Hydrazine production by anammox biomass with NO reversible inhibition effects

We explored the production of hydrazine from NO and ammonium by anammox biomass, which normally converts ammonium and nitrite to N-2 gas under anaerobic conditions. The key step was reversibly inhibiting cytochrome c in anammox biomass via exposure to NO gas or NO-EDTA. The conformation of cytochrome c was changed through exposure to NO or NO- EDTA, and this is what interrupted the oxidation of hydrazine to N-2, leading to hydrazine accumulation. Experimentally, the maximum hydrazine production climbed to 12 000 and 7800 mu g L-1 with the addition of NO and NO- EDTA, respectively. Because the inhibition by NO- EDTA and NO gas was reversible, the normal anammox capacity for nitrogen removal via N-2 recovered within 32 and 24 h after NO and NO-EDTA (respectively) were replaced with ammonium and nitrite substrates. These results demonstrate the promise of producing hydrazine via microbial conversion of NO and ammonium.