Degradation mechanisms and microbial remediation of micro- and nanoplastics: A comprehensive review.

Micro/nano plastics are emerging pollutants of global concerns due to their environmental persistence and potential ecological toxicity. We reviewed the generation pathways and microbial degradation mechanisms of micro/nano plastics, and assessed the application potential of microbial remediation. The abiotic degradation pro-cesses of micro/nano plastics mainly include photo-oxidation, thermal cracking, mechanical crushing, hydrolysis, and ozone degradation. Microorganisms gradually degrade high-molecular-weight polymers into oligomers and monomers by secreting depolymerases, and ultimately complete the biological mineralization process of micro/nano plastics. Microbial treatment technologies for the degradation of micro/nano plastics mainly include the use of high-tempera-ture resistant bacteria for ultra-high temperature composting and the genetic engineering of strains to synthesize enzymes capable of degrading micro/nano plastics. The bottlenecks for these technologies include low degradation efficiency, poor environmental adaptability, and difficulties in engineering scale-up. Future research should enhance experimental simulations of plastics under weathering or aging conditions, focus on exploring and utilizing microorganisms in extreme environments, and develop degradation enzyme systems based on synthetic biology for modification and optimization. Meanwhile, efforts should be made to promote their coupled application and large-scale verification with solid waste or sludge treatment processes, in order to provide technical support for the effective control of micro/nano plastic pollution.