Evaluation of nitrogen removal characteristics of Bacillus spizizenii HH1-2 by nitrogen assimilation: isolation, performance and genomics

초록

Excessive discharge of nitrogen from domestic, agricultural, and industrial sources has become a critical global environmental concern, triggering eutrophication, algal blooms, and water quality deterioration that threaten aquatic ecosystems and public health. Conventional biological nitrogen removal systems rely on separate aerobic nitrification and anoxic denitrification steps with strict operational controls and extensive greenhouse gas emissions, posing challenges to sustainable nitrogen management. A novel strain with excellent aerobic nitrogen removal capacity was screened from activated sludge and identified as Bacillus spizizenii HH1-2. The results revealed that the maximum removal rates for NH4+-N, NO2--N, and NO3--N were 2.97, 1.97, and 2.21 mg/L/h, with negligible nitrite accumulation, respectively. Additionally, strain HH1-2 exhibited strong tolerance ability to environment changes (e.g., carbon sources, C/N ratios, salinity, and pH) and high application potential for recirculating aquaculture system wastewater treatment. Moreover, whole genome analysis confirmed that the key functional genes involved in assimilatory nitrate reduction and the ammonia assimilation pathway, such as narK, nasC, narI, nasE, glnA, gudB, and gltD were detected in strain HH1-2. It is indicated that the nitrogen metabolism pathway of strain HH1-2 was NO3 --* NO2 - -* NH4+ -* glutamate. These findings suggest that the strain HH1-2 exhibits great application potential for sustainable nitrogen removal in engineered wastewater treatment processes.

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