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 N₂ 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.