Microbial degradation of biodegradable plastics: Enzymes, pathways, and applications

AbstractThe rapid accumulation of plastic waste has become one of the most pressing environmental challenges of the twenty-first century. Conventional petroleum-based plastics are highly resistant to natural degradation, leading to long-term persistence in terrestrial and aquatic ecosystems. In response, biodegradable plastics have been developed as sustainable alternatives designed to undergo biological decomposition under appropriate environmental conditions. However, the actual biodegradation of these materials depends largely on microbial activity, enzymatic mechanisms, polymer characteristics, and surrounding environmental factors. Microorganisms, particularly bacteria and fungi, play a central role in the degradation process by secreting extracellular enzymes that depolymerize complex plastic polymers into low-molecular-weight compounds that can be assimilated into microbial metabolic pathways. This review provides a comprehensive synthesis of current knowledge on microbial degradation of biodegradable plastics, focusing on polymer classification, microbial diversity, enzymatic systems, metabolic pathways, and environmental and industrial applications. In addition, factors affecting degradation efficiency, limitations of existing biodegradable plastics, and future perspectives for improving biodegradation through biotechnology and circular bioeconomy strategies are critically discussed. A deeper understanding of microbial–plastic interactions is essential for improving biodegradable plastic performance and ensuring their genuine environmental sustainability.