Screening Of Dibenzothiophene-degrading Strain And Its Desulfuration Feature

Sulfur is characteristically the most abundant element in petroleum except carbon and hydrogen. Organic sulfur compounds in fossil fuels have been the major cause of worldwide environmental problems including acid rain and air pollution.With the increasing demands for energy and more stringent environmental policies,deep desulfurization of petroleum is becoming more and more taken seriously. The conventional hydrodesulfurization technology at high temperature and pressure can’t remove some complex heterocyclic sulfur compounds, however biological desulfurization is analternative method of treating them with low cost and mild reaction conditions. Thus we consider DBT as the sulfur model compound for biodesulfurization to study desulfurization characteristics of microbial strains.Specific desulfurization Bacterium HPJ was selected utilized DBT as a sole source of sulfur. After the morphologic properties, taxonomic properties and the16 Sr RNA analysis were compared, the results showed that the 16 Sr RNA analysis of strain HPJ is 98% homologous to R.qingshengii and R.sp.Cm LB13 registered in Genebank. Therefore strain HPJ belongs to Rhodococcus erythropolis which was determined preliminarily.The influence of conditions and carbon-nitrogen source on growth and desulphurization with strain HPJ by single-factor and orthogonal experiment methods were studied. The optimal conditions were found such as p H7.2, temperature 30~35℃,inoculated volume 2%. Acid production decreased p H of culture medium during growth of strain HPJ, which had effect s on desulfurization enzyme activity. The value of p H need to be controlled nearly 7.2 to make strains always living in favorable environment in culture. Strain HPJ can grow utilizing a variety of carbon and nitrogen sources, but organic nitrogen source prevent them desulfurization. So the best carbon and nitrate source of growth and desulfurization are glucose and ammonium chloride,whose concentration in culture is 10g/L and 2g/L. DBT can be completely degraded in96 h when the initial concentration was 0.2mmol/L and 0.4mmol/L under the optimal conditions. Haldane type substrate inhibit model was used to simulate the cell growth on DBT and the kinetic parameters were: μmax=1.630, Ks=1.049, Ki=0.072(R2=0.933).The experimental data fitted close to the fitted curve.Metabolites produced by DBT desulfurization of strain HPJ were detected by GCMS. That is basically 4S desulfurization metabolic pathway. The effects of thedesulfurization metabolites SO42- and 2-HBP on the growth and desulfurization of strain HPJ were studied. Strain HPJ are more likely to use sulfate as sulfur source than DBT. The desulfurization enzyme of DBT were hindered once the concentration of SO42-was above 0.2mmol/L. What’s more, the growth and desulfurization of strain HPJ were both inhibited by higher concentration of 2-HBP.The desulfurization ability of strain HPJ to other sulphur-containing organic respectively in the oil phase and water phase were investigated. It were found that whatever in the oil phase or water phase, the desulfurization efficiency to TH、BTH and DPS were better. So the range of desulfurization substrates is wide and it should be useful for the practical microbial desulfurization of fossil fuels.