| Co-Investigator(Kenkyū-buntansha) |
SUTO Koichi Tohoku University, Graduate School of Engineering, Research Associate, 大学院・工学研究科, 助手 (90291252)
CHIDA Tadashi Tohoku University, Graduate School of Engineering, Professor, 大学院・工学研究科, 教授 (10005499)
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| Research Abstract |
Since the load to the environment is smaller than conventional pyrometallurgy process, bioleaching process using iron-oxidizing bacteria is expected as a next-generational metal smelting process. However, it is difficult to find the iron-oxidizing bacteria with high bioleaching ability. If such bacterium exists, the bioleaching becomes also applicable the processing of high-grade ore such as the flotation concentrate. The purpose of this study is to drastically improve the ability of iron-oxidizing bacteria. Using vector plasmids of which the mercury resistance gene was coupled as a selectable marker of transformants, the condition of the electroporation was examined. By contrivance of the pretreatment condition and improvement on the buffer solution, it was possible to transform the iron-oxidizing bacterium, strain Y4-3. This strain also transformed by vector plasmids containing iron oxidizing enzyme gene. However, the improvement of iron oxidizing rate could not be observed in the tr
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ansformant. The stability of vector plasmid was examined. It was confirmed that vector DNA existed stably, even if the subculture over 10 times was carried out. This stability was same even in the condition that the mercury ion did not exist. Wild type strain and the transformant were cultured in the same vessel, and both competition relation was analyzed. The ratio the transformant in the culture solution rapidly decreased, when it did not put on the selection pressure of mercury ion, and only the wild type strain remained in the culture. As a selectable marker except for the mercury resistance gene, the silver resistance gene was noticed. The strain E-24 showed the highest silver resistance in the 10 strains of iron-oxidizing bacteria tested. On strain E-24, the resistance mechanism was examined, and the possibility of discharging the silver ion to extracorporeal was found. As a result of examining the resistance mechanism, it was anticipated that the silver ion was discharged to extacellular. The cloning of the silver resistance gene to Escherichia coli was tried, and it ended in the failure. Less
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