A novel Zobellella endophytica W14 strain for nitrogen removal from hypersaline wastewater through simultaneous nitrification and denitrification

To address the challenges associated with biological treatment of high-salinity wastewater, a novel salt-tolerant strain, Zobellella endophytica W14, was isolated. This strain exhibited heterotrophic nitrification-aerobic denitrification (HN-AD) capabilities. Strain W14 could grow and remove ammonium in high-salinity environments with salinity levels ranging from 0 to 11% (w/v). At 5% salinity, strain W14 demonstrated high removal efficiencies for nitrite, ammonium, and nitrate (100%, 99.58%, and 98.85%, respectively), when these compounds were provided as the single source of nitrogen. In cases of mixed nitrogen sources, total nitrogen removal efficiency of strain reached 95.22%. The nitrogen balance analysis confirmed the utilization of nitrogen sources by strain W14 through both assimilation and dissimilation. Through the amplification of functional genes involved in nitrogen metabolism (i.e., hao, napA, nirS, and nosZ), the nitrogen metabolism pathway of strain W14 was predicted to be: NH4+ -* NH2OH -* NO2- -* NO3- -* NO2- -* NO -* N2O -* N2. The study reveals that the novel W14 strain can efficiently remove total nitrogen from high-salinity wastewater and has significant potential for biological treatment of such wastewater.