Recent trends in microbial and enzymatic plastic degradation: a solution for plastic pollution predicaments

Plastic pollution is an ever-escalating issue with detrimental effects on both the environment and human health. Plastic breaks down into smaller pieces, and depending on the size they are called macroplastics, microplastics (MPs), and nanoplastics (NPs). Some of these particles can easily enter the food chain causing toxicity to many plants and animals. The extensive use of synthetic polymers such as polyethylene (PE), polyvinyl chloride (PVC), polystyrene (PS), and polyethylene terephthalate (PET) poses substantial environmental concerns due to their degradation-resistant characteristics. One of the ways microorganisms address this issue is by producing enzymes. This review examines the recent advancements in enzymatic degradation of both commercial-grade and pure polymers, including the effectiveness of enzymes such as laccases, proteases, cutinases, PETase, and MHETase, and the governing mechanisms of degradation across various plastic categories. Bioinformatic tools such as multi-omics, molecular docking, and enzyme mining are particularly useful in identifying unconventional biocatalysts and plastic-degrading microbes in a culture-independent manner. Furthermore, techniques to enhance the catalytic efficiency of plastic degrading enzymes (PDEs) using modern approaches such as protein engineering, mutations, chimeric fusion, etc. have also been reviewed. This review accentuates the pivotal role of enzymatic and microbial degradation in mitigating plastic pollution, the associated challenges, and suitable prospects to achieve closed-loop plastic recycling in the future.