Stabilization of water/gas oil emulsions by desulfurizing cells of Gordonia alkanivorans RIPI90A.

It has been previously reported that resting-cells, non-proliferating cells, of Gordonia alkanivorans RIPI90A can convert dibenzothiophene (DBT) to 2-hydroxybiphenyl (2-HBP) via the 4S pathway in a biphasic system. The main goal of the current work was to study the behaviour of resting-cells of this strain in biphasic organic media. Resting-cells showed strong affinity for sulfurous organic substrates and were able to stabilize water/gas oil emulsions by attaching to the interface without decreasing the surface tension of their environment. This was consistent with the behaviour of the whole cells but not the surfactants, suggesting that microbial cell-mediated emulsification occurs. It was found that the emulsion-stabilizing activity of the resting-cells was influenced by the growth stage, but was not directly influenced by the metabolic activity of the resting-cells. This activity may be related to cell-surface hydrophobicity, which results from the unique chemical structure of the cell surface. In some biphasic biodesulfurization (BDS) bioreactors, emulsions are created without addition of any surfactant. Cell surface-mediated stabilization helps prolong the emulsions and therefore overcomes mass-transfer limitations in bioreactors. The simultaneous occurrence of emulsion-stabilizing and desulfurization activities of resting-cells was observed for what is believed to be the first time. The results suggest that this strain may have potential for the BDS of diesel oils.