A Robust Oxysalt-Tolerant Bacterium Marinobacter sp. for Simultaneous Nitrification and Denitrification of Hypersaline Wastewater

Robust strains with high simultaneous nitrification and denitrification (SND) capabilities in hypersaline wastewater, particularly those containing different oxysalts, are rarely reported. Here, an isolated oxysalt-tolerant bacterium, Marinobacter sp. Y2, showed excellent nitrogen removal capabilities of around 98% at 11% salinity of NaCl or oxysalts such as Na2SO4, Na2HPO4, NaHCO3, and NaNO3 through response surface methodology optimization. At >5% salinities, Marinobacter sp. Y2 showed superior nitrogen removal performance in oxysalt-laden wastewater compared to chloride-based wastewater. In contrast, other SND strains, including Pseudomonas sp. and Halomonas sp., experienced significant activity inhibition and even bacterial demise in oxysalt-rich wastewater, despite their high halotolerance to NaCl. The excellent SND activities of the oxysalt-tolerant strain were further validated using single and mixed nitrogen sources at 11% Na2SO4 salinity. Moreover, the amplification of nitrogen removal functional genes and the corresponding enzyme activities elucidated the nitrogen metabolism pathway of the strain in harsh oxysalt environments.