Characterization of nitrous oxide reduction byAzospirasp. HJ23 isolated from advanced wastewater treatment sludge

Abstract

A new nitrous oxide (N2O)-reducing bacterium was isolated from a consortium that was enriched using advanced wastewater treatment sludge as an inoculum and N2O as the sole nitrogen source. The isolated facultative anaerobe was identified asAzospirasp. HJ23.Azospirasp. HJ23 exhibited optimum N2O-reducing activity with a C/N ratio of 62 at pH 6 in the temperature range of 37 degrees C to 40 degrees C. The optimum carbon source for N2O reduction was a mixture of glucose and acetate. The maximum rate of N2O reduction byAzospirasp. HJ23 was 4.8 mmol center dot g-dry cell(-1)center dot h(-1), and its N2O-reducing activity was higher than other known N2O reducers.Azospirasp. HJ23 possessed several functional genes for denitrification. These includednarG(NO(3)(-)reductase),nirK(NO(2)(-)reductase),norB(NO reductase), andnosZ(N2O reductase) genes. These results suggest thatAzospirasp. HJ23 can be applied in the denitrification process to minimalize N2O emission.