Bio-transformation of untreated polyethylene sheet by Serratia marcescens with polyethylene-polymerase activity

Abstract

Polyethylene (PE) wastes is a threat to the ecosystem and microbes with variant enzymatic activities have been revealed as excellent degraders of PE wastes, however, knowledge of their physicochemical properties are essential to suggest an effective condition for the bio-degradation process. This study reveals the optimum working conditions for manganese peroxidase (MnP), laccase (Lac), and esterase produced by Serratia marcescens in polyethylene-based medium (PBM) incubated at pH 7.0, 37 ^oC, and 180 rpm for a month, and shows the biodegradation efficiency of Serratia marcescens on unmodified PE sheet. The activities of the enzymes, and their physicochemical properties were evaluated by spectrophotometric method, and the degradation activity of S. marcescens on unmodified polyethylene sheet was analyzed via scanning electron microscope (SEM) and fourier transform infrared spectrophotometer (FTIR). The result revealed maximum activities of MnP (6.88 U/mg) and esterase (5.62 U/mg) on day ten, while Lac activity (7.53 U/mg) was optimum on the eighth day of cultivation. The physicochemical study showed the enzymes were active and stable over a broad range of pH and temperature with optimum MnP activity at pH 7.0 and 60 °C, Lac activity at pH 5.0 and 50 ^oC, and esterase activity at pH 9.0 and 50 °C. Activities of MnP, Lac, and esterase were enhanced in the presence of Ca²⁺ and Mg²⁺ and chelated by EDTA. Pits and holes were displayed on the SEM profile of the S. marcescens-degraded PE sheet, while aromatic OH and carboxylic functional groups were seen on the FTIR spectra of the degraded PE sheet. In conclusion, this study shows S. marcescens has PE biodegradation potentials and produces thermostable activities of MnP, Lac, and esterase which can be adopted for industrial processes, and plastic biodegradation to achieve a green environment. © 2025 The Author(s)