Metabolic and enzymatic engineering strategies for polyethylene terephthalate degradation and valorization

Polyethylene terephthalate (PET) is one of the most marketed aromatic polyesters in the world with an annual demand in 2022 of approximately 29 million metric tons, expected to increase by 40% by 2030. The escalating volume of PET waste and the current inadequacy of recycling methods have led to an accumulation of PET in the terrestrial ecosystem, thereby posing significant global health risks. The pressing global energy and environmental issues associated with PET underscore the urgent need for “upcycling” technologies. These technologies aim to transform reclaimed PET into higher-value products, addressing both energy concerns and environmental sustainability. Enzyme-mediated biocatalytic depolymerization has emerged as a potentially bio-sustainable method for treating and recycling plastics. Numerous plastic-degrading enzymes have been identified from microbial origins, and advancements in protein engineering have been employed to modify and enhance these enzymes. Microbial metabolic engineering allows for the development of modified microbial chassis capable of degrading PET substrates and converting their derived monomers into industrial relevant products. In this review, we describe several engineering approaches aiming at enhancing the performances of PET-degrading enzymes and we present the current metabolic engineering strategies adopted to bio-upcycle PET into high-value molecules.