Soil Degradation of Solvent-Cast PHA Films Produced By Bacillus Tequilensis PWF Using Waste Polyethylene Terephthalate (PET)

Polyhydroxyalkanoate (PHA) aliphatic polymers however efficiently biodegradable, still pose a contradiction with the principles of green chemistry. Use of bacterial strains capable of degrading synthetic plastics for the production of biopolymers i.e., PHAs may aid in reduction of plastic pollution. Bacterial strains PWA; Bacillus subtilis (MH142143), PWF; Bacillus tequilensis (MH142145), and PWG; Bacillus safensis (MH142146) were grown on waste shredded PET and PET flakes. Highest bioconversion of PET to PHA was observed using PET flakes. Strain PWF produced 40.47 % (0.815 g/L) and 31.80 % (0.626 g/L) PHA using PET flakes and shredded PET at 48 h, respectively. Whereas highest PHA production (53.67 % PHA; 1.15 g/L) on glucose was obtained from 2.19 g/L CDW at 48 h. FT-IR analysis showed absorptions at known PHA marker bands at 1720.398 cm-1 in PHA sample of strain PWF. Polymer degradation in natural environment (20-week soil burial) was measured in terms of weight loss (decigrams; dg). PHA from Strain PWF showed up to 61 % degradation by weight i.e., from 1.0 dg to 0.391 dg. SEM analysis of degraded polymer films showed presence of cracks, crevices, bumps, and fractures. Bacterial and fungal colonization amidst crevices was also observed. This study provides a cost-and-time economic, green synthesis-based method for reliable repurposing of nondegradable plastic wastes. Focus of subsequent studies can be the role of ambient microbiota during polymer degradation and how it impacts the natural soil environment.