A novel Gordonia sp. PS3 isolated from the gut of Galleria mellonella larvae: Mechanism of polystyrene biodegradation and environmental toxicological evaluation.

Plastic pollution is a global concern, with polystyrene (PS) being a major source of plastic waste. In this study, a PS-degrading bacterial strain, Gordonia sp. PS3, was isolated from the gut of Galleria mellonella larvae. After 40 days, strain PS3 exhibited a 33.59 ± 1.12 % degradation rate of PS-microplastics (PS-MPs). The biodegradation mechanism of PS by strain PS3 was investigated using genomics, molecular docking, and metabolomics. Degradation resulted in a significant decrease in molecular weight, disappearance of characteristic aromatic peaks, and the appearance of new functional groups (e.g., hydroxyl and carbonyl), indicating oxidative depolymerization and enhanced hydrophilicity. Four key enzymes involved in PS degradation were identified, with alkane 1-monooxygenase initiating cleavage of C-C bonds in PS and cytochrome P450 monooxygenase catalyzing oxidation of the aromatic ring. Metabolomics analysis revealed upregulation of proline, branched-chain amino acids, and polyamines, indicating oxidative stress response and energy acquisition during PS degradation. The PS degradation products showed no significant adverse effects on Arabidopsis thaliana growth, and PS residues were less harmful to G. mellonella larvae than untreated PS-MPs. This study presents a novel strain for PS biodegradation and provides new insights into the microbial degradation mechanism of PS and the safety of its degradation products.