Chemo‐Biological Upcycling of Poly(ethylene terephthalate) to Multifunctional Coating Materials

Abstract

Chemo-biological upcycling of poly(ethylene terephthalate) (PET) developed in this study includes the following key steps: chemo-enzymatic PET depolymerization, biotransformation of terephthalic acid (TPA) into catechol, and its application as a coating agent. Monomeric units were first produced through PET glycolysis into bis(2-hydroxyethyl) terephthalate (BHET), mono(2-hydroxyethyl) terephthalate (MHET), and PET oligomers, and enzymatic hydrolysis of these glycolyzed products using Bacillus subtilis esterase (Bs2Est). Bs2Est efficiently hydro-lyzed glycolyzed products into TPA as a key enzyme for chemoenzymatic depolymerization. Furthermore, catechol solution produced from TPA via a whole-cell biotransformation (Escherichia coli) could be directly used for functional coating on various substrates after simple cell removal from the culture medium without further purification and water-evaporation. This work demonstrates a proof-of-concept of a PET upcycling strategy via a combination of chemo-biological conversion of PET waste into multifunctional coating materials.

Biochemical and structural characterization of an aromatic ring–hydroxylating dioxygenase for terephthalic acid catabolism

“…DK17 ( 11 ), Rhodococcus jostii RHA1 ( 14 ), Pseudomonas umsongensis GO16 ( 8 ), and Acinetobacter baylyi ADP1 (TPA importer) ( 21 ). Several studies have introduced TPA catabolism into microbes for metabolic engineering applications as well ( 22 – 26 ).…”

Selective, Sequential, and “One-Pot” Depolymerization Strategies for Chemical Recycling of Commercial Plastics and Mixed Plastics

“…After the successful depolymerization of the above series of plastics, the focus was turned to poly­(ethylene terephthalate) (PET). As the most widespread and multifunctional thermoplastics, large amounts of studies are devoted to the chemical recycling of PET to high-purity monomers. − Nevertheless, owing to its poor solubility and high stability, the alcoholysis of PET usually requires harsh reaction conditions such as high temperature and high pressure. − Herein, degradation breakthrough under mild conditions was attempted. The experiment results showed that the degradation catalyzed by Zn­(HMDS) 2 at 70 and 100 °C were proceeded steadily (Table , entries 17–18).…”

“…The commercial plastics that are currently used in a large-scale are primarily concerned with performance and durability rather than degradability and recyclability. As a result, the chemical recycling of plastics becomes a significant challenge. − Fortunately, polyester and polycarbonate plastics offer an opportunity for plastic sustainability due to the presence of easily cleaved carbon–oxygen bonds in the polymer backbones. − At present, studies on the conversion of polyester and polycarbonate materials such as poly­(ethylene terephthalate) (PET), − polylactide (PLA), − poly­(bisphenol A carbonate) (BPA-PC), − into starting monomers, or value-added chemicals have been widely reported, which are of great significance for plastic sustainability. The depolymerization of a single polyester has been investigated intensively.…”

Plastic Waste Valorization by Leveraging Multidisciplinary Catalytic Technologies

“…172 This work demonstrates the potential of integration of chemical deconstruction with biological fermentation as a mild approach to upcycle waste PET. In addition, other valuable chemicals, such as vanillin, 173 catechol, 174 and 2pyrone-4,6-dicarboxylic acid, 175 can also be obtained from PET by fermentation (Table 4).…”