Bacterial enzyme mixed preparation for PET plastic degradation and preparation method of bacterial enzyme mixed preparation

Abstract

The invention discloses a bacterium-enzyme mixed preparation for PET plastic degradation and a preparation method thereof, and belongs to the technical field of enzyme preparations, a lanthanum metal framework is formed, loaded on the surface of titanium dioxide and carbonized to obtain a lanthanum-doped porous carbon layer, and then nitric acid treatment and silane coupling agent treatment are performed to significantly increase the specific surface area and roughness, so that the specific surface area is increased; the calcium-based diatomite is taken as a carrier to form a sodium alginate microcapsule taking an enzyme preparation as an inclusion, and the sodium alginate microcapsule is loaded on the surface of the calcium-based diatomite, so that the situation that titanium dioxide generates hydroxyl free radicals in photocatalysis to directly attack the enzyme preparation is avoided, and the degradation effect on the PET plastic is prolonged; calcium ions in the calcium-based diatomite can increase the crosslinking degree with the sodium alginate, the load rate of the sodium alginate microcapsule is increased, the strength of the microcapsule is improved, and the slow release effect of an enzyme preparation in the microcapsule is further improved.

Description

Technical Field

[0001] The invention belongs to the technical field of enzyme preparations, and in particular relates to a bacterial enzyme mixed preparation for degrading PET plastics and a preparation method thereof. Background Art

[0002] Due to its good performance, PET is widely used in the production material of environmentally friendly garbage bags. This type of garbage bags must be degraded after large-scale use. Simple chemical degradation is relatively easy, but it is very polluting. The more environmentally friendly biological degradation has always been an industry problem. Plastic degradation refers to the decrease in polymer molecular weight and the decline in the physical properties of polymer materials. Typical manifestations are: plastic brittleness, cracking, softening, hardening, loss of mechanical strength, etc. The aging and deterioration of plastics are a kind of degradation phenomenon, but generally it takes decades or even hundreds of years for plastics to degrade into an environmentally harmless state and return to the natural cycle. The degradation products must eventually be decomposed into carbon dioxide and water before they can be called degradation.

[0003] Existing biodegradation methods for bio-based plastic garbage bags primarily include biocomposting, microbial degradation, and bioenzymatic methods, with biocomposting and microbial degradation being the most commonly used. Reportedly, bio-based plastic garbage bags can achieve a degradation rate of 60-80% after 2-3 months of biocomposting. However, these methods suffer from long processing cycles, difficulties in efficient waste transportation, and the resulting inability to commercialize them. Bioenzyme preparations, however, have proven viable for large-scale industrial production due to recent improvements in fermentation enzyme activity and significant reductions in production costs.

[0004] Chinese patent publication number CN119662600A discloses an enzyme preparation for catalytic degradation of bioplastics and its preparation method. The catalytic additive is prepared by using calcium-based bentonite as a carrier and loading nano-titanium dioxide. Nano-titanium dioxide is a common catalytic nanomaterial in the field of photocatalysis. It has low manufacturing cost and photocatalytic degradation activity. It can generate free radicals under light conditions, which can trigger the oxidative degradation reaction of bio-based plastics, thereby accelerating the degradation rate of bio-based plastics. However, in this solution, the hydroxyl radicals generated by nano-titanium dioxide during photocatalysis are highly oxidizing and can easily cause the inactivation of the enzyme preparation, thereby reducing the degradation efficiency. Summary of the Invention

[0005] The present invention aims to provide a bacterial-enzyme mixed preparation for PET plastic degradation and a preparation method thereof. A lanthanum metal skeleton is formed and loaded on the surface of titanium dioxide and carbonized to obtain a lanthanum-doped porous carbon layer. Calcium-based diatomaceous earth is used as a carrier to form sodium alginate microcapsules containing an enzyme preparation, which are loaded on the surface of the calcium-based diatomaceous earth. This prevents titanium dioxide from generating hydroxyl radicals during photocatalysis that directly attack the enzyme preparation, thereby prolonging the degradation effect on PET plastic.

[0006] The purpose of the present invention can be achieved through the following technical solutions: A method for preparing a bacterial enzyme mixed preparation for PET plastic degradation comprises the following steps: Step 1: A lanthanum metal skeleton is loaded on the surface of titanium dioxide and carbonized to obtain a lanthanum-doped porous carbon layer, which is then acid-washed to obtain acidified titanium dioxide; the acidified titanium dioxide, γ-aminopropyltriethoxysilane, anhydrous ethanol and deionized water are added to a reactor, stirred at 50-65°C and 400-500r / min for 3-4h, filtered, and the filter cake is washed with deionized water 2-4 times, and vacuum-dried at 60-80°C for 1-2h to obtain dispersed titanium dioxide.

[0007] Step 2: Add calcium-based diatomaceous earth, sodium alginate and deionized water into a reactor, stir for 10-15 minutes at 20-25°C and 500-600 r / min, then add 20-22g of enzyme preparation, and continue stirring for 30-40 minutes to obtain a mixed solution; dropwise add the mixed solution into a calcium chloride solution with a mass fraction of 3-4%, then add dispersed titanium dioxide, continue stirring for 1-2 hours, filter, wash the filter cake with deionized water and anhydrous ethanol for 2-4 times respectively, and vacuum dry at 60-80°C for 1-2 hours to obtain a bacterial enzyme mixed preparation for PET plastic degradation.

[0008] Furthermore, in step 1, the usage ratio of acidified titanium dioxide, γ-aminopropyltriethoxysilane, anhydrous ethanol and deionized water is 30-35 g: 20-30 mL: 300-400 mL: 800-900 mL.

[0009] Furthermore, in step 2, the usage ratio of calcium-based diatomaceous earth, sodium alginate, deionized water and enzyme preparation is 100-120 g: 80-90 g: 800-900 mL: 20-22 g.

[0010] Furthermore, in step 2, the usage ratio of the mixed solution, the calcium chloride solution and the dispersed titanium dioxide is 70-80 mL: 300-400 mL: 30-40 g.

[0011] Furthermore, the enzyme preparation in step 2 is any one of cutinase, alkaline lipase, neutral lipase, protease and laccase.

[0012] Furthermore, the acidified titanium dioxide in step 1 is prepared by the following steps: Add the modified titanium dioxide and a 1 mol / L nitric acid solution into a reactor, stir and pickle for 1-1.2 hours at 50-55°C and 400-500 r / min, filter, wash the filter cake with deionized water until the last washing liquid is neutral, and vacuum dry at 60-80°C for 1-2 hours to obtain acidified titanium dioxide.

[0013] Furthermore, the usage ratio of the modified titanium dioxide and the nitric acid solution is 70-80 g: 200-230 mL.

[0014] Furthermore, the calcium-based diatomaceous earth in step 2 is prepared by the following steps: 100-120 g of diatomaceous earth and 300-400 mL of a 10-15% sodium bicarbonate solution are added to a reactor, and the mixture is vacuum impregnated for 2-3 hours at 20-25° C. and 500-600 r / min. Then, 120-140 mL of a 40-50% calcium chloride solution is added, and the reaction is continued for 1-2 hours. The mixture is filtered, and the filter cake is washed 2-4 times with deionized water and anhydrous ethanol, respectively, and vacuum dried at 60-80° C. for 1-2 hours to obtain calcium-based diatomaceous earth.

[0015] Furthermore, the usage ratio of diatomaceous earth, sodium bicarbonate solution and calcium chloride solution is 100-120 g: 300-400 mL: 120-140 mL.

[0016] Furthermore, the modified titanium dioxide is prepared by the following steps: Add 2,5-diaminoterephthalic acid and N,N-dimethylformamide solution to a polytetrafluoroethylene-lined autoclave, stir at 20-25°C and 500-600r / min for 30-40min, then add lanthanum nitrate hexahydrate, heat to 120-130°C, continue to react for 10-12h, then add titanium dioxide powder with a particle size of 80-90nm, continue to react for 10-12h, naturally cool to room temperature, filter, wash the filter cake with methanol solution and deionized water 2-4 times respectively, vacuum dry at 60-80°C for 1-2h, transfer the product to a muffle furnace, calcined at 500-600°C for 2-3h under nitrogen protection, and naturally cool to room temperature to obtain modified titanium dioxide.

[0017] Furthermore, the usage ratio of 2,5-diaminoterephthalic acid, N,N-dimethylformamide solution, lanthanum nitrate hexahydrate and titanium dioxide powder is 80-90 g: 700-800 mL: 30-40 g: 80-90 g.

[0018] Beneficial effects of the present invention: 1. The present invention provides a bacterial enzyme mixed preparation for PET plastic degradation, which has good degradation efficiency, stable and long-term degradation ability for PET plastic. A lanthanum metal skeleton is formed and loaded on the surface of titanium dioxide and carbonized to obtain a lanthanum-doped porous carbon layer. The porous carbon layer can increase the porous properties of titanium dioxide. After treatment with nitric acid and a silane coupling agent, the specific surface area and roughness are significantly increased, and the adsorption effect with calcium-based diatomaceous earth can be enhanced. Lanthanum is doped into the titanium dioxide lattice. Due to the large difference in lanthanum ion radius and titanium ion radius, lattice distortion and local defects will occur, which reduces the probability of recombination of photogenerated electrons and holes, prolongs the carrier lifetime, and thus improves the photocatalytic efficiency.

[0019] 2. The present invention uses calcium-based diatomaceous earth as a carrier to form sodium alginate microcapsules containing an enzyme preparation, which are loaded on the surface of the calcium-based diatomaceous earth. The calcium ions in the calcium-based diatomaceous earth can increase the degree of cross-linking with sodium alginate, thereby increasing the loading rate of the sodium alginate microcapsules. The increased degree of cross-linking of the sodium alginate microcapsules means an increase in the strength of the microcapsules, preventing premature rupture and sudden release of the enzyme preparation inside, further improving the sustained release effect of the enzyme preparation in the microcapsules.

[0020] 3. The calcium-based diatomaceous earth of the present invention generates calcium carbonate precipitates that are deposited on the surface of the diatomaceous earth, thereby improving the ion exchange performance of the diatomaceous earth. The sodium alginate microcapsules loaded on the surface rupture under external force or water absorption to release the enzyme preparation. The calcium ions in the calcium-based diatomaceous earth can form a complex with the enzyme, thereby improving the catalytic activity of the enzyme. The calcium-based bentonite can also adsorb the substrate hydrolyzed by the enzyme, making the reaction more thorough and increasing the reaction rate. DETAILED DESCRIPTION

[0021] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0022] Example 1: A method for preparing a bacterial enzyme mixed preparation for PET plastic degradation, comprising the following steps: S1: Add 80g of 2,5-diaminoterephthalic acid and 700mL of N,N-dimethylformamide solution into a polytetrafluoroethylene-lined autoclave, stir at 20℃ and 500r / min for 30min, then add 30g of lanthanum nitrate hexahydrate, heat to 120℃, continue to react for 10h, then add 80g of titanium dioxide powder with a particle size of 80nm, continue to react for 10h, cool naturally to room temperature, filter, wash the filter cake with methanol solution and deionized water twice respectively, dry in vacuum at 60℃ for 1h, transfer the product to a muffle furnace, calcine at 500℃ for 2h under nitrogen protection, and cool naturally to room temperature to obtain modified titanium dioxide.

[0023] 2,5-Diaminoterephthalic acid is dispersed in N,N-dimethylformamide solution and coordinates with metallic lanthanum in lanthanum nitrate hexahydrate to generate a lanthanum metal skeleton loaded on the titanium dioxide surface.

[0024] S2: Add 70 g of modified titanium dioxide and 200 mL of 1 mol / L nitric acid solution into a reactor, stir and acid wash at 50°C and 400 r / min for 1 h, filter, wash the filter cake with deionized water until the last washing liquid is neutral, and vacuum dry at 60°C for 1 h to obtain acidified titanium dioxide.

[0025] After acid washing, the surface of modified titanium dioxide carries a large number of oxygen-containing groups, which can increase the adsorption effect with calcium-based diatomaceous earth and improve the loading rate of acidified titanium dioxide.

[0026] S3: Add 30 g of acidified titanium dioxide, 20 mL of γ-aminopropyltriethoxysilane, 300 mL of anhydrous ethanol and 800 mL of deionized water into a reactor, stir at 50°C and 400 r / min for 3 h, filter, wash the filter cake twice with deionized water, and vacuum dry at 60°C for 1 h to obtain dispersed titanium dioxide.

[0027] The silane bonds generated by the hydrolysis of γ-aminopropyltriethoxysilane combine with the hydroxyl groups on the surface of acidified titanium dioxide. This bonding method replaces the original weak interactions between titanium dioxide particles through hydrogen bonds and van der Waals forces, effectively inhibiting particle agglomeration.

[0028] S4: Add 100 g of diatomaceous earth and 300 mL of 10% sodium bicarbonate solution into the reactor, vacuum impregnate for 2 h at 20 ° C and 500 r / min, then add 120 mL of 40% calcium chloride solution, continue to react for 1 h, filter, wash the filter cake with deionized water and anhydrous ethanol twice respectively, and vacuum dry at 60 ° C for 1 h to obtain calcium-based diatomaceous earth.

[0029] Sodium bicarbonate can neutralize the acidic groups on the surface of diatomaceous earth, and at the same time use the pore structure to adsorb sodium ions and bicarbonate ions, providing active sites for subsequent reactions. After adding calcium chloride, the calcium ions in the solution react with the carbonate ions adsorbed on the surface of diatomaceous earth to generate calcium carbonate precipitates that are deposited on the surface of diatomaceous earth.

[0030] S5: Add 100g of calcium-based diatomaceous earth, 80g of sodium alginate and 800mL of deionized water into a reactor, stir at 20°C and 500r / min for 10min, then add 20g of cutinase and continue stirring for 30min to obtain a mixed solution; drop 70mL of the mixed solution into 300mL of 3% calcium chloride solution, then add 30g of dispersed titanium dioxide, continue stirring for 1h, filter, wash the filter cake with deionized water and anhydrous ethanol twice respectively, and vacuum dry at 60°C for 1h to obtain a bacterial enzyme mixed preparation for PET plastic degradation.

[0031] The carboxyl groups on the surface of sodium alginate dissociate in the solution and carry negative charges, which cross-link with the positively charged calcium ions in calcium chloride through electrostatic interaction, thereby coating the enzyme preparation and forming sodium alginate microcapsules. In this process, the calcium carbonate distributed on the surface of the calcium-based diatomaceous earth is dispersed in the deionized water solution to provide calcium ions. The provided calcium ions can increase the degree of cross-linking with sodium alginate and increase the loading rate of the sodium alginate microcapsules. The increase in the degree of cross-linking of the sodium alginate microcapsules means that the strength of the microcapsules is increased, further improving the sustained release effect of the enzyme preparation in the microcapsules.

[0032] Example 2: A method for preparing a bacterial enzyme mixed preparation for PET plastic degradation, comprising the following steps: S1: Add 85g of 2,5-diaminoterephthalic acid and 750mL of N,N-dimethylformamide solution into a polytetrafluoroethylene-lined autoclave, stir at 22.5℃ and 550r / min for 35min, then add 35g of lanthanum nitrate hexahydrate, heat to 125℃, continue to react for 11h, then add 85g of titanium dioxide powder with a particle size of 85nm, continue to react for 11h, cool naturally to room temperature, filter, wash the filter cake with methanol solution and deionized water three times respectively, dry in vacuum at 70℃ for 1.5h, transfer the product to a muffle furnace, calcine at 550℃ for 2.5h under nitrogen protection, and cool naturally to room temperature to obtain modified titanium dioxide.

[0033] S2: Add 75 g of modified titanium dioxide and 215 mL of 1 mol / L nitric acid solution into a reactor, stir and pickle at 52.5 ° C and 450 r / min for 1.1 h, filter, wash the filter cake with deionized water until the last washing liquid is neutral, and vacuum dry at 70 ° C for 1.5 h to obtain acidified titanium dioxide.

[0034] S3: Add 32.5 g of acidified titanium dioxide, 25 mL of γ-aminopropyltriethoxysilane, 350 mL of anhydrous ethanol and 850 mL of deionized water into a reactor, stir at 57.5 ° C and 450 r / min for 3.5 h, filter, wash the filter cake with deionized water three times, and vacuum dry at 70 ° C for 1.5 h to obtain dispersed titanium dioxide.

[0035] S4: 110 g of diatomaceous earth and 350 mL of 12.5% ​​sodium bicarbonate solution were added to the reactor, and vacuum impregnation was carried out at 22.5°C and 550 r / min for 2.5 h. Then, 130 mL of 45% calcium chloride solution was added, and the reaction was continued for 1.5 h. The mixture was filtered and the filter cake was washed three times with deionized water and anhydrous ethanol respectively, and vacuum dried at 70°C for 1.5 h to obtain calcium-based diatomaceous earth.

[0036] S5: Add 110g of calcium-based diatomaceous earth, 85g of sodium alginate and 850mL of deionized water into a reactor, stir for 12.5min at 22.5℃ and 550r / min, then add 21g of alkaline lipase, and continue stirring for 35min to obtain a mixed solution; drop 75mL of the mixed solution into 350mL of 3.5% calcium chloride solution, then add 35g of dispersed titanium dioxide, continue stirring for 1.5h, filter, wash the filter cake with deionized water and anhydrous ethanol three times respectively, and vacuum dry at 70℃ for 1.5h to obtain a bacterial enzyme mixed preparation for PET plastic degradation.

[0037] Example 3: A method for preparing a bacterial enzyme mixed preparation for PET plastic degradation, comprising the following steps: S1: Add 90g of 2,5-diaminoterephthalic acid and 800mL of N,N-dimethylformamide solution into a polytetrafluoroethylene-lined autoclave, stir at 25°C and 600r / min for 40min, then add 40g of lanthanum nitrate hexahydrate, heat to 130°C, continue to react for 12h, then add 90g of titanium dioxide powder with a particle size of 90nm, continue to react for 12h, cool naturally to room temperature, filter, wash the filter cake with methanol solution and deionized water four times respectively, dry in vacuum at 80°C for 2h, transfer the product to a muffle furnace, calcine at 600°C for 3h under nitrogen protection, and cool naturally to room temperature to obtain modified titanium dioxide.

[0038] S2: Add 80 g of modified titanium dioxide and 230 mL of 1 mol / L nitric acid solution into a reactor, stir and pickle at 55°C and 500 r / min for 1.2 h, filter, wash the filter cake with deionized water until the last washing liquid is neutral, and vacuum dry at 80°C for 2 h to obtain acidified titanium dioxide.

[0039] S3: Add 35 g of acidified titanium dioxide, 30 mL of γ-aminopropyltriethoxysilane, 400 mL of anhydrous ethanol and 900 mL of deionized water into a reactor, stir at 65°C and 500 r / min for 4 h, filter, wash the filter cake with deionized water 4 times, and vacuum dry at 80°C for 2 h to obtain dispersed titanium dioxide.

[0040] S4: Add 120 g of diatomaceous earth and 400 mL of 15% sodium bicarbonate solution into the reactor, vacuum impregnate for 3 h at 25 ° C and 600 r / min, then add 140 mL of 50% calcium chloride solution, continue to react for 2 h, filter, wash the filter cake with deionized water and anhydrous ethanol four times respectively, and vacuum dry at 80 ° C for 2 h to obtain calcium-based diatomaceous earth.

[0041] S5: Add 120g of calcium-based diatomaceous earth, 90g of sodium alginate and 900mL of deionized water into a reactor, stir at 25°C and 600r / min for 15min, then add 22g of neutral lipase, and continue stirring for 40min to obtain a mixed solution; drop 80mL of the mixed solution into 400mL of 4% calcium chloride solution, then add 40g of dispersed titanium dioxide, continue stirring for 2h, filter, wash the filter cake with deionized water and anhydrous ethanol four times respectively, and vacuum dry at 80°C for 2h to obtain a bacterial enzyme mixed preparation for PET plastic degradation.

[0042] Comparative Example 1: Based on Example 3, the modified titanium dioxide in step S2 was replaced with titanium dioxide powder with a particle size of 80-90 nm in step S1, and the other steps remained unchanged to prepare a bacterial enzyme mixed preparation for PET plastic degradation.

[0043] Comparative Example 2: Based on Example 3, the dispersed titanium dioxide in step S5 was replaced by the acidified titanium dioxide in step S2, and the other steps remained unchanged to prepare a bacterial enzyme mixed preparation for PET plastic degradation.

[0044] Comparative Example 3: Based on Example 3, without step S3, the calcium-based diatomaceous earth in step S4 was replaced by the diatomaceous earth in step S3, and the other steps remained unchanged to prepare a bacterial enzyme mixed preparation for PET plastic degradation.

[0045] The performance test of the bacterial enzyme mixed preparation for PET plastic degradation obtained in Examples 1-3 and Comparative Examples 1-3 was performed. Water was added to the PET biodegradable plastic to be treated to obtain a reaction substrate. The mass ratio of the biodegradable plastic to water was 1:10. The composite enzyme preparation was added to the reaction substrate in an amount of 1 kg / t based on the reaction substrate. After sufficient mixing, the reaction was carried out at 25 ° C and 100 r / min for 24 hours. The reaction temperature was then raised to 40 ° C, and the pH value was adjusted to 3.0 using citric acid for further reaction for 24 hours. After 15 days, a new PET plastic bag was added and the temperature was controlled at 25 ° C. The amount of the new PET plastic bag added was the same as the first input amount. Stirring was 100 / min, the reaction was carried out for 24 hours, and all remaining residues were collected. Each group of examples and comparative examples was repeated 3 times. The results are shown in Tables 1 and 2: Table 1 Degradation performance test table of bacterial enzyme mixture preparation project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Hydrolysis rate (%) 56.87±0.23 57.56±0.12 58.10±0.18 29.25±0.11 46.01±0.36 34.21±0.27 Resilience Toughness changes significantly and tensile strength weakens Toughness changes significantly and tensile force is significantly weakened Toughness changes significantly and mechanical properties are lost There is no significant change in toughness and tensile strength Slight change in toughness and tensile strength There is no significant change in toughness and tensile strength Crack situation A few cracks Significant cracks A large number of cracks No cracks A few cracks No cracks Table 2 Degradation performance test of bacterial enzyme mixture after 15 days project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Hydrolysis rate (%) 52.35±0.15 53.28±0.34 54.86±0.28 21.26±0.16 36.26±0.19 26.12±0.21 Resilience Toughness changes significantly and tensile strength weakens Toughness changes significantly and tensile force is significantly weakened Toughness changes significantly and mechanical properties are lost There is no significant change in toughness and tensile strength Slight change in toughness and tensile strength There is no significant change in toughness and tensile strength Crack situation A few cracks Significant cracks A large number of cracks No cracks A few cracks No cracks As can be seen from Tables 1 and 2, the hydrolysis rate of the PET plastic bag by the bacterial enzyme mixed preparation for PET plastic degradation obtained in Examples 1 to 3 is significantly higher than that of the comparative example, the toughness of the PET plastic bag is worse than that of the comparative example, and there are more cracks than that of the comparative example. After 15 days, the degradation ability can still be maintained well, indicating that the bacterial enzyme mixed preparation for PET plastic degradation prepared by the present invention has good degradation efficiency, stable and long-term degradation ability for PET plastic.

[0046] In Comparative Example 1, the modified titanium dioxide is replaced with titanium dioxide powder, and 2,5-diaminoterephthalic acid is dispersed in N,N-dimethylformamide solution to coordinate with the metallic lanthanum in lanthanum nitrate hexahydrate to generate a lanthanum metal skeleton loaded on the titanium dioxide surface and carbonized to obtain a lanthanum-doped porous carbon layer. The porous carbon layer can increase the porous properties of titanium dioxide. The lanthanum doping enters the titanium dioxide lattice. Due to the large difference in the radius of the lanthanum ion and the titanium ion radius, it will cause lattice distortion and local defects, reduce the probability of recombination of photogenerated electrons and holes, extend the carrier lifetime, and thus improve the photocatalytic efficiency.

[0047] In Comparative Example 2, the dispersed titanium dioxide is replaced with acidified titanium dioxide. The silane bonds generated by the hydrolysis of γ-aminopropyltriethoxysilane combine with the hydroxyl groups on the surface of the acidified titanium dioxide, thereby increasing the dispersibility of the dispersed titanium dioxide and avoiding agglomeration. In addition, the amino group contained in γ-aminopropyltriethoxysilane can increase the adsorption effect on calcium-based diatomaceous earth.

[0048] In Comparative Example 3, calcium-based diatomaceous earth is replaced with diatomaceous earth. By generating calcium carbonate precipitate and depositing it on the surface of the diatomaceous earth, the ion exchange performance of the diatomaceous earth is improved. The surface-loaded sodium alginate microcapsules rupture under external force or water absorption to release the enzyme preparation. The calcium ions in the calcium-based diatomaceous earth can form a complex with the enzyme, thereby improving the catalytic activity of the enzyme, and the calcium-based bentonite can adsorb the substrate after being hydrolyzed by the enzyme, making the reaction more thorough and increasing the reaction rate. In the diatomaceous earth that has lost calcium ions, the ion exchange capacity decreases, and the cross-linking degree of the sodium alginate microcapsules cannot be improved.

[0049] While the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations can be made to the embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for preparing a bacterial enzyme mixed preparation for PET plastic degradation, characterized in that: The steps include: Step 1: A lanthanum metal skeleton is loaded on the surface of titanium dioxide and carbonized to obtain a lanthanum-doped porous carbon layer, which is then acid-washed to obtain acidified titanium dioxide; the acidified titanium dioxide, γ-aminopropyltriethoxysilane, anhydrous ethanol and deionized water are added to a reactor, stirred at 50-65°C and 400-500 rpm for 3-4 hours, filtered, washed and vacuum-dried to obtain dispersed titanium dioxide; Step 2: Add calcium-based diatomaceous earth, sodium alginate and deionized water into a reactor, stir at 20-25°C and 500-600 r / min for 10-15 minutes, then add an enzyme preparation, and continue stirring for 30-40 minutes to obtain a mixed solution; drop the mixed solution into a 3-4wt% calcium chloride solution, then add dispersed titanium dioxide, continue stirring for 1-2 hours, filter, wash, and vacuum dry to obtain a bacterial enzyme mixed preparation for PET plastic degradation.

2. The method for preparing a bacterial enzyme mixed preparation for PET plastic degradation according to claim 1, characterized in that: The usage ratio of the acidified titanium dioxide, gamma-aminopropyltriethoxysilane, anhydrous ethanol and deionized water is 30-35 g: 20-30 mL: 300-400 mL: 800-900 mL.

3. The method for preparing a bacterial enzyme mixed preparation for PET plastic degradation according to claim 1, characterized in that: The usage ratio of the calcium-based diatomaceous earth, sodium alginate, deionized water and enzyme preparation in step 2 is 100-120g:80-90g:800-900mL:20-22g; the usage ratio of the mixed solution, calcium chloride solution and dispersed titanium dioxide is 70-80mL:300-400mL:30-40g.

4. The method for preparing a bacterial enzyme mixed preparation for PET plastic degradation according to claim 1, characterized in that: The enzyme preparation in step 2 is any one of cutinase, alkaline lipase, neutral lipase, protease and laccase.

5. The method for preparing a bacterial enzyme mixed preparation for PET plastic degradation according to claim 1, characterized in that: The acidified titanium dioxide described in step 1 is prepared by the following steps: Add the modified titanium dioxide and a nitric acid solution with a concentration of 1 mol / L into a reactor, stir at 50-55° C. and 400-500 r / min for acid washing for 1-1.2 hours, filter, wash, and vacuum dry to obtain acidified titanium dioxide.

6. The method for preparing a bacterial enzyme mixed preparation for PET plastic degradation according to claim 5, characterized in that: The usage ratio of the modified titanium dioxide and the nitric acid solution is 70-80 g: 200-230 mL.

7. The method for preparing a bacterial enzyme mixed preparation for PET plastic degradation according to claim 1, characterized in that: The calcium-based diatomaceous earth in step 2 is prepared by the following steps: Add diatomaceous earth and 10-15 wt% sodium bicarbonate solution into a reaction kettle, and vacuum impregnate at 20-25° C. and 500-600 r / min for 2-3 hours. Then add 40-50 wt% calcium chloride solution, continue to react for 1-2 hours, filter, wash the filter cake with deionized water and anhydrous ethanol 2-4 times respectively, and vacuum dry to obtain calcium-based diatomaceous earth; The usage ratio of the diatomaceous earth, the sodium bicarbonate solution and the calcium chloride solution is 100-120 g: 300-400 mL: 120-140 mL.

8. The method for preparing a bacterial enzyme mixed preparation for PET plastic degradation according to claim 6, characterized in that: The modified titanium dioxide is prepared by the following steps: Add 2,5-diaminoterephthalic acid and N,N-dimethylformamide solution into a polytetrafluoroethylene-lined autoclave, stir at 20-25°C and 500-600 r / min for 30-40 minutes, then add lanthanum nitrate hexahydrate, heat to 120-130°C, continue to react for 10-12 hours, then add titanium dioxide powder with a particle size of 80-90 nm, continue to react for 10-12 hours, naturally cool, filter, wash, and vacuum dry. Transfer the product to a muffle furnace and calcine at 500-600°C for 2-3 hours under nitrogen protection, and naturally cool to obtain modified titanium dioxide.

9. The method for preparing a bacterial enzyme mixed preparation for PET plastic degradation according to claim 8, characterized in that: The usage ratio of the 2,5-diaminoterephthalic acid, N,N-dimethylformamide solution, lanthanum nitrate hexahydrate and titanium dioxide powder is 80-90 g: 700-800 mL: 30-40 g: 80-90 g.

10. A bacterial enzyme mixed preparation for PET plastic degradation, characterized in that: Prepared by the preparation method according to any one of claims 1 to 9.