| An aerobic denitrifier named F1 was isolated from grass fish pond water by BTB culture medium preliminary screening and denitrification activity analysis. The isolate was identified as Pseudomonas stutzeri through morphological feature, biochemical characteristics and 16S rDNA sequence analysis. Further studies showed that the optimal carbon resources for F1 denitrification were sodium acetate, sodium citrate, glucose and sucrose, with which the nitrate removal rate could reach 100%. When C/N ratio was above 10, the nitrogen removal rate of strain F1 was more than 96% and no nitrite was accumulated. The optimum condition for F1 growth and aerobic denitrification was temperature 30℃ and pH 7.0. The F1 could tolerate dissolved oxygen level of 3.4-7.2 mg/L, and its nitrogen removal rate was more than 85% in 24 hours. Denitrification process of F1 mainly occurred in the exponential phase with NaNO3 or NaNO2 as nitrogen resource, and its denitrification rate reached 92.51% and 82.73%, respectively after 32 h of culture. These results suggest that strain F1 can denitrify NO-3 or NO-2 directly, and can tolerant a high dissolved oxygen level, and these characteristics make it a good candidate for aquaculture water quality treatment. |
