Mechanistic Insights into UV/H₂O₂-Aged Polystyrene Enable an Optimized Protocol for Fungal Biodegradation

Plastic pollution is a global environmental challenge, yet plastic biodegradation remains inefficient and poorly understood. In this study, a degradation strategy for polystyrene (PS) films was developed by combining ultraviolet (UV) irradiation and hydrogen peroxide (H₂O₂) pretreatment with subsequent biodegradation by Phanerochaete chrysosporium . UV/H₂O₂ pretreatment proved optimal, resulting in a mass loss of up to 25.75% and inducing the formation of oxygen-containing functional groups, including carbonyl, hydroxyl, and carboxyl groups. These groups act as electron donors, facilitating extracellular enzymatic chain-cleavage reactions, while also promoting fungal colonization and enhancing the activities of manganese peroxidase, lignin peroxidase, and laccase. The pretreated PS was degraded through three main pathways prior to entering the tricarboxylic acid cycle: direct assimilation of carboxylated compounds, enzymatic aromatic ring cleavage, and cytochrome P450-mediated oxidation. Overall, UV/H₂O₂ pretreatment significantly improves surface oxidation, microbial activity, and enzymatic reactivity, offering an effective strategy to accelerate plastic biodegradation.