TITLE:
Enzymatic Biorecycling of Polyethylene Terephthalate (PET): Mechanisms, Microbial Resources, and Protein Engineering Strategies
AUTHORS:
Ricardo Noé Meza-Puebla, Jorge Mulia-Rodríguez, Alma Velázquez-Rodríguez, Daniel Osorio-González
KEYWORDS:
Polyethylene Terephthalate (PET), Enzymatic Depolymerization, Biorecycling, Protein Engineering
JOURNAL NAME:
Open Journal of Applied Sciences,
Vol.16 No.5,
May
27,
2026
ABSTRACT: Polyethylene terephthalate (PET) is one of the most extensively used synthetic polymers worldwide due to its favorable mechanical strength, transparency, chemical resistance, and low manufacturing cost. However, its persistence in natural environments and the continuous increase in global plastic production have intensified the need for sustainable recycling technologies. Conventional PET recycling routes, including mechanical and chemical processing, remain constrained by polymer quality loss, high energy demand, and significant environmental burdens. In this context, enzymatic biorecycling has emerged as a promising alternative based on selective depolymerization under mild operating conditions. PET-hydrolyzing enzymes such as PETases, cutinases, lipases, and related polyester hydrolases catalyze the cleavage of ester bonds, releasing terephthalic acid (TPA), ethylene glycol (EG), bis (2-hydroxyethyl) terephthalate (BHET), and mono (2-hydroxyethyl) terephthalate (MHET), which can be recovered and reintroduced into manufacturing value chains. Recent studies have demonstrated substantial progress in the discovery of microbial degraders, metagenomic screening, structural biology, and computational protein engineering. Machine learning, directed evolution, rational design, and semi-rational mutagenesis have significantly improved enzyme thermostability, catalytic turnover, and tolerance to industrially relevant conditions. Nevertheless, several challenges remain, including PET crystallinity, substrate heterogeneity, additive interference, product inhibition, and scale-up limitations. This review summarizes the physicochemical basis of PET recalcitrance, the diversity of PET-degrading microorganisms, catalytic mechanisms of enzymatic depolymerization, and state-of-the-art enzyme engineering approaches driving next-generation PET circularity technologies.