Comprehensive approaches in the biodegradation of microplastics: a review of mechanisms, applications, and challenges

The growing accumulation of microplastics (MPs) in the environment highlights the urgent need for greener, more scalable treatment options compared to traditional physicochemical methods. In this review, we summarize progress in the microbial breakdown and enzymatic depolymerization of major plastic types, mapping out the distinct biochemical degradation routes for polyolefins, polystyrene, polyvinyl chloride, and polyesters. To clarify how these processes are validated experimentally, we detail the key analytical tools used to confirm MP biodegradation. We also evaluate the practical engineering limitations that currently prevent these technologies from being deployed at an industrial scale. Key hurdles discussed include short hydraulic retention times in standard wastewater treatment plants, interference from complex pollutants in real-world matrices, and the poor kinetic rates of enzymes when applied at economically realistic concentrations. To tackle these scalability issues, we explore several promising solutions, including advanced chemo-physical pretreatments and the genetic engineering of microbes for upcycling plastics into valuable biochemicals. Ultimately, these advances in biotechnology lay the groundwork for integrating biological plastic degradation into broader, closed-loop waste management systems, offering a practical route to achieving a true circular economy.