Unveiling gut microbiota and metabolic functions contributed to polyvinyl chloride degradation in Spodoptera...

The accumulation of synthetic plastic waste, particularly polyvinyl chloride (PVC), threatens ecosystems globally. While microbial biodegradation represents a sustainable solution, limited effective PVC-degrading microbial bioresources have been identified. Here, we investigated the gut microbiota of Spodoptera frugiperda larvae, revealing a consistent microbial profile dominated by Enterococcus in both gut contents and tissues. PVC film feeding induced significant microbiota shifts, with functional parallels to PVC powder-fed Tenebrio molitor larvae despite taxonomic divergence. Through enzyme-centric analysis, we found an Enterococcus casseliflavus strain from the gut of S. frugiperda larvae could encode a NAD-dependent oxidoreductase that directly dechlorinates additive-free PVC, representing the first case of enzymatic polymer dechlorination. This enzyme reduced PVC molecular weight (Mn: 12.02 %; Mw: 14.07 %) and notably liberated chloride ions (6.48 mg/L with NADH as a co-factor). Our findings demonstrate the PVC-degrading capacity of S. frugiperda gut microbiota and reveal its dechlorination mechanism, offering an enzymatic candidate for developing novel biocatalysts and engineered microbial strains for enhanced biodegradation. By unravelling insect-associated microbes and enzymes, this work lays a theoretical foundation for their application potentials in sustainable PVC wastes upcycling and microplastic remediation.