An efficient aerobic denitrification bacterium, strain NNA5, was isolated and identified as Marinobacter sp. NNA5. NNA5 did not perform heterotrophic nitrification. GC/IRMS analysis revealed that N-15(2) was produced from (NaNO2)-N-15 and (KNO3)-N-15. GC/MS and quantitative analyses showed that no N2O emission occurred when nitrite or nitrate was used as substrate. Single factor experiments indicated that optimal conditions for aerobic denitrification were: sodium succinate or sodium pyruvate as carbon source, temperature 35 degrees C, NaCl concentration 2-4%, C/N ratio 6-8, pH 7.5, rotation speed 150 rpm (giving dissolved oxygen concentration 6.08 mg/L), NO3-N concentration ranging from 140 to 700 mg/L. NNA5 displayed highly efficient aerobic denitrifying ability, with maximal NO3-N removal rate 112.8 mg/L/d. In view of its ability to perform aerobic denitrification with zero N2O emission, NNA5 has great potential for future application in aerobic denitrification processes in industrial and aquaculture wastewater treatment systems. (C) 2016 Elsevier Ltd. All rights reserved.