| With population growing and economy developing, a large number of sewage which included phosphorus and nitrogen richly have been discharged into water bodies. Eutrophication phenomenon has become one of the most serious global water quality problems. As we all know, large quantities of nutrient substances, such as phosphorus and nitrogen present in wastewater are the main cause of entrophication phenomenon. Simultaneously, the entrophication could lead to cyanobacteria eruption in massive water bodies. Of course, if the cyanobacteria could be utilized by biotechnology, the pollution caused by the algae will not only be eliminated, but also become the beneficial resource. If the cyanobacteria which include the sulfur-rich protein are fermented directly, large of H2S gas with certain corrosive effect will be produced. The purpose of this study is to isolate and screened strains for desulfurization. The cyanobacteria will be transformed with these special microorganisms, the sulfur of the cyanobacteria will eventually be converted to hydrogen sulfide. With sulfer released, the corrosive effect and pollution were decreased, which was helpful to enhance the proportion of hydrocarbons of the blue-green alga, and effectively to use cyhanobacteria as resource.In this study, the desulfurizing stain S4 was isolated from the soil of power plant in HuaiNan and active sludge of sewage treatment plant. It was identified by 16S rDNA sequence analysis. The result of sequence analysis and homology comparison suggested strain S4 was similary to Acinetobacter sp. in GenBank.Many factors which could affect the growth and the efficency of DBT removal of strain S4 were studied respectively in this paper. Studing showed that the maximum of biomass and DBT removal rate of strain S4 were obtained after 24h culture. The result showed that the optimum conditions of desulfurization of strain S4 was as follow: temperature 30℃, pH6-8. The optimum conditions of growth of the strain S4 was as follow:ethanol as carbon source, and the effects of nitrogen source on the growth of strain S4 was almost negative. By the Response Surface Analysis(RSA), it was easily to screen the main factors which had significant influences on the growth and the efficency of DBT removal of strain S4, and to determine the optimum levels of significant factors for the growth of strain S4. In this study, the Plackett-Burman design was carried out using the software Minitab15. The three significant factors of strain S4 were screened as follow:ethanol, beef-extract and KH2PO4·7H2O. Based on the Box-Behnken design and response surface analysis, the regression equation coefficients were calculated and the second-order polynomial model was established. The optimal values of three significant factors for stain S4 could be calculated as follows:ethanol 2.05g/L, beef-extract 3.0g/L, KH2PO4·7H2O 1.05g/L.Afterward, the Sulfate Reducing Bacteria (SRB), strain R1 was isolated and screened from anaerobic sludge and the sludge of ChaoHu Lake. It was identified by 16S rDNA sequence analysis. The result of sequence analysis and homology comparison suggested that strain R1 was similary to Bacillus sp. in GenBank.Studies showed that strain R1 gotted the maximum of biomass after 24h cuture, however the maximum rate of reducing sulfate appeared after 72h cuture. The biomass and rate of reducing sulfate of R1 which cultured in the medium with Fe2+, are obviously higher than in the medium without Fe2+. Regardless of the exist of Fe2+ in culture medium, the result showed that the optimum conditions of growth of strain R1 was as follow:temperature 30℃, pH6.5-9, FeSO4 lg/L, sodium-lactate as carbon source, the yeast extract and NH4Cl as nitrogen source. The optimum conditions for the rate of reducing sulfate of strain R1 was as follow:temperature 30℃, pH6.5-7.0. In the scope of the sulfur sources tested, strain R1 may takes the sulfate and the hyposulphite as the electron acceptors, however, the sulfite and the Na2S could not be used as the electron acceptor.By the Response Surface Analysis(RSA), the next step was to screen the main factors which had significant influences on the efficiency of reducing sulfate of strain R1, and to determine the optimum levels of significant factors for the rate of reducing sulfate of strain R1. In this study, the Plackett-Burman design was carried out using the software Minitab15. The three significant factors of strain R1 were screened as follow:sodium-lactate, NH4Cl, FeSO4·7H2O. Based on the Box-Behnken design and response surface analysis, the regression equation coefficients were calculated and the second-order polynomial model was established. The optimal values of three significant factors for stain R1 could be calculated as follows:sodium-lactate 0.95g/L, NH4Cl 0.14g/L, FeSO4-7H2O 0.13g/L. |
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