Degradation of weathered crude oil (Escravos Light) by bacterial strains from hydrocarbons-polluted site

Abstract

Two hydrocarbon degrading Gram-negative bacteria isolated from hydrocarbon polluted power plant soil in Lagos, Nigeria, were studied for their degradation potentials on weathered crude oil (Escravos Blend). These bacteria isolates were identified as Enterobacter cloacae strain LG1 and Burkholderia cepacia strain LG2. The highest population density for LG1 was 2.07 x 107 cfu/ml, while for LG2 it was 1.63 x 107 cfu/ml. In the two cases slight but consistent pH drops to < 6.51 were observed. LG1 had a growth rate of 0.38 d-1 and doubling time 1.83 d. The corresponding values for LG2 during the first log phase were 0.58 d-1 and 1.19 d, respectively, while in the second log phase the values were 0.14 d-1 and 5.13 d Gas chromatographic analysis showed that chrysene was degraded by LG and LG2 by 92.91 and 80.25%, respectively, anthracene by 92.21 and 91.53%, respectively, and Benzo (b) fluoranthene was degraded by 77.19 and 98.41%, respectively. LG2 had a higher degradative capability of the polyaromatic fractions with 80.15% while LG I was lower at 52.33%. Statistical analysis showed that there was a significant difference (p < 0.05) in the degradation of various aromatic components of the oil by LG1 and LG2.