Isolation and Optimization of Culture Conditions of a Nitrobacter Enrichment Culture
In order to enhance the removal efficiency of nitrite in aquaculture water under high temperature and high pH con-ditions,an enrichment culture WY-8,containing only one type of nitrite-oxidizing bacteria(NOB),was screened from wine wastewater.The enrichment culture was identified through 16S rDNA sequence and NxrA functional gene sequence analysis.The fermentation parameters of the enrichment culture were optimized through single-factor experiments,and its nitrite removal ability and generation time in three actual aquaculture waters was measured.The results showed that the NOB was identified as Nitrobacter winogradskyi and its relative abundance was as high as 96.27％.The optimal fermentation parameters for WY-8 were 29～38 ℃,pH 7.0～9.0,salinity 0.13％～0.63％and 50～400 mg/L nitrite,nitrate＜200 mg/L.Under the optimal conditions,the enrichment culture could convert 138 mg/L nitrite into nitrate in 108 h,with the maximum nitrite removal rate of 4.38 mg/(L·h),and the shortest generation time of 7.5 h.In aquaculture waters with a temperature of 35 ℃ and a pH of 8.5,the maximum nitrite removal rate of the enrichment culture reached 0.41 mg/(L·h).The shortest generation time of the enrichment culture was 7.8 h in actual aquaculture waters.The above results indicated that the enrichment culture has a potential application prospects in aquaculture water with high pH and high water temperature in summer.
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