Efficient hydroxylamine removal through heterotrophic nitrification by novel bacterium Glutamicibacter arilaitensis...

Hydroxylamine, an intermediate product in the nitrification process, is widely found in nature. However, hydroxylamine accumulation can decrease the biological nitrogen removal efficiency by reducing the activities, inhibiting the reproductions, and even causing the death of microorganisms. In this study, a novel heterotrophic nitrification bacterium was separated from biogas digester and identified as Glutamicibacter arilaitensis EM-H8. Strain EM-H8 exhibited efficient hydroxylamine removal (93.75%). The optimal conditions for hydroxylamine removal were as follows: Carbon source, glucose; C/N ratio, 25; temperature, 20 °C; inoculum size, 0.53 × 10⁸ CFU; and shaking speed, 150 rpm. The nitrogen balance results using strain EM-H8 showed that about 26.86% of the initial nitrogen was removed as nitrogenous gas, while 4.6% was converted into biomass under aerobic conditions, confirming that strain EM-H8 possessed the capacity for heterotrophic nitrification. Furthermore, the successful expression of hydroxylamine oxidase (0.065 U/mg protein) showed that strain EM-H8 had the ability to transform hydroxylamine from wastewater.