Biotechnology for plastic production, degradation, and upcycling

Plastics are essential to modern life, but their predominantly linear use, low recycling rates, and slow breakdown generate persistent pollution. Bio-based production and biodegradation are promising; however, achieving true plastic circularity requires a unified approach that links feedstock choice, polymer structure, material performance, end-of-life processing, and carbon recovery. In this review, we examine biotechnologies for plastic production, degradation, and upcycling across the plastic life cycle. We focus on microbial production of bio-based polymers and monomer platforms, abiotic and biological mechanisms of plastic degradation, and hybrid abiotic–biotic routes that convert plastic waste into recoverable carbon streams. We emphasize polymer chemistry, enzymatic depolymerization, microbial assimilation, chemical pretreatment, and the evidence needed to substantiate degradation claims. We show that ester-containing polymers, including PET, PLA, PHA, PBS, PBAT, and PCL, are generally more accessible to hydrolysis and enzymatic attack than C-C backbone polymers such as PE, PP, and PS. Real waste streams, however, remain challenging because additives, crystallinity, product geometry, aging history, and environmental conditions often limit depolymerization. We argue that future progress will depend on controlled depolymerization and carbon retention, rather than passive biodegradation alone. Abiotic processes can open otherwise stable polymer structures, enzymes can add selectivity, and microbial metabolism can funnel mixed intermediates into monomers, bioplastics, and high-value chemicals. Finally, we propose an evidence framework and design principles to guide plastic circularity by linking production, material function, and end-of-life carbon recovery.