Aerobic Denitrification of Pseudomonas putida AD-21 at Different C/N Ratios

An aerobic denitrifier was newly isolated from soil and its denitrification activity under different C/N (carbon/nitrogen) ratios was investigated. The isolate was identified as Pseudomonas putida AD-21 by biochemical studies and 16s rDNA sequencing analysis. P. putida AD-21 tolerated oxygen levels of 5.0–6.0 mg/l. An 15NH4/14NO3 analysis indicated that the nitrogen of NH4 was preferentially assimilated into the cell mass and that the nitrate removed could be considered an indication of bacterial denitrification efficiency. Increasing the C/N ratio increased the nitrate removal rates, whereas nitrogen assimilation into the cell mass was not affected. The optimal C/N ratio was 8 with a maximum nitrate removal rate of 254.6 mg/l/h and a nitrate removal efficiency of 95.9%. The results suggest that P. putida AD-21 may be a good candidate for aerobic wastewater treatment.