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

Abstract

Mealworm larvae (Tenebrio molitor) 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, versus 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 T. molitor adapted significantly to PS and PE exposure, reshaping microbial diversity and ecological niches. Notably, Spiroplasma sp., Lactococcus sp., and Enterococcus sp. were associated with all four plastics, whereas Staphylococcus sp. and Providencia 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.