Study of Hydrocarbon degraders and Metal Bioremediation

Abstract

Due to incomplete decomposition of pollutants and high cost of operation there is a need for the better methods of pollution control. The aim of present study was to screen hydrocarbon emulsifying and degrading bacteria from oil contaminated soils and to detect their efficiency for heavy metal bioremediation. Ninteen different isolates were obtained from soils of ten oil polluted areas in and around Navi Mumbai using Bushnell and Hass broth as selective medium with engine oil. The oil degradative capacity of these isolates was evaluated using Emulsification index, Gravimetric analysis and Gas Chromatography (with Mass Spectrometer). The oil emulsification index was found to be in the range of 3 to 54% whereas oil degradative capacity was between 10 to 41%. GC-MS study showed the conversion of Heneicosane to hexadecane indicating that the oil is partially degraded by the organism. The isolates were further screened for exopolysaccharide (EPS) production. Culture 1 was selected based on the EPS production. EPS optimization study for culture 1 showed emulsification index and EPS production to be 68% and 520mg/ml respectively. Biochemical tests and 16SRNA sequencing confirmed that the isolate was Bacillus cereus(NCBI Accession no KX346898). The Fourier Transform Infrared Spectroscopy study indicated the presence of polysaccharides with carboxyl group and the absence of proteins. Scanning Electron Microscopy was also performed to confirm the cell morphology and presence of EPS. newlineThe isolated culture was used for heavy metal (copper and cadmium) bioremediation. With 88% metal sorption total contact time of 90 min was required for 100 ppm copper (pH 5) sorption whereas 180 min was required for 30 ppm cadmium (pH 7). Equilibrium adsorption experiments were carried out and the experimental data fits both Langmuir and Freundlich isotherm. The surface adsorption of metals was confirmed using SEM with EDS. newlineIn conclusion, the present study shows that Bacillus cereus strain isolated from oil contaminated soil can be effective