A New Coleoptera Member (Ulomoides dermestoides) to Biodegrade Plastics

The larvae of U. dermestoides (Coleoptera: Tenebrionidae), a beetle with traditional uses in folk medicines, exhibits a remarkable capacity for plastic degradation. This study investigates their ability to depolymerize and biodegrade common polymers, i.e., polystyrene (PS), polyethylene (PE), and polypropylene (PP) in direct comparison to the well-studied T. molitor larvae. U. dermestoides larvae effectively depolymerized and biodegraded ingested PS, PE, and PP as T. molitor larvae did with respective mass reduction of 55.3%, 50.2%, and 49.4% versus 63.6%, 57.6%, and 55.8%. The biodegradation was further verified by the δ¹³C signature, molecular weight change, and formation of oxidative functional groups. U. dermestoides and T. molitor larvae degraded PS and PP via broad depolymerization but degraded PE via a limited extent depolymerization. Analyses of gut microbiome and transcriptome tests indicated that both species performed the biodegradation of PS and PP polymers via gut microbiota, while PE degradation occurred through a synergistic effort between the larval host and the gut microbiota. However, interspecies differences existed in plastic biodegradation due to different initial dietary behaviors. The microbiome of T. molitor larvae was more diverse than that of U. dermestoides larvae; therefore, the microbiota of the former larvae more effectively adapted to PS, PE, and PP diets and achieved relatively higher biodegradation performance. In addition, U. dermestoides larvae, which have larval size of only one-third of T. molitor larvae, biofragmented ingested polymers into smaller sized microplastics (MPs) and even nanoplastics (NPs) than T. molitor larvae did in excrement, suggesting the larval size-dependent generation of MP/NPs during the biodegradation. This discovery has added a new member to the plastivore insect list and provides novel insights into the biodegradation of plastics.