Biotechnology-enabled plastic valorization across enzymatic, microbial, and hybrid conversion systems: A review

Plastic valorization is shifting from disposal-oriented approaches toward carbon-retentive conversion pathways enabled by biotechnology. Advances in enzyme discovery, protein engineering, microbial metabolism, and hybrid catalytic processing have expanded the range of polymers that can be selectively transformed and upgraded into defined chemicals and materials. Yet inconsistent terminology, heterogeneous feedstocks, additive interference, and the absence of standardized performance metrics continue to blur the distinction between degradation and value-retentive conversion. This review develops a systems framework for biotechnology-enabled plastic valorization that integrates enzymatic depolymerization, microbial assimilation, insect-derived discovery platforms, and hybrid bio-catalytic and thermochemical processing. Quantitative benchmarking reveals a widening performance divergence between polyester depolymerization-where near-closed-loop monomer recovery is achievable-and polyolefin transformation, which remains dominated by oxidative activation and partial carbon routing. Feedstock complexity, particularly dye-containing plastics, further exposes critical requirements for detoxification, modular processing, and carbon-efficient integration. Across scales, effective plastic conversion emerges less as a problem of polymer breakdown than of controlled carbon routing. Hybrid systems expand substrate accessibility but introduce trade-offs in energy demand, separations, and operational complexity. Concurrent advances in synthetic consortia, enzyme engineering, and reactor design are enabling distributed metabolic platforms capable of upgrading heterogeneous waste streams into bioproducts, although challenges remain in polyolefin activation, scalable reactor interfaces, and techno-economic alignment with existing waste infrastructure. By linking molecular mechanisms with process translation, this review positions plastic biotechnology as a programmable carbon-management strategy and outlines research priorities required to move from laboratory depolymerization toward industrial plastic biomanufacturing.