ABSTRACT The rapid growth in global plastic production has resulted in unprecedented accumulation of plastic waste, posing severe environmental, ecological, and human‐health challenges. Conventional end‐of‐life management strategies, including landfilling, incineration, and mechanical recycling, remain insufficient to establish a truly circular plastics economy because of material downcycling, high energy demand, and greenhouse‐gas emissions. In this context, biological deconstruction, direct upcycling, and downstream valorization of intermediates derived from plastic‐waste streams have emerged as compelling catalytic strategies that exploit the selectivity and efficiency of enzymes and microbial systems to depolymerize waste plastics and transform the resulting intermediates into value‐added chemicals, fuels, and functional materials under mild conditions. This review critically examines recent advances in the biocatalytic degradation, upcycling, and downstream valorization of intermediates from major synthetic polymers, including polyethylene terephthalate, polyurethanes, polyamides, polyethylene, polypropylene, polystyrene, and poly(vinyl chloride). Emphasis is placed on enzyme discovery and engineering, structure–activity relationships, metabolic pathway design, and integrated chemo‐bio catalytic platforms that enable selective depolymerization and downstream valorization. We further analyze current limitations related to polymer recalcitrance, feedstock heterogeneity, catalyst stability, process scalability, and techno‐economic feasibility. Finally, future opportunities are outlined, highlighting the roles of machine‐learning‐guided enzyme design, synthetic biology, hybrid catalytic systems, and decentralized recycling infrastructures in advancing sustainable plastic circularity. Collectively, this review positions biocatalytic deconstruction, direct upcycling, and downstream biological valorization as key catalytic pillars for next‐generation circular plastics technologies.
Kumar et al. (Fri,) studied this question.