Biodegradation of Plastics in Tenebrio Genus (Mealworms)

Abstract

Most petroleum-based plastics are resistant to biodegradation in the environment. Observation of damage, penetration, and ingestion of plastics by insects and their larvae lead to research on biodegradation of plastics by insects. The larvae of darkling beetles (Coleoptera: Tenebrionidae), especially Tenebrio molitor and Tenebrio obscurus larvae, showed the capacity of rapid gut microbe-dependent degradation of polystyrene (PS). T. molitor larvae also degrade low-density polyethylene (LDPE). The biodegradation was evaluated on the basis of plastic mass balance, modification of ingested polymers, formation of biodegraded intermediates, as well as 13C isotopic tracer tests. Ingested PS or LDPE polymer can be depolymerized by up 60–70% within 12–24 h after 1- or 2-week adaption. Ingested PS or PE supports the larvae with energy for life activities but not growth. Co-feeding normal diet (e.g., bran) enhances PS and PE consumption rate significantly. Gut microbial communities shifted after the larvae were fed with PS or PE. A few plastic-degrading gut bacterial strains have been isolated from gut of T. molitor, but they grow on plastics slowly. The rapid biodegradation of PS and PE is likely a result of synergistic effects of intestinal microbial activities and host digestive system, and further research is needed to understand the mechanisms.