Biodegradation of Crude Oil-Polluted Soil by Bacterial Isolates from Nigeria

Biodegradation of crude oil-polluted soils by bacterial isolates was carried out experimentally, to determine the ability of bacterial isolate to utilize and detoxify crude oil-polluted soils. Three soil samples were collected from crude oil-polluted sites of Owazangboko, Abia State, Aguleri-otu, Anambra State and Obi-igbo, Rivers State, Nigeria. Microbiological analysis and physico-chemical analysis were carried out in the Microbiology Laboratory of Chukwuemeka Odumegwu Ojukwu University, Uli. Physico-chemical analysis was carried out to determine the pH, moisture content, water holding capacity and total organic carbon of the soil samples. Microbiological analysis was carried out using serial dilution and spread plate methods to determine the total viable count, enumeration of hydrocarbon utilizing bacteria (HUB) was done using vapour phase method on mineral salt agar monitored at the wavelength of 600nm for 5 days. Adaptation test was carried out and monitored for 5 days using mineral salt broth containing 1ml and 2ml of sterile crude oil separately. A consortium of six effective isolates was taken for the biodegradation of the crude oil, which was monitored for 14 days. Biochemical tests were carried out on the isolates. Polymerase chain reaction (PCR) technique was used to confirm the identity of the isolates. Gas chromatographic flame ionization detector (GC-FID) was used to monitor the amount of the residual total petroleum hydrocarbon after the biodegradation study. Results of physic-chemical analysis showed; pH value of 3.7– 6.6, moisture content 1.6 – 4.4., water holding capacity 28.0 – 32.0., total organic carbon 3.4 – 7.1. Results of total viable count were in the range of 7.1×106 - 5.9×1010. Results of vapour phase method ranged from 0.16 – 0.66. Adaptability test revealed values, 0.11 – 0.54. Biochemical test results revealed Bacillus spp., Pseudomonas spp., Serratia spp., Micrococcus spp., Arthrobacter spp., Proteus spp., Shigella spp. PCR results gave the identity of the organisms to be Lysinibacillus spp. M2c, Serratia marcescens Mb4, Bacillus aerius TPM-23, Proteus mirabilis LS-3 and a new unidentified bacterium. TPH concentrations were in the range of 582.67 mg/l – 123.67 mg/l for Lysinibacillus spp. M2c and Serratia marcescens Mb4, 682.65 – 203.85 mg/l for Bacillus aerius TPM-23and 753.32 mg/l – 324.77 mg/l for Proteus mirabilis LS-3 and the new unidentified bacterium. The effect of bacterial growth across the days showed a p-value of 0.000 less than the α-value 0.01, this concluded that the growth of the bacteria across the days was