Plastic Waste Treatment through Biological Pathways: Biodegradation of Polypropylene using Fungi and Isolated Microorganisms

Abstract

The global increase in synthetic petrochemical-based plastics has created serious environmental problems due to their resistance to degradation, leading to accumulation in landfills and oceans. Traditional recycling methods are insufficient to address this issue, necessitating innovative solutions. This study focuses on polypropylene (PP), a commonly used plastic with low recycling rates, aiming to explore a bio-based approach using fungi and newly isolated microorganisms. Fungi possess enzymes capable of breaking down and utilising carbon in polymers, offering a potential pathway for PP degradation. This research investigates previously untested fungi for PP degradation, elucidating the degradation mechanism and end-product formation to identify effective strategies. Specific microorganisms were selected, and pre-treatment strategies were employed to enhance enzymatic degradation of PP. Initial assessments focused on Aspergillus terreus and Engyodontium album, with UV and heat pre-treatments proving most effective, especially for PP film. Further analyses confirmed the degradation process, revealing chemical changes, reduced thermal stability, and alterations in surface morphology and composition. GC-MS analysis identified smaller biodegradable molecules as degradation products. Subsequent investigation led to the discovery of Aspergillus hiratsukae and Bacillus safensis, with improved degradation rates. A. hiratsukae showed significant potential for degrading heat-treated PP, with laccase enzyme activity assays indicating positive correlations between degradation parameters and enzyme activity. A comprehensive enzymatic pathway-driven mechanism for PP degradation was proposed, with future research directions including exploring uncharacterised enzymes and metabolites and establishing a complete PP degradation system. These efforts could significantly improve PP degradation and contribute to more sustainable plastic waste management practices.