Biodegradation of hydrocarbon by bacteria isolated from crude oil contaminated soil

Crude oil contaminated soil has posed major environmental problems in recent years. Hence, this work was designed to evaluate the potential of microorganisms isolated from crude oil contaminate soil, to degrade hydrocarbon. Samples of crude oil contaminated soil were collected from Warri Refining and petrochemical Company in Delta State and characterized using standard microbiological procedure. Isolates were assayed for their ability to degrade hydrocarbon using mineral salt medium containing crude oil as source of carbon. Soil samples were treated as follows: A – untreated/control soil plus sterile crude oil, B – untreated soil plus crude oil and carrier, C – treated soil (with Enterobacter aerogenes) plus crude oil and carrier, D – treated soil (with Actinomycetes) plus crude oil and carrier, E – treated soil (with Enterobacter aerogenes and Actinomycetes) plus crude oil and carrier. After 14 days treatment, A had no growth while B, C, D and E had bacterial count of 2.6 x104 cfu/g, 7.68x1011, 1.42x1012 and 1.96x102 cfu/g respectively. At the end of 28 days period, A, B, C, D and E had count of 1.2 x 103cfu/g, 5.22 x 1011cfu/g, 9.30 x 1014cfu/g, 1.79 x1017cfu/g and 2.52 x.1019 cfu/g respectively. Serratia marcescens, Actinomycetes and Enterobacter aerogenes showed crude oil reduction of 44.3 %, 79.26 % and 61.69 % respectively. The results showed that Actinomycetes had the highest reduction rate of hydrocarbon content of soil more than other bacterial isolates.