Hydrocarbon Degradation by Free-Living Nitrogen-Fixing Bacteria
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Free-living nitrogen-fixing bacteria that could utilize crude oil as sole carbon and energy source were isolated from agricultural soil samples. Four isolates identified as Paenibacillus lautus, Brevibacillus agri, Bacillus sp. and Paenibacillus polymyxa with the highest capability to utilize the substrate were selected for further studies. The isolates degraded crude oil significantly, achieving a percentage degradtion of 97.97% for Paenibacillus polymyxa, 97.00% for Bacillus sp., 95.54% for Brevibacillus agri and 94.13% for Paenibacillus lautus with corresponding increases in bacterial populations after 21 days of incubation. A loss of 10.74% crude oil was obtained in the control medium. The isolates were able to utilize n-hexadecane, diesel, n-dodecane, kerosene and crude oil, but none of the organisms could utilize phenol. In bioremediation experiments with soil microcosms polluted with crude oil over a 60-day period, hydrocarbon degradation of 92.72%, 90.6%, 89.25%, 89.92%, 92.26% and 23.19% was recorded in soils seeded with Brevibacillus agri, Paenibacillus lautus, Bacillus sp., Paenibacillus polymyxa, a consortium of the isolates and the non- bioaugmented control soil respectively. At 0.05 (95%) level of significance, there was a significant difference in the level of crude oil degradation between the bioaugmented soils and non-bioaugmented control soil. Cowpea seedlings grown on the bioaugmented soils had better growth in terms of percentage germination and stem height when compared with those grown on the polluted non-bioaugmented control soil.
Hydrocarbon, Crude Oil, , Bacteria, Soil
Omotayo, A. E, Egbomeade,L.O etal (2013) Hydrocarbon Degradation by Free-Living Nitrogen-Fixing Bacteria