Bacterial Utilization of Petroleum in Liquid and Simulated Soil Environments

Abstract

Ten bacterial isolates designated S1 to S10 were obtained from hydrocarbon. Polluted soils in Nsukka and studied for their hydrocarbonoclastic potentials. After screening for hydrocarbon utilizing capability, isolates S2 and S8, identified as Bacillus subtilis and Pseudomonas aeruginosa respectively, were selected for the study owing to their impressive utilization of crude oil as sole carbon source. Hydrocarbon utilization in liquid medium as assessed by the parameters of optical density (OD600), surface tension and pH showed engine oil as the worst substrate for the growth of the two isolates. S2 grew best on kerosene (maximum OD600 = 1.56). Optical density increased progressively with a concomitant fall in medium pH and surface tension for the two isolates during the 96h-experiment. A simulated bioremediation study was conducted using soil samples dispensed in 50.0g weights into 250ml conical flasks and contaminated with different levels (2.5%, 5.0%, 7.5% or 10.0%v/w) of Bonny light crude oil. A saturated solution of NPK (15:15:15) compound fertilizer was added at the ratio of crude oil to NPK of 10.0:1.0 and each flask inoculated with 1.0ml of S8 isolate containing 3x108 cells. Microbial utilization of the oil in the soil as assessed by the weight of extracted residual oil indicated that the extents of oil removal in the stimulated and/or bioaugmented soils were significantly high in relation to unsupplemented and uninoculated controls. Keywords: Bacterial utilization, Petroleum in liquid, Petroleum in soil, EnvironmentsBio-Research Vol. 6 (2) 2008: pp. 375-379