Abstract：The aerobic denitrification characteristics of Diaphorobacter sp. PDB3 in a fermentor were studied. The sodium citrate was determined as the best carbon source for aerobic denitrification. The response surface methodology was used to optimize the aerobic denitrification conditions (temperature, pH, rotation speed, C/N ratio), and the mathematical model of aerobic denitrification was constructed. The predicted value and the measured value correlated very well. The optimum conditions for the aerobic denitrification in the fermentation broth of strain PDB3 were pH 7.3, C/N ratio 8.1, temperature 30.1℃ and rotation speed 299.9r/min, respectively. The optimum specific aerobic denitrification rate was 2.25h-1.The results showed that the specific aerobic denitrification rate of PDB3 strain in the fermentor was 2.12h-1 and the error was only 5.8%. Finally, the nitrogen balance analysis showed that 29.0% of the total nitrogen removal was converted to intracellular nitrogen and nitrogen loss accounted for 67.3% of the total nitrogen removal. The nitrogen was mainly removed by aerobic denitrification and cellular assimilation.The expression level of denitrifying gene (napA, nirS, cnorB, nosZ) was determined by RT-qPCR analysis to further explain the nitrogen removal characteristics, and provide theoretical basis for the practical application of Diaphorobacter sp.PDB3.
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