Biodegradation of polyethylene terephthalate (PET) : a critical review

Abstract

Polyethylene terephthalate (PET) is a highly persistent plastic pollutant that undergoes minimal natural degradation, prompting increasing interest in biological strategies as alternatives to conventional recycling methods. This critical review systematically analyzed 152 peer-reviewed studies, categorized into four methodological groups: enzyme-only, microbial-only, combined, and unconventional approaches to PET biodegradation. Studies were identified through structured searches and selected based on relevance, methodological quality, and availability of degradation data. Enzymatic systems - particularly engineered variants of PETase and cutinase - demonstrated high depolymerization efficiencies under optimized laboratory conditions. Microbial approaches effectively metabolized PET breakdown products across diverse environments but generally exhibited slower performance. Hybrid systems integrating enzymes, microorganisms, or pretreatments showed enhanced overall conversion, while unconventional strategies offered proof-of-concept insights with limited validation. Despite these advances, key challenges remain, including the lack of standardized degradation metrics, difficulties in scaling processes, and inconsistent substrate characterization. This review consolidates existing findings into systematic pathways, highlights recurring limitations, and outlines application contexts. The future of PET biodegradation will depend on continued innovations in enzyme engineering, microbial design, and integrated systems, with emphasis on improving efficiency and scalability to enable practical, real-world implementation within sustainable plastic waste management frameworks.