Novel heterotrophic nitrification-aerobic denitrification strain Acinetobacter haemolyticus JS-1 mediates...

A novel heterotrophic nitrification-aerobic denitrification (HNAD) bacterium, Acinetobacter haemolyticus JS-1, was characterized for efficient nitrogen removal. In a mixed-nitrogen system, JS-1 simultaneously removed >98 % of NH₄⁺-N, NO₃^--N, and NO₂^--N within 24 h. Nitrogen balance analysis revealed that assimilation is the dominant pathway, converting 74.5 % of NH₄⁺-N and 85.9 % of NO₃^--N into biomass. Optimal removal occurred at 30 °C, pH 7-8, a carbon-to-nitrogen ratio (C/N) of 10-14, and with sodium acetate as the carbon source. Genomic and enzymatic analyses confirmed the absence of key genes (hao, nor and nos) and intermediates, defining a unique non-canonical HNAD pathway that is primarily driven by assimilation, thereby minimizing greenhouse gas emissions. Notably, high-nitrogen inhibition was effectively alleviated by increasing inoculum density. When immobilized in a sequencing batch biofilm reactor (SBBR), JS-1 achieved stable total nitrogen (TN) removal (83 %). This study highlights the potential of strain JS-1 for low-emission, single-strain bioaugmentation in wastewater treatment.