Microbial degradation of microplastics: Effectiveness, challenges, and sustainable solutions

Microplastics (MPs), defined as plastic particles ranging from 1 µm to 5 mm, have emerged as pervasive contaminants in both terrestrial and aquatic environments, posing significant ecological and human health risks. Their sources are broadly categorized as primary, such as microbeads, microfibres, paints and pharmaceutical additives, and secondary, which result from the degradation of larger plastic products. This growing concern of MPs led to development of different mitigation techniques but the recent advancements in microbial biodegradation present a promising approach to mitigating MPs pollution. Thus, microbial biodegradation could play a crucial role in developing sustainable solutions to tackle global MPs pollution. This review explores the potential of various microorganisms, including bacteria, fungi, and algae, in degrading MPs through enzymatic processes, thereby shortening the half-life of these pollutants. A detailed examination of the degradation mechanisms of commonly used polymers such as polyethylene, polystyrene, and polyvinyl chloride highlights the efficacy and limitations of microbial biodegradation. Despite the promising capabilities of certain strains, the overall weight loss rate of MPs remains quite low, typically ranging from 0 to 15%, necessitating further investigation into optimizing enzymatic activity and environmental conditions. Advancements in metagenomics and enzyme engineering offer pathways to enhance degradation efficiency, potentially achieving up to 90% degradation within 10 hrs under optimized conditions. This review underscores the need for comprehensive research to identify key microbial strains and enzymes involved, understand their degradation pathways, and investigate the influence of different environmental matrices on biodegradation processes.