High Nitrite Research Articles

Endogenous Nitrous Oxide Emission for Denitrifiers Acclimated with Different Organic Carbons

Nitrous oxide (N2O) emission occurs during denitrification, such as in biological wastewater treatments, but few studies have focused on N2O emission during denitrification under endogenous conditions. In the present study denitrifiers were acclimated with acetate or methanol as the electron donor, and endogenous denitrification kinetics including denitrification rates and N2O emission were examined in batch experiments for the acclimated denitrifiers. Oxidized nitrogen was denitrified slowly during endogenous respiration for denitrifiers acclimated with acetate or methanol, with the denitrification rate of lower than 2mg/g VSS h. When the nitrate was used as electron acceptor, a low N2O emission ratio (lower than 1%) was obtained, while a high emission ratio (above 10%) was observed with nitrite as electron acceptor for both organic carbon acclimated denitrifiers. More attention should be paid to N2O emission during denitrification under endogenous conditions (such as in the settlement tanks) especially for systems with short-cut biological nitrogen removal through nitrite or systems with a high nitrite accumulation.

Effects of operational parameters on the treatment of nitrate‐rich wastewater by autohydrogenotrophic denitrifying bacteria

AbstractThe effects of the C/N ratio, as well as hydrogen gas and substrate concentrations, on the treatment of nitrate‐rich wastewater by autohydrogenotrophic denitrifying bacteria in sequencing batch reactors were investigated. Among the various C/N ratios applied in this study, a C/N ratio of 4 was found to be the most suitable ratio that resulted in faster growth and adaptation. The denitrification rate improved with less accumulation of nitrite with increasing H2 sparging time. Moreover, an increase in nitrate concentration resulted in high nitrite accumulation. The nitrite accumulated to 601 mg/L NO2‐N when the nitrate concentration was 1000 mg/L NO3–‐N. The specific degradation rates for nitrate and nitrite were found to be 27.8 mg NO3−‐N/g MLVSS/d and 50 mg NO2−‐N/g MLVSS/d, respectively, when the C/N ratio was 2, and H2 as electron donor was sparged for 1 min with 2 h interval.

Non-pollen palynomorphs as indicators of water quality in Lake Simcoe, Ontario, Canada

The distribution of non-pollen palynomorphs (NPP) in a core from Cook's Bay, Lake Simcoe, shows a response to changes in water quality accompanying agriculture, urbanization and industrialization. Low concentrations of nutrients in sediments with little non-arboreal pollen (NAP) record low disturbance prior to European settlement ∼1850s. These sediments are rich in desmids such as Cosmarium spp., Euastrum spp., and Staurastrum spp., an assemblage indicative of oligotrophic conditions. A decline in desmids together with an increase in dinoflagellates and thecamoebians up-core is consistent with increased nutrients. Abundant phytoliths in sediments that are relatively rich in Poaceae and other NAP records the draining of the Holland Marshes. A sharp increase in nutrient levels, together with a transition from high nitrite (NO2) to high nitrate (NO3) concentrations, records a sudden increase in biological oxygen demand leading to depletion of dissolved oxygen associated with the creation of polders in the 1920s and 1930s. A second influx of phytoliths immediately preceded the sharp rise in Ambrosia, recording rapid land clearing accompanying the five-fold post-World War II population boom in the Cook's Bay watershed. These Ambrosia-rich sediments are rich in metals and have high total phosphorus and NO3, with abundant Pediastrum spp. and Peridinium spp., notably Peridinium willei and Peridinium volzii, recording eutrophication. The abundance of the ciliate Codonella cratera and the difflugiid thecamoebians Cucurbitella tricuspis and Difflugia protaeiformis in palynological preparations as well as in washed thecamoebian samples from the upper part of the core records low dissolved oxygen associated with continued eutrophication of Cook's Bay.

Enhanced nitrogen removal from ammonium-rich wastewater containing high organic contents by coupling with novel high-rate ANAMMOX granules addition

The ANAMMOX process with sequential biocatalyst addition (SBA-ANAMMOX process) was developed in sequencing batch reactor (SBR) to enhance nitrogen removal from ammonium-rich wastewater containing glucose content up to 800mgCOD/L. The nitrogen removal performance of the SBR operated with 800mgCOD/L was significantly enhanced after sequential adding 0.5gVSS/d of high-rate ANAMMOX granules (HASGs). Kinetics analyses showed that the HASGs possessed high nitrite affinity and strong resistance to organic matter, both of which contributed to the enhancement of autotrophic nitrogen removal. Consequently, ANAMMOX became the dominant reaction to metabolize nitrite under organic conditions; denitrification was limited due to the lack of electron acceptors (nitrite and nitrate); while sulfate reduction emerged as an important process for consumption of organic matter in the SBA-ANAMMOX system. It is suggested that employing the SBA-ANAMMOX process for treatment of organic ammonium-rich wastewater, the simultaneous removal of nitrogenous compounds as well as organic matter was quite possible.

Prevalence of Nitrite and Nitrate Contents and Its Effect on Edible Bird Nest's Color

Edible bird nests (EBNs) are important ethnomedicinal commodity in the Chinese community. Recently, But and others showed that the white EBNs could turn red by vapors from sodium nitrite (NaNO2) in acidic condition or from bird soil, but this color-changing agent remained elusive. The aim of this study was to determine the prevalence of nitrite and nitrate contents and its affects on EBN's color. EBNs were collected from swiftlet houses or caves in Southeast Asia. White EBNs were exposed to vapor from NaNO2 in 2% HCl, or bird soil. The levels of nitrite (NO2-) and nitrate (NO3-) in EBNs were determined through ion chromatography analysis. Vapors from NaNO2 in 2% HCl or bird soil stained white bird nests to brown/red colors, which correlated with increase nitrite and nitrate levels. Moreover, naturally formed cave-EBNs (darker in color) also contained higher nitrite and nitrate levels compared to white house-EBNs, suggesting a relationship between nitrite and nitrate with EBN's color. Of note, we detected no presence of hemoglobin in red "blood" nest. Using infrared spectra analysis, we demonstrated that red/brown cave-EBNs contained higher intensities of C-N and N-O bonds compared to white house-EBNs. Together, our study suggested that the color of EBNs was associated with the prevalence of the nitrite and nitrate contents.

Influence of Successive Badminton Matches on Muscle Strength, Power, and Body-Fluid Balance in Elite Players

The aim was to analyze the influence of competitive round on muscle strength, body-fluid balance, and renal function in elite badminton players during a real competition. Body mass, jump height during a countermovement jump, handgrip force, and urine samples were obtained from 13 elite badminton players (6 men and 7 women) before and after the 2nd-round and quarterfinal matches of the national Spanish badminton championship. Sweat rate was determined by using prematch-to-postmatch body-mass change and by weighing individually labeled fluid bottles. Sweat rates were 1.04 ± 0.62 and 0.98 ± 0.43 L/h, while rehydration rate was 0.69 ± 0.26 and 0.91 ± 0.52 L/h for the 2nd round and quarterfinals, respectively. Thus, dehydration was 0.47% ± 1.03% after the 2nd round and 0.23% ± 0.43% after the quarterfinals. There were no differences in prematch-to-postmatch jump height, but jump height was reduced from 37.51 ± 8.83 cm after the 2nd-round game to 34.82 ± 7.37 cm after the quarterfinals (P < .05). No significant differences were found in handgrip force when comparing prepost matches or rounds, although there were significant differences between dominant and nondominant hands (P < .05). The succession of rounds caused the appearance of proteinuria, hematuria, glycosuria, and higher nitrite and ketone concentrations in urine. Rehydration patterns during a real badminton competition were effective to prevent dehydration. A badminton match did not affect jump height or handgrip force, but jump height was progressively reduced by the competitive round. Badminton players' renal responses reflected diminished renal flux due to the high-intensity nature of this racket sport.

Start-up and stable operation of partial nitritation prior to ANAMMOX in an internal-loop airlift reactor

The feasibility of implementing a novel strategy to start up and stably operate a partial nitritation (PN) process in an internal-loop airlift reactor was investigated. The results suggested that the PN process was successfully set up through initial complete nitrification followed by adjusting the alkalinity-to-ammonium ratio (Alk/NH4+–N), also known as the ‘initial complete nitrification and subsequent partial nitrification’ (CNin–PNsub) strategy. A high nitrite accumulation ratio of approximately 98% and a maximum nitrite production rate of 0.91kgNm−3day−1 were attained under the conditions of 1.0molmol−1Alk/NH4+–N, 1.24±0.71mgL−1 dissolved oxygen, 3.99±2.29mgL−1 free ammonia and 0.69±0.30mgNL−1 free nitrous acid. The stabilized effluent with an NO2-–N/NH4+–N ratio of 1.15±0.06 was suitable for subsequently feeding the anaerobic ammonium oxidation (ANAMMOX) process. The modified Stover-Kincannon model was used to analyze the kinetic parameters, and the saturation constant (KB) and maximum ammonium utilization rate (Umax) were determined to be 5.8 and 5.4kgm−3day−1, respectively.

The characteristics of nitrate removal by the psychrotolerant denitrifying bacterium Acinetobacter johnonii DBP-3, isolated from a low-temperature eutrophic body of water

A psychrotolerant denitrifying bacterial strain, DBP-3, was isolated from a eutrophic body of water by low-temperature-oriented acclimation culture. Based on its morphologicalandbiochemicalcharacteristics and 16S rDNA gene sequence, the bacterium was identified as belonging to the genus Acinetobacter and closely related to A. johnonii. The satisfactory growth of DBP-3 was observed at 10–30°C and pH 7–9. Strain DBP-3 was able to utilize three types of carbon sources (sodium acetate > sodium citrate > glucose) to support growth and denitrification. DBP-3 grew faster, but with lower nitrate removal efficiency and higher nitrite accumulation, under aerobic conditions than under anoxic conditions. DBP-3 was extremely susceptible to tetracycline and rifampicine and less sensitive to ampicillin and penicillin. The growth of DBP-3 was significantly affected by Hg (II), Cr (VI), Pb (II), Cd (II), and As (III) at 0.32, 0.63, 1.25, 2.5, and 25.0 mg L−1, respectively. Interestingly, chromium (VI) significantly promoted DBP-3 growth at concentrations lower than 0.32 mg L−1. These data may be helpful to support the use of strain DBP-3 in the purification of eutrophic water bodies at low temperatures.

Achieving partial denitrification with sludge fermentation liquid as carbon source: The effect of seeding sludge

The partial denitrification (nitrate to nitrite) has been a promising way for nitrate wastewater treatment combined with ANAMMOX system subsequently. This work investigated the effect of seeding sludge on partial denitrification by using sludge fermentation liquid as carbon source, with the sludge taken from: anoxic/oxic reactor (SA), anaerobic-anoxic-oxic reactor (SA-A-O) and alternately anaerobic sludge fermentation coupling anoxic denitrification reactor (SA-A). The results showed that transient accumulation of nitrite was observed in SA and SA-A-O. However, at the initial nitrate concentration of 30 mg/L, a high nitrite of 20.91 ± 0.52 mg/L was accumulated under complete nitrate reduction in the SA-A system, which indicated that partial denitrification could be realized. Furthermore, as much as 80% nitrate-to-nitrite transformation ratio (NTR) was achieved in a 108-day operation with inoculating SA-A, which illustrated the stability of partial denitrification under long-term operation.

Simultaneous energy recovery and autotrophic nitrogen removal from sewage at moderately low temperatures

This study assessed the technical feasibility of treating sewage with a combination of direct anaerobic treatment and autotrophic nitrogen removal, while simultaneously achieving energy recovery and nitrogen removal under moderately low temperatures. The concentrations of ammonia, nitrite, and COD in effluent were below 1, 0.1, and 30 mg/L, respectively. In the up-flow, anaerobic sludge fixed-bed, there was no obvious change observed in the total methane production at temperatures of 35 ± 1 °C, 28 ± 1 °C, 24 ± 3 °C, and 17 ± 3 °C, with the accumulation of volatile fatty acids occurring with decreasing temperatures. The control strategy employed in this study achieved a stable effluent with equimolar concentrations of nitrite and ammonium, coupled with high nitrite accumulation (>97 %) in the partial nitrification sequencing batch reactor system at moderately low temperatures. In the anaerobic ammonium oxidation (anammox) reactor, a short hydraulic retention time of 0.96 h, with a nitrogen removal rate of 0.83 kgN/(m(3)/day) was achieved at 12-15 °C. At low temperatures, the corresponding fluorescence in situ hybridization image revealed a high amount of anammox bacteria. This study demonstrates that efficient nitrogen removal and energy recovery from sewage at moderately low temperatures can be achieved by utilizing a combined system. Additionally, this system has the potential to become energy-neutral or even energy-producing.

Biogeographical patterns of phytoplankton community size structure in the oceans

AbstractAimDevelop a biogeographical classification of phytoplankton size distributions for the Atlantic Ocean and predict the global phytoplankton size composition based on prevailing environmental conditions.LocationAtlantic Ocean and Global OceanMethodsUsing phytoplankton size composition data, nutrient concentrations (nitrite+nitrate, phosphate, and silicate), irradiance, temperature and zooplankton abundances of the Atlantic Meridional Transect programme, we derived and tested an environmental classification method of phytoplankton size distribution with a k‐means clustering technique. We then used principal component and Dirichlet multivariate regression analyses to disentangle the relative influence of different environmental conditions on the phytoplankton size composition. Subsequently, we evaluated different probabilisitic models and selected the most parsimonious one to estimate the global phytoplankton size distributions in the world oceans based on global climatology data of the World Ocean Atlas 2009.ResultsBased only on prevailing environmental conditions and without a priori knowledge concerning, for example, the position of oceanic fronts, the primary productivity, the distribution of organisms or any geographical information, our classification method captures the size structures of phytoplankton communities across the Atlantic. We find a strong influence of temperature and nitrite+nitrate concentration on the prevalence of the different size classes, and we present evidence that both factors may act independently on structuring phytoplankton communities. While at low nitrite+nitrate concentrations temperature has a major structuring impact, at high nitrite+nitrate concentrations its influence is reduced. Finally, we show that the global distribution of phytoplankton community size structure can be predicted by a probabilistic model based only on temperature and nitrite+nitrate.Main conclusionThe global distribution of phytoplankton community size structure can be predicted with good approximation using a parsimonious probabilistic model forced by only temperature and nitrite+nitrate data.

Evaluating the main and side effects of high salinity on aerobic granular sludge

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.

Sustainable nitrification in fluidised bed reactor with immobilised sludge pellets

Sustainable immobilised microbial pellets were developed with water-borne polyurethane (WPU) material together with powdered activated carbon (PAC) and activated sludge as microbial inoculums for nitrification or partial nitrification. The nitrification performance and the influencing factors were studied with lab-scale aerobic fluidised bed reactors (FBR) under various temperature conditions. During the start-up period, quickly increasing the influent ammonium concentration from 40 to 320 mg N·ℓ-1 led to a stable nitrification performance with high nitrite accumulation (&gt;80%). Characterisation of the FBR performance indicated that the desired partial nitrification could be achieved at pH 7.8–8.5, dissolved oxygen (DO) 3-5 mg·ℓ-1 and temperature between 24 and 29°C. Addition of organic carbon (glucose) improved the ammonium removal but decreased the nitrite accumulation ratio significantly. TOC concentration above 800 mg·ℓ-1 was not able to cause the inhibition of the heterotrophs over the nitrifiers. PCR-DGGE results indicated the presence of Nitrosomonas (ammonia-oxidising bacteria) and Nitrobacter (nitrite-oxidising bacteria) in the immobilised pellets.Keywords: bioimmobilisation, ammonium, partial nitrification, wastewater treatment

Modelling the photochemical generation kinetics of 2-methyl-4-chlorophenol, an intermediate of the herbicide MCPA (2-methyl-4-chlorophenoxyacetic acid) in surface waters

2-Methyl-4-chlorophenol (MCP) is the main transformation intermediate of the herbicide MCPA in surface waters and it is more toxic than its parent compound. MCP is produced from MCPA by both direct photolysis and •OH reaction. The latter process has higher yield of MCP from MCPA: 0.5 vs. 0.3 for the direct photolysis. Our model results show that the formation rate of MCP would be higher in waters that contain low organic matter and high nitrate and nitrite. Such conditions are favourable to MCPA direct photolysis and •OH-induced transformation, which are both inhibited by organic matter, while •OH formation is enhanced by nitrate and nitrite. Good agreement is obtained between model predictions and field data of MCPA transformation in the Rhône river delta (Southern France). The field data also suggest that MCP undergoes slightly faster transformation than MCPA in that environment.

Nitrous oxide generation in denitrifying phosphorus removal process: main causes and control measures

Despite the many benefits of denitrifying phosphorus removal process, the significant generation of nitrous oxide (N2O), a potent greenhouse gas, remains a problem for this innovative and promising process. To better understand and more effectively control N2O generation in denitrifying phosphorus removal process, batch experiments were carried out to investigate the main causes of N2O generation, based on which the control measures were subsequently proposed. The results showed that N2O generation accounted for 0.41 % of the total nitrogen removal in denitrifying phosphorus removal process, whereas, in contrast, almost no N2O was generated in conventional denitrification process. It was further demonstrated that the weak competition of N2O reductase for electrons and the high nitrite accumulation were the two main causes for N2O generation, evidenced by N2O production and reduction rates under different conditions. Accordingly, the reduction of N2O generation was successfully achieved via two control measures: (1) the use of continuous nitrate addition reducing N2O generation by around 91.4 % and (2) the use of propionate as the carbon source reducing N2O generation by around 69.8 %.

Impact of iron overload on interleukin-10 levels, biochemical parameters and oxidative stress in patients with sickle cell anemia.

ObjectiveThe aim of this study was to evaluate the impact of iron overload on the profile of interleukin-10 levels, biochemical parameters and oxidative stress in sickle cell anemia patients. MethodsA cross-sectional study was performed of 30 patients with molecular diagnosis of sickle cell anemia. Patients were stratified into two groups, according to the presence of iron overload: Iron overload (n = 15) and Non-iron overload (n = 15). Biochemical analyses were performed utilizing the Wiener CM 200 automatic analyzer. The interleukin-10 level was measured by capture ELISA using the BD OptEIAT commercial kit. Oxidative stress parameters were determined by spectrophotometry. Statistical analysis was performed using GraphPad Prism software (version 5.0) and statistical significance was established for p-values < 0.05 in all analyses. ResultsBiochemical analysis revealed significant elevations in the levels of uric acid, triglycerides, very low-density lipoprotein (VLDL), alanine aminotransferase (ALT), lactate dehydrogenase (LDH), urea and creatinine in the Iron overload Group compared to the Non-iron overload Group and significant decreases in the high-density lipoprotein (HDL) and low-density lipoprotein (LDL). Ferritin levels correlated positively with uric acid concentrations (p-value < 0.05). The Iron overload Group showed lower interleukin-10 levels and catalase activity and higher nitrite and malondialdehyde levels compared with the Non-iron overload Group. ConclusionThe results of this study are important to develop further consistent studies that evaluate the effect of iron overload on the inflammatory profile and oxidative stress of patients with sickle cell anemia.

Circulating Anti-Beta2-Glycoprotein I Antibodies Are Associated with Endothelial Dysfunction, Inflammation, and High Nitrite Plasma Levels in Patients with Intermittent Claudication

Our aim is to investigate a possible association of circulating anti-beta2-glycoprotein I antibodies (ABGPI) with the endothelial dysfunction, nitric oxide bioactivity dysregulation, and the inflammatory status that surrounds peripheral arterial disease. We carried out an observational translational study, including 50 male patients with intermittent claudication and a healthy control group of 10 male subjects, age and sex matched with the cases. Flow-mediated arterial dilatation (FMAD) was assessed as a surrogate of endothelial dysfunction, and C-reactive protein (hsCRP) was determined as a marker of inflammation. Nitrite plasma levels were measured by colorimetric analysis. Circulating ABGPI titer was detected with indirect immunofluorescence. Titers <1 : 10 represented the reference range and the lower detection limit of the test. Circulating ABGPI titer ≥1 : 10 was detected in 21 (42%) patients and in none of the control subjects (P < 0.01). Patients with ABGPI titer ≥1 : 10 had a lower FMAD (P = 0.01). The CRP levels were higher in patients with ABGPI titer ≥1 : 10 (P = 0.04). The nitrite plasma levels were higher in patients with ABGPI titer ≥1 : 10 (P < 0.01). These data suggest that these circulating ABGPI may collaborate in the development of atherosclerosis; however, further prospective studies are required to establish a causal relationship.

Response Surface Evaluation of the Sensory Quality of Turkish Dry Fermented Sausage (sucuk) as Affected by Ripening Period, Nitrite Level and Heat Treatment

Abstract In order to determine the potential for the reduction of nitrite levels and ripening period with heat treatment, the effects of the ripening period (1, 3, 7, 11 and 13 days), nitrite level (45, 70, 120, 170 and 195 ppm) and heat treatment (30, 40, 60, 80 and 90 °C) on the sensory quality of sucuk were investigated using central composite rotatable design setup based upon response surface methodology. The linear and quadratic effects of the ripening period and heat treatment were found to be significant for the sensory quality. However, the effects of higher nitrite levels on the sensory parameters of sucuk were not found to be significant (p&gt;0.05). Optimum values for the ripening period, heat level and nitrite level for overall acceptability were 8 days, 59.3 °C and 109.4 ppm, respectively.

The oxidative denitrosylation mechanism and nitric oxide release from human fetal and adult hemoglobin, an experimentally based model simulation study

Generation of unbound nitric oxide (NO) via the oxidative denitrosylation (ODN) mechanism is proposed to involve the simultaneous reaction of nitrite with oxy and deoxy hemoglobin (Hb(O2) (k1) and Hb (k13)) to yield respectively, *NO2 and Hb(+2)(NO). These two reaction pathways are coupled when *NO2 reacts with Hb(+2)(NO) to yield Hb(+3)(NO) (k22), a species that releases NO rapidly. Here, I have constructed an experimentally based molecular model of the ODN mechanism (k1-k31), focusing on the high nitrite reductase activity of R-state hemoglobin. This model was used to test the hypothesis that human fetal hemoglobin (HbF) can generate unbound NO faster and to a greater extent than HbA, consequent to a 25-fold larger value of k1, which was determined in an earlier study. The results show that despite the use of identical values for k22, there was a 44-fold larger apparent rate of reaction of *NO2 with HbF(NO) compared to HbA(NO), for reactions simulated at 410 μM nitrite and 100 μM hemoglobin (heme basis), 50% oxygen saturation at pH 7.4 and 37°C. This faster reaction was associated with the generation of about 11 μM peak unbound NO. In contrast, HbA failed to generate unbound NO rapidly under the same conditions. However, raising the concentration of nitrite into the millimolar range did generate unbound NO in the HbA simulation, in agreement with the experimental literature, and that result was associated with acceleration in the rate of reaction of NO2 with HbA(NO). Unbound NO could be generated at 410 μM nitrite in the HbA simulation by lowering the pH. This too was associated with an acceleration in the rate of reaction of NO2 with HbA(NO). Furthermore, generation of unbound NO could be assigned to the pH-dependent increase in k1, independent of the associated increase in k(13). Finally, selective exchange of the HbA value of k1 for the HbF value, keeping all other constants and conditions unchanged, generated kinetic patterns for the various species of the "k1-modified" HbA simulation, which were virtually indistinguishable from those seen in the HbF simulation. Taken together, these findings show that rapid and extensive generation of unbound NO within the ODN mechanism is controlled by the value of k1. The faster and more extensive generation of unbound NO by HbF at micromolar nitrite concentration suggests a possible second function for HbF in sickle cell disease, namely enhanced vasodilation. The failure of 410 μM nitrite to generate unbound NO in the HbA simulation at pH 7.4, contrasts with evidence in the literature showing that exposure of intact red cells to 100 to 200 μM nitrite in PBS, promoted NO release into the gas phase. I point out that this difference in outcome may be due to the higher activity of HbA when bound to the cytoplasmic domain of the red cell membrane anion transport protein SLC4A1 (band 3) and to the demonstrated capacity of band 3 to transport nitrite.

The effect of high hydrostatic pressure, sodium nitrite and salt concentration on the growth of Listeria monocytogenes on RTE ham and turkey

Growth of Listeria monocytogenes was evaluated for up to 182days after inoculation on ready-to-eat (RTE) sliced ham and turkey breast formulated with sodium nitrite (0 or 200ppm), sodium chloride (1.8% or 2.4%), and treated (no treatment or 600MPa) with high hydrostatic pressure (HHP). HHP at 600MPa for 3min resulted in a 3.85–4.35log CFU/g reduction in L. monocytogenes. With formulations at similar proximate analyses, one of the evaluation days (day 21) without HHP showed significantly greater growth of L. monocytogenes in ham than in turkey breast, but there were no significant differences on other evaluation days or with HHP. There were no differences in growth of L. monocytogenes due to sodium chloride level. Sodium nitrite provided a small, but significant inhibition of L. monocytogenes without HHP, but addition of sodium nitrite did not significantly affect growth of L. monocytogenes with use of HHP.