Screening and characterization of Bacillus sp. PE4 with polyethylene degradation capacity

Polyethylene (PE) is considered to be among the most extensively utilized plastics globally, and its extensive applications have led to significant environmental pollution. Therefore, finding a safe and efficient approach to degrade PE is crucial to mitigate its environmental impact. This study isolated five bacterial strains capable of degrading PE from agricultural soil covered with plastic mulch films. All strains were identified as Bacillus species, with Bacillus sp. PE4 demonstrating the highest degradation efficiency, as evidenced by a weight loss of 4.93% for PE films over 30 days. Scanning electron microscopy revealed cavities and cracks on the film surface after degradation by Bacillus sp. PE4. Culture conditions under pH 7.5, inoculum size 4.0%, and thermal pretreatment for PE samples significantly enhanced the degradation efficiency of Bacillus sp. PE4, and the weight loss rate reached up to 27.8% over 100 days, accompanied by a significant increase in extracellular peroxidase and polyphenol oxidase activities. This study established Bacillus sp. PE4 as an efficient PE-degrading bacterium, paving the way for investigating its degradation mechanisms and opening a new avenue for tackling PE pollution.IMPORTANCEPolyethylene (PE) has been widely utilized in various fields, including packaging materials, agricultural films, and daily necessities. However, PE is not easily decomposed in the natural environment, leading to the accumulation of its residues. To find the efficient microbial degrading strains for PE, PE-degrading bacterial strains were isolated and screened from agricultural soil containing residual plastic mulch in Zhejiang province, China. The obtained Bacillus sp. PE4, one of the isolated PE-degrading strains, showed good degradation ability, and many approaches, including process optimization, were conducted to improve its degradation efficiency. The findings would provide valuable insights for screening novel PE-degrading microbial strains and developing more efficient microbial-based PE degradation strategies.