Bio-degradation of polyethylene waste by simultaneous use of two bacteria: Bacillus licheniformis for production of bio-surfactant and Lysinibacillus fusiformis for bio-degradation†
A unique method of biodegradation of commercial polyethylene by using simultaneously a bio-surfactant produced by Bacillus licheniformis and Lysinibacillus bacterium in various combinations was investigated in this study. Bio-surfactant produced by B. licheniformis did not have any anti-adhesive property for bio-film formation unlike other types of bio-surfactant produced by other strains of the same bacterium. It was also observed that the lower the surface tension, the higher is the level of oxidation of polyethylene. Lysinibacillus was able to form a bio-film on the control polyethylene without any pre-oxidation step and simultaneously oxidize the polyethylene. Polyethylene samples which were treated with Lysinibacillus along with bio-surfactant showed weight loss. A maximum weight loss of 2.97 ± 0.05% was achieved in the case of polyethylene treated with Lysinibacillus for 1 month, then treated with bio-surfactant for 1 month, followed by treatment with Lysinibacillus for another 1 month. Polyethylene is biodegraded via conversion of carbonyl groups into unsaturated hydrocarbon by both bio-surfactant and Lysinibacillus bacterium. In GC-MS analysis, partial oxidation of anti-oxidant used in commercial polyethylene was also observed. So, our present method of biodegradation by simultaneous use of two bacteria is very environmentally friendly as well as very efficient.