Oxidation Characteristics And Main Metabolic Pathways Of Aquatic Blackening S^2- By Stenotrophomonas Sp.sp3

In April 2015,China issued the Action Plan for Water Pollution Prevention and Control,which put forward the goal of phased regulation of urban black-stinking water bodies.Among them,eliminating the"blackening"of water body is one of the main tasks of the treatment for black-stinking water body.Microbial method has been widely used in the treatment of black-stinking water because of its simple operation and no secondary pollution.In view of the key blackening pollutant S^2-,the preparation of efficient microbial agents can reduce the concentration of S^2-,thus reducing the production of metal sulfides such as FeS and MnS,and eliminating the phenomenon of"blackening"in black-stinking water,which has become one of the effective ways to treat black-stinking water.Sulfur oxidizing bacteria can completely oxidize low-valent reducing sulfides such as S^2-or S⁰ to SO₄^2-or partially to higher-valent sulfides.A strain of highly efficient sulfur oxidizing bacteria,Stenotrophomonas sp.sp3,has been screened from black-stinking water in our research group,and the sulfur oxidizing gene of Stenotrophomonas sp.sp3 has been studied.By investigating the effects of temperature,initial pH,initial glucose concentration and initial bacterial concentration on the growth of Stenotrophomonas sp.sp3 and the oxidation of S^2-,the conditions of S^2-oxidation by Stenotrophomonas sp.sp3 were optimized,the oxidation process of S^2-was analyzed,and the main metabolic pathways of Stenotrophomonas sp.sp3 for bio-oxidation of inorganic sulfur were studied by transcriptome sequencing technology.Response surface methodology was used to optimize the preparation conditions of immobilized Stenotrophomonas sp.sp3.The main results are as follows:?1?The optimum conditions of S^2-oxidation by Stenotrophomonas sp.sp3 were obtained by single factor experiment.The optimum conditions were as follows:reaction temperature 25?,initial pH 7.0,initial glucose concentration 0.25%,initial bacterial concentration 1.00 g/L.Under these optimum conditions,the oxidation rate of S^2-in the artificial wastewater can reach 86.6%after 60 hours of reaction by Stenotrophomonas sp.sp3.?2?The transcriptome study of Stenotrophomonas sp.sp3 in the oxidation of S^2-indicated that the expression levels of hdrA gene,cysIJ gene and cybB gene increased significantly at 1¹8h,mainly regulating the oxidation of S^2-to S⁰ and SO₃^2-.At 18³0 h,the expression levels of tst gene,sbp gene and sox gene cluster increased significantly,mainly affecting the differentiation reaction of S₂O₃^2-and the production of SO₄^2-.At the last 30⁶0 hours,the expression level of sox gene cluster regulating SO₄^2-production was higher,and the concentration of SO₄^2-increased steadily to 9.28 mg/L.?3?Stenotrophomonas sp.sp3 has only paracoccus sulfur oxidation?PSO?pathway as the main oxidative metabolic pathway for S^2-.In this pathway,some of the substrates S^2-were oxidized to S⁰ by sulfide:quinone oxidoreductase?SQR?pathway,while others are oxidized directly to SO₃^2-by sulfite reductase?SRN?pathway.S⁰ and SO₃^2-generated during oxidation can spontaneously react to form S₂O₃^2-,while S₂O₃^2-can release SO₃^2-and S⁰through disproportionation by thiosulfate sulfurtransferase?TST?pathway.SO₃^2-is further oxidized under the regulation of sox gene cluster to SO₄^2-.?4?The immobilization conditions of Stenotrophomonas sp.sp3 were optimized by response surface methodology.The results showed that the optimal combination of fixed adsorption pH,adsorption time,inoculation amount and carrier dosage was 8.14,37.35 h,6.02%and 0.98 g.Under these optimum conditions,the oxidation rate of S^2-in black-stinking water can reach 2.4%.