Systematic optimization and characterization of bacterial depolymerization of poly(ethylene terephthalate) plastics

Biodepolymerization of poly(ethylene terephthalate) (PET) plastics using microorganisms has emerged as a promising and sustainable approach for mitigating pollution caused by PET waste. In this study, Glutamicibacter mysorens ASR14, a mesophilic bacterium isolated from Kodungaiyur dumpyard (Chennai, India), showed 27.6% PET biodepolymerization in terms of weight loss in 30 d. A customized screening of 20 trials was designed using JMP statistical software to evaluate the influence of various variables. Furthermore, a Central Composite Design (CCD) of Response Surface Methodology (RSM) was adopted and validated using four variables at five levels, with 25 trials, to correlate the relationship for enhanced PET biodepolymerization. A maximum PET weight loss of 75.6% was achieved in 60 d, representing a 2.73-fold improvement compared to that under unoptimized conditions. Enzymatic assays confirmed the involvement of esterase (5,690 U/mL) and lipase (962 U/mL) activities in accelerating the breakdown of PET. The analytical characterization techniques revealed significant surface erosion, reduction in crystallinity, and high yield of terephthalic acid (TPA), which also holds potential value for biorefinery applications. This work represents the first comprehensive report on process optimization for PET biodepolymerization using G. mysorens ASR14 as a whole-cell biocatalyst. The findings establish G. mysorens ASR14 as a promising candidate for developing scalable, green bioremediation strategies.