Synergistic growth of Bacillus and Pseudomonas and its degradation potential on pretreated polypropylene

ABSTRACTThis study investigated biodegradation of physically pretreated polypropylene (PP) by using two different combinations of microorganisms, namely, Bacillus flexus + Pseudomonas azotoformans(B1) and B. flexus + B. subtilis(B2), for a period of 12 months. The growth rate of (B1) was found to be high throughout the study period, and reached a maximum of 1 × 1014 colony-forming units (CFU)/mL. At the end of the experiment, the polymers become hydrophilic. Carbonyl indices showed that ultraviolet (UV)-treated polymers started degrading faster than the thermally treated PP. The thermogravimetric analysis also revealed that UV-treated PP exposed to the B. flexus + P. azotoformans combination for 1 year exhibited maximum degradation (22.7%). The gravimetric weight loss method showed 1.95% weight loss followed by 1.45% with B. flexus + B. subtilis. The changes in the carbonyl indices of the polymer through Fourier-transform infrared (FTIR) analysis also support the degradation.