Genomic and proteomic insights into extracellular enzymes associated with polyethylene microplastics biodegradation by the native strain Fusarium oxysporum FOCIC01

Abstract

Plastic pollution represents a major environmental challenge, particularly due to the persistence of polyethylene microplastics in natural ecosystems. In this study, the biodegradation potential of the native fungal strain Fusarium oxysporum FOCIC01, isolated from polyethylene gas distribution pipelines in Colombia, was evaluated through an integrated genomic, proteomic, and experimental approach. A high-quality genome assembly revealed a diverse repertoire of extracellular carbohydrate-active enzymes (CAZymes), including auxiliary activity enzymes, carbohydrate esterases, glycoside hydrolases, glycosyltransferases, polysaccharide lyases, and carbohydrate-binding modules. Among these, enzymes previously associated with polymer degradation were identified, including laccases, peroxidases, monooxygenases, and cutinases. Biodegradation assays conducted over 30 days demonstrated extensive fungal colonization of low-density polyethylene (LDPE) microplastics. Scanning electron microscopy revealed structural alterations such as cracks, pits, and surface erosion, while matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry detected polymer fragmentation, including oligomeric compounds consistent with polyethylene glycol-like structures and lower molecular weight fragments. Fourier-transform infrared spectroscopy showed subtle changes in methylene-associated absorption bands, suggesting early-stage surface modifications of the polymer. Integration of genomic, proteomic, and analytical evidence enabled the proposal of a metabolic pathway involving extracellular oxidative and hydrolytic enzymes, progressive depolymerization, and assimilation of intermediate compounds into central metabolic pathways through β-oxidation. Additionally, the potential degradation of plastic additives highlights the metabolic versatility of the strain. These findings position F. oxysporum FOCIC01 as a promising candidate for biotechnological applications aimed at mitigating polyethylene microplastic pollution and provide new insights into fungal-mediated polymer biodegradation.