Two-stage aerobic biodegradation of recalcitrant plastics by Tenebrio molitor gut and frass microbiota: a respirometric approach

Plastic pollution persists due to the degradation resistance of polyethylene (PE), polypropylene (PP), and polystyrene (PS). Mealworms ( Tenebrio molitor ) ingest these plastics, but the role of gut and frass microbiota in biodegradation remains unclear. This study compared biodegradation of PS, PP, and PE films by microbial communities isolated from plastic-fed mealworm gut and frass. In sealed aerobic microcosms, oxygen consumption and CO 2 production were monitored over 60 days. Gut microbiota degraded PS, PP, and PE by 13.6%, 11.6%, and 9.8%, respectively; frass microbiota achieved 13.3%, 8.9%, and 7.4%. FTIR analysis revealed new C=O, C-O, and O-H groups indicating oxidation, while SEM showed surface erosion and biofilm formation. Respiratory quotients (RQ < 1) suggested incomplete mineralization consistent with oxidative metabolism. 16S rRNA sequencing showed higher diversity and oxidative degraders ( Pseudomonas , Rhodococcus ) in gut communities, while frass retained fermentative taxa. Predicted pathways included alkane monooxygenases and β-oxidation enzymes. Gut microbiota initiate oxidative depolymerization, while frass communities sustain post-egestion degradation, demonstrating a two-stage biodegradation system with potential for plastic waste remediation.