Biodegradation of polyvinyl chloride using vermibacteria under variable physicochemical conditions

Abstract

Plastic has a significant hazard to the environment, but its impact could be mitigated through degradation processes. Biodegradation of plastic wastes by using microorganisms is an environment-friendly method. In the current study, vermibacterial strains i.e. Bacillus mycoides, Bacillus megaterium, Bacillus mojavensis, Bacillus thuringiensis, and Bacillus paranthracis, were selected to evaluate the degrading impact on polyvinyl chloride (PVC) and tested under various physicochemical conditions such as pH (7, 5, 9), temperature (37 °C and 50 °C), carbon sources (Glucose and sucrose), and nitrogen sources (yeast extract and peptone). Liquid culture technique was used to investigate the chloride production and solid media experiment was employed for biodegradation of polyvinylchloride films. Bacillus mojavensis and Bacillus paranthracis showed maximum chloride production of 88.4 % and 87.8 % at pH 7 and 50 °C in the absence of carbon and nitrogen sources. On the other hand, Bacillus megaterium and Bacillus mojavensis showed maximum chloride production (91 % and 91.7 %) at pH 7 and 50 °C in the presence of glucose and yeast extract after 5 days of incubation while all vermibacteria indicated the highest chloride production at pH 9 and 50 °C in the presence of sucrose and yeast extract except Bacillus thuringiensis. Similarly, Bacillus mojavensis, Bacillus paranthracis, and Bacillus thuringiensis showed maximum chloride production in the presence of sucrose and peptone. Scanning electron microscopy was used to check the morphological changes of the PVC film after vermibacteria treatments and results revealed that vermibacteria attached to PVC films and validated the changes in surface topography. Fourier-transform infrared spectroscopy also revealed the changes in functional group intensity on both vermibacteria-treated PVC films compared to the control. It was concluded that plastic biodegradation via vermibacteria could be a potential source not only to eliminate plastic-based environmental issues but also holds the potential to significantly improve human health, reduce pollution, and support sustainable practices for a cleaner and healthier environment.