Biostimulation of the In Situ Production of Biosurfactants During the Bioremediation of Diesel Oil in Clayey Soil

Despite the continuous advances in the understanding of the mechanisms related to the bioremediation of soils contaminated with hydrocarbons, there are gaps regarding the assessment of the production of biosurfactants in situ. The objective of this work was to verify the effects of biostimulation (ammonium sulfate or whey) and bioaugmentation (B. methylotrophicus) on the in situ production of biosurfactants in soil, evaluated by the determination of surface tension, during the bioremediation of diesel oil. Biostimulation (ammonium sulfate/whey) achieved a total removal of the contaminant of 40%. The application of biostimulation and bioaugmentation together resulted in the removal of 61.64% of the contaminant, 28.04% higher in relation to natural attenuation. For bioaugmentation and biostimulated soils, a decrease in surface tension was observed, indicating the production of biosurfactants in the soil (44.33 mN/m), which was not observed in natural attenuation (61.49 mN/m) or control treatment (64.45 mN/m). In sterile soil, the sorption values were around 20%, showing that there were no different rates of adsorption of the contaminant. Thus, it was found that the joint application of biostimulation and bioaugmentation techniques helped in the production of biosurfactants directly in the soil and increased the biodegradation of diesel oil in the soil.