Statistical optimization of process variables for improved poly(ethylene terephthalate) plastic degradation by a rhizospheric bacterial consortium

The current study focuses on the poly(ethylene terephthalate) (PET) powder degradation potential of a rhizobacterial consortium screened from the rhizosphere of plants growing at plastic-polluted sites. The rhizobacterial consortium were screened and ability of PET powder degradation was studied up to 18 days. For observing the efficiency of degradation, all three rhizobacterial strains with highest percentage of degradation were combined to formulate the consortium. The Response Surface Methodology (RSM) was used to optimize the process variables. The combinations demonstrating highest weight reduction percentage for PET were selected for further degradation studies. The changes in the structure and surfaces that occurred after biodegradation on the plastic were observed through SEM and FTIR analysis. The obtained results showed the disappearance and elongation of the peak, signifying that the rhizobacterial consortium could modify the PET plastic. The weight reduction percentage of PET powder (300 µm) was 71.12% at optimized conditions (29.8 °C, 7.02 pH and 1 g/L carbon source). The mathematical model developed through RSM is found to be significant (P < 0.05), and optimization and validation experiments were also well correlated for the process.