Oxidative decomposition of polystyrene (PS) by insects has been previously demonstrated, yet little is known about the oxidation mechanism and its effect on the metabolism of plastics within the insect gut. Here, we demonstrate the generation of reactive oxygen species (ROS) in the gut of superworms (Zophobas atratus larvae) under different feeding trails, which in turn induced the oxidative decomposition of ingested PS. The ROS were commonly generated in the larva gut, and PS consumption resulted in a significant increase of ROS with a maximum ·OH of 51.2 μmol/kg, which was five times higher than in the bran feeding group. Importantly, scavenging of ROS significantly decreased the oxidative depolymerization of PS, indicating a vital role of ROS in effective PS degradation in the gut of superworms. Further investigation suggested that the oxidative depolymerization of PS was caused by the combinatorial effect of ROS and extracellular oxidases of gut microbes. These results demonstrate that ROS were extensively produced within the intestinal microenvironment of insect larvae, which greatly favored the digestion of ingested bio-refractory polymers. This work provides new insights into the underlying biochemical mechanisms of plastic degradation in the gut.
Keywords: Zophobas atratus; gut microbes; oxidative degradation; polystyrene; reactive oxygen species.