Degradation of low density polyethylene by Bacillus species

Since its invention, polyethylene (PE) has brought many conveniences to human production and life. In recent years, however, environmental pollution and threats to human health caused by insufficient PE recycling have attracted widespread attention. Biodegradation is a potential solution for preventing PE pollution. In this study, Bacillus subtilis and Bacillus licheniformis, which are widespread in the environment, were examined for their PE degradation abilities. Biodegradation of low-density polyethylene (LDPE) was assessed by weight loss, Fourier transform infrared spectroscopy (FTIR), and high performance liquid chromatography (HPLC) analyses. Weight losses of 3.49% and 2.83% were observed for samples exposed to strains B. subtilis ATCC6051 and B. licheniformis ATCC14580 for 30 days. Optical microscopy revealed obvious structural changes, such as cracks, pits, and roughness, on the surfaces of the microorganism-exposed LDPE sheets. Oxidation of the LDPE sheet surfaces was also demonstrated by the FTIR-based observation of carbon-unsaturated, -OH, -NO, -C=C, and -C-O bonds. These results support the notion that B. subtilis ATCC6051 and B. licheniformis ATCC14580 can degrade PE and could potentially be used as PE-biodegrading microorganisms. Further research is needed to examine potential relevant degradation mechanisms, such as those involving key enzymes.