Optimisation of Environmental Factors on Oil Degrading Bacteria Isolated from Coastal Water and Sediments in Sri Lanka

Abstract

Better understanding of the mechanisms of hydrocarbon degrading microorganisms and effect of some environmental factors is critical for the optimisation of the bioremediation processes. Temperature, pH, nitrate and phosphate are the major factors that influence there mediation process of bacterium. In the present study, optimisations some selected physico-chemical parameters (temperature, pH, nitrate and phosphate) were carried out on Bacillus cereus, Enterobacter sp. and Enterobacter ludwigii which were previously isolated as potential oil degraders. The bacteria showed maximum degradation of crude oil at 33^o C where the desirable pH was 8.6 for all the isolates except E. ludwigii (pH 5.4). A significant degradation (p < 0.05) of oil was detected by B. cereus (80% to 98%), Enterobacter sp. (73% to 90%) and E. ludwigii (70% to 83%) respectively with increasing of nitrate concentration from 0.1 to 2.5 ppm. Significant degradation of oil was not detected in the control and when bacteria were enriched with phosphate. Results of this study revealed that the bacterial remediation of oil is governed by nutritional status with special emphasis of nitrate enrichment in the environment. Thus, the results revealed that bacteria could be a useful tool to remove oil from the contaminated environment as eco-friendly, low cost application.