Degradation of polyethylene by Klebsiella pneumoniae Mk-1 isolated from soil

Abstract

The massive accumulation of polyethylene (PE) in the natural environment has caused persecution to the ecological environment. At present, the mechanism of microbial degradation of PE remains unclear, and the related enzymes for degrading PE need to be further explored. In this study, a strain of Klebsiella pneumoniae Mk-1 which can effectively degrade PE was obtained from the soil. The degradation performance of the strains was evaluated by weight loss rate, SEM, ATR/FTIR, WCA, and GPC. The key gene of PE degradation in the strain was further searched, which may be the laccase-like multi-copper oxidase gene. Then, the laccase-like multi-copper oxidase gene (KpMco) was successfully expressed in E.coli and its laccase activity was verified, which reached 85.19 U/L. The optimum temperature and pH of the enzyme are 45 °C and 4.0, respectively; it shows good stability at 30–40 °C and pH 4.5–5.5; Mn2+ and Cu2+ can activate the enzyme effect. After the enzyme was applied to the degradation of PE film, it was found that the laccase-like multi-copper oxidase did have a certain degradation effect on PE film. This study provides new strain and enzyme gene resources for the biodegradation of PE, thereby promoting the process of PE biodegradation.

Keywords

• Polyethylene
• Klebsiella pneumoniae Mk-1
• Laccase-like multi-copper oxidase
• Enzymatic properties
• Polyethylene degradation characterization