Energy recovery in the form of N2O by denitrifying bacteria

Nitrous oxide (N2O) is a highly energetic oxidant. This work documents a novel process that recovers N2O by inhibiting the activity of the nitrous-oxide reductase (N2OR) in denitrifying bacteria. N2O recovery was demonstrated in batch experiments in which NO was the only electron-acceptor, with Fe(II) EDTA being the chelating agent for NO. Increasing NO-Fe(II) EDTA led to greater accumulation of N2O over N-2 in batch studies (up to 70% of total gas produced), and N2O accumulation correlated to loss of nitrous-oxide reductase (N2OR) activity and conformational changes to cytochrome c, the immediate electron donor for N2OR. Stable and high production of N2O was also documented in long-term experiments with NO-Fe(II) EDTA as the only acceptor for denitrifying biomass. Mechanistically, the conformational change of cytochrome c was the dominant cause for the loss of electron-transfer capacity, which led to a decrease of N2OR activity and the accumulation of N2O. And this is the first time to recover energy source from flue gas in the form of N2O. Recovery of N2O by suppressing N2OR widens the options for energy recovery from nitrogen-based wastes.