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

Abstract

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.

Biocatalytic desulfurization (BDS) of petrodiesel fuels

“…The production of DBT desulfurizing enzymes has been shown to be inhibited by inorganic sulfate (Alves et al, 2005;Gunam et al, 2006;Lee et al, 1995;Li et al, 1996;Mohebali et al, 2007a;Noda et al, 2002;Ohshiro et al, 1996b;Rhee et al, 1998;Wang & Krawiec, 1996). No radiolabelled sulfite was produced in incubations of sulfate-grown R. erythropolis IGTS8 resting cells with […”

“…The hydrophobic nature of several desulfurizing bacteria, e.g. R. erythropolis IGTS8 (Monticello, 2000) and Gordonia alkanivorans RIPI90A (Mohebali et al, 2007b), makes the resting cells adhere preferentially to the oil-water interface in oil-water systems. This property is advantageous, as the sulfur compounds are directly transferred from the oil into the cells, decreasing process mass transfer limitations.…”

An Indigenous Biosurfactant Producing Burkholderia cepacia with High Emulsification Potential towards Crude Oil

“…The mixture was mixed vigorously for 2 min and allowed to stand for 24 h at room temperature. The emulsification index (E 24 ) was calculated by dividing the measured height of the emulsion layer by the total height of the mixture and multiplying it by 100 [29,32,33].…”

Production of biosurfactants through biodesulfurization of spent engine oil – an experimental study

“…The reduction of sulfur in the spent engine oil is necessary to obtain ultra low sulfur diesel through pyrolysis. Biodesulfurization of spent oil using suitable microorganisms may serve as a promising process to eliminate the organosulfur compounds, as already studied in case of hydrodesulfurized diesel obtained from petroleum crude (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24). In case of diesel, dibenzothiophene (DBT) and its alkylated homologues are biodesulfurized by the action of microorganisms like Rhodococcus sp.…”

“…These biosurfactants are value-added products which can be used for different industrial purposes, mainly as drilling mud in advanced oil recovery from wells (25). Although a few research studies on the biodesulfurization of diesel have already been reported (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24). Only a few (26) have been reported on the biodesulfurization of spent engine oil are available in the literature.…”