Nitrite

About: Nitrite is a research topic. Over the lifetime, 15425 publications have been published within this topic receiving 484581 citations.

Chemical nature of nitric oxide storage forms in rat vascular tissue

Abstract: Endothelial NO production results in local formation of adducts that may act as storage forms of NO. Because little is known about their chemical nature, concentrations, and possible role in vascular biology, we sought to characterize those species basally present in rat aorta, using two independent approaches. In the first approach, tissue homogenates were analyzed by using chemiluminescence- and ion-chromatography-based techniques that allow trace-level quantification of NO-related compounds in complex biological matrices. In the second approach, NO stores were characterized by their ability to release NO when illuminated with light and subsequently relax vascular smooth muscle (photorelaxation). The latter included a careful assessment of action spectra for photorelaxation, taking into account the light-scattering properties of the tissue and the storage depletion rates induced by exposure to controlled levels of light. Biochemical analyses revealed that aortic tissues contained 10 ± 1 μM nitrite, 42 ± 7 μM nitrate, 40 ± 6 nM S-nitroso, and 33 ± 6 nM N-nitroso compounds (n = 4–8). The functional data obtained suggest that the NO photolytically released in the tissue originated from species with photophysical properties similar to those reported for low-molecular-weight S-nitrosothiols, as well as from nitrite. The relative contribution of these potential NO stores to the extent of photorelaxation was consistent with their concentrations detected biochemically in vascular tissue when their photoactivity was taken into account. We conclude that intravascular nitroso species and nitrite both have the potential to release physiologically relevant quantities of NO independent of enzymatic control by NO synthase.

Anaerobic degradation of alkylated benzenes in denitrifying laboratory aquifer columns.

Abstract: Toluene and m-xylene were rapidly mineralized in an anaerobic laboratory aquifer column operated under continuous-flow conditions with nitrate as an electron acceptor. The oxidation of toluene and m-xylene was coupled with the reduction of nitrate, and mineralization was confirmed by trapping 14CO2 evolved from 14C-ring-labeled substrates. Substrate degradation also took place when nitrous oxide replaced nitrate as an electron acceptor, but decomposition was inhibited in the presence of molecular oxygen or after the substitution of nitrate by nitrite. The m-xylene-adapted microorganisms in the aquifer column degraded toluene, benzaldehyde, benzoate, m-toluylaldehyde, m-toluate, m-cresol, p-cresol, and p-hydroxybenzoate but were unable to metabolize benzene, naphthalene, methylcyclohexane, and 1,3-dimethylcyclohexane. Isotope-dilution experiments suggested benzoate as an intermediate formed during anaerobic toluene metabolism. The finding that the highly water-soluble nitrous oxide served as electron acceptor for the anaerobic mineralization of some aromatic hydrocarbons may offer attractive options for the in situ restoration of polluted aquifers.

Nitrification at low oxygen concentration in biofilm reactor

Abstract: A nitrification process under low dissolved oxygen (DO) concentration is proposed in a completely stirred biofilm reactor. The reactor was fed with a synthetic wastewater containing 250 mg NH\d4–N/L. A stable nitrite accumulation in the effluent was obtained during >110 days’ operation; NO\d2–N(NO\d2–N+NO\d3–N) in the effluent reached >90% under 0.5 mg DO/L. Ammonium was completely converted and NH\d4–N in the outlet was as low as 5 mg/L. A transient increase of the DO concentration in the reactor induced a complete conversion of ammonia and nitrite to nitrate after only 2 days. A return to a low DO concentration again induced nitrite accumulation. These results show that the nitrite oxidizers were always present in the reactor but were outcompeted at low DO concentration, due to their lower affinity for oxygen, compared with ammonia oxidizers. Nitrite accumulation could also be favored by free nitrous acid accumulation inside the biofilm.

Achieving Mainstream Nitrogen Removal through Coupling Anammox with Denitratation

Abstract: Achieving maintream anammox is critical for energy-neutral sewage treatment. This study presents a new way to achieve mainstream anammox, which couples anammox with denitratation (nitrate reduction to nitrite) instead of nitritation (ammonium oxidation to nitrite). An anoxic/oxic (A/O) biofilm system treating systhetic domestic wastewater was used to demonstrate this concept for over 400 days. This A/O biofilm system achieved a total nitrogen (TN) removal efficiency of 80 ± 4% from the influent with a low C/N ratio of 2.6 and a TN concentration of 60.5 mg/L. Nitrogen removal via anammox was found to account for 70% of dinitrogen production in the anoxic reactor. Batch tests confirmed that the anoxic biofilm could oxidize ammonium using nitrite as electron acceptor, and that it had a higher nitrate reduction rate than the nitrite reduction rate, thus producing nitrite for the anammox reaction. Metagenomic analysis showed that Candidatus Jettenia caeni and Candidatus Kuenenia stuttgartiensis were the top two dominant species in anoxic biofilm. Genes involved in the metabolism of the anammox process were detected in anoxic biofilm. The abundance of nitrate reductase (73360 hits) was much higher than nitrite reductase (13114 hits) in anoxic biofilm. This system can be easily integrated with the high-rate activated sludge technology, which produces an effluent with a low C/N ratio. While this new design consumes 21% more oxygen in comparison to the currently studied nitritation/anammox process, the nitrite-producing process appears to be more stable.