The Effects of Different Aquatic Environments on the Rate of Polyethylene Biodegradation by Bacillus subtilis

(1) The Harker School, San Jose, California

The proliferation of plastics in consumer products results in the release of countless tons of plastic waste into the environment. Because of their chemical composition, plastics take hundreds of years to decompose. The world today is overrun by plastic waste that occupies landfills, makes its way into rivers and oceans, and overwhelms several ecosystems. Current methods of handling the waste namely recycling, landfills and incineration, are inadequate, ineffective or harmful. In recent years, scientists have discovered that certain bacteria can degrade and assimilate polyethylene. Microbes have been shown to have the ability to “eat” petroleum-based products like natural gas and light sweet crude oil from oil spills. The ability of bacteria to decompose certain types of plastic makes them a potential bioremediation option. Current research indicates that the bacterium Bacillus subtilis (B. subtilis) is proficient at degrading polyethylene utilizing a biosurfactant called surfactin. Studies show that the bacterium is versatile and can thrive in various environments, while surfactin can withstand high concentrations of salinity. The aim of this study is to test the ability of B. subtilis to degrade high-density and low-density polyethylene in aquatic environments. Rates of degradation were studied and compared across fresh water, brackish water, and ocean water samples. Degradation occurred across all samples, although it was the highest in fresh water and lowest in ocean water. This study supports the hypothesis that B. subtilis can potentially be used to help degrade plastic in aquatic environments.

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