Corn straw co-feeding enhances polystyrene biotransformation in mealworms through redox regulation and gut microbiota-host interactions.

Plastic-degrading insects ("plastivores") have emerged as promising biological systems for mitigating plastic pollution, yet the mechanisms linking dietary supplementation, gut microbiota, and host physiology remain poorly understood. Here, we investigated the effects of corn straw (CS) co-feeding on the biotransformation of polystyrene (PS) microplastics (Mw 142.6 kDa) versus PS plus natural lignocellulose-containing diet CS at a 4:1 (w/w) ratio versus CS as sole at 25.0 ± 0.5 °C for 32 days by yellow mealworms (Tenebrio molitor). Compared with a PS-only diet, CS co-feeding increased PS removal efficiency from 47.3% to 58.5% and enhanced the specific PS consumption rate by 38%. Stable-isotope analysis (with a Δδ13C of 1.60 ‰), gel permeation chromatography (GPC), and Fourier transform infrared spectroscopy (FTIR) confirmed enhanced PS depolymerization and biotransformation. CS co-feeding elevated gut ROS levels by approximately 30% while maintaining antioxidant homeostasis. Integrated metabolomic, microbiome, metatranscriptomic, and host transcriptomic analyses revealed coordinated shifts in redox metabolism, microbial activity, and host signaling pathways. The results suggest that redox regulation and gut microbiota-host interactions jointly contribute to enhanced PS biotransformation during CS co-feeding.