Optimizing mealworm rearing conditions and gut microbiome function for enhanced plastics biodegradation.

Insects have become an efficient and eco-friendly bioreactor for plastics and even micro/nano-plastics biodegradation. However, the optimal conditions for rearing insects to maximize plastic biodegradation and the underlying mechanisms remain unclear, hindering its practical applications. We investigated the effects of multiple rearing factors on plastics degradation efficiency of Tenebrio molitor larvae, including larval instar, water addition frequency, plastic specific surface area and plastic types. The functional gut microbes and enzymes associated with the improved efficiency were further explored. Our findings revealed that adult larvae achieved the highest plastics degradation efficiency when receiving regular water additions without causing drowning of insects on hydrophobic plastics. Additionally, they effectively ingested foam plastics of polystyrene, polyethylene and polyurethane without prior comminution and densification. The biodegradation processes involving oxidation, cleavage and depolymerization of plastics were all demonstrated. Furthermore, foam plastic type-dependent functional microbes and enzymes that contributed to the efficient plastic degradation were identified. This work provides valuable insights into the practical applications of insects for sustainable plastics biodegradation.