Bacteria isolated from soil degrade low-density polyethylene for growth and polyhydroxyalkanoate synthesis.

Abstract

The low-density polyethylene (LDPE) used in food packaging contributes significantly to the environmental accumulation of microplastics and plastic waste. The aim of this study was to identify and characterize bacteria from plastic waste-contaminated soils that degrade LDPEs. After 16 weeks of degradation, the greatest percentage of LDPE weight loss were achieved with the bacterial consortium and Chitinophaga oryzae NT1-2 (21.97 ± 8.81 % and 16.14 ± 0.46 %, respectively). After bacteria were exposed to LDPE, numerous new functional groups, including aldehydes, ketones, and carboxylic acids, were identified by Fourier transform infrared spectroscopy (FTIR) analysis, while field emission scanning electron microscopy showed that the treated LDPE film surface had more grooves and cracks and was rougher than the control LDPE film surface. The highest total (1781.20 ± 42 U/min/mL) and specific (2.53 ± 0.06 U/min/mg protein) activities of alkane hydroxylase were detected in Bothriochloa intermedia MK2-8, whereas the total and specific alcohol dehydrogenase activities of the MK2-8 strain were 95.57 ± 4.16 U/min/mL and 0.14 ± 0.01 U/min/mg protein, respectively. In Pseudomonas aeruginosa CB1-2, the highest total and specific lipase activities were 10.00 ± 0.20 U/min/mL and 0.10 ± 0.03 U/min/mg protein, respectively. These LDPE-degrading bacteria produced polyhydroxyalkanoate (PHA), with C. oryzae NT1-2 giving the highest yield of 26.27 ± 8.40 mg PHA/g-glucose. Thus, bacteria isolated from plastic contaminated soil possess the capability to enzymatically degrade LDPE and convert it into the PHA biopolymer, thereby contributing to environmental sustainability and resource efficiency.