Efficacy of inorganic nitrogen removal by a salt-tolerant aerobic denitrifying bacterium, Pseudomonas sihuiensis LK-618.

An aerobic denitrifying bacterium, stain LK-618, was isolated from lake sediment surface and the efficacy of inorganic nitrogen removal was tested. Stain LK-618 identified as Pseudomonas sihuiensis by 16S rRNA sequencing analysis. Trisodium citrate was found to be the ideal carbon source for this strain. When an initial nitrogen sources of approximately 50 mg/L nitrate, ammonium, or nitrite was solely selected as the nitrogen source, the nitrogen removal efficiencies were 91.4% (3.86 mg/L/h), 95.07% (2.47 mg/L/h) and 97.7% (2.41 mg/L/h), respectively. Nitrogen balance analysis revealed that 55.12% NO3--N was removed as N2. Response surface methodology (RSM) analysis demonstrated that the optimal Total Nitrogen (TN) removal ratio for strain LK-618 was under C/N ratio of 12.63, shaking speed of 52.06 rpm, temperature of 28.5 °C and pH of 6.86. In addition, strain LK-618 could tolerate NaCl concentrations up to 20 g/L, and its most efficient denitrification capacity was presented at NaCl concentrations of 0-10 g/L. Therefore, strain LK-618 has potential application on the removal of inorganic nitrogen from saline wastewater under aerobic conditions.