A facile biodegradation of polystyrene microplastic by <i>Bacillus subtilis</i>

Abstract The extensive application of polystyrene (PS) in the industry and the release of polystyrene microplastics (PS-MPs) in the environmental compartments has raised global concerns. The ability of microbes to utilize PS as a carbon source has been currently established. This study utilized Bacillus subtilis (ATCC 11774) to break down environmentally relevant sized PS-MPs (5 µm) with and without abiotic (thermal and UV radiations) pretreatment for a period of 4 weeks. The biodegradation rate was validated using UV–visible (UV–Vis) and Fourier transform infrared (FTIR) spectrophotometry, scanning electron microscopy coupled with EDX analysis. After 4 weeks, all inoculated PS-MP samples with and without pretreatment showed marked changes in the UV–vis spectra in comparison to the pristine PS-MPs. Additionally, FTIR spectra displayed surface modifications of functional groups in all inoculated samples linked to chain scission/oxidation were highlighted by a notable increase in the carbonyl index during biodegradation. SEM micrographs confirmed the marked fragility of the particles, and a probable oxidation degree was evaluated as an atomic O/C ratio that corroborates the biodegradative potential of B. subtilis . The core finding underscores that B. subtilis can grow on, alter, and use PS as a carbon source, either with or without abiotic pretreatment, emphasizing the role of biological pathways as a sustainable strategy for plastic waste management.