Isolation and nitrogen removal characteristics of a novel aerobic denitrifying strain Achromobacter xylosoxidans GR7397

Abstract

Aerobic denitrifying bacteria have the potential for engineering applications due to the efficient nitrate removal capacity from wastewater. In this study, a novel aerobic denitrifying strain was isolated and identified as Achromobacter xylosoxidans GR7397 from the activated sludge of a wastewater treatment plant, which possessed efficient nitrate removal capacity. Moreover, the denitrification capacity and properties of the strain were investigated in the presence of nitrate as the only nitrogen source. Five denitrification reductases encoding genes were harbored by strain GR7397 determined by electrophoretic analysis of PCR amplification products, consisting of periplasmic nitrate reductase (NAP), nitrate reductase (NAR), nitrite reductase (NIR), nitrous oxide reductase (NOS), and nitric oxide reductase (NOR), demonstrating that the strain has a complete denitrification metabolic pathway. The optimum denitrifying condition of strain GR7397 included sodium acetate adopted as the electron donor, COD/TN ratio at 4, pH at 8, temperature at 30{degrees}C, under which condition, the nitrate removal rate reached 14.86 mg {middle dot} L-1 {middle dot} h-1 that the [Formula] concentration decreased from 93.90 mg/L to 4.73 mg/L within 6 h with no accumulation of nitrite. In addition, the bioaugmentation performance of strain GR7397 to enhance nitrate removal was evaluated to be effective and stabilized in a sequential batch reactor (SBR). The removal rate of [Formula] was the highest during each cycle with a range of 15.48-28.56 mg{middle dot}L-1{middle dot}h-1 in the SBR with inoculating 30% of the strain concentrate. The current research demonstrated that strain GR7397 has significant potential for application in enhancing nitrogen removal in wastewater treatment.