Pleurotus ostreatus-Mediated Bioremediation of Polylactic Acid Microplastics: Unveiling a Sustainable Solution

Polylactic acid (PLA) is a compostable biopolymer with strong potential to replace petroleum-based plastics, yet its end-of-life degradation pathways under real-world conditions remain insufficiently understood at the molecular and structural levels. In this study, we investigate the physical-chemical mechanisms underlying the biodegradation of PLA microplastics by the edible white-rot fungus Pleurotus ostreatus. Detailed studies on the microplastics' morphological, structural, and chemical changes reveal that after 30 days of fungal treatment, their surface presents small pores, with the concomitant formation of new carbonyl (CO), carboxyl (-COOH), and hydroxyl (-OH) groups, consistent with oxidative scission of ester bonds. Concomitantly, differential scanning calorimetry and X-ray diffraction indicate a significant increase in crystallinity, attributed to a preferential enzymatic attack on amorphous domains, followed by chain reorganization. These observations elucidate the interplay between enzymatic oxidation (driven predominantly by laccase activity) and polymer chain mobility, demonstrating how enzymatic catalysis induces coupled chemical and morphological transformations in PLA. The findings provide a promising environmentally friendly solution for bioremediation of PLA materials by edible fungi, helping to overcome current limitations in industrial composting and enabling a standardized, efficient decomposition and a more predictable, sustainable end-of-life strategy within circular waste management systems. Furthermore, this approach offers new insights into the synthesis of lignocellulosic enzymes during the bioprocess.