The Screening, Identification, and Efficient Nitrogen Removal Performance of a Novel Heterotrophic Nitrifying-Aerobic...

A novel bacterium with heterotrophic nitrification-aerobic denitrification (HN-AD) capability, designated Pseudomonas sp. L5, was isolated from the activated sludge of an aerobic denitrification reactor in our laboratory and subsequently identified. This strain can efficiently conduct nitrogen metabolism using NH₄ ⁺-N, NO₃ ^--N and NO₂ ^--N as nitrogen sources. Single-factor experiments combined with response surface methodology (RSM) were used to optimize the culture conditions of strain L5. The predicted optimal conditions for growth and nitrogen removal were a C/N ratio of 31.29, sodium acetate as the carbon source, a temperature of 31.18°C, and an initial pH of 7.25. Notably, even under mildly alkaline conditions (pH 9.0), the strain maintained high aerobic denitrification efficiency, with a NO₃ ^--N removal rate of 86.236%. The nitrogen metabolism pathway of strain L5 was elucidated through a combined analysis of the expression of key HN-AD genes and enzyme activities. The denitrification capacity of strain L5 under alkaline conditions provides a theoretical basis and technical support for the application of aerobic denitrifying bacteria in high-pH wastewater treatment.