Enhancement of phase separation by the addition of de-emulsifiers to three-phase (diesel oil/biocatalyst/aqueous phase) emulsion in diesel biodesulfurization

Abstract

Ethanol, added as a de-emulsifier to separate oil and biocatalyst (or bacterial cells) from a three-phase (oil/biocatalyst/aqueous phase) emulsion, formed in diesel biodesulfurization employing Gordonia nitida, improved oil recovery by centrifugation from about 50% in its absence to almost 100% at 3% (v/v). The biocatalyst recovered with ethanol addition showed similar specific growth rates (0.03 h⁻¹) and dibenzothiophene desulfurization rates (6–7.2 mol l⁻¹ h⁻¹) to those (0.03 h⁻¹ and 7.1 mol l⁻¹, respectively) of the biocatalyst recovered with no ethanol addition. The desulfurization activity significantly increased as the number of the repeated recovery and reuse of the biocatalyst.