Metabolic properties of a mixed culture of aerobic ammonia oxidizers and its optimal reaction conditions

► Ammonia oxidation capacity was in direct proportion to biomass concentration. ► Half-saturation constant Ks = 78.5 mg L−1, inhibition concentration Ki = 393.4 mg L−1. ► Acetic acid and beef extract had great inhibition effects on ammonia oxidation. ► Methanol and glucose had no evident effects on ammonia oxidation. ► Optimal reaction conditions: 30-32 °C, pH 7.8-8.0, and 150-200 mg L−1NH4+-N.