Showing papers on "Nitrite published in 2014"
TL;DR: This pilot-scale study demonstrates that application of the proposed online aeration control is able to out-select NOB in mainstream conditions providing relatively high nitrogen removal without supplemental carbon and alkalinity at a low HRT.
363 citations
TL;DR: Circulating nitrite derived from shear stress–dependent stimulation of endothelial nitric oxide synthase at the remote site of rIPC contributes to cardioprotection during I/R.
Abstract: Rationale: Remote ischemic preconditioning (rIPC) with short episodes of ischemia/reperfusion (I/R) of an organ remote from the heart is a powerful approach to protect against myocardial I/R injury. The signal transduction pathways for the cross talk between the remote site and the heart remain unclear in detail. Objective: To elucidate the role of circulating nitrite in cardioprotection by rIPC. Methods and Results: Mice were subjected to 4 cycles of no-flow ischemia with subsequent reactive hyperemia within the femoral region and underwent in vivo myocardial I/R (30 minutes/5 minutes or 24 hours). The mouse experiments were conducted using genetic and pharmacological approaches. Shear stress–dependent stimulation of endothelial nitric oxide synthase within the femoral artery during reactive hyperemia yielded substantial release of nitric oxide, subsequently oxidized to nitrite and transferred humorally to the myocardium. Within the heart, reduction of nitrite to nitric oxide by cardiac myoglobin and subsequent S -nitrosation of mitochondrial membrane proteins reduced mitochondrial respiration, reactive oxygen species formation, and myocardial infarct size. Pharmacological and genetic inhibition of nitric oxide/nitrite generation by endothelial nitric oxide synthase at the remote site or nitrite bioactivation by myoglobin within the target organ abrogated the cardioprotection by rIPC. Transfer experiments of plasma from healthy volunteers subjected to rIPC of the arm identified plasma nitrite as a cardioprotective agent in isolated Langendorff mouse heart preparations exposed to I/R. Conclusions: Circulating nitrite derived from shear stress–dependent stimulation of endothelial nitric oxide synthase at the remote site of rIPC contributes to cardioprotection during I/R. Clinical Trial Registration— URL: http://www.clinicaltrials.gov. Unique identifier: NCT01259739.
295 citations
TL;DR: Intriguingly, nitrate supplementation also reduces the oxygen cost of submaximal exercise and can, in some circumstances, enhance exercise tolerance and performance.
Abstract: Dietary nitrate is growing in popularity as a sports nutrition supplement. This article reviews the evidence base for the potential of inorganic nitrate to enhance sports and exercise performance. Inorganic nitrate is present in numerous foodstuffs and is abundant in green leafy vegetables and beetroot. Following ingestion, nitrate is converted in the body to nitrite and stored and circulated in the blood. In conditions of low oxygen availability, nitrite can be converted into nitric oxide, which is known to play a number of important roles in vascular and metabolic control. Dietary nitrate supplementation increases plasma nitrite concentration and reduces resting blood pressure. Intriguingly, nitrate supplementation also reduces the oxygen cost of submaximal exercise and can, in some circumstances, enhance exercise tolerance and performance. The mechanisms that may be responsible for these effects are reviewed and practical guidelines for safe and efficacious dietary nitrate supplementation are provided.
285 citations
TL;DR: In this article, the fabrication and testing of nitrite sensor based on the use of Fe 2 O 3 /rGO composite was reported, which was prepared by a facile one-step hydrothermal approach.
Abstract: Nitrite is one of the most frequent measurements in environmental analysis due to their detrimental effect on environment. The development of simple and sensitive analytical method for the detection of nitrite is highly important. In this study, we report the fabrication and testing of nitrite sensor based on the use of Fe 2 O 3 /rGO composite. The Fe 2 O 3 /rGO composites were prepared by a facile one-step hydrothermal approach. Field emission scanning electron microscope studies and powder X-ray diffraction analysis revealed that the Fe 2 O 3 nanoparticles were successfully grafted on the rGO nanosheets. Further, the prepared Fe 2 O 3 /rGO composites have been examined for the electrochemical detection of nitrite using cyclic voltammetry and differential pulse voltammetry techniques. The electrochemical studies demonstrated that Fe 2 O 3 /rGO composite detects nitrite linearly over a concentration range of 5.0 × 10 −8 to 7.8 × 10 −4 M with a detection limit of 1.5 × 10 −8 M. The obtained detection limit for Fe 2 O 3 /rGO composite is very much comparable to the recent literature values. Furthermore, the Fe 2 O 3 /rGO composite modified electrode showed an excellent anti-interference ability against electroactive species and metal ions.
281 citations
TL;DR: The modified biosensor was applied to the determination of AA, DA, UA and NO2(-) in urine samples by using standard adding method with satisfactory results.
274 citations
TL;DR: The results suggest that archaea may contribute to N2O production in terrestrial ecosystems, however, they are not capable of nitrifier-denitrification and thus do not produce increasing amounts of the greenhouse gas when oxygen becomes limiting.
Abstract: Soil emissions are largely responsible for the increase of the potent greenhouse gas nitrous oxide (N2O) in the atmosphere and are generally attributed to the activity of nitrifying and denitrifying bacteria. However, the contribution of the recently discovered ammonia-oxidizing archaea (AOA) to N2O production from soil is unclear as is the mechanism by which they produce it. Here we investigate the potential of Nitrososphaera viennensis, the first pure culture of AOA from soil, to produce N2O and compare its activity with that of a marine AOA and an ammonia-oxidizing bacterium (AOB) from soil. N. viennensis produced N2O at a maximum yield of 0.09% N2O per molecule of nitrite under oxic growth conditions. N2O production rates of 4.6±0.6 amol N2O cell−1 h−1 and nitrification rates of 2.6±0.5 fmol NO2− cell−1 h−1 were in the same range as those of the AOB Nitrosospira multiformis and the marine AOA Nitrosopumilus maritimus grown under comparable conditions. In contrast to AOB, however, N2O production of the two archaeal strains did not increase when the oxygen concentration was reduced, suggesting that they are not capable of denitrification. In 15N-labeling experiments we provide evidence that both ammonium and nitrite contribute equally via hybrid N2O formation to the N2O produced by N. viennensis under all conditions tested. Our results suggest that archaea may contribute to N2O production in terrestrial ecosystems, however, they are not capable of nitrifier-denitrification and thus do not produce increasing amounts of the greenhouse gas when oxygen becomes limiting.
263 citations
231 citations
TL;DR: It is found that nitrate-stressed D. vulgaris cultures grown in lactate-sulfate conditions eventually grew in the presence of high concentrations of nitrate, and their resistance continued through several subcultures, suggesting adaptation to nitrate.
Abstract: Nitrate is an inhibitor of sulfate-reducing bacteria (SRB). In petroleum production sites, amendments of nitrate and nitrite are used to prevent SRB production of sulfide that causes souring of oil wells. A better understanding of nitrate stress responses in the model SRB, Desulfovibrio vulgaris Hildenborough and Desulfovibrio alaskensis G20, will strengthen predictions of environmental outcomes of nitrate application. Nitrate inhibition of SRB has historically been considered to result from the generation of small amounts of nitrite, to which SRB are quite sensitive. Here we explored the possibility that nitrate might inhibit SRB by a mechanism other than through nitrite inhibition. We found that nitrate-stressed D. vulgaris cultures grown in lactate-sulfate conditions eventually grew in the presence of high concentrations of nitrate, and their resistance continued through several subcultures. Nitrate consumption was not detected over the course of the experiment, suggesting adaptation to nitrate. With high-throughput genetic approaches employing TnLE-seq for D. vulgaris and a pooled mutant library of D. alaskensis, we determined the fitness of many transposon mutants of both organisms in nitrate stress conditions. We found that several mutants, including homologs present in both strains, had a greatly increased ability to grow in the presence of nitrate but not nitrite. The mutated genes conferring nitrate resistance included the gene encoding the putative Rex transcriptional regulator (DVU0916/Dde_2702), as well as a cluster of genes (DVU0251-DVU0245/Dde_0597-Dde_0605) that is poorly annotated. Follow-up studies with individual D. vulgaris transposon and deletion mutants confirmed high-throughput results. We conclude that, in D. vulgaris and D. alaskensis, nitrate resistance in wild-type cultures is likely conferred by spontaneous mutations. Furthermore, the mechanisms that confer nitrate resistance may be different from those that confer nitrite resistance.
226 citations
TL;DR: In this article, an improved fast and sequential protocol that permits the determination of low concentrations of nitrite and nitrate in marine and freshwater samples using small volumes is presented. But the method has a detection limit <0.05 µM, a high precision (ranging from 0.2 to 11%) and accuracy (0.07 µM) for the determination OF NO 3 + NO 2 concentrations lower than 30 µM.
205 citations
TL;DR: The contamination of commercial 15-nitrogen (15N) N2 gas stocks with 15N-enriched ammonium, nitrate and/or nitrite, and nitrous oxide is reported, indicating that past reports of N2 fixation should be interpreted with caution, and demonstrating that the purity ofcommercial 15N2 gas must be ensured prior to use in future N2fix rate determinations.
Abstract: We report on the contamination of commercial 15-nitrogen (15N) N2 gas stocks with 15N-enriched ammonium, nitrate and/or nitrite, and nitrous oxide. 15N2 gas is used to estimate N2 fixation rates from incubations of environmental samples by monitoring the incorporation of isotopically labeled 15N2 into organic matter. However, the microbial assimilation of bioavailable 15N-labeled N2 gas contaminants, nitrate, nitrite, and ammonium, is liable to lead to the inflation or false detection of N2 fixation rates. 15N2 gas procured from three major suppliers was analyzed for the presence of these 15N-contaminants. Substantial concentrations of 15N-contaminants were detected in four Sigma-Aldrich 15N2 lecture bottles from two discrete batch syntheses. Per mole of 15N2 gas, 34 to 1900 µmoles of 15N-ammonium, 1.8 to 420 µmoles of 15N-nitrate/nitrite, and ≥21 µmoles of 15N-nitrous oxide were detected. One 15N2 lecture bottle from Campro Scientific contained ≥11 µmoles of 15N-nitrous oxide per mole of 15N2 gas, and no detected 15N-nitrate/nitrite at the given experimental 15N2 tracer dilutions. Two Cambridge Isotopes lecture bottles from discrete batch syntheses contained ≥0.81 µmoles 15N-nitrous oxide per mole 15N2, and trace concentrations of 15N-ammonium and 15N-nitrate/nitrite. 15N2 gas equilibrated cultures of the green algae Dunaliella tertiolecta confirmed that the 15N-contaminants are assimilable. A finite-differencing model parameterized using oceanic field conditions typical of N2 fixation assays suggests that the degree of detected 15N-ammonium contamination could yield inferred N2 fixation rates ranging from undetectable, <0.01 nmoles N L−1 d−1, to 530 nmoles N L−1 d−1, contingent on experimental conditions. These rates are comparable to, or greater than, N2 fixation rates commonly detected in field assays. These results indicate that past reports of N2 fixation should be interpreted with caution, and demonstrate that the purity of commercial 15N2 gas must be ensured prior to use in future N2 fixation rate determinations.
201 citations
TL;DR: The FNA-based strategy for establishing the nitrite pathway substantially improved total nitrogen removal, and did not increase N2O emission or deteriorate sludge settleability.
TL;DR: This study assessed the technical feasibility of removing nitrogen from municipal wastewater by partial nitrification (nitritation) in a continuous plug-flow step feed process and found that without addition of external carbon sources, the above wastewater treatment process reached 86.0% of total nitrogen removal with only 7.23 ± 2.31 mg/L of TN in the effluent, which met the discharge requirements.
TL;DR: A low-cost disposable colorimetric microfluidic paper-based analytical device (μPAD) was developed and successfully applied to the determination of nitrate and nitrite in both synthetic and natural water samples.
Abstract: A low-cost disposable colorimetric microfluidic paper-based analytical device (μPAD) was developed for the determination of nitrite and nitrate. Nitrite is determined directly by the Griess reaction while nitrate is first reduced to nitrite in a hydrophilic channel of the μPAD with immobilized zinc microparticles. This μPAD is fabricated by a simple and inexpensive inkjet printing method. Under optimal conditions, the limits of detection and quantification for nitrite are 1.0 and 7.8 μM, respectively, while the corresponding values for nitrate are 19 and 48 μM, respectively. The repeatability, expressed as relative standard deviation (RSD), is less than 2.9% and 5.6% (n ≤ 8) for the determination of nitrite and nitrate, respectively. This μPAD was successfully applied to the determination of nitrate and nitrite in both synthetic and natural water samples. It is user and environmentally friendly and suitable for on-site measurement of the analytes mentioned above in environmental and drinking waters.
TL;DR: The proposed chemically modified electrode was used to the determination of NO2(-) in several foodstuffs and water samples and the results were found to be consistent with the values obtained by the Griess protocol.
TL;DR: Competition for oxygen between ammonia-oxidizing bacteria (AOB) and NOB was found to be essential for NOB repression even when the suppression of nitrite oxidation is assisted by nitrite reduction by anammox (AMX).
TL;DR: In this article, a method to analyse nitrate in marine pore water, seawater and freshwater is presented, which replaces the well-known cadmium column method for the reduction of nitrate to nitrite.
TL;DR: The results demonstrate a chemolithoautotrophic lifestyle of nitrite-oxidizing bacteria outside the nitrogen cycle, suggesting greater ecological flexibility than previously assumed and suggesting a broader distribution of these organisms in natural settings.
Abstract: The bacterial oxidation of nitrite to nitrate is a key process of the biogeochemical nitrogen cycle. Nitrite-oxidizing bacteria are considered a highly specialized functional group, which depends on the supply of nitrite from other microorganisms and whose distribution strictly correlates with nitrification in the environment and in wastewater treatment plants. On the basis of genomics, physiological experiments, and single-cell analyses, we show that Nitrospira moscoviensis, which represents a widely distributed lineage of nitrite-oxidizing bacteria, has the genetic inventory to utilize hydrogen (H2) as an alternative energy source for aerobic respiration and grows on H2 without nitrite. CO2 fixation occurred with H2 as the sole electron donor. Our results demonstrate a chemolithoautotrophic lifestyle of nitrite-oxidizing bacteria outside the nitrogen cycle, suggesting greater ecological flexibility than previously assumed.
TL;DR: Both nitrate and nitrite were removed by autotrophic denitrification using thiosulfate as an electron donor at concentrations up to 800 mg-N/L, and biomass yield for denitration was relatively higher than that of denitritation, showing less sludge production and resulting in lower sludge handling costs.
TL;DR: To estimate the food safety of the dry fermented sausages available on the Belgian market, a screening of the residual sodium nitrite and nitrate contents, biogenic amines and volatile N-nitrosamine concentrations was performed on 101 samples.
TL;DR: Different proposed mechanisms of nitrite bioactivation are reviewed, focusing on analysis of kinetics and experimental evidence for the relevance of each mechanism under different conditions.
TL;DR: The results obtained were in good agreement with those using spectrophotometry based on the National Food Safety Standard (GB 5009.33-2010), which indicates that these novel and sensitive biosensors have promising application for determination of nitrite in food.
TL;DR: The results indicate that human mARC-1 and m ARC-2 are capable of catalyzing reduction of nitrite to NO through reaction with its molybdenum cofactor, and indicate that mARC can generate nitric oxide from nitrite when forming an electron transfer chain with NADH, cytochrome b5, and NADH-dependent cyto chrome b5 reductase.
TL;DR: The bacterial diversity from the initial inoculum (return sludge) changed at the end of bioelectrochemical denitrification operation after 55 days, and the microbial community composition was different depending on the type of electron acceptor.
TL;DR: The effect of salt concentrations on the bio-P removal process was shown to be negligible up to 13 g Cl− l−1, although granule size decreased and a significant effluent turbidity was observed at the highest salinity tested.
Abstract: Salinity can adversely affect the performance of most biological processes involved in wastewater treatment. The effect of salt on the main conversion processes in an aerobic granular sludge (AGS) process accomplishing simultaneous organic matter, nitrogen, and phosphate removal was evaluated in this work. Hereto, an AGS sequencing batch reactor was subjected to different salt concentrations (0.2 to 20 g Cl− l−1). Granular structure was stable throughout the whole experimental period, although granule size decreased and a significant effluent turbidity was observed at the highest salinity tested. A weaker gel structure at higher salt concentrations was hypothesised to be the cause of such turbidity. Ammonium oxidation was not affected at any of the salt concentrations applied. However, nitrite oxidation was severely affected, especially at 20 g Cl− l−1, in which a complete inhibition was observed. Consequently, high nitrite accumulation occurred. Phosphate removal was also found to be inhibited at the highest salt concentration tested. Complementary experiments have shown that a cascade inhibition effect took place: first, the deterioration of nitrite oxidation resulted in high nitrite concentrations and this in turn resulted in a detrimental effect to polyphosphate-accumulating organisms. By preventing the occurrence of the nitrification process and therefore avoiding the nitrite accumulation, the effect of salt concentrations on the bio-P removal process was shown to be negligible up to 13 g Cl− l−1. Salt concentrations equal to 20 g Cl− l−1 or higher in absence of nitrite also significantly reduced phosphate removal efficiency in the system.
TL;DR: The exploitation of a lag phase in nitrate production after anoxic periods is a promising approach to suppress nitrite oxidizing bacteria, which is crucial for implementation of the combined partial nitritation-anammox process.
Abstract: The exploitation of a lag phase in nitrate production after anoxic periods is a promising approach to suppress nitrite oxidizing bacteria, which is crucial for implementation of the combined partial nitritation-anammox process. An in-depth study of the actual lag phase in nitrate production after short anoxic periods was performed with varied temperatures and air flow rates. In monitored batch experiments, biomass from four different full-scale partial nitritation-anammox plants was subjected to anoxic periods of 5-60 min. Ammonium and the nitrite that was produced were present to reproduce reactor conditions and enable ammonium and nitrite oxidation at the same time. The lag phase observed in nitrite oxidation exceeded the lag phase in ammonium oxidation after anoxic periods of more than 15-20 min. Lower temperatures slowed down the conversion rates but did not affect the lag phases. The operational oxygen concentration in the originating full scale plants strongly affected the length of the lag phase, which could be attributed to different species of Nitrospira spp. detected by DGGE and sequencing analysis.
TL;DR: In this article, a moving-bed biofilm reactor (MBBR) was used for biological pretreatment of low ammonia concentration polluted raw water and the impacts of temperature and the nitrifying community were studied.
TL;DR: In hypoxia, NO3 (-) supplementation enhances V̇o2 kinetics during moderate- intensity exercise and improves severe-intensity exercise tolerance and these findings may have important implications for individuals exercising at altitude.
Abstract: We investigated the effects of dietary nitrate (NO3−) supplementation on the concentration of plasma nitrite ([NO2−]), oxygen uptake (Vo2) kinetics, and exercise tolerance in normoxia (N) and hypo...
TL;DR: The technique here has several advantages and the potential to be used as a routine method for (15)N/(14)N analysis of NH4(+): substantially simplified preparation procedures and reduced preparation time particularly compared to the methods in which diffusion or distillation is involved.
Abstract: We report a new chemical method to determine the 15N natural abundance (δ15N) for ammonium (NH4+) in freshwater (e.g., precipitation) and soil KCl extract. This method is based on the isotopic analysis of nitrous oxide (N2O). Ammonium is initially oxidized to nitrite (NO2–) by hypobromite (BrO–) using previously established procedures. NO2– is then quantitatively converted into N2O by hydroxylamine (NH2OH) under strongly acid conditions. The produced N2O is analyzed by a commercially available purge and cryogenic trap system coupled to an isotope ratio mass spectrometer (PT-IRMS). On the basis of a typical analysis size of 4 mL, the standard deviation of δ15N measurements is less than 0.3‰ and often better than 0.1‰ (3 to 5 replicates). Compared to previous methods, the technique here has several advantages and the potential to be used as a routine method for 15N/14N analysis of NH4+: (1) substantially simplified preparation procedures and reduced preparation time particularly compared to the methods in w...
TL;DR: Site preference measurements indicated that both the AOB denitrification and hydroxylamine (NH2OH) oxidation pathways contributed to N2O production, and DO had an important effect on the relative contributions of the two pathways.
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16 Jun 2014
TL;DR: In this paper, water sampling and preservation methods by enumerating the different ways to measure physical, chemical, organoleptical, and radiological characteristics are discussed. And step-by-step descriptions of separation, residue determination, and cleanup techniques for a variety of fresh and salt-water.
Abstract: This work details water sampling and preservation methods by enumerating the different ways to measure physical, chemical, organoleptical, and radiological characteristics. It provides stepby-step descriptions of separation, residue determination, and cleanup techniques for a variety of freshand salt-waters. It also discusses information regarding the analysis and detection of bacteria and algae.