Study Of Bio-desulfurization Of DBT In Oil By Gordonia Sp.WQ-01

A strain WQ-01was isolated from polluted water of Dagang Oil-field and it iscapable of specifically desulfurizing DBT as its sulfur source. HPLC shows the strainWQ-01can remove sulfur from DBT, yielding2-HBP through “4S” pathway, bywhich breaks the C-S-bond but remains the C-C-bond so that it can greatly keep thecaloric value of fuel.According to the morphologic properties, taxonomic properties and the16SrRNAanalysis of the strain, we identified it as Gordonia, named Gordonia sp. WQ-01.Laser was employed to irradiate the cells of the strain WQ-01to obtain themutant with the higher ability to desulfurize DBT. The effect of He-Ne laserirradiation on the induction of biodesulfuring activity and surviving fraction of cellsof Gordonia sp. WQ-01was studied. With WQ-01and laser-induced mutation strainWQ-01A, we studied the effects of laser-induced mutation on desulfurization of theGordonia sp. WQ-01by checking temperature effect, the permeability of cell, theactivity of enzyme related to desulfurization, the sequences of genes coded enzymeand the structures of enzyme. Based on the above analysis, it can be draw theconclusion that the improved desulfurizing activity of the mutant Gordonia sp.WQ-01was due to the increased activity of the enzymes involved in the “4S” pathway.The essential reason is the change of the sequences of the genes coding desulfurizingenzymes, not the temperature effect or the change of permeability of cell.At last, immobilization of Gordonia sp. WQ-01A resting cells was studied. Theeffects of immobilization conditions on biodesulfurization were investigated.Microstructure of alginate gel beads was observed by SEM and the biodesulfurizationcharacteristics between immobilized cells and resting cells was compared in waterphase. The results showed that the optimum immobilization condition is: bacteria iscultivated at30℃for36hours after activation twice; the concentration of carrier,sodium alginate (SA), is4%(w/v) and the ratio of cells (g) to SA (mL) is1:20withthe3%(w/v)calcium chloride as the precipitator under4℃.Batch DBT biodesulfurization in the oil-water-immobilization system wasconducted. A mathematical model was developed to simulate the biodesulfurizationprocess, which took into account the internal and external mass transfer resistances of DBT and oxygen and the intrinsic kinetics of bacteria. The good agreement betweenthe model simulations and the experimental measurements of DBT concentrationprofiles validated the proposed model. Moreover, the time and radius courses of DBTand oxygen concentration profiles within the alginate gel beads were reasonablypredicted and analysed by the proposed model.