Heterotrophic nitrification and aerobic denitrification by a novel groundwater origin cold-adapted bacterium at low temperatures

Abstract

The cold-adapted bacterium Pseudomonas migulae (AN-1), which has nirS and nosZ genes, was isolated from an aniline-contaminated groundwater system. AN-1 could remove ammonium, nitrate, and nitrite at 1.56, 1.57, and 0.69 mg L⁻¹ h⁻¹, respectively, at 10 °C under aerobic conditions. Nitrate removal followed Monod kinetics under a non-competitive substrate inhibition (k = 270.27 mg NO₃⁻–N g X⁻¹ h⁻¹, K_S = 43.65 mg L⁻¹, and K_SI = 185 mg L⁻¹). The putative gaseous denitrification pathway in AN-1 was via nitrite to N₂ using nitrogen balance assays. Moreover, the pH, dissolved oxygen, and NO₃⁻–N concentration were used as independent variables for the optimization of nitrate removal by AN-1 at 10 °C, and a statistically significant (R² = 0.9840, p < 0.0001) quadratic polynomial mathematical model was found. This study highlights the potential of AN-1 for nitrogen removal from wastewaters at low temperatures.