BIODEGRADABILITY OF POLYETHYLENE PLASTICS BY FUNGI ISOLATES FROM PLASTIC COMPOSTED WASTE SOIL

Biodegradation is a complete degradation process of a polymer through the activity of enzymes produced by microorganisms. The biodegradation process of plastic wastes is the breakdown of complex polymers into simpler oligomers and monomers. The study investigated the biodegradation of low-density polyethylene (LDPE) and high-density polyethylene (HDPE) plastics using fungal species isolated from plastic composted waste soil. Soil samples were collected from Oluku dumpsite and Sawmill sites in Benin City, Nigeria. The samples were subjected to physicochemical analysis to provide baseline environmental characteristics. Fungal isolation was carried out using dilution and pour plate methods on Potato Destrose Agar (PDA). Fungal isolates were identified through cultural and microscopic characterization, followed by PCR sequencing using ITS gene markers. Electrophoresis confirmed successful amplification, and sequencing analysis using NCBI BLAST validated the identity of the fungal strains. The primary fungal isolated included Fusarium oxysporum, Aspergillus flavus and Aspergillus niger. Polyethylene sheets were pretreated by abiotic exposure to sunlight for up to 50 days to simulate natural weathering. The sheets were then cut into fragment and incubated with fungal isolated in mineral salt medium broth at 25oC for varying durations (10-50 days). Data on biodegradation potential were generated by monitoring percentage weight loss and optical density (OD 600).The result of the study revealed that abiotic exposure alone caused minimal weight loss, whereas fungal inoculation significantly enhanced degradation. LDPE exhibited greater degradation than HDPE, consistent with its lower crystallinity and simpler structure. Individual isolates and consortium all had equal degradative activity, meaning any isolate can be used for degradation because there was no significant difference between them. These findings highlight microbial degradation as an eco-friendly strategy for plastic waste management, with scope for further optimization of environmental conditions and fungal consortia to enhance efficiency