Novel heterotrophic nitrogen removal and assimilation characteristic of the newly isolated bacterium Pseudomonas stutzeri AD-1

AD-1, an aerobic denitrifier, was isolated from activated sludge and identified as Pseudomonas stutzeri. AD-1 completely removed NO3- or NO2- and removed 99.5% of NH4+ during individual culturing in a broth medium with an initial nitrogen concentration of approximately 50 mg L−1. Results showed that larger amounts of nitrogen were removed through assimilation by the bacteria. And when NH4+ was used as the sole nitrogen source in the culture medium, neither NO2- nor NO3- was detected, thus indicating that AD-1 may not be a heterotrophic nitrifier. Only trace amount of N2O was detected during the denitrification process. Single factor experiments indicated that the optimal culture conditions for AD-1 were: a carbon-nitrogen ratio (C/N) of 15, a temperature of 25°C and sodium succinate or glucose as a carbon source. In conclusion, due to the ability of AD-1 to utilize nitrogen of different forms with high efficiencies for its growth while producing only trace emissions of N2O, the bacterium had outstanding potential to use in the bioremediation of high-nitrogen-containing wastewaters. Meanwhile, it may also be a proper candidate for biotreatment of high concentration organic wastewater.