BIODEGRADATION OF POLYSTYRENE AND POLYPROPYLENE BY BACILLUS SUBTILIS SUBSP. SPIZIZENI: INFLUENCE OF TEMPERATURE AND GROWTH MEDIA

This study investigates the biodegradation of polystyrene (PS) and polypropylene (PP) using Bacillus subtilis subsp.spizizeni (ATCC 6633) under varied conditions, aiming to identify optimal parameters for microbial degradation.Polymeric samples were exposed to the bacterium in nutrient broth and agar at temperatures of 15C, 25C, and 35C, over a 56-day period, with periodic assessments of weight loss, structural changes, and surface morphology using scanning electron microscopy (SEM), Xray diffraction (XRD), and Fourier-transform infrared (FTIR) spectroscopy analyses.The results show that PS exhibited the highest degradation rates at 35C in broth, with weight loss peaking at 17% by the 6-week mark.PP displayed a more complex pattern, with significant degradation (up to 20.9%) also at 35C in broth but followed by a sharp decline, suggesting rapid initial degradation.FTIR and XRD analyses confirmed changes in chemical bonds and crystallinity, indicative of polymer breakdown.SEM images corroborated these findings, revealing increased surface roughness, cracking, and porosity postexposure.While both polymers degraded more effectively at elevated temperatures and in broth media, their overall resistance was also evident.This study reinforces the role of temperature and media in enhancing microbial degradation, demonstrating that B. subtilis can be utilized for bioremediation of nonbiodegradable plastics under specific conditions.However, further research into optimizing environmental factors and understanding microbial interactions at molecular levels is essential for developing efficient plastic waste management strategies.This work highlights B. subtilis' potential as a sustainable solution for mitigating plastic pollution, emphasizing the need for continued exploration into microbial biodegradation mechanisms.