A New Coleoptera Member ( <i>Ulomoides dermestoides</i> ) to Biodegrade Plastics

The larvae of <i>U. dermestoides</i> (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 <i>T. molitor</i> larvae. <i>U. dermestoides</i> larvae effectively depolymerized and biodegraded ingested PS, PE, and PP as <i>T. molitor</i> 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. <i>U. dermestoides</i> and <i>T. molitor</i> 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 <i>T. molitor</i> larvae was more diverse than that of <i>U. dermestoides</i> 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, <i>U. dermestoides</i> larvae, which have larval size of only one-third of <i>T. molitor</i> larvae, biofragmented ingested polymers into smaller sized microplastics (MPs) and even nanoplastics (NPs) than <i>T. molitor</i> 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.