Enzymatic Decomposition for PET Bottle Recycling

Genetically engineering Pseudomonas putida bacteria to selectively degrade and convert polyethylene terephthalate (PET) plastic into valuable chemicals. The engineered bacteria express PETase and MHETase enzymes from Ideonella sakaiensis to break down PET into terephthalate and ethylene glycol. They also have genes for transporting and metabolizing terephthalate. This allows converting the PET deconstruction products into chemicals like beta-ketoadipate. The engineered bacteria can grow on PET as the sole carbon source. The strategy involves using PETase and MHETase to degrade PET into monomers, then converting those monomers into useful chemicals in the engineered bacteria.

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Esterases with improved activity and thermostability for breaking down polyester plastics like PET. The enzymes have mutations compared to a reference sequence like SEQ ID No. 1. Examples of mutations are L210A/C/D/E/G/H/I/K/M/N/P/Q/R/S/T/V/W/Y, R205C, S251C, Q95G/P, G136A, T169Q, V172I, S184E, N213M/D. These mutations can be combined to create customized esterases with optimized polyester degradation activity and stability.

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Enzymatic depolymerization of polymers like PET and polycarbonate using moist-solid reaction mixtures. The method involves combining the polymer with an enzyme like cutinase or esterase and optional additives, then mechanochemically milling or mixing the mixture. The enzyme-catalyzed reaction is allowed to proceed by aging the mixture. This allows direct depolymerization of high crystallinity polymers like PET without pre-milling or solvent. The enzyme can be wild-type or engineered.

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A process for degrading polyester-containing materials like plastic products using enzymes in acidic conditions. The process involves contacting the polyester-containing material with enzymes like PETase and MHETase at acidic pH between 3 and 6. The enzymes degrade the polyester into monomers and oligomers. The acidic conditions allow avoiding salt production and reducing base consumption. The process can be scaled up for industrial use. The degraded polyester products can be recovered and purified.

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Neutral hydrolysis method for waste polyester without waste liquid discharge. The method involves a two-step process: (1) alcohol treatment with ethylene glycol to partially depolymerize and dissolve impurities in the waste polyester, (2) hydrolysis in ethylene glycol to completely depolymerize and separate the polyester into pure terephthalic acid and ethylene glycol. This allows recycling the polyester without generating waste water. The alcohol treatment reduces polyester molecular weight and impurity content, making hydrolysis milder and more efficient.

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Improved process for depolymerizing PET plastic into BHET, which is a valuable chemical used to make new PET. The process involves converting PET into BHET using a specific solvent mixture in a reactive distillation column. The solvent is a mixture of ethanol and sodium ethoxide, prepared by reacting ethanol and sodium hydroxide in the distillation column. This solvent selectively breaks down the PET into BHET with less byproducts compared to traditional solvents. The BHET can then be purified and used to make new PET.

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A selective and efficient chemical recycling process for polyethylene terephthalate (PET) plastics that can recycle contaminated, colored, or heterogeneous PET waste that cannot be recycled through conventional mechanical processes. The chemical recycling uses a catalytic system with a base and an aprotic solvent to depolymerize the PET into its monomers by reacting with excess nucleophiles like alcohols or amines. This enables selective degradation of pure PET while avoiding degradation of contaminants like metals, fillers, or other polymers. The low temperature, catalytic conditions make it scalable and energy-efficient compared to harsh methods like radiation or microwaves.

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A PET hydrolase enzyme derived from bacteria that can degrade PET plastic into harmless soluble products. The hydrolase enzyme, named PpPETase from Pseudomonas paralcaligenes and ScPETase from Streptomyces calvus, can be used to break down PET into monohydroxyethyl terephthalate (MHET), terephthalic acid (TPA), and ethylene glycol (EG). The enzyme is isolated and expressed from bacteria, allowing it to be used in biotechnological applications like waste treatment to degrade PET plastics in an environmentally friendly way.

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A method to degrade polyethylene terephthalate (PET) plastic waste using a combined chemical-enzymatic process. The method involves dissolving PET in an organic solvent, adding a small amount of alkali, and pre-degrading the PET in solution at moderate temperature. The pre-degraded PET suspension is then enzymatically hydrolyzed to fully degrade the PET into monomers like terephthalic acid. This two-step process allows efficient bioconversion of high-crystallinity PET waste into valuable monomers using mild conditions and a trace amount of alkali.

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Method to recycle waste PET into higher value PETG/PCTG copolyester using mixed alcohol depolymerization followed by polycondensation. The recycling process involves alcoholysis of waste PET using a catalyst to break down the polymer into BHET/BHCT monomers and oligomers using a mixture of ethylene glycol (EG) and 1,4-cyclohexanedimethanol (CHDM). These depolymerization products are then polycondensed using a catalyst to make PETG/PCTG copolyester with properties like improved light transmittance, environmental friendliness, and heat resistance compared to virgin PET.

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A double depolymerization method for recycling waste polyester like PET that involves using two different depolymerization techniques in series to improve product yield and purity compared to single methods. The first step is an initial depolymerization using a method like alkaline hydrolysis or methanolysis to partially break down the polyester into monomers or oligomers. The second step is a final depolymerization using a different method like glycolysis or alcoholysis to fully depolymerize the partially broken polymer into monomers. This two-step process allows higher yields and better purification compared to using just one depolymerization method.

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A process for degrading plastic products containing polyesters like PET by enzymatic depolymerization at acidic pH without base addition. The process involves two steps: a preliminary step at pH 6.5-10 to reach high terephthalic acid concentration in the reaction medium, followed by main depolymerization at pH 4-6. The high terephthalic acid concentration in the medium allows acidic depolymerization without pH adjustment. Enzymes degrade the polyesters. The acidic depolymerization provides economic benefits by reducing base consumption and salt production.

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Recycling PET-based materials like disposable bottles, trays, fabrics, and insulation into terephthalate esters like dimethyl terephthalate (DMT) using a simple, room temperature process without pre-treatment. The method involves grinding the PET waste into chips, then reacting it with an alcohol like methanol or ethanol at atmospheric pressure and room temperature for less than an hour. The PET breaks down into terephthalate esters and the alcohol. This allows recycling of contaminated PET materials like fabrics with elastane or cotton blends.

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Recycling of polyethylene terephthalate (PET) waste into new PET using a two-step process that involves partial depolymerization followed by complete depolymerization. This reduces the time and ethylene glycol required compared to direct depolymerization. The partial depolymerization step involves heating PET with excess ethylene glycol to 200-250°C to produce partially depolymerized PET. This intermediate is then depolymerized with ethylene glycol and catalyst at 170-200°C to form bis(2-hydroxyethyl) terephthalate (BHET). The BHET is purified and polymerized to regenerate PET.

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Chemical-biological integrated method to efficiently recycle PET into high-value products using a catalyst like betaine instead of heavy metal catalysts in the initial glycolysis step. The method involves glycolyzing PET in ethylene glycol with betaine as a catalyst to produce oligomers. These oligomers are then enzymatically hydrolyzed to monomers and platform chemicals. The betaine-catalyzed glycolysis prevents pH drops that inhibit enzymatic hydrolysis. This integrated approach allows efficient recycling of PET into valuable chemicals without adverse impacts on subsequent biological steps.

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Improved method for depolymerization of polyethylene terephthalate (PET) plastics to recycle them into the starting material ethylene glycol. The method involves using alkali metal alkoxides like sodium ethoxide or potassium ethoxide obtained by reactive distillation of ethanol and alkali metal hydroxide, instead of pure ethoxide, as the catalyst for PET depolymerization. The reactive distillation step allows in situ formation of the catalyst by reacting ethanol with alkali metal hydroxide in the distillation column. This provides a catalyst-rich environment for PET depolymerization without separate catalyst addition. The reactive distillation also enables simultaneous separation of ethanol and ethylene glycol byproduct.

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A method for recycling polyethylene terephthalate (PET) plastic that involves depolymerizing it using an electrolysis cell with an alkali metal glycolate solution. The PET is reacted with the glycolate solution to produce bis-2-hydroxyethyl terephthalate (BHET) at high yields. The method involves using an electrolysis cell with alkali metal glycolate solution instead of acid to depolymerize PET. The cell contains an alkali metal glycolate solution made by electrolysis. This method allows recycling PET into BHET with higher yields and less waste compared to other methods.

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Process for depolymerizing PET plastics into BHET using sodium or potassium glycolate obtained by reactive distillation. The process involves reacting glycol with alkali metal alcoholate like sodium or potassium ethoxide in a reactive distillation column. This produces a crude product stream containing glycolate, water, alcohol, and unreacted alcoholate. The glycolate can then be separated and used for depolymerizing PET to BHET. The reactive distillation provides higher yields of BHET compared to using glycolate directly. After depolymerization, the BHET can be polymerized again into PET if desired. This provides a recycling loop for PET plastics.

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Recycling of polyethylene terephthalate (PET) plastics by depolymerization to dimethyl terephthalate (DMT) using mild reaction conditions and catalysts. The process involves treating crushed PET waste with excess methanol, a guanidine or squid-based organic base, and a second base like an inorganic base or oxide ether. The reaction conditions are mild (25-80°C) compared to traditional methods. This allows selective depolymerization without structural changes or degradation products. The DMT can then be filtered and washed without further purification.

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Selective depolymerization of waste polyester like PET using aqueous metal salts to produce depolymerized monomers and oligomers. This allows recycling of waste plastics into new polymers without significant degradation. The process involves heating waste polyester in metal salt solution to break down the polymer. The depolymerized products can then be polymerized again to make renewable polyesters. The metal salt residue is removed. This selective depolymerization avoids the energy-intensive separation steps of conventional methods.

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Method for producing high purity recycled bis(2-hydroxyethyl) terephthalate (BHET) from waste polyester using a multi-stage depolymerization process. The method involves depolymerizing waste polyester twice, first at high temperature and then at lower temperature, followed by ion exchange, distillation, and final distillation steps. This reduces impurities like diethylene glycol esters compared to single stage depolymerization. The recycled BHET has >96% BHET content and <2% diethylene glycol esters.

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Recycling polyester-based materials like PET by incorporating a distillation step before depolymerization to improve product purity and consistency. The process involves treating the polyester feed with distillation to remove volatile impurities like water and acetaldehyde. This distilled feed is then depolymerized using an organic catalyst and alcohol solvent to produce monomeric or oligomeric diesters. The distillation step removes impurities that degrade product quality and avoids the need for pre-drying the feed. It also enables consistent reaction times without adjustment between batches.

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Using specific esterases to degrade polyester plastics like PET under acidic conditions between pH 3 and 6. The esterases have improved activity and thermal stability compared to the parent enzyme at these pH levels. The modified esterases contain specific amino acid substitutions like T11E, R12D, S13E, F90A, Y92G, W155A, T157S, Q182D, F208M, N204D, N204E, S206D, N211D, S212F, N213P, V219I, Y220M, Q237D, N241E, N243E, L247T, V170I,

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Method to degrade plastic products like PET bottles into monomers using enzymes. The method involves amorphizing the plastic by heating above the crystallization temperature, followed by enzymatic depolymerization. This allows breaking down the polyester chains into smaller units like monomers. The amorphization step is important to increase the polymer's susceptibility to enzymatic degradation. It can be done by heating to melting or just above crystallization temperatures. The method provides an alternative to mechanical recycling and chemical recycling for plastics like PET without sorting or expensive pretreatment.

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A method for efficiently upcycling waste polyethylene terephthalate (PET) plastics into valuable chemicals like terephthalic acid (TA) using a single enzyme. The method involves treating PET with a catalyst to decompose it into dimeric BHET, then enzymatically hydrolyzing BHET with the Bs2Est enzyme to convert it into TA and ethylene glycol (EG). This one-step, catalyst-assisted enzymatic depolymerization eliminates the need for purification steps, making it a more economically feasible PET upcycling method.

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Enzymatic degradation of polyethylene terephthalate (PET) using lipases from plant and microbial sources along with Yarrowia lipolytica yeast cells. This process provides a less complex, less expensive, and faster alternative for degrading PET into oligomers and monomers. The enzymatic degradation involves using lipases from vegetable and microbial sources, as well as Yarrowia lipolytica yeast cells, to catalyze the breakdown of PET into useful inputs for the petrochemical industry. The process avoids the lengthy biological degradation methods and provides faster enzyme kinetics.

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A method to degrade polyester plastics like PET into high-purity monomers and esters using organic acids as solvent and catalyst. The degradation reaction involves mixing waste polyester with an organic acid like acetic acid to depolymerize the polyester into terephthalic acid (TPA) and esters like ethylene glycol diacetate (EGDA) and ethylene glycol monoacetate (EGMA). The degradation products can be purified and used for repolymerization or other applications. The organic acid solvent allows efficient depolymerization and recovery of the monomers and esters compared to water-based methods.

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A method to improve the degradation efficiency of polyethylene terephthalate (PET) using bacteria and enzymes. The method involves combining the action of the enzyme cutinase from Humicola insolens with Klebsiella variicola bacteria to jointly degrade PET. This reduces the buildup of inhibitory degradation products like BHET and MHET that can limit the cutinase activity. The combined degradation using bacteria and enzymes allows more complete conversion of PET into monomers.

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A method to efficiently depolymerize waste polyester materials like PET bottles and textiles into monomers that can be easily repolymerized without extensive purification. The method involves depolymerizing the waste polyester in a vessel to form a mixture containing the regenerated diacid (e.g., terephthalic acid) and catalyst. The diacid and catalyst are then isolated and separated from the regenerated diol (e.g., ethylene glycol) to produce a concentrated composition of the regenerated diacid and catalyst. This composition can be used as feedstock for direct repolymerization without further purification, as the catalyst is already present. This avoids the need for costly purification steps and allows more efficient downstream polymerization compared to highly purified monomers.

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Recycling polyethylene terephthalate (PET) plastics using base-catalyzed transesterification followed by enzymatic hydrolysis. The PET is reacted with a C6-C10 monoalcohol in the presence of base to produce ester and alcohol derivatives. An esterase enzyme then converts the ester derivatives back into terephthalic acid. This allows separating the PET from co-materials during transesterification since they do not react with the monoalcohol. The separated PET can be recycled into new PET products. The base-catalyzed transesterification step also reduces PET molecular weight and yellowing compared to melt processing.

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Chemical recycling method for polyester-based polymer waste like PET that enables recovering high-purity monomers without forming high molecular weight impurities. The recycling involves depolymerizing the waste using a catalyst and alcohol to make a reactant containing monomers. Then, contacting the reactant with an ion exchange resin to remove catalysts and impurities. Finally, separating residual alcohols. This allows directly obtaining monomer-rich solutions with low catalyst and impurity levels compared to conventional recycling.

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Recycling waste PET by directly mixing it with aliphatic polyester or precursor, catalytically inserting the aliphatic repeating units into the PET chain, and then polymerizing under reduced pressure to generate volatile small molecules that can be removed. This simplified chemical conversion process avoids the need to alcoholyze PET into monomers and then react with other components.

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Method to improve the efficiency of enzymatic degradation of waste PET bottles by pretreating the bottles before enzymatic degradation. The pretreatment involves cleaning the bottles in pure water for 30 minutes and then drying them in an oven at 65°C. This preprocessing step helps to remove impurities and improve the crystallinity of the PET, making it more susceptible to degradation by enzymes.

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A process for degrading polyester containing materials like plastic products using enzymatic depolymerization in acidic conditions. The process involves contacting the polyester material with enzymes like PETase and MHETase at pH 3-6 and temperatures around 60°C. This allows breaking down the polyester into monomers and oligomers without coproduct formation. The low pH and addition of MHETase improves efficiency compared to neutral pH. The process can degrade polyester waste from sources like domestic plastic or textiles.

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A faster, less complex, and less expensive process for enzymatic degradation of polyethylene terephthalate (PET) using plant lipases and yeast cells. The process involves contacting PET with lipases from vegetable sources and Yarrowia lipolytica cells to degrade PET into useful oligomers and monomers like terephthalic acid. The enzymes are selected for their hydrolysis properties on vegetable oils and aromatic compounds. The process offers faster degradation kinetics compared to traditional fungal degradation processes.

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A novel plastic degrading enzyme that can decompose plastics like PET in an environmentally friendly manner. The enzyme is a protein derived from the bacteria Rhizobacter gumiphilus. It has higher activity compared to existing PET degrading enzymes like PETase from Ideonella saciensis. The enzyme can degrade PET, MHET, and BHET plastics. The enzyme can be produced using recombinant DNA techniques and used in compositions and methods for decomposing plastics.

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Recycling method for mixed plastic waste containing PET and other polymers like BPA-PC. The method involves sequential depolymerization of the mixed plastics using a zinc catalyst, initiated by alcohol compounds, under inert gas protection and without additional solvents. The depolymerization is done at temperatures between 20-300°C. This allows selective breakdown of PET while leaving other polymers intact. The depolymerized PET can be separated and recycled.

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A method for recycling polyethylene terephthalate (PET) waste to produce high quality PET suitable for clear and colorless bottles. The method involves depolymerizing PET using ethylene glycol to form bis(2-hydroxyethyl) terephthalate (BHET) monomers. The BHET solution is then purified by decolorization steps using solvents, resins, and decolorizing agents to remove impurities like dimers and trimers. This purified BHET can be used to make new high quality PET without the yellow tint often found in recycled PET. The decolorization steps allow recovering more of the PET feedstock compared to conventional methods that discard the dimers and trimers.

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Process for depolymerizing resistant PET waste from oil and gas industry using enzymes to improve recycling and reduce environmental impact. The process involves pre-treatments to reduce PET recalcitrance before enzymatic depolymerization. Pre-treatments include microwave, ultrasound, and surfactant treatments to reduce PET crystallinity, making it more susceptible to enzymatic degradation. Enzymatic depolymerization uses sea water as the solvent instead of organic solvents. This allows using lower enzyme concentrations and reduces the energy required for solvent removal. The sea water also facilitates PET dissolution.

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Producing glycolic acid from ethylene glycol using wild yeast strains for applications like biodegradable packaging, adhesives, and textiles. The process involves depolymerizing poly(ethylene terephthalate) (PET) into ethylene glycol using enzymes from Yarrowia lipolytica yeast. Then, the yeast biotransforms the ethylene glycol into glycolic acid. This avoids chemical synthesis and reduces costs and pollution compared to traditional methods. The yeast strain can selectively oxidize hydroxyl groups on ethylene glycol to make glycolic acid.

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A recycling system and method for polyethylene terephthalate (PET) that allows efficient recycling of PET waste into high-quality PET with high purity and properties similar to virgin PET. The system involves a multi-step process to clean and break down waste PET into BHET monomers. These monomers are then polymerized to produce recycled PET (rPET) with better quality and properties compared to traditional recycling methods. The key steps include mechanical separation, esterification, glycolysis, filtration, and solid-state polymerization.

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Enzymatic depolymerization of polyethylene terephthalate (PET) at temperatures close to the glass transition temperature of PET. This allows accessibility of the enzyme to the PET chains as they become more mobile at those temperatures. The depolymerization time is shorter than the crystallization time to prevent recrystallization. The PET has an initial crystallinity of 25% or less. The enzyme used can depolymerize PET faster than it crystallizes. The method involves contacting amorphous or semi-crystalline PET with the enzyme at temperatures between Tg-10°C and Tg+10°C.

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Recycling multilayer plastic waste like PET bottles by depolymerization to recover the monomers. The process involves adding alkali hydroxides like sodium hydroxide to the waste, heating and kneading it to saponify the PET into mono- and disodium terephthalate. An alkylene glycol like MEG produced in the saponification reaction is added as a reactant. This allows complete conversion of the PET in short reaction times by mechanical stressing and uniform mixing. The alkali terephthalates can be separated and the glycol recycled. The process enables reprocessing multilayer plastics without separation steps.

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Efficient and economical process for recycling PET plastic waste into dimethyl terephthalate (DMT) and monoethylene glycol (MEG) for reuse in new PET production. The process involves depolymerizing PET using methanol and sodium methoxide at controlled ratios and temperatures. The key steps are: (i) adding sodium methoxide to PET waste, (ii) adding methanol in multiple fractions, (iii) heating to depolymerize, and (iv) separating DMT and MEG. This allows selective degradation of PET into the desired products with high yields. The optimized conditions are: 1:5-1:20 mol/mol sodium methoxide:PET, 0.2-3.0% mol/mol sodium methoxide in

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A recycling process for PET plastic waste that allows repeated recycling without degradation by hydrolyzing PET back to its monomers. The process involves crushing the PET waste into fragments, soaking the fragments in a mixture of solvents like DMAc, DMF, MEK, phenolic esters, or biphenyl ethers for less than 18 hours at below 50°C, then separating the solvent and fragments. This step partially dissolves the PET but leaves it still solid. The fragments are then depolymerized by heating them in a mixture of alcohol, polar aprotic solvent like DMSO or NMP, and base to fully hydrolyze the PET into terephthalic acid and ethylene glycol. The solvent mixture helps dissociate the ester bonds. The recovered monomers can be used to make new

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Degrading PET plastic using a synergistic combination of two enzymes, PETase and MHETase, to rapidly break down PET into its constituent monomers. The enzymes are used in a 3:1 ratio at 30°C for 48 hours. This method improves upon using each enzyme separately to degrade PET, as it allows faster and more complete breakdown into terephthalic acid and ethylene glycol. The synergistic effect is achieved by mixing the enzymes in optimized ratios to degrade PET into its monomers.

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Enzymatic recycling of post-consumer PET plastic waste into new PET using glycolysis. The process involves breaking down the polyester structure of PET into bis-hydroxyethylene terephthalate (BHET) monomers using enzymes. The enzymatic glycolysis reaction is carried out on pretreated PET waste, such as ground-up bottles, to enrich the BHET content. The BHET-rich stream can then be repolymerized into new PET. The enzymatic recycling avoids using catalysts that could contaminate the recycled PET.

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Efficient recycling of post-consumer polyethylene terephthalate (PET) waste into new PET products. The recycling involves partially depolymerizing the PET using heat and ethylene glycol. This breaks down the PET into oligomers. The oligomers are then repolymerized with virgin PET monomers to make new PET. This allows recycling PET waste without needing extensive purification steps. The process involves heating the PET with ethylene glycol at elevated pressures to depolymerize it into oligomers. The oligomers are then mixed with virgin PET monomers and repolymerized.

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Efficient depolymerization of polymers like PET, PEF, PLA, polycarbonate, etc. into valuable products using acidic ionic liquids as catalysts. The process involves heating the polymer with the ionic liquid in a solvent mixture, followed by water washing and acidification. This converts the polymers into monomers and oligomers with 100% yield. The acidic ionic liquids can be l-methyl-3-(3-sulfopropyl)-imidazolium hydrogensulfate or other analogs. The solvent ratio is 1:0.25 ethylene glycol:dioxane.

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A method for recycling and degrading PETG (polyethylene terephthalate glycol) plastic waste, which involves crushing, degradation, and reuse programs to convert degraded PETG into new usable substances without generating waste. The method involves breaking down the PETG into smaller pieces, then degrading the PETG further using chemicals or enzymes. The degraded PETG can then be reused in new applications, such as making coatings or adhesives. The method aims to provide a closed-loop recycling solution for PETG plastic that avoids waste generation.

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