Simultaneous Heterotrophic Nitrification and Aerobic Denitrification at High Concentrations of NaCl by Halomonas Bacteria

Abstract

Halomonas bacteria can remove nitrogen (N) by simultaneous heterotrophic nitrification and aerobic denitrification (SND) in highsalt nitrogenous matrix was reported in this paper. The Halomonas strains were isolated, screened and identified from the sediment of a saltern pool in the city of Dalian, China. Ectoine synthesis of Halomons strains under highsalt were investigated. The cloning and analysis of N-removal-related enzyme-encoding genes were performed. The N removal rates were determined and the typical strain was selected to describe its SND process. 14 Halomonas strains were able to synthesize ectoine at 60 g/L NaCl concentration. The encoding genes amo A, nar H and nir S fragments of ammonia monooxygenase, nitrate reductase and nitrite reductase were cloned in the genomic DNA of some Halomonas strains. The N removal rates of 14 Halomonas strains by SND were in the range of 21.7% to 91.8%. The N removal rate of Halomonas venusta DSM 4743 was maximum, and it reached 91.8%. The N removal of H. venusta DSM 4743 by SND was performed under the conditions of 60 g/L NaCl and 4000 mg/L initial -N, after 192 h the residual total inorganic N concentration was 218.7 mg/L. This study provides theoretical and technical support for microbial denitrification technology for highsalt nitrogenous wastewater.