Frontiers in plastic biodegradation: unraveling the mechanisms and impacts of macro- and microplastic pollution.

The widespread accumulation of macro- and microplastics in terrestrial and marine environments has emerged as a pressing global challenge due to their persistence, ecotoxicological effects, and disruption of biogeochemical processes. Conventional plastic waste management strategies remain inadequate, thereby driving interest in biodegradation as a sustainable alternative. This review critically evaluates microbial, enzymatic, and physicochemical mechanisms involved in the degradation of commonly used polymers, including polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), and polystyrene (PS). Microorganisms such as Pseudomonas, Ideonella, and Aspergillus spp. have demonstrated promising degradation potential, mediated by enzymes such as PETase, cutinase, and laccase. The ecological implications of plastic fragmentation and its degradation byproducts on marine ecosystems, biodiversity, food webs, and human health are also highlighted, with particular attention to major plastic-emitting regions such as the Philippines, India, and China. Finally, the review discusses current limitations and future directions, including genetic engineering of plastic degraders, integration of biodegradation with circular bioeconomy frameworks, and the design of inherently biodegradable polymers. Addressing plastic pollution effectively will require an interdisciplinary strategy that integrates microbiology, materials science, and environmental policy.