A comprehensive review on microbial degradation of polyethylene plastics: ecotoxicity, deterioration process, recurrent intermediates and key enzymes involved.

Plastic contamination is a universal threat that affects the flora and fauna in the environment. This review focuses on biodegradation of polyethylene (PE). PE is a widely used plastic in food packaging, agricultural materials (mulch films) and disposable single-use plastic bags owing to its durability and cost-effectiveness. Being a hydrophobic, recalcitrant and persistent polymer, PE contaminates air, soil and water. The ecotoxicity, sources, fate and transport of PE and detection techniques like micro-Fourier Transform Infrared Spectroscopy (micro-FTIR) are discussed. Considering the environmental impact, microbial degradation of PE by bacteria, fungi, and gut microbes of larvae supporting sustainability has been addressed. In particular, potential microbial enzymes (diguanylate cyclase, laccase, latex clearing protein, alkane monooxygenase, and lipase) involved in PE disintegration were elucidated based on the reviewed mechanisms and pathways. These pathways include oxidative, hydrolytic and peroxidative steps, which assist in degradation. This review details the ecotoxicity of PE, microbial PE degradation and their enzymatic degradation mechanisms that offer key knowledge in plastic remediation for future insights.