Unveiling fungal degradation pathways for polyurethane and polyethylene through enrichment cultures and metabolic analysis

Abstract

The increasing accumulation of plastics in the environment poses significant threats to marine and terrestrial ecosystems. However, recent research highlights the potential of Lasiodiplodia iranensis, a tropical ascomycete fungus, to degrade synthetic plastics. The intrinsic molecular mechanisms and metabolic responses during the interaction and hydrolysis of plastics, particularly for polyurethane (PU) and polyethylene (PE), remain largely unexplored. This study was conducted to investigate its degradation activity and metabolic responses to PU and PE and showed L. iranensis could colonise and significantly degrade PU (11.05 % weight loss), showcasing its impressive capabilities but having minimal effect on commercial PE (0.53 %) in 60 days. Metabolomic analysis identified 51 and 63 differentially expressed metabolites in response to PU and PE, respectively, with 30 common metabolites. Pathways for enzyme production, metal ion chelation, nutrient uptake, and Krebs cycle intermediates were activated in the fungus exposed to PU, likely contributing to its enhanced hydrolysis of PU. In contrast, pathways for stress response, antioxidant activity, signal transduction, and membrane integrity were predominant for PE, likely due to its limited degradability. Increased metabolism of compounds like 2-oxoarginine, proline, L-valine and 1-methyl histidine, which serve as carbon and nitrogen sources, osmoprotectants, and derivatives for fungal enzymes were observed in both treatments, thus supporting nutrient and enzyme synthesis. Hydrolytic and oxidative enzymes, mainly esterase, lipase, cutinase, laccase, and peroxidase, were implicated in PU and PE biodegradation, with PU showing more robust degradation potential. This study provides useful insights into the metabolic pathways that facilitate plastic degradation in L. iranensis, identifying potential fungal metabolites and enzymes that could be harnessed for bioremediation efforts, thereby advancing the development of fungal-based solutions for plastic waste reduction.