Search

Chemical depolymerization of poly(ethylene terephthalate) (PET) waste is a possible remedy to huge amount of solid waste generation as it results in degradation products that possess a potential of recyclability. PET bottle waste was depolymerized by aminolysis using diethanolamine. Novel synthesis of N1, N1,N4,N4-tetrakis (2-hydroxyethyl) terephthalamide (THETA) with 73-76% yield and terephthalic acid (TPA) with 78-82% yield was achieved. The purified products were analyzed by FTIR, melting point, DSC, DTG and1H-NMR. THETA has various applications in the synthesis of rigid polyurethane foam, unsaturated polyester resins and also as a cross linking agent/ hardener for epoxy resins. [ABSTRACT FROM AUTHOR]

Terephthalic acid (TPA) is widely applied as a raw material in making polyester fiber, polyethylene terephthalate (PET) bottles, polyester films, etc. TPA is toxic and is known to act as endocrine disruptor. TPA wastewater is traditionally treated by biological process and this study aims to evaluate the effectiveness of several advanced oxidation processes on TPA removal. The oxidation processes studied were: UV–TiO2, UV–H2O2, UV–H2O2–Fe, O3, O3/Fe, O3/TiO2, UV–O3–H2O2–Fe and UV–O3–H2O2–Fe–TiO2. The results indicate that the time required for the complete destruction of 50ppm of TPA can be minimized from 10h using UV–TiO2 system, to less than 10min by UV–H2O2–Fe–O3 system. Some of the likely organic intermediates identified during TPA destruction include, benzoquinone, benzene, maleic acid and oxalic acid. Possible destruction pathway of TPA has been proposed. TPA degradation by various systems was also analyzed based on the reaction kinetics and operating costs. [Copyright &y& Elsevier]

Catalytic upcycling of polyethylene terephthalate (PET) into high-value oxygenated products is a fascinating process, yet it remains challenging. Here, we present a one-step tandem strategy to realize the thermal catalytic oxidation upcycling of PET to terephthalic acid (TPA) and high-value glycolic acid (GA) instead of ethylene glycol (EG). By using the Au/NiO with rich oxygen vacancies as catalyst, we successfully accelerate the hydrolysis of PET, accompanied by obtaining 99% TPA yield and 87.6% GA yield. The results reveal that the oxygen vacancies in NiO (NiO-Ov) support tend to adsorb hydrolysis product TPA, preferentially ensuring the strong adsorption of EG at the Au-NiO interface. Moreover, during the EG oxidation process, the Au-NiO interface, composed of two types of structures, quasi "AuNi alloy" and NiO-Ov, simultaneously promote the C-H bond activation, where Ni in "AuNi alloy" exhibits an oxytropism effect to anchor the C = O bond of the intermediate, while the residual O in NiO-Ov pillages the H in the C-H bond. Such Au/NiO catalyst is further extended to promote the thermal catalytic oxidation upcycling of other polyethylene glycol esters to GA with excellent catalytic performance. Catalytic upcycling of polyethylene terephthalate (PET) into high-value oxygenated products is a fascinating process, yet it remains challenging. Here, the authors present a one-step tandem strategy to realize the thermal catalytic oxidation upcycling of PET to terephthalic acid and high-value glycolic acid. [ABSTRACT FROM AUTHOR]

The development of an efficient and environmentally sustainable chemical hydrolysis process for recycling waste plastics, based on green chemistry principles, is a key challenge. In this work, we investigated the role of subcritical CO2 on the hydrolysis of polyethylene terephthalate (PET) into terephthalic acid (TPA) at 180–200 °C for 10–100 min. The addition of CO2 into the reaction mixture led to the in situ formation of carbonic acid that helps to catalyze PET hydrolysis relative to hot compressed H2O (i.e. N2– H2O). The highest TPA yield of 85.0 ± 1.3% was obtained at 200 °C, PET loading of 2.5 g PET in 20 mL H2O for 100 min, and 208 psi of initial CO2 pressure. In addition, the subcritical CO2–H2O system demonstrated high selectivity toward hydrolyzing PET in a mixture with polyethylene (PE) at 200 °C for 100 min, thus providing “molecular sorting” capabilities to the recycling process. The robustness of the process was also demonstrated by the ability to hydrolyze both colored Canada Dry and transparent Pure Life® waste PET bottles into high yields of TPA (>86%) at 200 °C. In addition, subcritical CO2–H2O hydrolysis of colored PET bottles resulted in a white TPA product similar to that generated from transparent PET bottles. Overall, this work shows that, under optimized reaction conditions, subcritical CO2 can provide acid tunability to the reaction medium to favor waste PET hydrolysis for subsequent recycling. [ABSTRACT FROM AUTHOR]

Efficient recycling of polyethylene terephthalate (PET) plastics is a global concern due to the growing volume of plastic waste and its environmental impact. We studied PET hydrolysis and acidolysis processes to recover the PET monomer terephthalic acid (TPA) using various acid catalysts (zeolites, inorganic acids, ionic liquids, carboxylic acids, metal salts, and CO2) below the PET melting point and under identical conditions. TPA yield depended largely on the solution pH for some catalysts, especially aliphatic carboxylic acids, nitric acid, and CO2. However, TPA yields from hydrolysis with metal salts, ionic liquids, sulfuric acid, and aromatic carboxylic acids are also influenced by factors such as solubility limits, oxidation, and anion effects (for metal salts). Under mild hydrolysis conditions at 200 °C for 2 hours, carboxylic acids and metal salts achieved TPA yields > 80%, outperforming nitric acid, which required much more corrosive conditions at pH = 0.7. Zeolites have minimal impact on TPA yields in hydrolysis below the PET melting point. CO2 as a catalyst precursor to carbonic acid did not increase TPA yields significantly. We also explored using acetic acid as the sole reaction medium (acidolysis), which exhibited high TPA yields and a similar environmental energy impact to acid-catalyzed hydrolysis. Propanoic acid showed comparable efficiency, offering promising avenues for chemical recycling of PET. [ABSTRACT FROM AUTHOR]

Micro- and nanoparticles of plastic waste are considered emerging pollutants with significant environmental and health impacts at high concentrations or prolonged exposure time. Here we report the synthesis and characterization of a known metal-organic framework (MOF) using terephthalic acid (TPA) recovered from the hydrolysis of polyethylene terephthalate (PET) bottle waste. This approach adds value to the existing large amounts of bottle waste in the environment. Fully characterized zinc-TPA MOF (MOF-5) was used for the extraction and removal of engineered polyvinyl chloride (PVC) and polymethylmethacrylate (PMMA) nanoparticles from water with a high efficiency of 97% and 95%, respectively. Kinetic and isotherm models for the adsorption of polymer nanoparticles (PNPs) on the MOF surface were investigated to understand the mechanism. The Qmax for PVC and PMMA NPs were recorded as 56.65 mg/g and 33.32 mg/g, respectively. MOF-5 was characterized before and after adsorption of PNPs on the surface of MOF-5 using a range of techniques. After adsorption, the MOF-5 was successfully regenerated and reused for the adsorption and removal of PNPs, showing consistent results for five adsorption cycles with a removal rate of 83–85%. MOF-5 was characterized before and after adsorption of PNPs on the surface using a range of techniques. The MOF-5 with PNPs on the surface was successfully regenerated and reused for the adsorption and removal of polymer nanoparticles, showing consistent results for five extraction cycles. As a proof of concept, MOF-5 was also used to remove plastic particles from commercially available body scrub gel solutions. Such methods and materials are needed to mitigate the health hazards caused by emerging micro- and nanoplastic pollutants in the environment. [ABSTRACT FROM AUTHOR]

Energy-efficient and fast depolymerisation technologies present as new sustainable and green recycling routes for achieving a circular economy for plastics. Herein, we present a highly efficient 2-step microwave-based (MW) degradation of polyethylene terephthalate (PET). Initially, a MW-assisted pre-treatment was evaluated using glycerol as a non-toxic reagent for the conversion of PET into a modified form that makes it easily depolymerised. Box Behnken Design was employed to determine the optimised pre-treatment conditions attaining maximum PET weight loss and favourable crystallinity and carbonyl indices for the pre-treated PET. Glycerol of 12 mL volume and 3 min of 182W MW irradiation resulted in 11% PET weight loss at onset temperature of degradation and gave rise to carbonyl index up to 4.22 and 33% crystallinity of pre-treated PET. MW assisted hydrolysis of the pre-treated PET was then performed in the presence of sodium bicarbonate and ethylene glycol as depolymerizing agents. Within 3 min, the proposed depolymerisation methodology provided 99.9% conversion of PET into 79.1% terephthalic acid (TPA), 17.6% monohydroxyethyl terephthalate (MHET), and 1.8% bis (2-hydroxyethyl) terephthalate (BHET). The obtained TPA was separated from the monomers mixtures and its purification was evaluated via different characterization techniques against a standard TPA. A purity of 95%, 82.4 APHA colour value, 645.3 mgKOH/g acid number and acceptable heavy metal content indicated that the purified TPA can be repolymerised as virgin PET. [ABSTRACT FROM AUTHOR]

The escalating crisis of polyethylene terephthalate (PET) microplastic contamination in biological wastewater treatment systems is a pressing environmental concern. These microplastics inevitably accumulate in sewage sludge due to the absence of effective removal technologies. Addressing this urgent issue, this study introduces a novel approach using DuraPETase, a potent enzyme with enhanced PET hydrolytic activity at ambient temperatures. Remarkably, this enzyme was successfully secreted from Comamonas testosteroni CNB-1, a dominant species in the active sludge. The secreted DuraPETase showed significant hydrolytic activity toward p-NPB and PET nanoplastics. Furthermore, the CNB-1 derived whole-cell biocatalyst was able to depolymerize PET microplastics under ambient temperature, achieving a degradation efficiency of 9% within 7 days. The CNB-1-based whole biocatalysts were also capable of utilizing PET degradation intermediates, such as terephthalic acid (TPA) and ethylene glycol (EG), and bis(2-hydroxyethyl)-TPA (BHET), for growth. This indicates that it can completely mineralize PET, as opposed to merely breaking it down into smaller molecules. This research highlights the potential of activated sludge as a potent source for insitu microplastic removal. [ABSTRACT FROM AUTHOR]

Due to the extensive utilization of poly (ethylene terephthalate) (PET), a significant amount of PET waste has been discharged into the environment, endangering both human health and the ecology. As an eco-friendly approach to PET waste treatment, biodegradation is dependent on efficient strains and enzymes. In this study, a screening method was first established using polycaprolactone (PCL) and PET nanoparticles as substrates. A PET-degrading strain YX8 was isolated from the surface of PET waste. Based on the phylogenetic analysis of 16S rRNA and gyrA genes, this strain was identified as Bacillus safensis. Strain YX8 demonstrated the capability to degrade PET nanoparticles, resulting in the production of terephthalic acid (TPA), mono (2-hydroxyethyl) terephthalic acid (MHET), and bis (2-hydroxyethyl) terephthalic acid (BHET). Erosion spots on the PET film were observed after incubation with strain YX8. Furthermore, the extracellular enzymes produced by strain YX8 exhibited the ability to form a clear zone on the PCL plate and to hydrolyze PET nanoparticles to generate TPA, MHET, and BHET. This work developed a method for the isolation of PET-degrading microorganisms and provides new strain resources for PET degradation and for the mining of functional enzymes. [ABSTRACT FROM AUTHOR]

Recently developed enzymes for the depolymerization of polyethylene terephthalate (PET) such as FAST-PETase and LCC-ICCG are inhibited by the intermediate PET product mono(2-hydroxyethyl) terephthalate (MHET). Consequently, the conversion of PET enzymatically into its constituent monomers terephthalic acid (TPA) and ethylene glycol (EG) is inefficient. In this study, a protein scaffold (1TQH) corresponding to a thermophilic carboxylesterase (Est30) was selected from the structural database and redesigned in silico. Among designs, a double variant KL-MHETase (I171K/G130L) with a similar protein melting temperature (67.58 °C) to that of the PET hydrolase FAST-PETase (67.80 °C) exhibited a 67-fold higher activity for MHET hydrolysis than FAST-PETase. A fused dual enzyme system comprising KL-MHETase and FAST-PETase exhibited a 2.6-fold faster PET depolymerization rate than FAST-PETase alone. Synergy increased the yield of TPA by 1.64 fold, and its purity in the released aromatic products reached 99.5%. In large reaction systems with 100 g/L substrate concentrations, the dual enzyme system KL36F achieved over 90% PET depolymerization into monomers, demonstrating its potential applicability in the industrial recycling of PET plastics. Therefore, a dual enzyme system can greatly reduce the reaction and separation cost for sustainable enzymatic PET recycling. A study on the computational design of enzymes for plastic (MHET and PET) degradation yielded an efficient dual enzyme degradation system for PET recycling with a substantially increased activity and a near pure concentration of product TPA. [ABSTRACT FROM AUTHOR]

Polyethylene terephthalate (PET) pollution has significant environmental consequences; thus, new degradation methods must be explored to mitigate this problem. We previously demonstrated that a consortium of three Pseudomonas and two Bacillus species can synergistically degrade PET in culture. The consortium more readily consumes bis(2-hydroxyethyl) terephthalate (BHET), a byproduct created in PET depolymerization, compared to PET, and can fully convert BHET into metabolically usable monomers, namely terephthalic acid (TPA) and ethylene glycol (EG). Because of its crystalline structure, the main limitation of the biodegradation of post-consumer PET is the initial transesterification from PET to BHET, depicting the need for a transesterification step in the degradation process. Additionally, there have been numerous studies done on the depolymerization reaction of PET to BHET, yet few have tested the biocompatibility of this product with a bacterial consortium. In this work, a two-step process is implemented for sustainable PET biodegradation, where PET is first depolymerized to form BHET using an orange peel ash (OPA)-catalyzed glycolysis reaction, followed by the complete degradation of the BHET glycolysis product by the bacterial consortium. Results show that OPA-catalyzed glycolysis reactions can fully depolymerize PET, with an average BHET yield of 92% (w/w), and that the reaction product is biocompatible with the bacterial consortium. After inoculation with the consortium, 19% degradation of the glycolysis product was observed in 2 weeks, for a total degradation percentage of 17% when taking both steps into account. Furthermore, the 10-week total BHET degradation rate was 35%, demonstrating that the glycolysis products are biocompatible with the consortium for longer periods of time, for a total two-step degradation rate of 33% over 10 weeks. While we predict that complete degradation is achievable using this method, further experimentation with the consortium can allow for a circular recycling process, where TPA can be recovered from culture media and reused to create new materials. [ABSTRACT FROM AUTHOR]

Multi‐layer plastic films are widely used in various fields especially for packaging, but due to complex composition, it is very difficult to recover single‐material polymers or high‐purity monomers from them after usage. In this study, we proposed a hydrothermal process for recycling PET/PE (PET: Polyethylene terephthalate; PE: Polyethylene) films. PET can be hydrolyzed to monomers of terephthalic acid (TPA) and ethylene glycol (EG). Using a hydrothermal system equipped with two filters, PE, TPA, and EG were collected separately, indicating the simultaneous material and chemical recycling of PET/PE films was firstly achieved. At 300 °C and 10 MPa for 60 min, PET conversion reached around 100 %, and TPA yield of 83.0 % was obtained with a high TPA purity of 96.1 %. In addition, the effect of the holding time on PET conversion, TPA yield, EG yield, and TPA purity was studied. This research opened up a new and sustainable pathway to recycle multi‐layer plastic films in both lab and industry. [ABSTRACT FROM AUTHOR]

Accumulation of polyethylene terephthalate (PET) polyester in ecosystems across the globe is a major pollution of concern. Microbial degradation recently generated novel insights into the biodegradation of varieties of plastics. In this study, a PET degrading bacterium Brucella intermedia IITR130 was isolated from a contaminated lake ecosystem at Pallikaranai, Chennai, India. Incubation of the bacterium along with the PET sheet (0.1 mm thickness) for 60 days resulted in 26.06% degradation, indicating a half-life of 137.8 days. Considerable changes in the surface morphology of the PET sheet were found as holes, pits, and cracks on incubation with strain IITR130, as revealed by scanning electron microscopy (SEM). After bacterial treatment of PET, the formation of new functional groups, most notably in the area of 3326 cm−1 suggestive of O–H stretch, leading to carboxylic acid and alcohol as products were suggested by fourier transform infrared (FTIR) analysis. Monomethyl terephthalate (MMT) and terephthalic acid (TPA) were identified by gas chromatography–mass spectrometry (GC–MS) analysis as PET degradation metabolites. Tributyrin clearance assay confirmed the presence of a lipase/esterase enzyme in the strain IITR130. In this study, a degradation pathway for PET by an isolated and identified bacterium Brucella intermedia IITR130 was characterized in detail. [ABSTRACT FROM AUTHOR]

Recycling spent polyesters, a widely used type of plastic, is highly important for a circular economy but remains a great challenge. Herein, biomass-derived dimethyl isosorbide (DMI) was developed as an emerging solvent for recycling waste polyethylene terephthalate (PET). DMI showed a good ability to rapidly dissolve PET in 10 min at 170 °C to obtain a solubility of 0.3 gPET gDMI -1, originating from the matched Hansen solubility parameters between PET and DMI. Moreover, the dissolved PET in DMI could be regenerated with a PET degradation ratio of only 2.9% using water as an anti-solvent. More importantly, DMIbased solvents were highly effective for alkaline (KOH) hydrolysis of PET to generate terephthalic acid (TPA). In a solvent composed of DMI and ethylene glycol (EG) with a volume ratio of 6: 4, complete conversion of PET could be achieved in 30 min at 100 °C, and the yield of TPA was nearly quantitative (99.6%). Systematic investigation revealed that the good performance of DMI/EG mixed solvents resulted from the formation of hydrogen-bonding interactions between DMI and EG. The renewability and good performance for PET recycling confirmed the great potential of DMI in practical applications of recycling waste plastics. [ABSTRACT FROM AUTHOR]

Recycling plastics is the key to reaching a sustainable materials economy. Biocatalytic degradation of plastics shows great promise by allowing selective depolymerization of man‐made materials into constituent building blocks under mild aqueous conditions. However, insoluble plastics have polymer chains that can reside in different conformations and show compact secondary structures that offer low accessibility for initiating the depolymerization reaction by enzymes. In this work, we overcome these shortcomings by microwave irradiation as a pre‐treatment process to deliver powders of polyethylene terephthalate (PET) particles suitable for subsequent biotechnology‐assisted plastic degradation by previously generated engineered enzymes. An optimized microwave step resulted in 1400 times higher integral of released terephthalic acid (TPA) from high‐performance liquid chromatography (HPLC), compared to original untreated PET bottle. Biocatalytic plastic hydrolysis of substrates originating from PET bottles responded to 78 % yield conversion from 2 h microwave pretreatment and 1 h enzymatic reaction at 30 °C. The increase in activity stems from enhanced substrate accessibility from the microwave step, followed by the administration of designer enzymes capable of accommodating oligomers and shorter chains released in a productive conformation. [ABSTRACT FROM AUTHOR]

Exploring new solutions to improve the environmentally friendly degradation of fossil based postconsumer plastic waste is key in the development of effective techniques to increase the efficiency of plastics degradation while using mild, green depolymerization conditions. In this context, we introduce a novel, ultrafast mechanical pretreatment for postconsumer (PC) polyethylene terephthalate (PET) plastics that is based on a dissolution/reprecipitation approach under microwave (MW) irradiation. Fourier transform infra-red (FTIR) and Differential scanning colorimetry (DSC) analyses indicates a significant increase, up to 3.78 in the carbonyl index and a 2-fold decrease in crystallinity index of the pretreated PC PET sample when compared to the untreated one. Degradation efficiency of both untreated and pretreated PC PET was evaluated using enzymatic and MW assisted chemical degradation techniques. Results show that following MW assisted hydrolytic depolymerization, pretreated PC PET conversion rate of 95 % and terephthalic acid (TPA) monomer yield of 87.4 % were obtained and were significantly higher than that of untreated PC PET. While the proposed pretreatment approach did not show a significant improvement on the enzymatic degradation of PC PET, it did result in a 1.2-fold increase in the pretreated PC PET conversion rate, yielding solely TPA as a value-added monomer. This presents an advantage in the economic cost of the degradation process if applied on a larger scale. [ABSTRACT FROM AUTHOR]

In the conventional polyethylene terephthalate (PET) pyrolysis process, the formation of char by excessive pyrolysis is mainly due to the dehydration mechanism, so water is considered an auxiliary agent that can effectively inhibit excessive pyrolysis. The preparation of terephthalic acid (TPA) by steam‐assisted pyrolysis of PET is an effective method to achieve closed‐loop recycling of waste PET. To ensure that the reaction is mild enough to reduce excessive cracking products such as char and benzoic acid and thus increase the yield of TPA, it is critical to reduce the reaction rate while maintaining a sufficient excess steam coefficient. Under the optimal operating conditions, when the temperature rise rate was 0.5 °C min−1 and the excess steam coefficient was 150, the yield of TPA was 72.5 wt.%, and the purity was 85.5%. Noticeably, the steam‐assisted pyrolysis system is a heterogeneous reaction system whose reaction mechanism is different from the conventional hydrolysis and pyrolysis reactions and has a unique reaction path. The mechanistic study indicates that, in addition to the thermal cracking of PET molecules occurring in conventional pyrolysis, hydroxyl attack and transfer, and supplementation of benzene ring hydrogen also occur between water and intermediate molecules. Meanwhile, it has also been proven that the intermolecular hydrogen transfer between intermediate molecules and water molecules is the key to reduce the intensity of the reaction and inhibit the formation of char. This discovery illustrates the mechanism of the reaction between water and PET in the steam‐assisted pyrolysis process in the fixed pyrolyzer and justifies the distinction between it and the pyrolysis and hydrolysis processes of PET. It provides a theoretical basis for optimizing the pyrolysis process of PET, which is essential for the industrialization of TPA preparation from PET steam‐assisted pyrolysis. [ABSTRACT FROM AUTHOR]

Aqueous hydrolysis is used to chemically recycle polyethylene terephthalate (PET) due to production of high‐quality terephthalic acid (TPA), the PET monomer. PET hydrolysis depends on various factors including PET size, catalyst concentration, and reaction temperature. So, modeling PET hydrolysis by considering the effective factors can provide useful information for material researchers to specify how to design and run these reactions. It will save time, energy, and materials by optimizing the hydrolysis conditions. Machine learning algorithms enable to design models to predict the output results. For the first time, 381 experimental data were gathered to model aqueous hydrolysis of PET. Effective factors on PET hydrolysis were connected to the TPA yield. The logistic regression was applied to rank the effective factors. Two algorithms were proposed, artificial neural network multi‐layer perceptron (ANN‐MLP) and adaptive network‐based fuzzy inference system (ANFIS). The dataset was divided into training, validating, and testing sets to train, validate, and test the models, respectively. The models predicted TPA yield sufficiently where the ANFIS model outperformed. R‐squared (R2) and Root Mean Square Error (RMSE) loss functions were employed to measure the efficiency of the models and evaluate their performance. [ABSTRACT FROM AUTHOR]

In this polymer-governing era, polyethylene terephthalate (PET) has become one of the most demanding consumables. This growing interest in the production and consumption of plastic products results in an increase in the volume of post-consumer plastic waste. However, due to the growing concern for environmental protection, recycling PET waste to the valuable ones has become one of the hot topics in contemporary research. In this study, PET waste was depolymerized using ethanolamine as a depolymerizing agent. N,N0-Bis (2-hydroxyethyl)terephthaldiamide (BHETA) (yield 77%) was obtained after depolymerization of PET via ethanolamine. The characterization of the monomer BHETA was done using FTIR, 1H NMR, and FE-SEM. The thermal stability of PET and BHETA was done using TGA analysis. To avoid the extreme reaction condition (high temperature and high pressure) of conventional way to form terephthalic acid (TPA) via hydrolysis of PET waste, in this study, a facile way is performed. The monomer BHETA was converted to a main building block of PET (TPA) (yield 67%) using strong oxidizing agent KMnO4 in mild reaction conditions at room temperature and pressure. The synthesized TPA was characterized using FTIR and 1H NMR. This work also focuses on the anticipation of the reaction progress of aminolysis of PET using simple analytical tools namely, FTIR and TGA. [ABSTRACT FROM AUTHOR]

Degradation of solid polyethylene terephthalate (PET) by leaf branch compost cutinase (LCC) produces various PET‐derived degradation intermediates (DIs), in addition to terephthalic acid (TPA), which is the recyclable terminal product of all PET degradation. Although DIs can also be converted into TPA, in solution, by LCC, the TPA that is obtained through enzymatic degradation of PET, in practice, is always contaminated by DIs. Here, we demonstrate that the primary reason for non‐degradation of DIs into TPA in solution is the efficient binding of LCC onto the surface of solid PET. Although such binding enhances the degradation of solid PET, it depletes the surrounding solution of enzyme that could otherwise have converted DIs into TPA. To retain a subpopulation of enzyme in solution that would mainly degrade DIs, we introduced mutations to reduce the hydrophobicity of areas surrounding LCC's active site, with the express intention of reducing LCC's binding to solid PET. Despite the consequent reduction in invasion and degradation of solid PET, overall levels of production of TPA were ~3.6‐fold higher, due to the partitioning of enzyme between solid PET and the surrounding solution, and the consequent heightened production of TPA from DIs. Further, synergy between such mutated LCC (F125L/F243I LCC) and wild‐type LCC resulted in even higher yields, and TPA of nearly ~100% purity. [ABSTRACT FROM AUTHOR]

The current society has an increasing demand for poly(ethylene terephthalate) (PET). Due to its high crystallinity and hydrophobicity, PET could be hardly degraded for high-value utilization. Besides, the escalating accumulation of waste PET has also led to significant environmental issues. In this study, a convenient and cost-efficient industrial strategy featuring the integration of glycolysis and enzymatic catalysis has been developed for the selective conversion of PET into terephthalic acid (TPA), which provides a method for colored waste PET degradation. Without the need for complex purifying processes, the products of glycolysis directly initiate the next round of the enzymatic system. Through this system, a total yield of 72.47 % of bis-2-(hydroxyethyl) terephthalate(BHET) and mono-(2-hydroxyethyl) terephthalate(MHET) was produced by glycolysis loading sodium bicarbonate (NaHCO 3) catalyst, and the enzyme system almost completely converted a substrate concentration of 100 g/L within 48 h, producing 50.36 g/L TPA. Besides, the product problem of pink color in the air after acidification caused by cobalt ions was solved by resin adsorption. In general, the glycolysis and enzymatic catalysis system in this study has prospects for commercial application due to its value for colored waste PET recycling, which reduces the environmental burden caused by waste PET. [Display omitted] • A strategy combining chemical and biological degradation of colored waste PET has been established. • The process simplifies complex purification steps and reduces energy consumption. • The enzymatic hydrolysis in this process can reach a high substrate concentration of 100 g/L. • The dual enzyme system can maximize the utilization of glycolysis products. • The whole degradation process was carried out in a bio-friendly reaction. [ABSTRACT FROM AUTHOR]

Poly(ethylene terephthalate) (PET) is a synthetic polymer widely used globally. The high PET resistance to biotic degradation and its improper destination result in the accumulation of this plastic in the environment, largely affecting terrestrial and aquatic animals. This work investigated post-consumer PET (PC-PET) degradation using five commercial hydrolase enzymes (Novozym 51032, CalB, Palatase, Eversa, Lipozyme TL). Humicola insolens cutinase (HiC, Novozym 51032) was the most active among the enzymes studied. Several important reaction parameters (enzyme type, dual enzyme system, enzyme concentration, temperature, ultrasound treatment) were evaluated in PC-PET hydrolysis using HiC. The concentration and the proportion (molar ratio) of hydrolysis products, terephthalic acid (TPA), mono(2-hydroxyethyl) terephthalate (MHET), and bis(2-hydroxyethyl) terephthalate (BHET), were significantly changed depending on the reaction temperature. The TPA released at 70 °C was 3.65-fold higher than at 50 °C. At higher temperatures, the conversion of MHET into TPA was favored. The enzymatic PET hydrolysis by HiC was very sensitive to the enzyme concentration, indicating that it strongly adsorbs on the polymer surface. The concentration of TPA, MHET, and BHET increased as the enzyme concentration increased, and a maximum was achieved using 40–50 vol % of HiC. The presented results add relevant data to optimizing enzyme-based PET recycling technologies. [ABSTRACT FROM AUTHOR]

A novel industrial cleaning process (DEECOM®, B&M Longworth, Blackburn) hydrolyses polyethylene terephthalate (PET) on contaminated filters using superheated steam at elevated temperature and pressure (300°C and 3 barg). The technology is being adapted to depolymerise waste textiles. This study first involved an assessment of the current large-scale cleaning process’ PET conversion and yield of terephthalic acid (TPA). Then a zinc chloride homogenous catalyst, and, zinc and platinum loaded zeolite beta heterogeneous catalysts, were investigated using a laboratory-scale autoclave reactor to mimic the process. In addition, the industrial waste stream of crude terephthalic acid (TPA) was then purified, repolymerised into PET via the dimethyl terephthalate (DMT) synthesis route, characterised and compared with commercial PET data. Characterisation methods of the repolymerised PET include DSC, TGA, GPC. While still a work in progress, this shows proof-ofconcept in terms of closing the loop and moving to a circular economy. [ABSTRACT FROM AUTHOR]

Compared with conventional pyrolysis, steam-assisted pyrolysis of polyethylene terephthalate (PET) can effectively eliminate char and upgrade terephthalic acid (TPA). However, during steam-assisted pyrolysis of PET, the degree of cracking still varies greatly, and while some of the product is excessively cracked to gas, the other part is still insufficiently cracked. In addition, these two types of products seriously affect the yield and purity of TPA. To further enhance the TPA, an attempt was made to reduce these impurities simultaneously by synergistic catalysis among the different components of the metal–acid catalyst. Through a series of experiments, Pt@Hzsm-5 was screened as the optimal catalyst. In the catalytic steam-assisted pyrolysis of PET, the optimum reaction temperature decreased to 400 °C, the calculated yield of TPA increased to 98.23 wt%, and the purity increased to 92.2%. The Pt@Hzsm-5 could be recycled three times with no significant decrease in the obtained yield of TPA. The catalytic mechanism of the Pt@Hzsm-5 was investigated through the analysis of the products and isotope tracing experiments. The Pt catalyzed the hydrogen transfer reaction between the water molecules and PET molecules, which inhibited the excessive cracking of TPA by improving the hydrogen transfer efficiency, reduced the generation of gaseous products, and improved the calculated yield of TPA. In contrast, the Hzsm-5 catalyzed the reaction of monovinyl ester cracking to TPA, effectively reducing the impurities in the solid product, increasing the olefin yield, and improving the purity of TPA. This discovery not only clarifies the synergistic catalytic effect of the Pt@Hzsm-5 in the steam-assisted pyrolysis of the PET reaction but also lays the foundation for further screening of other inexpensive metal–acid catalysts. This is of great significance to realize the industrial application of TPA preparation by PET pyrolysis. [ABSTRACT FROM AUTHOR]

Featured Application: The potential use of bacteria and their enzymes for the degradation of plastic waste and the recovery of value-added products considering bio-up recycling for the circular economy. A polyethylene terephthalate (PET)-degrading bacterium identified as Stenotrophomonas maltophilia PRS8 was isolated from the soil of a landfill. The degradation of the PET bottle flakes and the PET prepared as a powder were assessed using live cells, an extracellular medium, or a purified cutinase-like enzyme. These treated polymers were analyzed using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The depolymerization products, identified using HPLC and LC-MS, were terephthalic acid (TPA), mono(2-hydroxyethyl)-TPA (MHET), and bis(2-hydroxyethyl)-TPA (BHET). Several physicochemical factors were optimized for a better cutinase-like enzyme production by using unique single-factor and multi-factor statistical models (the Plackett–Burman design and the central composite design software). The enzyme was purified for homogeneity through column chromatography using Sephadex G-100 resin. The molecular weight of the enzyme was approximately 58 kDa. The specific activity on para nitrophenyl butyrate was estimated at 450.58 U/mg, with a purification of 6.39 times and a yield of 48.64%. The enzyme was stable at various temperatures (30–40 °C) and pH levels (8.0–10.0). The enzyme activity was significantly improved by the surfactants (Triton X-100 and Tween-40), organic solvent (formaldehyde), and metals (NiCl2 and Na2SO4). The extracellular medium containing the cutinase-type enzyme showed a depolymerization yield of the PET powder comparable to that of Idonella skaiensis IsPETase and significantly higher than that of Humicola insolens thermostable HiCut (HiC) cutinase. This study suggests that S. maltophilia PRS8 is able to degrade PET at a mesophilic temperature and could be further explored for the sustainable management of plastic waste. [ABSTRACT FROM AUTHOR]

Volatile global oil prices, owing to the scarcity of fossil resources, have impacted the cost of producing petrochemicals. Therefore, there is a need to seek novel, renewable chemicals from biomass feedstocks that have comparable properties to petrochemicals. In this study, synthesis, thermal and mechanical properties, and degradability studies of a novel series of sustainable thiophene-based copolyesters like poly(hexylene 2,5-thiophenedicarboxylate-co-bis(2-hydroxyethoxybenzene) (PTBxHy) were conducted via a controlled melt polymerization method. Fourier-transform infrared (FTIR) and nuclear magnetic resonance (1H NMR) spectroscopy techniques elucidated the degree of randomness and structural properties of copolyesters. Meanwhile, gel permeation chromatography (GPC) analysis showed a high average molecular weight in the range of 67.4–78.7 × 103 g/mol. The glass transition temperature (Tg) was between 69.4 and 105.5 °C, and the melting point between 173.7 and 194.2 °C. The synthesized polymers outperformed poly(ethylene 2,5-thiophenedicarboxylate) (PETF) and behaved similarly to polyethylene terephthalate. The copolyesters exhibited a high tensile strength of 46.4–70.5 MPa and a toughness of more than 600%, superior to their corresponding homopolyesters. The copolyesters, which ranged from 1,4-bis(2-hydroxyethyl)benzene thiophenedicarboxylate (TBB)-enriched to hexylene thiophenedicarboxylate (THH)-enriched, offered significant control over crystallinity, thermal and mechanical properties. Enzymatic hydrolysis of synthetized polymers using porcine pancreatic lipase (PP-L) over a short period resulted in significant weight losses of 9.6, 11.4, 30.2, and 35 wt%, as observed by scanning electron microscopy (SEM), with perforations visible on all surfaces of the films. Thus, thiophene-based polyesters with cyclic aromatic structures similar to terephthalic acid (TPA) show great promise as PET mimics. At the same time, PP-L appears to be a promising biocatalyst for the degradation of bioplastic waste and its recycling via re-synthesis processes. [ABSTRACT FROM AUTHOR]

Post-consumer polyethylene terephthalate (PET) plastic bottles, after some pre-processing, were chemically depolymerized for the production of terephthalic acid (TPA), an important monomer of PET resin. The optimized condition of PET hydrolysis was 100°C with 80% v/v aqueous sulfuric acid liquor for 30 min reaction time. The terephthalic acids (TPAs) were filtered out from the reaction mixtures with a sintered glass filter. The viscosity of recycled hydrolysis liquor was measured before it was used in a successive batch of PET depolymerization. The viscosity of hydrolysis liquor increased gradually from 5 mm2/s to 87 mm2/s. TPA yields were obtained from 85.03 ± 0.03% to 99.20 ± 0.06% and the color of TPA changed from bright white to off-white in the final batches. The structure of TPA was confirmed by FTIR, mass analysis, and 1H-NMR spectroscopy. The purity of TPA was found to be 95–98% from the HPLC study via external calibration technique. Thermogravimetric analysis (TGA) determined the thermal degradation patterns of TPAs and residual weights. This experiment reveals that repeated use of sulfuric acid hydrolysis liquor would be a good option for PET depolymerization in terms of resource utilization, TPA quality as well as sustainability. Graphical Abstract [ABSTRACT FROM AUTHOR]

Waste polyester textiles are not recycled due to separation challenges and partial structural degradation during use and recycling. Chemical recycling of polyethylene terephthalate (PET) textiles through depolymerization can provide a feedstock of recycled monomers to make "as‐new" polymers. While enzymatic PET recycling is a more selective and more sustainable approach, methods in development, however, have thus far been limited to clean, high‐quality PET feedstocks, and require an energy‐intensive melt‐amorphization step ahead of enzymatic treatment. Here, high‐crystallinity PET in mixed PET/cotton textiles could be directly and selectively depolymerized to terephthalic acid (TPA) by using a commercial cutinase from Humicola insolens under moist‐solid reaction conditions, affording up to 30±2 % yield of TPA. The process was readily combined with cotton depolymerization through simultaneous or sequential application of the cellulase enzymes CTec2®, providing up to 83±4 % yield of glucose without any negative influence on the TPA yield. [ABSTRACT FROM AUTHOR]

Background: Over the 70 years since the introduction of plastic into everyday items, plastic waste has become an increasing problem. With over 360 million tonnes of plastics produced every year, solutions for plastic recycling and plastic waste reduction are sorely needed. Recently, multiple enzymes capable of degrading PET (polyethylene terephthalate) plastic have been identified and engineered. In particular, the enzymes PETase and MHETase from Ideonella sakaiensis depolymerize PET into the two building blocks used for its synthesis, ethylene glycol (EG) and terephthalic acid (TPA). Importantly, EG and TPA can be re-used for PET synthesis allowing complete and sustainable PET recycling. Results: In this study we used Saccharomyces cerevisiae, a species utilized widely in bioindustrial fermentation processes, as a platform to develop a whole-cell catalyst expressing the MHETase enzyme, which converts monohydroxyethyl terephthalate (MHET) into TPA and EG. We assessed six expression architectures and identified those resulting in efficient MHETase expression on the yeast cell surface. We show that the MHETase whole-cell catalyst has activity comparable to recombinant MHETase purified from Escherichia coli. Finally, we demonstrate that surface displayed MHETase is active across a range of pHs, temperatures, and for at least 12 days at room temperature. Conclusions: We demonstrate the feasibility of using S. cerevisiae as a platform for the expression and surface display of PET degrading enzymes and predict that the whole-cell catalyst will be a viable alternative to protein purification-based approaches for plastic degradation. [ABSTRACT FROM AUTHOR]

Public health concerns associated with the potential leaching of substances from Polyethylene terephthalate (PET) packaging have been raised due to the role of phthalates as endocrine-disrupting chemicals or obesogens. In particular, changes in the environment such as pH, temperature, and irradiation can improve contaminant migration from PET food packaging. In this study, the in vitro effects of p-phthalates terephthalic acid (TPA) and dimethyl terephthalate (DMT) on murine adipocytes (3T3-L1) were evaluated using concentrations that might be obtained in adult humans exposed to contaminated sources. TPA and, in particular, DMT exposure during 3T3-L1 differentiation increased the cellular lipid content and induced adipogenic markers PPAR-γ, C/EBPß, FABP4, and FASN, starting from low nanomolar concentrations. Interestingly, the adipogenic action of TPA- and DMT-induced PPAR-γ was reverted by ICI 182,780, a specific antagonist of the estrogen receptor. Furthermore, TPA and DMT affected adipocytes' thermogenic program, reducing pAMPK and PGC-1α levels, and induced the NF-κB proinflammatory pathway. Given the observed effects of biologically relevant chronic concentrations of these p-phthalates and taking into account humans' close and constant contact with plastics, it seems appropriate that ascertaining safe levels of TPA and DMT exposure is considered a high priority. [ABSTRACT FROM AUTHOR]

Several microorganisms have been reported as capable of acting on poly(ethylene terephthalate) (PET) to some extent, such as Yarrowia lipolytica, which is a yeast known to produce various hydrolases of industrial interest. The present work aims to evaluate PET depolymerization by Y. lipolytica using two different strategies. In the first one, biocatalysts were produced during solid-state fermentation (SSF-YL), extracted and subsequently used for the hydrolysis of PET and bis(2-hydroxyethyl terephthalate) (BHET), a key intermediate in PET hydrolysis. Biocatalysts were able to act on BHET, yielding terephthalic acid (TPA) (131.31 µmol L−1), and on PET, leading to a TPA concentration of 42.80 µmol L−1 after 168 h. In the second strategy, PET depolymerization was evaluated during submerged cultivations of Y. lipolytica using four different culture media, and the use of YT medium ((w/v) yeast extract 1%, tryptone 2%) yielded the highest TPA concentration after 96 h (65.40 µmol L−1). A final TPA concentration of 94.3 µmol L−1 was obtained on a scale-up in benchtop bioreactors using YT medium. The conversion obtained in bioreactors was 121% higher than in systems with SSF-YL. The results of the present work suggest a relevant role of Y. lipolytica cells in the depolymerization process. [ABSTRACT FROM AUTHOR]

• Technology proof-of-concept for chemical recycling of mixed waste streams. • PET depolymerization and pyrolysis process integration for mixed waste streams. • Pressureless alkaline PET depolymerization to high purity TPA from waste. • Pretreatment to prevent PET negative effect in mixed waste pyrolysis. This study presents a proof of concept for a technology train that integrates polyethylene terephthalate (PET) recovery from mixed plastic waste and plastic pyrolysis. PET is depolymerized into terephthalic acid (TPA) by hydrolysis using a low volatility oil as medium, which enables (i) low-pressure operation, and (ii) a selective separation and recovery of TPA from the product mix by a simple process of filtration, washing, and precipitation. Full PET conversion and high TPA recovery (>98 %) were achieved at 260 °C. This technology train is demonstrated to be effective for processing mixed waste streams, leading to higher yield and quality of liquid product from thermal pyrolysis when compared with feedstock that has not been pre-treated. Further, the technology could be readily integrated with a plastics pyrolysis process, whereby a by-product from the pyrolysis could be used as the low-volatility oil. [ABSTRACT FROM AUTHOR]

A simple and efficient microwave depolymerization methodology to recycle disposable polyethylene terephthalate (PET) was demonstrated. Different conditions of microwave irradiation and sample pretreatments were applied to increase the decomposition yield as well as products quality, and three important products were obtained. Terephthalic acid (TPA) was the major product, and its purity was tested by using it to synthesize metal organic framework (MOF) compounds namely MIL-53-Fe and UIO-66-Zr. The second valuable product was carbon black, which was separated and its specific surface area was 400 m2.g−1 after activation. Trisodium phosphate (TSP), another valuable product, was obtained as byproduct when phosphoric acid was used as digester. The yields of TPA were dependent on PET pretreatment routines. They were 64%, 69% and 89% for as received, 100 kGy gamma irradiated and 24 h ultra violet (UV) irradiated PET respectively. These results signified the positive impact of radiation on the yield of depolymerization process. The proposed method and pretreatments are very useful in upcycling of PET bottles and other containers due to the increasing applications of TPA as the main monomer in the industrial production of PET and other engineering materials. [ABSTRACT FROM AUTHOR]

Enzymatic hydrolysis of poly(ethylene terephthalate) (PET) is a chemical recycling approach intended to enable a circular economy for polyesters. To quantitatively compare this technology to other recycling and synthesis approaches for PET, it is critical to conduct rigorous and transparent process analyses. We recently reported a detailed process model that was used to conduct economic, energy, and greenhouse gas emissions analyses for enzymatic PET recycling. Here, we expand upon this previous work by conducting a process-based life cycle assessment (LCA) of the same enzymatic hydrolysis system, to produce both terephthalic acid (TPA) and ethylene glycol (EG) for use in a closed-loop PET recycling scheme. This LCA shows that enzymatic hydrolysis currently performs 1.2 to 17 times worse than virgin TPA and PET production across most impact categories, excepting ecotoxicity and fossil fuel depletion. The top contributors to these impacts include post-consumer PET collection and processing, sodium hydroxide, and electricity. Sensitivity analysis shows that improving yields throughout the recycling process and eliminating certain process steps, such as amorphization pre-treatment and reaction pH control, can reduce the overall environmental impacts of enzymatic PET recycling to levels statistically equivalent to virgin TPA and PET production, thereby highlighting crucial areas for further research and innovation. [ABSTRACT FROM AUTHOR]

At temperatures supporting a glass transition in solid polyethylene terephthalate (PET), thermostable cutinases access the backbones of PET chains at the liquid–solid interface and hydrolyse ester bonds through endolytic and exolytic cuts. These lead to the production of three degradation intermediates [oligoethylene terephthalates (OETs), bis-hydroxyethyl terephthalate (BHET), and mono-hydroxyethyl terephthalate (MHET)] and two terminal degradation products [terephthalic acid (TPA) and ethylene glycol (EG)]. All five products are water-soluble to different degrees and diffuse away from PET to reach progressively higher concentrations in the surrounding solution, where they accumulate in proportion with the binding of cutinase to PET (through hydrophobic and cation–pi interactions). Importantly, however, the binding of cutinase to PET (which is essential for PET degradation) results in depletion of cutinase in solution, negatively impacting the conversion of degradation intermediates into terminal reaction products. The immediate and direct consequence of this is that the produced TPA and EG are contaminated by OET, BHET and MHET and, therefore, become unfit for recycling through re-condensation into PET. Here, we describe a 'two-enzyme' solution to the problem, consisting of a cocktail containing equimolar amounts of a PET-degrading enzyme [leaf-branch compost cutinase (LCC)] and a degradation intermediate-hydrolysing enzyme [Thermus thermophilus carboxylesterase (TTCE)]. The former produces OET, BHET, MHET, TPA and EG at PET's surface, while the latter works in solution to degrade the produced OET, BHET and MHET into TPA and EG. Through their synergy, the enzymes produce pure TPA and EG in yields that are 30–100% higher than those obtained with LCC alone. [ABSTRACT FROM AUTHOR]

Vanillin, as a promising aromatic aldehyde, possesses worthy structural and bioactive properties useful in the design of novel sustainable polymeric materials. Its versatility and structural similarity to terephthalic acid (TPA) can lead to materials with properties similar to conventional poly(ethylene terephthalate) (PET). In this perspective, a symmetrical dimethylated dialkoxydivanillic diester monomer (DEMV) derived from vanillin was synthesized via a direct-coupling method. Then, a series of poly(ether-ester)s were synthesized via melt-polymerization incorporating mixtures of phenyl/phenyloxy diols (with hydroxyl side-chains in the 1,2-, 1,3- and 1,4-positions) and a cyclic diol, 1,4-cyclohexanedimethanol (CHDM). The polymers obtained had high molecular weights (Mw = 5.3–7.9 × 104 g.mol−1) and polydispersity index (Đ) values of 1.54–2.88. Thermal analysis showed the polymers are semi-crystalline materials with melting temperatures of 204–240 °C, and tunable glass transition temperatures (Tg) of 98–120 °C. Their 5% decomposition temperature (Td,5%) varied from 430–315 °C, which endows the polymers with a broad processing window, owing to their rigid phenyl rings and trans-CHDM groups. These poly(ether-ester)s displayed remarkable impact strength and satisfactory gas barrier properties, due to the insertion of the cyclic alkyl chain moieties. Ultimately, the synergistic influence of the ester and ether bonds provided better control over the behavior and mechanism of in vitro degradation under passive and enzymatic incubation for 90 days. Regarding the morphology, scanning electron microscopy (SEM) imaging confirmed considerable surface degradation in the polymer matrices of both polymer series, with weight losses reaching up to 35% in enzymatic degradation, which demonstrates the significant influence of ether bonds for biodegradation. [ABSTRACT FROM AUTHOR]

Polyethylene terephthalate (PET) is a widely used thermoplastic polymer in the packaging and materials industries, and is predicted to have continuous market growth in the future. Methods such as glycolysis and methanolysis of PET have been identified as promising approaches in sustainable chemical recycling of PET. The latter produces dimethyl terephthalate (DMT), which can be easily hydrolyzed to terephthalic acid (TPA) at elevated temperatures and pressures, and further reused for PET production. The aim of this study was to develop a kinetic model for the hydrolysis of dimethyl terephthalate, using the experimental data. Various reaction conditions (temperature, pressure, time) have been investigated and used to calculate the activation energies and reaction rate constants, while the variation in reactor setup with methanol (MeOH) removal was conducted to show its detrimental effect on the efficiency of the reaction and selectivity towards terephthalic acid. The first reaction step of DMT to monomethyl terephthalate (MMT) is relatively irreversible, while the second reaction step of MMT to TPA ceases, as soon as the equilibrium is reached. Highest yields of TPA (76.7 %) were obtained after 40 min at 265 °C, with MeOH removal, and the activation energy was calculated to be 95 and 64 kJ mol−1 for the first and second hydrolysis reaction step, respectively. [Display omitted] • Kinetics of dimethyl terephthalate (DMT) hydrolysis during reactive distillation. • Reversible reaction between monomethyl terephthalate (MMT) and terephthalic acid (TPA). • The removal of methanol (MeOH) from the reaction mixture improves the final TPA yield. • Carbon balance loss is attributed to unavoidable sublimation of TPA during reactive distillation. [ABSTRACT FROM AUTHOR]

2,5‐Furandicarboxylic acid (FDCA) is a green and renewable substitute to terephthalic acid (TPA), the fundamental monomer of polyethylene terephthalate (PET) plastic. This work investigated novel supported Keggin phosphormolybdic acids (HPMs) for the synthesis of FDCA from 5‐hydroxymethylfurfural (HMF) in imidazole ionic liquids. Among four supporters, Al2O3, SiO2, ZSM‐5 and SBA‐15, SBA‐15 exhibited highest stability and specific surface area 507 m2/g. FDCA yield achieved 76 % by using HPM/SBA‐15, and maintained 60 % after 5 runs. Particularly, [Bmim]Cl ionic liquid was stable both in thermal and chemical properties by confirmation of FTIR and NMR. HPM/SBA‐15 was also employed in different monosaccharides to FDCA, and led to acceptable yields. A moderate FDCA yield of 34 % from glucose was obtained, revealing a great potential of one‐pot synthesis of FDCA from renewable and accessible carbohydrates. [ABSTRACT FROM AUTHOR]

Melt extrusion pretreatment of poly(ethylene terephthalate) (PET) prior to enzymatic depolymerization with an unpurified leaf branch compost cutinase enzyme cocktail is explored to ascertain the efficiency gained by different processing methods on the enzymatic depolymerization of PET. Specific surface area (SSA) is investigated as a key factor in reducing depolymerization time. Higher SSA substrates (>5.6 mm2 mg−1) show higher depolymerization rates (≈0.88 g L−1 terephthalic acid [TPA] per day) and no induction phase, while lower SSA substrates (≈4.3, 4.4, and 5.6 mm2 mg−1) show, after an initial induction phase, similar depolymerization rates (≈0.46, 0.45, and 0.44 g L−1 TPA per day) despite increases in SSA of up to 30%. The mechanism of enzymatic depolymerization manifests in the appearance of anisotropic pitting. Longer incubation time used to overcome the induction phase in low SSA substrates allows for nearly full recovery of monomeric products, but manual pregrinding of extruded PET sharply increases SSA, depolymerization rate, and substrate crystallinity which may decrease the maximum recycled yield of the product materials. An estimate of the energy cost of increasing SSA is made and its effects on material properties are discussed. This work highlights key material structure and pretreatment aspects influencing the enzymatic recycling of PET. [ABSTRACT FROM AUTHOR]

Funneling and functionalization of a mixture of lignin‐derived monomers into a single high‐value chemical is fascinating. Reported herein is a three‐step strategy for the production of terephthalic acid (TPA) from lignin‐derived monomer mixtures, in which redundant, non‐uniform substitutes such as methoxy groups are removed and the desired carboxy groups are introduced. This strategy begins with the hydro‐treatment of corn‐stover‐derived lignin oil over a supported molybdenum catalyst to selectively remove methoxy groups. The generated 4‐alkylphenols are converted into 4‐alkylbenzoic acids by carbonylation with carbon monoxide. The Co‐Mn‐Br catalyst then oxidizes various alkyl chains into carboxy groups, transforming the 4‐alkylbenzoic acid mixture into a single product: TPA. For this route, the overall yields of TPA based on lignin content of corn stover could reach 15.5 wt %, and importantly, TPA with greater than 99 % purity was obtained simply by first decanting the reaction mixture and then washing the solid product with water. PET project: Terephthalic acid (TPA) is obtained in high yield and purity from corn stover lignin by a three‐step conversion strategy. Thus, TPA is available for making polyethylene terephthalate and other plastics. [ABSTRACT FROM AUTHOR]

The accumulation of polyethylene terephthalate (PET) wastes has caused severe environmental pollution and resource waste due to its widespread use. Hydrolysis of waste PET into terephthalic acid (TPA) is a promising recovery approach and can be a valuable supplement to the route starting from the petrochemical industry. However, the main roadblocks include low-efficiency degradation and tedious/ecounfriendly separation. Herein, we develop a mild non-aqueous hydrolysis for the selective ester cleavage of PET and facile product separation. This work applies ethylene glycol (EG, one of the monomers for PET polymerization) and tetrahydrofuran (THF) as the reaction solvent to obtain the hydrolysis product terephthalate in the presence of KOH. 100% of PET degradation and 97.5% of TPA yield can be achieved at 60 °C in 1 h. The addition of THF promotes mass transfer by etching of the PET surface while it makes the product auto-precipitate from the degradation solution sufficiently. Besides, THF showed an activating effect on the hydroxyl group of EG, and the ester bonds of PET were cleaved due to a synergy of potassium hydroxide and alkoxide. The degradation even took place at 30 °C. There was no decline in the degradation rate of PET after the degradation solution was recycled 5 times. The cosolvent system can also accomplish the selective degradation of PET into TPA while spandex remained unchanged for colored waste blended textiles. Besides, the system showed excellent elution properties for dyes on the textiles and made it possible to recycle complex wastes. This work provides a promising approach for the efficient and selective degradation of PET, as well as simple product separation by introducing a cosolvent and also provides a useful reference for the recycling of other waste polymers containing ester groups. [ABSTRACT FROM AUTHOR]

The search for a straightforward technology for post-consumer poly(ethylene terephthalate) (PC-PET) degradation is essential to develop a circular economy. In this context, PET hydrolases such as cutinases can be used as bioplatforms for this purpose. Humicola insolens cutinase (HiC) is a promising biocatalyst for PC-PET hydrolysis. Therefore, this work evaluated a kinetic model, and it was observed that the HiC seems not to be inhibited by any of the main PET hydrolysis products such as terephthalic acid (TPA), mono-(2-hydroxyethyl) terephthalate (MHET), and bis-(2-hydroxyethyl) terephthalate (BHET). The excellent fitting of the experimental data to a kinetic model based on enzyme-limiting conditions validates its employment for describing the enzymatic PC-PET hydrolysis using two-particle size ranges (0.075–0.250, and 0.250–0.600 mm) and temperatures (40, 50, 55, 60, 70, and 80 °C). The Arrhenius law provided a reliable parameter (activation energy of 98.9 ± 2.6 kJ mol−1) for enzymatic hydrolysis, which compares well with reported values for chemical PET hydrolysis. The thermodynamic parameters of PC-PET hydrolysis corresponded to activation enthalpy of 96.1 ± 3.6 kJ mol−1 and activation entropy of 78.9 ± 9.5 J mol−1 K−1. Thus, the observed rate enhancement with temperature was attributed to the enthalpic contribution, and this understanding is helpful to the comprehension of enzymatic behavior in hydrolysis reaction. [ABSTRACT FROM AUTHOR]

Common technologies for waste polyethylene terephthalate (PET) hydrolysis generally use strong acids or alkalis as catalysts; however, these processes are costly and generate a large amount of acid, alkali, and salt wastewater. In addition, these catalysts are difficult to recycle and reuse, which is not in line with the concept of sustainable development. This study describes the use of concentrated p-toluenesulfonic acid (PTSA) as an acid catalyst for PET hydrolysis under relatively mild conditions, enabling the degradation of approximately 100% of PET into 96.2% of terephthalic acid (TPA) within 90 minutes at 150 °C. A similar degradation efficiency can only be achieved at 150 °C using concentrated sulfuric acid for over 5 h. The generated TPA was easily separated from the hydrolysis system via filtration. The used PTSA was easily recovered from the filtrate after TPA collection using simple concentration and crystallization technologies. The recovered PTSA still maintained excellent catalytic efficiency for PET hydrolysis after five consecutive cycles. Furthermore, the kinetics of the reaction confirmed that the PET hydrolysis catalyzed by concentrated PTSA conforms to a first-order reaction with a relatively low apparent activation energy of 76.4–125.4 kJ mol−1. Finally, the technical feasibility and environmental impact of a scale-up were evaluated using Aspen Plus simulations. Overall, this work proposes a feasible and green strategy for the low-cost and environmentally friendly hydrolysis of waste PET. [ABSTRACT FROM AUTHOR]

Certain members of the Actinobacteria and Proteobacteria are known to degrade polyethylene terephthalate (PET). Here, we describe the first functional PET-active enzymes from the Bacteroidetes phylum. Using a PETase-specific Hidden-Markov-Model- (HMM-) based search algorithm, we identified several PETase candidates from Flavobacteriaceae and Porphyromonadaceae. Among them, two promiscuous and cold-active esterases derived from Aequorivita sp. (PET27) and Kaistella jeonii (PET30) showed depolymerizing activity on polycaprolactone (PCL), amorphous PET foil and on the polyester polyurethane Impranil® DLN. PET27 is a 37.8 kDa enzyme that released an average of 174.4 nmol terephthalic acid (TPA) after 120 h at 30°C from a 7 mg PET foil platelet in a 200 μl reaction volume, 38-times more than PET30 (37.4 kDa) released under the same conditions. The crystal structure of PET30 without its C-terminal Por-domain (PET30ΔPorC) was solved at 2.1 Å and displays high structural similarity to the Is PETase. PET30 shows a Phe-Met-Tyr substrate binding motif, which seems to be a unique feature, as Is PETase, LCC and PET2 all contain Tyr-Met-Trp binding residues, while PET27 possesses a Phe-Met-Trp motif that is identical to Cut190. Microscopic analyses showed that K. jeonii cells are indeed able to bind on and colonize PET surfaces after a few days of incubation. Homologs of PET27 and PET30 were detected in metagenomes, predominantly aquatic habitats, encompassing a wide range of different global climate zones and suggesting a hitherto unknown influence of this bacterial phylum on man-made polymer degradation. [ABSTRACT FROM AUTHOR]

Polyethylene terephthalate (PET) biodegradation is regarded as an environmentally friendly degradation method. In this study, an artificial microbial consortium composed of Rhodococcus jostii , Pseudomonas putida and two metabolically engineered Bacillus subtilis was constructed to degrade PET. First, a two-species microbial consortium was constructed with two engineered B. subtilis that could secrete PET hydrolase (PETase) and monohydroxyethyl terephthalate hydrolase (MHETase), respectively; it could degrade 13.6% (weight loss) of the PET film within 7 days. A three-species microbial consortium was further obtained by adding R. jostii to reduce the inhibition caused by terephthalic acid (TPA), a breakdown product of PET. The weight of PET film was reduced by 31.2% within 3 days, achieving about 17.6% improvement compared with the two-species microbial consortium. Finally, P. putida was introduced to reduce the inhibition caused by ethylene glycol (EG), another breakdown product of PET, obtaining a four-species microbial consortium. With the four-species consortium, the weight loss of PET film reached 23.2% under ambient temperature. This study constructed and evaluated the artificial microbial consortia in PET degradation, which demonstrated the great potential of artificial microbial consortia in the utilization of complex substrates, providing new insights for biodegradation of complex polymers. [ABSTRACT FROM AUTHOR]

BACKGROUND: Every minute, 1 million bottled drinks were purchased worldwide in 2017. Poly(ethylene terephthalate) (PET) bottles are highly recalcitrant wastes, taking at least 450 years to decompose naturally, and their accumulation in the environment triggers a series of environmental impacts. Recycling is an environmentally friendly alternative to PET waste management. A two‐step PET depolymerization approach was studied in this work, comprising chemical glycolysis followed by enzymatic hydrolysis. RESULTS: In the glycolysis reaction, 100% PET was depolymerized in the presence of a eutectic solvent‐based catalyst and ethylene glycol, releasing bis(2‐hydroxyethyl) terephthalate (BHET) as the main product (70% yield). The recovered BHET was then hydrolysed by the highly efficient Candida antarctica lipase B, releasing terephthalic acid (TPA), achieving 0.98 of mole fraction in the best result of the experimental design. The overall yield of chemo‐enzymatic depolymerization of PET into TPA was 57%. CONCLUSION: Using this integrated approach, a high overall yield of TPA from PET could be achieved within a short process timeframe (24 h). © 2021 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]