Screening And Biodesulfurization Characteristics Of The Removal Of Inorganic Sulfur Microorganism

Coal has been one of important energys for human being, the demand of which increases sharplywith the increasing of population. Although coal has a certain economic value, the utilization of coal hasalso brought a series of environmental problems. SO2,one of coal combustion byproducts, is the"culprit" of acid rain. Sulfur in coal include organic sulfur and inorganic sulfur, wherein the inorganicsulfur exists in pyrite primarily. In order to remove inorganic sulfur coal, ferrous sulfate, pattern ofinorganic sulfur compounds, was used for the screening of inorganic sulfur removal strain in this work.Results were as follows:Modified Leathen medium was selected for strain screen. LI strain with strong Fe2+oxidationcapability was isolated from soil samples around the Nanshan coal mine in Shihezi, Initial Fe2+oxidation rate was about90%. Through colony and microscopic analysis, L1showed ferrooxidanscharacteristics. Bacterial16S rDNA of L1was amplied by PCR with total DNA as template. Sequenceof the amplified fragment was analyzed according to the NCBI Blast website sequence homologydetection. L1was identified and named as Thiobacillus ferrooxidans L1finally.Optimization of culture conditions showed that glycerol and (NH4)2SO4were favor to theoxidationof ferrous sulfate in Thiobacillus ferrooxidans L1.Basis on single factor experiments, response surfacecurve analysis (RSM, Response Surface Method) were modeled to further optimize the oxidation offerrous. Three significant factors were rotation speed, substrate concentration and incubationtemperature. Under the condition of rotaiton speed of185r/min, FeSO4concentration of2.58g/L, andculture temperature of35℃, oxidation rate was93.46%after optimization.APS and SIR reductase were separated and purified by ammonium sulfate saturation salting from T.ferrooxidans L1. Ammonium sulfate saturation concentrations were chosen as50%-65%, and60%-70%for APS and SIR reductase respectively. Enzyme activities were increased about10fold after salting.The optimal temperature and pH of APS reductase were34℃and3.2,and SIR reductase were36℃and3.0. CysH of APS reductase, rate-limiting enzyme of inorganic sulfur removal, was cloned and fragmentsize was about650bp, which was similar with reported gene fragments.