Biodegradation of polyethylene by some bacteria Bacillus isolated from marine sediments in Khanh Hoa province, Vietnam

Abstract

Marine pollution caused by plastic waste is a worldwide concern. Of which, plastic waste originating from Polyethylene (PE) accounts for the highest proportion. This study focuses on evaluating the biodegradation ability of PE plastic of some bacteria belonging to the genus Bacillus isolated from marine sediments collected in Khanh Hoa province, Vietnam. Four bacterial strains including: C1.2, C3.4, C13.1, C17.1 reduced the weight of PE substrate after 45 days of culture (compared to the initial) by (%): 4.5 ± 0.058 d , 3.6 ± 0.100 c , 6.4 ± 0.100 b , 6.7 ± 0.058 a , respectively, completely equivalent to the results of determining laccase enzyme activity (U/ml): 974.0 ±3.61 d , 649.3±3.06 c , 791.7±1.53 b , 1,206.0±3.61 a . Scanning electron microscopy (SEM) images showed that bacteria created distinct cracks and dents on the surface of plastic pellets. The bacteria were then studied for a number of biological characteristics including colony and cell morphology, pH, temperature, salinity and PE substrate concentration limits, and identified through 16S rRNA gene sequencing. The four bacterial strains C1.2, C3.4, C13.1, C17.1 were closely related to species of the genus Bacillus including: Bacillus cereus, Bacillus amyloliquefaciens, Bacillus safensis, Bacillus megaterium. This study could be a premise for further studies on the treatment of saline PE plastic waste using marine bacteria.