Isolation and identification of an alkaline-tolerant aerobic denitrifying bacterium and its denitrification performance.

To improve the low efficiency of microbial denitrification under strong alkaline environment, an aerobic denitrifying strain with strong alkaline adaptability was isolated from Shanghai paddy soil. The strain was identified as Acinetobacter junii by cell morphology and 16S rDNA analysis, and named as Acinetobacter junii strain 5-2. The effect of denitrification under different environmental conditions was investigated with single-factor effect experiments, and it was found that it could maintain a high nitrate removal rate(>90%) within a certain pH(7.0-12.0) and salt mass concentration range(10-30 g/L). After 120 h incubation with sodium acetate as carbon source, potassium nitrate as nitrogen source, m(C)/m(N) of 12, temperature of 35°, rotation of 90 r/min, initial pH of 10.0 and initial nitrate-nitrogen content of 41.07 mg/L, the removal rates of nitrate-nitrogen and total nitrogen by this strain were 97.83% and 65.85% respectively. Meanwhile, the activity and genes of enzymes related to aerobic denitrification of this strain were examined. The results show that Acinetobacter junii strain 5-2 has high aerobic denitrification capacity and is expected to be applied to treat actual nitrogenous wastewater. [ABSTRACT FROM AUTHOR]