From insect biodegradation to microbial upcycling: A closed-loop framework for plastic waste valorization.

Global plastic waste management requires low-energy, value-oriented strategies capable of handling heterogeneous and contaminated feedstocks. Insect-mediated plastic degradation offers a promising biological route, as larvae physically fragment plastics and, together with oxidative reactions, gut microorganisms, and host-derived enzymes, promote polymer depolymerization under mild conditions. However, this process generates frass containing residual micro- and nanoplastics (MNPs), which limits the direct reuse of insect residues and may cause secondary environmental release. This review proposes an insect-centered closed-loop framework for plastic waste valorization. In this framework, larvae reduce plastic waste and generate MNP-containing frass and chitin-rich exuviae, exuviae-derived chitin is used to capture residual MNPs from frass, and the enriched plastics are further depolymerized by enzymatic cascades and converted by engineered microbes into value-added products. By integrating insect biodegradation, chitin-based adsorption, enzymatic depolymerization, and microbial biotransformation, this framework extends insect-mediated plastic treatment from waste reduction to carbon recovery. Key challenges for scale-up, mass balance control, process integration, and techno-economic and life-cycle assessment are also discussed.