Microplastic pollution in aquatic environments: a systematic review of bacterial degradation efficacy, mechanisms, and future pathways

The pervasive accumulation of microplastics (MPs) in aquatic ecosystems constitutes a critical environmental threat, necessitating sustainable remediation strategies. Bacterial degradation has emerged as a promising solution, yet a systematic synthesis of its efficacy, mechanisms, and practical feasibility is lacking. Following PRISMA guidelines, a comprehensive search of Scopus, Web of Science, and PubMed databases (2000–2025) was conducted, yielding 80 eligible studies out of 639 identified records. Qualitative thematic synthesis was employed to analyze the evidence. The analysis reveals a conserved consortium of bacteria primarily Pseudomonas , Bacillus , and Rhodococcus capable of colonizing the “plastisphere” and degrading major polymers through specific enzymatic pathways. Hydrolases (e.g., PETase) enable rapid depolymerization of hydrolysable polymers like PET, while oxidoreductases (e.g., alkane hydroxylases) slowly oxidize recalcitrant polyolefins (PE, PP). Degradation efficacy is highly polymer-dependent, with PET showing the most promise (up to 50% mass loss in days) compared to significantly slower PE/PP degradation (<12% over months). Key factors influencing kinetics include temperature, pH, nutrient availability, and the synergistic effects of microbial consortia within biofilms. However, translation to field applications faces formidable barriers, including ecological competition, scalability challenges, and difficulties in monitoring efficacy in open environments. Critical knowledge gaps persist regarding long-term environmental fate, ecotoxicity of degradation by-products, and the rational design of effective microbial consortia. While bacterial degradation presents a scientifically validated mechanism for MP bioremediation, its near-term application is most viable in controlled, ex-situ systems like enzymatic recycling of PET. For in-situ remediation, a tailored, hybrid bioaugmentation-biosimulation approach is recommended, though significant research and policy hurdles remain. Future work must prioritize standardized methods, long-term ecological studies, and integrated risk assessment to translate this promising biotechnology into practical environmental solutions.