Abstract
PurposeAt present, the nitrogen (N) removal efficiency of the microbial treatment in the high-salinity nitrogenous wastewaters is relatively low. Study on the N removal behavior and properties of moderately halophilic bacteria Halomonas under high salinity is of great significance for the microbial treatment of high-salinity nitrogenous wastewater.MethodsThe response mechanism of Halomonas sp. B01 to high osmotic pressure stress was investigated by measuring the compatible solute ectoine concentration and superoxide dismutase (SOD) activity. The salt tolerance during growth and N removal of the strain was evaluated by measuring the activities of growth-related and N removal–related enzymes and the mRNA expression abundance of ammonia monooxygenase-encoding gene (amoA). The process of simultaneous heterotrophic nitrification and aerobic denitrification (SND) under high salinity was described by measuring the concentration of inorganic N.ResultHalomonas sp. B01 synthesized ectoine under NaCl stress, and the intracellular ectoine concentration increased with increased NaCl concentration in the growth medium. When the NaCl concentration of the medium reached 120 g L−1, the malondialdehyde concentration and SOD activity were significantly increased to 576.1 μg mg−1 and 1.7 U mg−1, respectively. The growth-related and N removal–related enzymes of the strain were active or most active in medium with 30–60 g L−1 NaCl. The amoA of the strain cultured in medium with 60 g L−1 NaCl had the highest mRNA expression abundance. In the N removal medium containing 60 g L−1 NaCl and 2121 mg L−1 NH4+-N, SND by Halomonas sp. B01 was performed over 96 h and the N removal rate reached 98.8%.ConclusionIn addition to the protective mechanism of synthetic compatible solutes, Halomonas sp. B01 had the repair mechanism of SOD for lipid peroxidation. The growth-related and N removal–related enzymes of the strain were most active at a certain salt concentration; amoA also had the highest mRNA expression abundance under high salinity. Halomonas sp. B01 could efficiently perform N removal by SND under high salinity.
Highlights
Simultaneous heterotrophic nitrification (SND) and aerobic denitrification constitute a nitrogen (N) removal method in which nitrification and denitrification are performed simultaneously in the same reaction system with a supplied organic carbon source and oxygen
Halomonadaceae, Halomonas is a genus of moderately halophilic bacteria that currently includes 79 species
The concentration of compatible solute ectoine synthesized by Halomonas sp
Summary
Simultaneous heterotrophic nitrification (SND) and aerobic denitrification constitute a nitrogen (N) removal method in which nitrification and denitrification are performed simultaneously in the same reaction system with a supplied organic carbon source and oxygen. Halomonadaceae, Halomonas is a genus of moderately halophilic bacteria that currently includes 79 species (de la Haba et al 2014). Some of these strains have been reported to be capable of nitrification, denitrification, or simultaneous nitrification and denitrification at certain salt concentrations (Berendes et al 1996; Mormile et al 1999; Guo et al 2013; Wang et al 2017). Halomonas spp. show unique potential in the treatment of wastewater with respect to N removal In addition to their strong growth and metabolism and N removal while significantly reducing the COD of wastewater, the most notable feature is their resistance to high salinity growth and N removal
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