The emissions of nitrous oxide (N(2)O) and nitric oxide (NO) from biological nitrogen removal (BNR) operations via nitrification and denitrification is gaining increased prominence. While many factors relevant to the operation of denitrifying reactors can influence N(2)O and NO emissions from them, the role of different organic carbon sources on these emissions has not been systematically addre...

Denitrification is an alternative form of respiration in which bacteria sequentially reduce nitrate or nitrite to nitrogen gas by the intermediates nitric oxide and nitrous oxide when oxygen concentrations are limiting. In Bradyrhizobium japonicum, the N(2)-fixing microsymbiont of soya beans, denitrification depends on the napEDABC, nirK, norCBQD, and nosRZDFYLX gene clusters encoding nitrate-,...

Two laboratory-scale sequencing batch reactors were used to study biological treatment of carbon and nitrogen in a new combined anaerobic-aerobic system. Piggery wastewater was used as a model effluent. The anaerobic reactor, fed with raw wastewater and nitrite/nitrate recycling from the aerobic reactor, carried out denitrification and anaerobic digestion of organic carbon. In the aerobic react...

A pilot-scale primary maturation pond was spiked with (15)N-labelled ammonia ((15)NH(4)Cl) and (15)N-labelled nitrite (Na(15)NO(2)), in order to improve current understanding of the dynamics of inorganic nitrogen transformations and removal in WSP systems. Stable isotope analysis of delta(15)N showed that nitrification could be considered as an intermediate step in WSP, which is masked by simul...

Thiosphaera pantotropha is capable of simultaneous heterotrophic nitrification and aerobic denitrification. Consequently, its nitrification potential could not be judged from nitrite accumulation, but was estimated from complete nitrogen balances. The maximum rate of nitrification obtained during these experiments was 93.9 nmol min mg of protein. The nitrification rate could be reduced by the p...

The present study aims in investigating simultaneous heterotrophic nitrification and aerobic denitrification (SND) ability of a newly isolated bacterium. The bacterial strain GS5 was isolated from a laboratory scale denitrifying bioreactor and characterized. Based on phenotypic and phylogenetic characteristics as derived from partial 16S rRNA gene sequence, the isolate was identified to be Baci...

The cold-adapted bacterium Pseudomonas putida Y-9 was investigated and exhibited excellent capability for nitrogen removal at 15°C. The strain capable of heterotrophic nitrification and aerobic denitrification could efficiently remove ammonium, nitrate, and nitrite at an average removal rate of 2.85 mg, 1.60 mg, and 1.83 mg NL-1 h-1, respectively. Strain Y-9 performed nitrification in preferenc...

Cumene hydroperoxide supported oxidative denitrification of 2-nitropropane was investigated in uninduced mouse liver microsomes. The cytochrome P-450 peroxygenase catalyzed reaction resulted in the production of nitrite and acetone. Several lines of evidence suggested the involvement of multiple forms of cytochrome P-450. Acetone production was at least two times greater than nitrite release po...

Denitrification often occurs in the water column, underlying zones of intense productivity and decomposition in upwelling regions. In the denitrifying zone off the southwest coast of India, high concentrations of nitrite (>15 μM) and nitrous oxide (>500 nM) have been reported near the sediment-water interface (<80 m). We investigated the chemical and molecular indicators of denitrification alon...

The metabolism of nitric oxide in Paracoccus denitrificans has been studied using a Clark-type electrode. The uncoupler carbonyl cyanide m-chlorophenylhydrazone (CCCP) and the SH reagent N-ethylmaleimide, both of which released nitric oxide from cells respiring nitrite, were found to be efficient inhibitors of nitric oxide reductase activity. Control experiments with another uncoupler, pentachl...