Mohebali Ghasemali, Ball Andrew, Kaytash Ashk, Rasekh Behnam
Department of Petroleum Biotechnology, Biotechnology Research Center, Research Institute of Petroleum Industry, Tehran, Iran.
School of Biological Sciences, Flinders University of South Australia, Adelaide SA 5001, Australia.
Microbiology (Reading). 2007 May;153(Pt 5):1573-1581. doi: 10.1099/mic.0.2006/002543-0.
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.
先前已有报道称，戈登氏嗜烷菌RIPI90A的静息细胞（即非增殖细胞）能够在双相体系中通过4S途径将二苯并噻吩（DBT）转化为2-羟基联苯（2-HBP）。当前工作的主要目标是研究该菌株的静息细胞在双相有机介质中的行为。静息细胞对含硫有机底物表现出很强的亲和力，并且能够通过附着于界面来稳定水/瓦斯油乳液，而不会降低其周围环境的表面张力。这与完整细胞而非表面活性剂的行为一致，表明发生了微生物细胞介导的乳化作用。研究发现，静息细胞的乳液稳定活性受生长阶段的影响，但不受静息细胞代谢活性的直接影响。这种活性可能与细胞表面疏水性有关，而细胞表面疏水性源于细胞表面独特的化学结构。在一些双相生物脱硫（BDS）生物反应器中，无需添加任何表面活性剂就能形成乳液。细胞表面介导的稳定性有助于延长乳液的存在时间，从而克服生物反应器中的传质限制。据信首次观察到了静息细胞同时具有乳液稳定和脱硫活性。结果表明，该菌株在柴油的生物脱硫方面可能具有潜力。
