Recent Advances in Plastic Waste Biodegradation: Microorganisms, Enzymes, Invertebrates, and Evidence Standards

The uncontrolled and rapidly increasing use of synthetic polymers has created persistent environmental contamination. Millions of tonnes of plastic waste accumulate annually, and fragmentation generates microplastics that threaten terrestrial and aquatic ecosystems and may affect human health. Biodegradation has therefore attracted attention as a complementary strategy for plastic-waste management. Reported biological agents include bacteria and fungi, their enzymes, and plastic-consuming invertebrates such as mealworms and waxworms. This review synthesizes evidence on microbial, enzymatic, and invertebrate-mediated degradation of common synthetic polymers and examines the physicochemical changes used to assess degradation, including changes in molecular weight, surface morphology, hydrophilicity, functional groups, and mineralization products. It also considers biodegradable polymers derived wholly or partly from renewable feedstocks as alternatives to conventional petroleum-based plastics. Emphasis is placed on the evidence required to demonstrate genuine biodegradation, because surface damage, biofilm formation, or mass loss alone can be misleading. Current research gaps, methodological limitations, and priorities for standardized, reproducible testing are discussed to support the development of credible biological approaches to plastic-waste reduction.