Abstract
Removal of nitrogen from hydroxylamine could effectively improve the wastewater treatment efficiency. In this work, Bacillus thuringiensis EM-A1 was obtained from a biogas digester with hydroxylamine as the only nitrogen source. Hydroxylamine (100%) and total nitrogen (71.86%) were efficiently removed under the following conditions: 30°C, sucrose as carbon source, carbon to nitrogen ratio 40, rotation speed 150 rpm, pH 9.58, and inoculant concentration of 0.58×108 colony-forming units. Ammonium was completely consumed by strain EM-A1, and 8.32 ± 0.08 mg/L of nitrate was produced during the ammonium removal process. During aerobic denitrification, the removal efficiencies of NO2−-N and NO3−-N by strain EM-A1 were 100 and 76.67%, respectively. There were about 29.34 ± 0.18%, 26.71 ± 0.36%, and 23.72 ± 0.88% initial total nitrogen lost as nitrogenous gas when NH4+, NO3−, and NO2− were separately used as the sole nitrogen source. The specific activities of ammonia monooxygenase, hydroxylamine oxidoreductase, nitrate reductase, and nitrite oxidoreductase were successfully detected as 0.37, 0.88, 0.45, and 0.70 U/mg protein, respectively. These results indicated that B. thuringiensis EM-A1 is a promising candidate for bioremediation of inorganic nitrogen from wastewater.
Highlights
In recent years, human activities have resulted in surface water and groundwater pollution by nitrogen (N) compounds in many areas of China
BLAST alignment analysis exhibited that strain EM-A1 had the highest similarity (99%) with the B. thuringiensis
A phylogenetic tree was constructed and revealed that strain EM-A1 belongs to B. thuringiensis based on its phylogenetic relationship (Figure 2)
Summary
Human activities have resulted in surface water and groundwater pollution by nitrogen (N) compounds in many areas of China. The death of aquatic animals caused by the eutrophication of water bodies is a typical example of the destruction of the nitrogen cycle through human activities (Heil et al, 2016; Soler-Jofra et al, 2021). Accumulation of large amounts of inorganic N could affect the reproduction and metabolic activities of humans and animals (Jiang, 2000). The efficient and effective removal of inorganic N from wastewater has become an important research field. N removal by classical biological nitrification–denitrification has been widely used as one of the most effective and economical processes for wastewater treatment
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