Studies toward biotreating hypersaline wastewater containing different salts and halotolerant mechanism of robust strains are important but still rare. Here an isolated bacterium Halomonas salifodinae can perform simultaneous nitrification and denitrification (SND) at 15% salinity, showing high nitrogen removal efficiencies of over 98% via response surface methodology optimization. Besides NaCl, this robust strain had high resistance to other salts (KCl, Na2SO4, and K2SO4) and can efficiently remove nitrogen in saline wastewater containing heavy metals such as Fe(II), Mn(II), Zn(II), Cr(VI), Ni(II), and Cu(II). After repeated-batch culturing at different salinities, the treated strains with different halotolerant capabilities were used as single strain model to study halotolerant mechanism via metabolic analysis. The halotolerant bacterium can convert D-proline and glutamic acid to glutamine as well as lactulose to trehalose. The accumulated intracellular compatible solutes can resist high osmotic pressure and bound water molecule in hypersaline wastewater to accomplish high-efficiency SND processes.
Keywords: Aerobic denitrification; Halotolerant mechanism; Heavy metals; Heterotrophic nitrification; Hypersaline wastewater.
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