Characterization of an aerobic denitrifier Pseudomonas stutzeri strain XL-2 to achieve efficient nitrate removal
Bin Zhao1, Dan Yang Cheng2, Pan Tan2
1Key Laboratory of the Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, Chongqing University, Chongqing 400045, PR China; National Centre for International Research of Low-carbon and Green Buildings, Chongqing University, Chongqing 400045, PR China.
Abstract:
An aerobic denitrifier was newly isolated and identified as Pseudomonas stutzeri strain XL-2. Strain XL-2 removed 97.9% of nitrate with an initial concentration about 100 mg/L. Nitrogen balance indicates that 12.4% of the initial nitrogen was converted to N2O, and 62.4% was converted to N2. Single factor experiments indicate that the optimal conditions for nitrate removal were C/N ratio of 10, temperature of 30 °C and shaking speed of 120 rpm. Sequence amplification indicates that the denitrification genes of napA, nirS, norB and nosZ were present in strain XL-2. Combined with nitrogen balance, strain XL-2 presents the metabolic pathway of NO3- → NO2- → NO → N2O → N2 under aerobic conditions. The expression of napA and nirS might be responsible for the tolerance of dissolved oxygen by strain XL-2 during denitrification process.
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