Uncovering the aerobic degradation dynamics of polystyrene (PS) and polyethylene (PE) by mealworms through real-time oxygen monitoring

Mealworm larvae (<i>Tenebrio molitor</i>) exhibit the potential for biodegrading synthetic plastics, providing a sustainable strategy to reduce plastic waste. Real-time data on plastic consumption rates and degradation mechanisms, particularly those linked to oxygen consumption, remain limited. This study aimed to quantify the ability of mealworms to consume commercial plastics-polystyrene (PS) and polyethylene (PE)-over a 28 day period under controlled conditions (75% ± 5% humidity, 25 ± 0.5 °C) using a respirometer. Twenty-eight-day survival rates exceeded 80% in plastic-fed groups, <i>versus</i> 44.2% in the unfed control. Daily plastic consumption per 100 larvae was 15.9 ± 0.5 mg (PS) and 17.9 ± 0.9 mg (PE). Reductions in the molecular weights (Mw, Mn, and Mz) of residual PS and PE in larval frass, compared to feedstock, confirmed plastic depolymerization and biodegradation. GC-MS identified surface chemical changes with oxygen-rich functional groups and short alkanes, while ¹H-NMR and FTIR analyses revealed chemical modifications consistent with the partial oxidation of the polymer. The gut microbiome of <i>T. molitor</i> adapted significantly to PS and PE exposure, reshaping microbial diversity and ecological niches. Notably, <i>Spiroplasma</i> sp., <i>Lactococcus</i> sp., and <i>Enterococcus</i> sp. were associated with all four plastics, whereas <i>Staphylococcus</i> sp. and <i>Providencia</i> sp. played key roles in PS metabolism. Our finding demonstrates for the first time that oxygen consumption can serve as a quantitative indicator of plastic biodegradation, highlighting the mealworm gut microbiome as a promising tool for plastic biodegradation while expanding scientific insights into its microbial functions.