Identification of aerobic-denitrifying Psychrobacter cryohalolentis strain F5-6 and its nitrate removal at low temperature

Biological denitrification is suppressed when temperature is lower than 10 degrees C. In this study, Psychrobacter cryohalolentis F5-6 was isolated from Harbin region and showed high aerobic-denitrifying rate at low temperature. It contained high percentage of unsaturated fatty acids (87.32%) and short chain saturated acid (3.4% C10:0 and 4.0% C12:0 3-OH). Acetate was the best carbon source for the strain F5-6 performing denitrification. Aerobic denitrification (napA gene) and nitrate assimilation (nasA gene) were the nitrate metabolism processes for the strain F5-6. Its biological nitrate removal (BNR) rate at 10 degrees C showed fit with Monod equation (R2 = 0.9808). The maximum BNR rate was 23.71 mg NO3- -N g- 1DW h-1 and KS was 116.96 mg L-1. The optimal denitrifying condition was pH 7.5, 15 degrees C with shaking speed of 180 rpm and C/N of 2. Results of this study supplied a bacterial resource for improving nitrate removal from low C/N water at low temperature.