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Effects of nutritional and physicochemical parameters on the production of biosurfactants by Bacillus subtilis RI4914 were evaluated. Effects of three different concentrations of NH₄NO₃ and/or yeast extract were tested. The treatment with 2.0 g l⁻¹ of NH₄NO₃ without yeast extract resulted in the highest biosurfactant, organic acid, solvent and polymer concentrations, and this cultivation condition was selected for the residual oil recovery experiments. The lower interfacial tension between crude oil and the culture supernatant was 0.07 mN/m and this result was achieved at NaCl concentrations up to 120 g l⁻¹. Culture fluid with 600 mg l⁻¹ biosurfactant and the polymer produced by the bacterium resulted in residual oil recoveries up to 88%. The attainment of low interfacial tensions and high oil recoveries with the biosurfactant concentrations used at high salinity and temperature indicated that B. subtilis RI4914 is an …