Biodegradation of Polyethylene Fragments and Microbeads using Bacillus subtilis and Pseudomonas putida

Abstract:

More than five trillion plastic pieces are afloat in the world's oceans. Microplastics are less than five millimeters in length, problematic to remove using filters, and cause other ecological damages. Over the course of the several years, microplastics have increased in quantity in San Francisco Bay Water (SFEI, 2015). Studies have shown that there are multiple morphologies and polymers. The highest contributors to microplastic pollution in the Bay Area are polyethylene microbeads and fragments (SFEI, 2015). Previous studies have demonstrated that different species of bacteria and fungi can biodegrade the level of plastics. This investigation examined two species of non-pathogenic bacteria, Bacillus subtilis and Pseudomonas putida, and their impact on the degradation of polyethylene microbeads and fragments. 108 culture tubes were each filled with twenty milligrams of plastic that were submerged in two milliliters of nutrient broth with 100 microliters of bacteria. The cultured tubes were observed over the course of six weeks. The mass of the plastics was measured by wet-sieving, disinfecting, and drying plastics to weigh on an analytical balance. The results show significant plastic removal by both bacteria; however, P. putida was able to degrade an average of 13.0 milligrams of microbeads and an average of 2.3 milligrams of polyethylene fragments. B. subtilis removed an average of 8.0 milligrams of microbeads and an average of 1.7 milligrams of polyethylene fragments. This investigation has shown that the species of bacteria are able to reduce the level of microplastics, leading to safer ecosystems, and safer water and water supplies.