figure 1 This is a schematic diagram illustrating the mechanism of action of an enzyme composition of the present invention in degrading microplastics; Figure 2 This is a particle size distribution diagram of the keratinase in Example 1; Figure 3 The particle size distribution of keratinase in Comparative Example 1 is shown. Figure 4 The chromatogram is of the degradation product in Example 5. Detailed Implementation

[0034] In existing technologies, the use of bio-enzymes to degrade plastics faces several technical challenges. First, microplastics generally exhibit strong hydrophobicity, low surface energy, and high crystallinity, making it difficult for enzyme molecules to effectively contact the plastic surface in aqueous systems. This results in low interfacial mass transfer efficiency and limits the reaction rate. Second, some plastic-degrading enzymes lack stability in complex aqueous environments, easily undergoing conformational changes or activity decay, affecting their sustained catalytic capacity. Furthermore, microplastics are typically highly dispersed in environmental systems, lacking effective interfacial control mechanisms, making it difficult to construct a reaction microenvironment conducive to enzyme catalysis.

[0035] Existing research on enzymatic treatment of microplastics for plastic degradation mostly employs the traditional method of directly mixing enzyme solutions with microplastic particles in water. However, traditional single-enzyme treatment systems lack the ability to actively regulate the interfacial microenvironment, resulting in poor substrate accessibility and high mass transfer resistance during the reaction, leading to low degradation efficiency and long reaction cycles. Enzymes must be tightly adsorbed onto the plastic surface to exert their catalytic effect; therefore, improving the effective collision rate between enzymes and microplastics remains a challenge in this field.

[0036] To address the aforementioned technical problems, this application innovatively mixes specific types of emulsifiers with enzymes and optional oil phase components to construct an enzyme composition system suitable for the effective degradation of microplastics. The specific types of emulsifiers in the enzyme composition simultaneously improve the dispersibility of microplastics, protect enzyme activity, and optimize the interfacial reaction environment, thereby synergistically enhancing the degradation efficiency of microplastics while ensuring safety.

[0037] The enzyme composition of the present invention may not contain an oil phase component, for example, it may contain only a degrading enzyme and a specific type of emulsifier. This composition system is relatively simple, yet it can effectively degrade microplastics.

[0038] The enzyme composition of the present invention can also be further supplemented with an oil phase component. When an oil phase component, such as paraffin oil, is added, it not only adjusts the oil phase density and enhances the interfacial stability of the system, but also endows the oil phase with magnetic responsiveness or easy sedimentation and recovery properties. When the enzyme composition is used to degrade microplastics, after the degradation reaction is completed, the oil phase can be rapidly and efficiently separated from the reaction system by external magnetic adsorption or static separation. This facilitates the enrichment of degradation products, the recycling of the oil phase, and the simplification and greening of the entire treatment process, further enhancing the engineering applicability and environmental friendliness of the technology.

[0039] For example, when the enzyme composition of the present invention contains an oil phase component and is used to degrade PET microplastics, its mechanism of action is illustrated as follows: Figure 1As shown, the system is composed of three synergistic components: an oil phase, a plastic-degrading enzyme, and an emulsifier. The emulsifier, as the core component, constructs a stable interfacial layer between the oil and aqueous phases, effectively dispersing hydrophobic microplastic particles, preventing their aggregation and sedimentation, and providing a favorable microenvironment for the degradation enzyme to contact the plastic surface. Therefore, this degradation system can achieve significantly improved degradation performance. Of course, even without the addition of the oil phase component, the microplastics can still achieve improved contact with the enzyme component, thus resulting in improved degradation performance.

[0040] Unless otherwise specified, all raw materials used in the following embodiments or comparative examples are commercially available or prepared using conventional methods in the art. The preparation and testing methods involved are all based on existing technologies.

[0041] Example 1 This embodiment provides an enzyme composition and uses it to degrade PET microplastics: (1) Preparation of enzyme composition Take 52.5 mg (200 U) of keratinase (commercially purchased, enzyme activity test result shows that each 26.25 mg of keratinase corresponds to an enzyme activity of 100 U) and 10 mg of sodium lignosulfonate emulsifier to obtain an enzyme composition.

[0042] (2) Preparation of aqueous dispersion of polyethylene terephthalate (PET) nanoparticles Take 1g of PET fragments (e.g., from shredded waste PET plastic bottles) and dissolve them in 100mL of hexafluoroisopropanol. Seal the container with aluminum foil and set aside. Take approximately 800mL of deionized water and cool it in a refrigerator or ice maker at 4°C. After the deionized water has completely cooled, take a beaker rinsed with deionized water. Turn on the sonicator and pour the aforementioned hexafluoroisopropanol solution containing PET into the beaker. Then, quickly pour all the cooled deionized water into the beaker. A milky white liquid will quickly form in the beaker. Continue sonicating for about 5 minutes, then turn off the sonicator and remove the emulsion. Next, use a rotary evaporator to distill the prepared emulsion under reduced pressure to remove the hexafluoroisopropanol. Set the rotary evaporation temperature to approximately 60-63°C and the rotation speed to approximately 80-90 rpm. Finally, filter the liquid after rotary evaporation using a Buchner funnel and qualitative filter paper to remove the PET flocculents generated during rotary evaporation and mixing, obtaining a PET nanoparticle suspension. The suspension was dried to obtain PET nanoparticles. These nanoparticles were then redispersed in water to prepare an aqueous dispersion of PET nanoparticles with a concentration of 0.1 mg / mL. The average particle size of the nanoparticles was determined to be 120 nm using a particle size analyzer.

[0043] (3) Degradation The enzyme composition from step (1) was mixed with 2 mL of the PET nanoparticle aqueous dispersion from step (2) to obtain a mixture. The mixture was incubated in a constant temperature shaker at 50°C and 150 rpm for 2 h to carry out the degradation reaction. After the reaction was completed, the sample was heated at 100°C for 30 minutes to completely inactivate the enzyme.

[0044] The effects of emulsifiers on enzymes were studied using particle size and zeta potential measurements. Specifically: Preparation of control sample solution: Accurately weigh 10 mg of keratinase and dissolve it in 10 mL of water. Gently shake to ensure complete dissolution to obtain the control sample solution. Preparation of test sample solution: Accurately weigh 10 mg of keratinase and 20 mg of emulsifier sodium lignosulfonate, dissolve them together in 10 mL of water, gently shake to fully dissolve and mix evenly to obtain a test sample solution containing emulsifier; The two sample solutions were left to stand at the same temperature of 25°C to allow the system to reach equilibrium. Using a particle size potential analyzer, appropriate amounts of the balanced sample solutions of the control and test were injected into the sample cell. Following the instrument's standard operating procedure, the zeta potential value, particle size distribution, and average particle size were measured and recorded under the same measurement conditions.

[0045] The particle size of the test sample (containing emulsifier) ​​was as follows: Figure 2 As shown. The particle size is 482.5 ± 84.9 nm, and the particle size distribution (PDI) is 0.202. The zeta potential was measured to be -9.392 ± 0.735 mV.

[0046] The particle size of the control sample is as follows Figure 3 As shown. The particle size is 1234.7 ± 97.7 nm, and the particle size distribution (PDI) is 0.218. The zeta potential was measured to be -7.19 ± 0.65 mV.

[0047] Comparison with the corresponding results of the test samples shows that by adding the emulsifier sodium lignosulfonate to the enzyme composition, the particle size of the keratinase was significantly reduced from 1234.7 ± 97.7 nm to 482.5 ± 84.9 nm. Simultaneously, the absolute value of the system's zeta potential increased from -7.19 ± 0.65 mV to -9.392 ± 0.735 mV. These results indicate that sodium lignosulfonate, as an emulsifier, successfully adsorbs onto the enzyme molecule surface, effectively improving the dispersibility of enzyme particles in the aqueous phase and making the potential more negative. This contributes to the enzyme's dispersion stability and inhibits its aggregation and sedimentation, thus enabling the construction of a stable enzyme-plastic interface microenvironment when used for microplastic degradation.

[0048] The concentration of degradation products was tested in the system after enzyme inactivation in step (3). Specifically: After degradation, polyethylene terephthalate (PET) mainly produces three products: terephthalic acid (TPA), mono(hydroxyethyl) phthalate (MHET), and bis(hydroxyethyl) terephthalate (BHET). High-performance liquid chromatography (HPLC) was used to analyze the standards at various concentrations. Standard curves were plotted with the peak area of ​​the three target substances as the ordinate (Y-axis) and the concentration of the corresponding standard solution as the abscissa (X-axis) for each, which were then used for subsequent quantitative calculations of the samples.

[0049] Y TPA = 9.87465X + 8.89093 (R) 2 =0.999) Y MHET = 7.09699X - 8.91417 (R) 2 =0.999) Y BHET = 11.62443X + 8.17042 (R) 2 =0.999) The enzyme-inactivated system was centrifuged at 10,000 r / min for 5 minutes. The supernatant was filtered through a 0.22 μm aqueous microporous membrane to obtain a clear test solution. High-performance liquid chromatography (HPLC) was used at 240 nm to detect the peak areas of each degradation product, TPA, MHET, and BHET. The concentrations of each peak area were calculated by substituting them into the corresponding standard curves and denoted as C0. TPA C MHET With C BHET Finally, by summing the concentrations of each product, the total release of PET degradation products is obtained as C. TPA + C MHET + C BHET .

[0050] The results are shown in Table 1.

[0051] Comparative Example 1 This comparative example provides a control enzyme composition and uses it to degrade PET microplastics: it is basically the same as Example 1, except that in step (1), only keratinase is added and sodium lignin sulfonate is not added.

[0052] The degradation products are shown in Table 1.

[0053] Examples 2-4, Comparative Examples 2-5 The process is basically the same as in Example 1, except that in step (1), the type of emulsifier is changed, as shown in Table 1 below. The corresponding degradation product results are also shown in Table 1. Example 5 The process is basically the same as in Example 1, except that in step (1), 20 μL of paraffin oil (with a concentration of 10 μL / mL in the final plastic degradation system) was added to the enzyme composition. That is, an oil phase component was added to the enzyme composition. The degradation product results are shown in Table 2. The chromatogram is shown below. Figure 4 As shown.

[0054] Examples 6-8, Comparative Examples 6-10 The process is basically the same as in Example 5, except that in step (1), the emulsifier sodium lignosulfonate is not added to the enzyme composition (Comparative Example 6), or the type of emulsifier is changed (Comparative Examples 7-10), as shown in Table 2 below. The degradation product results are shown in Table 2. As shown in Tables 1 and 2, when sodium lignosulfonate, hexadecyl sulfobetaine, sodium fatty alcohol polyoxyethylene ether sulfate, and sodium lauryl polyoxyethylene ether sulfate are used as emulsifiers, they all effectively degrade PET microplastics regardless of whether paraffin oil is added to the enzyme composition system. However, when no emulsifier is added, or when other types of emulsifiers such as cocamidopropyl betaine, sodium dodecyl sulfonate, alkyl glycosides, and fatty alcohol polyoxyethylene ether are added, the degradation effect is significantly reduced; with the latter two emulsifiers, PET microplastics may not degrade at all.

[0055] Example 9 The process is basically the same as in Example 1 (without paraffin oil), except that in step (1), the amount of sodium lignosulfonate is adjusted to 50 mg. That is, its concentration in the final plastic degradation system is 25 mg / mL. The total molar concentration of the degradation products was measured to be 174.919 μM / L.

[0056] Example 10 The process is basically the same as in Example 1 (without paraffin oil), except that in step (1), the amount of sodium lignosulfonate is adjusted to 100 mg. That is, in the final plastic degradation system, its concentration is 50 mg / mL. The total molar concentration of degradation products was measured to be 105.743 μM / L.

[0057] As can be seen from the comparison between Examples 1 and Examples 9-10, when the concentration of the emulsifier sodium lignosulfonate in the degradation system is too high, it may cause a decrease in the degradation effect.

[0058] Example 11 The process is basically the same as in Example 5 (with paraffin oil), except that in step (1), the amount of paraffin oil is adjusted to 100 μL. That is, the concentration in the final plastic degradation system is 50 μL / mL. The total molar concentration of degradation products was measured to be 274.669 μM / L. That is, when adding paraffin oil, the concentration range of paraffin oil can be relatively large, and excellent degradation effect can be achieved in all cases.

[0059] Example 12 The process is basically the same as in Example 8 (with paraffin oil added and sodium lauryl polyoxyethylene ether sulfate as emulsifier), except that in step (1), keratinase is replaced with lipase (commercially available). The total molar concentration of degradation products was measured to be 137.142 μM / L. It can be seen that the enzyme composition system of the present invention can use various conventional degradation enzymes and achieve good degradation effects.

[0060] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

Claims

1. An enzyme composition for plastic degradation, characterized in that: The enzyme composition includes a plastic-degrading enzyme and an emulsifier; the emulsifier is selected from one or more combinations of lignin sulfonate, sulfobetaine emulsifier, fatty alcohol polyoxyethylene ether sulfate, and C12-C18 alkyl polyoxyethylene ether sulfate.

2. The enzyme composition for plastic degradation according to claim 1, characterized in that: The lignin sulfonate is selected from sodium lignin sulfonate and potassium lignin sulfonate; and / or, the sulfobetaine emulsifier is selected from hexadecyl sulfobetaine, octadecyl sulfobetaine, and dodecyl sulfobetaine; and / or, the fatty alcohol polyoxyethylene ether sulfate is selected from sodium fatty alcohol polyoxyethylene ether sulfate and potassium fatty alcohol polyoxyethylene ether sulfate; and / or, the C12-C18 alkyl polyoxyethylene ether sulfate is selected from lauryl polyoxyethylene ether sulfate, hexadecyl polyoxyethylene ether sulfate, and octadecyl polyoxyethylene ether sulfate.

3. The enzyme composition for plastic degradation according to claim 1 or 2, characterized in that: The plastic-degrading enzyme is selected from one or a combination of several of keratinase, lipase, polyethylene terephthalate hydrolase, and carboxylesterase; and / or, the ratio of the enzyme activity of the plastic-degrading enzyme to the mass of the emulsifier is 100U:(2-10)mg.

4. The enzyme composition for plastic degradation according to claim 1, characterized in that: The enzyme composition further includes an oil phase; the oil phase is selected from one or more of paraffin oil, hexadecane, octadecane, dodecane, and silicone oil.

5. The enzyme composition for plastic degradation according to claim 4, characterized in that: The ratio of the volume of the oil phase to the mass of the emulsifier is (10-50) μL: (2-10) mg; and / or, the oil phase contains nano-ferric oxide.

6. A method for degrading plastics, characterized in that: The method includes the steps of mixing plastic and enzyme composition and carrying out a degradation reaction; the enzyme composition is the enzyme composition for plastic degradation according to any one of claims 1-5.

7. The plastic degradation method according to claim 6, characterized in that: The plastic is selected from one or more combinations of polyethylene terephthalate, propylene terephthalate, and butylene terephthalate; and / or, the plastic exists in the form of an aqueous dispersion of nanoparticles.

8. The plastic degradation method according to claim 6, characterized in that: The method includes the following steps: preparing the plastic into an aqueous dispersion of nanoparticles, adding the enzyme composition to the aqueous dispersion of nanoparticles to obtain a reaction system, and subjecting the reaction system to a degradation reaction.

9. The plastic degradation method according to claim 8, characterized in that: In the reaction system, the mass concentration of the plastic is 0.01-0.5 mg / mL, and the mass-volume concentration of the emulsifier is 2-10 mg / mL.

10. The plastic degradation method according to claim 7, characterized in that: The degradation reaction is carried out at a temperature of 30-80℃ for 1-8 hours; and / or the average particle size of the nanoparticles is 50-200 nm.

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