Differences in the properties of polyolefin and polyester plastics biodegradation by insects and gut microbiome responses

Abstract

The issue of plastic pollution is becoming increasingly severe, and the potential of insects to biodegrade plastics offers new insights for the development of harmless and resource-efficient plastic waste treatment technologies. However, plastic wastes discarded in the environment are complex and diverse. There is limited knowledge regarding the feeding preferences, degradation efficiency, and impact on growth performance of different insects for various types of plastics, all of which would affect the plastics degradation effectiveness in practical applications involving insects. This study compared the degradation efficiency and growth index of two typical insects (mealworm Tenebrio molitorand superworm Zophobas atratus) on two types of typical foam plastics, i.e., a polyolefin plastic of polyethylene (PE), and a polyester plastic of polyurethane (PU). The results indicated that: (1) Insects exhibited higher feeding efficiency and degradation degree on polyester plastics than polyolefin plastics. Superworms showed higher plastic feeding efficiency than mealworms, while mealworms achieved a higher degradation degree, with their degradation products exhibiting lower toxicity than superworms; (2) Significant changes occurred in the microbial community of insects during the ingestion and degradation of plastics. Key microbial species involved in PE and PU biodegradation were distinct, with un_Enterobacteriaceaesp., Hafnia-Obesumbacteriumsp. and Acinetobactersp. predominating PE degradation, while Morganellasp., un_Lachnospiraceaesp. and Providenciasp. predominating PU degradation; (3) Potential plastic-degrading enzymes were enriched, with dehydrogenase (betB), monooxygenase (ssuD), and peroxidase (EfeB) playing significant roles in PE degradation, while dehydrogenase (dapdh), laccase (aes), and hydroxylase (mhpA) being crucial for PU degradation. These findings provided essential guidance for the development of insect-based plastic biodegradation processes and harmless treatment of plastic wastes.