Bacterial degradation of polyethylene and polypropylene microplastics in a mangrove ecosystem

Microplastics (MPs) contamination presents a major environmental challenge, with accumulation of thousands of tons of MPs in ecosystems worldwide posing significant risks to human health and biodiversity. Identifying bacteria capable of degrading MPs offers a promising long-term solution to this issue. While several bacterial strains have demonstrated varying degrees of plastic degradation, the mechanisms underlying these processes remain poorly understood. In this study, 16S rDNA analysis was used to screen ten bacterial strains isolated from mangrove water samples for their potential to degrade MPs. Among these, Bacillus cereus strain ZRY and Pseudochrobactrum saccharolyticum strain ZRY emerged as the most effective candidates. The degradation of polyethylene (PE) and polypropylene (PP) was monitored through weight loss measurements over a 60-day incubation period. B. cereus strain ZRY achieved weight losses of 1.1% for PE and 1.0% for PP, while P. saccharolyticum strain ZRY recorded losses of 0.6% for PE and 0.4% for PP. Morphological and structural changes during degradation were analyzed using scanning electron microscopy, Fourier transform infrared spectroscopy, and atomic force microscopy, which also identified key enzymes produced by both bacterial strains that facilitate the degradation of MPs. Additionally, the effect of pH, salt concentrations, inorganic ions, and incubation duration on degradation efficiency were evaluated. Our findings demonstrate the potential of these bacterial strains for MPs degradation, underscoring their potential for future applications in addressing MP pollution. This research lays the foundation for optimizing conditions to enhance bioremediation efforts utilizing these microbial candidates.