Enhanced nitrogen removal via simultaneous nitrification and denitrification by a newly isolated strain Enterobacter cloacae GW6 from estuarine sediment

Abstract

Excessive nitrogen has been discharged into natural environments due to anthropogenic activities, leading to numerous negative impacts on natural ecosystems worldwide and becoming a global environmental issue. Therefore, effective removal of nitrogenous contaminants from natural ecosystems is crucial for the protection of both ecological sustainability and human interests. In this study, a strain of Enterobacter cloacae GW6 was newly isolated from natural estuarine sediment. This strain could utilize ammonium, nitrite and nitrate, with removal efficiencies of 99.60%, 93.73% and 98.79%, and the maximum removal rates of 39.96, 40.39 and 44.65 mg/L/h, respectively. Importantly, Strain GW6 showed excellent simultaneous heterotrophic nitrification and aerobic denitrification (HN-AD) capability with the maximum TN removal rate of 35.27 mg/L/h, which is greater than those of many other HN-AD bacteria reported previously, indicating that Strain GW6 was suitable for the efficient nitrogen removal in aquatic ecosystems with high ammonium, nitrite and nitrate concentrations. The detection of functional genes amoA, hao, napA, nirK and nosZ from Strain GW6 further confirmed its HN-AD capability. Strain GW6 exhibited strong nitrogen removal capability across a wide range of environmental conditions, which makes it a promising candidate as a HN-AD bacterium for the effective biological treatment of nitrogen contamination and eutrophication in natural aquatic ecosystems, thereby contributing to better environmental protection.