[Biodegradation of Expanded Polystyrene Foams in Zophobas morio: Effects of Gut Microbiota]

Polystyrene (PS) foam is one of the main plastic materials dispersed in the environment. In this study, we observed that the insect-super mealworms (Zophobas morio), which belong to a species of the Tenebrio genus, are able to consume and degrade PS foam. Individual Z. morio consumed an extracellular polymeric substance (EPS) over 50 days with high survival rates. Analyses of the frass egested using fourier transform infrared spectroscopy (FTIR) confirmed the formation of a new oxygen-bearing functional group in the EPS. Gel permeation chromatography (GPC) analyses indicated that the depolymerization of ingested EPS with decreases in both M_w and M_n was observed, suggesting that the EPS was biodegraded. We also used 16S rRNA gene sequences to analyze the gut bacteria of Z. morio under three different feeding conditions, including with polystyrene, bran, and bran plus polystyrene. Under different dietary conditions, the gut microbiota of Z. morio showed significant differences, such as Klebsiella and Citrobacter becoming significantly enriched. In vitro studies using 90-days gut microbial culturing experiments indicated that gut microbiota contributed to PS degradation. Our research demonstrates that intestinal bacteria played an essential role in the degradation of PS by Z. morio, and provides a new theoretical basis and application ideas for the biodegradation of PS.