Abstract
As part of the research for estimating the impact of nitrate on the safety of a repository for radioactive wastes, the isolation and characterization of nitrate-reducing bacteria in alkaline conditions were conducted. One microbial strain (No. 3－2) that showed nitrate-reducing activity at pH 10 was isolated from soil sample. On the basis of 16S rDNA sequence analysis and phylogenetic analysis, strain No. 3－2 was estimated to be a novel strain in the genus Bacillus.The isolated bacteria were studied to determine the optimal conditions in terms of temperature and pH for growth and concentration of electron receptor for nitrate reduction. As the results, optimal temperature for growth was 25 to 35 ℃ and optimal pH for growth was pH 9 to 10. This result suggested that strain No. 3－2 was an alkaliphilic bacteria. The strain No. 3－2 showed the best performance for nitrate reduction rates of 1.3×10–6 mmole-Nitrite/CFU/d under optimal condition at 25 ℃, pH 10 after 2 days cultivation.
