| Biological desulfurization is widely concerned as green desulfurization technology with the advantages of mild reaction conditions and none secondary pollution. Microorganism is the main carrier of biological desulfurization. It is cricual to screen efficient desulfurization bacterium. In the study, biological desulfurization bacterium is firstly screened and identified from physiological and molecular characterization. Then salt-tolerant characteristic and mechanism. Finally, the traits of biological desulfurization was also detailedly studied.(1) Isolation and identification physiological and molecular characterization of desulfurization bacterium CYJN-1. A salt-tolerated and sulfur-oxidizer bacteria was screened from the cooling pond sludge in Shanghai power plant. The strain was identified and named as Halothiobacillus neapolitanus(H. neapolitanus) CYJN-1. The strain belonged to strictly chemolithoautotroph and maintained cell growth via oxidizing reduced sulfur. The optimum growth temperature and p H were 30°C and 7.0, respectively. The bacteria had low tolerance for formic acid, acetic acid and other low carbon organics, and showed a greater resistance to Zn2+, Mn2+ and Pb2+. The strain CYJN-1 was stuitable to be preserved in fresh medium, 4°C and the survival rate was maintained about 90% in the 1-3 months preservation term.(2) The research of salt-tolerant characteristic of H. neapolitanus CYJN-1. The strain CYJN-1 has certain salt-tolerant characteristic. The strain could grow in the concentration of 1-5% Na Cl, optimum growth salinity was identified as 1%. However, the growth of strain CYJN-1 was restained with higher salinity. The effects of cell morphology, total protein contents, the difference of intracellular free amino acid and admixtures compatibility substances under different salinity conditions on the bacterial growth was studied for analyzing the salt tolerance mechanism of strain CYJN-1. The cellular capsular was thickened to resist the external enviroment under low salinity condition. The cells were induced to produce halophilic proteins in high salinity condition. However, the newly-produced halophilic proteins were constantly hydrolyzed to form amino acid for cellular physiological activities. Trehalose could be directly obtained from the additive compatibility substances to resist the high salinity conditions, however, glutamic acid, glysine, proline and betaine could not be directly utilized.(3) The research of desulfurization characterization of H. neapolitanus CYJN-1. The best conditions for elemental sulfur accumulation with strain CYJN-1 was consisten with optimum growth condition. 64.84% reduced-state sulfur of sodium thiosulfate were oxidazed as elemental sulfur and the elemental sulfur content was 0.83 g·L-1 after 36 h under the best condition. When the concentration of sodium thiosulfate is 20.0 g·L-1, the yeild of elemental sulfur was the highest 68.84%, which indicated that desulfurization effect was most obvious. The conversion rates of sodium thiosulfate were 94.65% and 98.78%, respectively within 24 h throughshake flask and air lift reactor desulfurization experiments. The generated elemental sulfur was dried and collected. It was yellowish color, strong smell of sulfur, easy caking. The particle size of elemental sulfur was eneven and particle was about 5-10 μm. The shape was also irregular. The characterization of the generated elemental sulfur is similar to sulphur by XRD and FIRT technology. However, due to the results of microbial activities, the surface had some tiby gap and structure was complicated. Additinally, some impurities was contained. The above results showed that strain CYJN-1 was of some potential in the industrial desulfurization application. |
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