Characterization and Performance of Priestia aryabhattai for Nitrogen Assimilation of Soymilk-Processing Wastewater

Soy products are among the most common sources of protein, and large volumes of wastewater are produced from legume processing. In this study, the Priestia aryabhattai FM5 strain, isolated from soil, was found to be capable of nitrogen assimilation. The NH₄⁺ and NO₃^- removal characteristics of P. aryabhattai FM5 were investigated to better understand its removal capability. The optimal conditions for NH₄⁺ removal were pH 8.0, temperature-25 °C, and C/N ratio-20, with sodium succinate as the carbon source. Under the conditions of pH 7.0, temperature-35 °C, and C/N ratio-10, with sodium acetate as the carbon source, strain FM5 reached the highest NO₃^- removal efficiency. The genome of FM5 revealed genes involved in assimilatory nitrate reduction and glutamate metabolism, such as nasA, nirA, nrt, glnA, gltB/D, and gdhA. When cultured in wastewater from soymilk processing with activated carbon for 72 h (h), the NH₄⁺ concentration and chemical oxygen demand (COD) decreased from 29.5 to 4.8 mg·L^-1 and 2058.3 mg·L^-1 to 295.3 mg·L^-1, respectively. This study provides deeper insights into the NH₄⁺ and NO₃^- removal-capable bacterial strain FM5 and improves the application of Priestia in wastewater.