Enzymatic depolymerization of polyethylene terephthalate by Glutamicibacter mysorens ASR 14: Kinetics and mechanisms

Polyethylene terephthalate (PET) is one of the most widely used plastics and poses risk to ecosystems and human health. In this study, incubation experiments were performed to examine the degradation of bottle-grade PET by Glutamicibacter mysorens ASR 14, a bacterium isolated from landfill soil. The microbial degradation resulted in a 31.7 % weight loss after 180 days of treatment, with a half-life of 326.8 days and a 20.2 % reduction in the density of the treated PET. Sequential surface erosion from microcracks occurred from day 30 to extensive porosity by day 180, while terephthalic acid (TPA), the aromatic monomer of PET, increased from 0.437 mM on day 30 to 0.456 mM on day 60 and then decreased to 0.208 mM on day 180. Enzyme-catalyzed oxidative reactions resulted in PET degradation, with extracellular hydrolytic activities detected using p-nitrophenyl ester substrates. These enzymes not only had the ability to depolymerize semi-crystalline PET film but were also capable of metabolizing the residual polymer. This study highlights that G. mysorens ASR 14 is a promising candidate for biotechnological applications in PET waste management, aligning with the UN Sustainable Development Goals (SDGs) 12 (Responsible Consumption and Production), SDG 14 (Life Below Water) and SDG 15 (Life on Land).