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. However, real-time data exist 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 unfed control. Daily plastic consumption per 100 larvae were 15.9 ± 0.5 mg (PS), and 17.9 ± 0.9 mg (PE). Reduction in molecular weights (Mw, Mn, and Mz) of residual PS, and PE in larvae’s frass, compared to feedstock, confirmed the plastic depolymerization and biodegradation. GC-MS identified surface chemical changes with oxygen-rich functional groups and shorter alkanes, while, 1H-NMR and FTIR analyses revealed chemical modifications consistent with partial oxidation of the polymer. T. molitor gut microbiome of 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, wheres 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.