Biomimetic and microbial reduction of nitric oxide

The biomimetic reduction of nitric oxide (NO) to nitrous oxide (N₂O) by dithiothreitol in the presence of cyanocobalamin and cobaltcentered porphyrins has been investigated. Reactions were monitored directly using Fourier Transform Infrared (FTIR) Spectroscopy vapor-phase spectra. Reaction rates were twofold faster for the corrin than for the cobalt-centered porphyrins. The stoichiometry showed the loss of two molecules of NO per molecule of N₂O produced. We have also demonstrated that the facultative anaerobe and chemoautotroph,Thiobacillus denitrificans, can be cultured anoxically in batch reactors using NO as a terminal electron acceptor with reduction to elemental nitrogen (N₂). We have proposed that the concentrated stream of NO_x, as obtained from certain regenerable processes for the gas desulfurization and NO_x removal, could be converted to N₂ for disposal by contact with a culture ofT. denitrificans. Four heterotrophic bacteria have also been identified that may be grown in batch cultures with succinate, yeast extract, or heat and alkali pretreated sewage sludge as carbon and energy sources and NO as a terminal electron acceptor. These areParacoccus dentrificans, Pseudomonas denitrificans, Alcaligens denitrificans, andThiophaera pantotropha.