Bioremediation of soils from oil spill impacted sites using bioaugmentation with biosurfactants producing, native, free-living nitrogen fixing bacteria

Oil spills are the most common source of environmental damage in areas with oil extraction activities. Bioaugmentation is a bioremediation technology that involves increasing microbiotas that can remove contaminant compounds from soils or water. This can be achieved by supplying exogenous microorganisms or by increasing the abundance of native microorganisms able to remove the contaminants. As biosurfactants enhance the solubility and bioavailability of hydrophobic compounds, the addition of native bacteria that produce biosurfactants may improve the rates of hydrocarbons biodegradation at oil spill impacted sites. The objective of this study was to investigate the effectiveness of using the bioaugmentation of native, free-living nitrogen fixing bacteria (NFB) that are able to remove hydrocarbons and produce biosurfactant compounds, to bioremediate soils at long term oil spill impacted sites containing total hydrocarbon (TH) levels of 120 000 ppm. For this study, two NFB that produce biosurfactants were selected from a group of 24 previously isolated from a long-term oil spill impacted site. After 16 months of bioaugmentation, the hydrocarbons removal reached 80%. The NFB count increased from 13×10⁴ colony-forming units (CFU) to 2×10⁹ CFU, and the total bacterial population increased from 5×10⁴ CFU to 22×10¹¹ CFU. According to literature, this is the first bioaugmentation study using native NFB biosurfactant producers to bioremediate soils from aged oil spill impacted sites. As such, these results demonstrate the potential of this bioaugmentation strategy for the bioremediation of oil spill impacted sites, especially those low in nitrogen.