Plastic-to-CO₂: measuring mealworm-induced plastics degradation via aerobic respiration rates

Mealworm larvae (Tenebrio molitor) have emerged as a promising biological agent for degrading synthetic plastics. This study aimed to establish a non-invasive method to monitor plastic biodegradation by linking oxygen consumption to metabolic activity and to investigate microbial and chemical changes associated with plastic degradation. Larvae were maintained under controlled conditions (25 ± 0.5 °C; 75 ± 5% relative humidity) and fed expanded polystyrene (EPS) or polypropylene (PP) for 28 days. Survival rates, daily plastic consumption, and oxygen uptake were recorded. Frass was analyzed for molecular weight changes, while GC-MS, FTIR, and NMR were used to detect chemical modifications in degraded polymers. Gut microbiota composition was assessed by sequencing to identify taxa associated with plastic diets. Survival exceeded 80% in plastic-fed groups compared to 44.2% in unfed controls. Mean daily plastic consumption per 100 larvae was 15.7 ± 2.2 mg (EPS) and 16.4 ± 1.5 mg (PP). Frass analysis revealed significant depolymerization, while GC-MS, FTIR, and NMR confirmed oxidative modifications and the formation of shorter-chain alkanes. Microbiome profiling showed consistent presence of Spiroplasma, Lactococcus, and Enterococcus, with enrichment of Staphylococcus and Providencia in EPS-fed groups. Oxygen uptake correlated with plastic degradation, validating it as a real-time metabolic indicator. This study demonstrates that oxygen uptake can serve as a real-time proxy for plastic degradation in vivo, providing higher temporal resolution than endpoint assays. The findings highlight the dual role of larvae and their gut microbiome in polymer breakdown, offering new insights into sustainable bioconversion strategies for plastic waste.