Increase In Nitrite Concentration Research Articles

Rapid detection of nitrite in food by multi-colorimetric and fluorescence dual-mode based on crystal violet modulated carbon dots

A new method for the determination of nitrite (NO2–) by multicolor colorimetry and fluorescence dual-mode is presented. This sensing system involves the reaction of crystal violet modulated carbon dots (CV-CDs) with different concentrations of nitrite to produce multiple color signals, while the fluorescence intensity of CV-CDs increases with the increase of nitrite concentration. Therefore, the absorption wavelength shift and fluorescence intensity change can be used for the quantitative determination of nitrite. Furthermore, we combine the multicolor colorimetric output with a smartphone platform to perform on-site determination of nitrite without the need for a spectrometer. Intelligent recognition software was designed to take pictures of color signals and analyze R, G, and B channels. Good results of nitrite analysis were obtained.

Effects of Ammonia Nitrogen, Nitrite and pH on Embryo In Vitro Incubation of Red Crayfish

As an important economic aquatic animal, red crayfish’s reproduction and incubation can affect its breeding efficiency. With aquaculture developing, the study of factors affecting aquaculture species growth has gradually become an important research direction. To study the effects of ammonia nitrogen, nitrite and pH on red crayfish embryos, the In Vitro incubation experiment of red crayfish embryos was conducted. The residual module was used to design the embryo counting method of red crayfish. And different ammonia nitrogen, nitrite and PH gradients were set to analyze the hatching rate and emergence rate of red crayfish’s embryo development.When conducting research method performance testing, the training loss value of the research method decreased to 84 after 200 iterations. On the 6th day in an ammonia nitrogen environment, the number of water microbiota was only 4.74 M. The emergence rate of red crayfish decreases to a lower level when the ammonia nitrogen concentration is above 0.6 mg/L. The emergence rate of red crayfish decreased with the increase of nitrite concentration, and decreased to 0 when the nitrite concentration reached 1.25 mg/L. When the pH value of water body is 8.1, the emergence rate of red crayfish reaches the highest value of 68.92%. Ammonia nitrogen and nitrite concentration will inhibit the In Vitro hatching of crayfish embryos, and the appropriate PH value can improve the emergence rate of crayfish hatching In Vitro.

Bioremediation of RDX and HMX contaminated soil employing a biochar-based bioformulation

Compounds like Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and Octahydro-1, 3, 5, 7-tetranitro-1, 3, 5, 7-tetrazocine (HMX) are categorised as a secondary explosive. These secondary explosives are widely employed for defence and civil purposes worldwide. The release of explosive compounds in the environment during their production, storage and usage results in severe soil and water contamination. Pollution caused by explosives is a major concern as it is recalcitrant in nature and has toxic effects on human beings, animals and plants. There is a need to find an eco-friendly and sustainable approach to deal with explosive contaminated soil. In the present study, bioformulation was prepared with explosive degrading bacteria to treat explosive contaminated soil. Bioformulation consisted of coconut husk-derived biochar as a carrier material and Arthrobacter subterraneus as an active ingredient. The survivability of bacteria and performance of bioformulation with different concentrations of explosive compounds were analysed. Results showed that Arthrobacter subterraneus could immobilise with biochar and can survive up to 6 months. The prepared bioformulation was able to degrade up to 85.98% RDX and 80.4% HMX in contaminated soil in a time duration of 30 days. A significant increase in nitrite concentration, a major byproduct of RDX and HMX biodegradation, was found in soil treated with bioformulation. Thus, bioformulation can be applied to remediate explosive-contaminated sites as an eco-friendly technique.Graphical

The Essential Oil of Hyptis crenata Inhibits the Increase in Secretion of Inflammatory Mediators.

Hyptis crenata is a plant of great ethnopharmacological importance widely distributed in South American countries. In Northeast Brazil, teas or infusions of its aerial parts are used in folk medicine to treat several acute and chronic inflammatory diseases. In a previous work we have demonstrated that the essential oil of H. crenata (EOHc) has an antiedematogenic effect. The aim of this work was to evaluate the effect of EOHc on cytokines secretion and cellular infiltration. Peritonitis and paw edema models induced by carrageenan were used to determine leucocyte count, myeloperoxidase (MPO) activity, nitrite, and cytokines secretion. EOHc (10-300 mg/kg) significantly inhibited leucocyte migration and reduced the neutrophil count (control: 1.46 × 103 ± 0.031 × 103/mL) of the total leucocytes population in extracellular exudate (control: 2.14 × 103 ± 0.149 × 103/mL) by 15.00%, 43.29%, 65.52%, and 72.83% for the doses of 10, 30, 100, and 300 mg/kg EOHc, respectively (EC50: 24.15 mg/kg). EOHc (100 mg/kg) inhibited the increase in myeloperoxidase activity and completely blocked the increase in nitrite concentration induced by carrageenan. EOHc markedly reduced the pro-inflammatory cytokines (IL-6, MCP-1, IFN-γ, TNF-α, and IL-12p70) and increased IL-10, an anti-inflammatory cytokine (compared to control group, p < 0.05). This study demonstrates that EOHc has a long-lasting anti-inflammatory effect mediated through interference on MPO activity, and nitrite, and cytokines secretion. This effect, coupled with low EOHc toxicity, as far as results obtained in mice could be translated to humans, suggests that EOHc has great potentiality as a therapeutic agent.

A turn-on fluorescent nano-probe base on methanobactin-AuNPs for simple and efficient detection of nitrite

Nitrite ions are important markers threatening humans and environmental security. A highly selective method for rapid detection of nitrite needs to be developed. Herein, a novel and rapid fluorescence method for nitrite determination is established on the basis of diazotization-coupling reaction of methanobactin (Mb) extracted by Methylosinus trichosporium OB3b with nitrite on the fluorescence. In the presence of gold nanoparticles (AuNPs), the fluorescence of AuNPs was strongly quenched by the Mb because the sulfhydryl or amino structures on the surface of Mb could be bound to the surface of AuNPs by forming Au-S or Au-N bonds. Upon addition of nitrite, the Mb easily reacts with nitrite to form azo products in the acidic medium. Then, with the increase of nitrite concentration, the Mb-AuNPs fluorescence was gradually recovered, realizing the turn-on fluorescence sensing of nitrite. Under optimal conditions, the proposed method has a good linear relationship with nitrite concentration in the range of 0–8.0 μM and 8.0–50.0 μM, and the detection limit is 16.21 nM. In addition, satisfactory results were obtained for nitrite analysis using milk, ham sausage and leaf mustard as real samples, which demonstrated that the method as-developed would have great practical application prospects.

Construction of integrated and portable fluorescence sensor and the application for visual detection in situ

The development of portable and low-cost fluorescence sensors is significant for on-site detection. Herein, a novel fluorescence sensor integrating power source, light source, filter, sample cell and smartphone was constructed. The model of fluorescence sensor was designed by using Autodesk Computer Aided Design (CAD) software, and printed with 3D printing technology, followed by assembling with various components. With advantages of convenient carrying, good stability, wide applicability and low cost, the fluorescence sensor showed great adaptability for on-site visual detection. Nitrite was chosen as the model of analyte, and ratiometric fluorescent probe (B/R-CDs) was employed as the identification and signal element for detecting nitrite. With the increase of nitrite concentration, the fluorescence intensity of B/R-CDs at 460 nm decreased, while that at 615 nm kept stable. Therefore, the fluorescence color of B/R-CDs changed from blue to red. By using the portable sensor to collect RGB value of fluorescence color, the R/B channel values showed a linear relationship with nitrite concentration in 2.5–600 µM, with detection limit of 0.8 µM. Then the fluorescence sensor was used to detect nitrite in preserved meat and pickles, and recovery rate was among 94.0%−105%. The detection results were consistent with those of fluorescence method and spectrophotometry. This work provides a novel detection device for on-site analysis, and also offers an effective approach for developing miniature fluorescence sensors.

Cambios metabólicos y cinéticos de los lodos activados como consecuencia de las fallas en el sistema de aireación en una PTAR

The classic question from wastewater treatment plant (WWTP) operators is, how long can a secondary reactor be kept unaerated after an aeration system failure? Therefore, in the present research, samples of activated sludge (AS) were taken from a WWTP and left without aeration for 12, 18, 24, and 36 h; simulating an aeration failure. Subsequently, the activity of AS lacking aeration was evaluated in batch cultures. The results showed that the lack of AS oxygenation affected its metabolism. For example, the heterotrophic activity stopped completely when AS was not aerated for 24 h. The nitrifying activity, in the experiments from 12 to 24 h without aeration, the ammonium removal did not change, but there was an increase in nitrite concentration. In the 36-h experiment without aeration, the ammonium consumption rate and removal efficiency decreased by 56% and 43%, respectively, regarding the control. N2O was produced in the period when the AS was not aerated, which could be responsible for these metabolic and kinetic changes. Finally, this study suggested don't leave for more than 24 h the activated sludge without aeration for a quick recovery or to diminish the damage.

Effects of nitrite concentrations on the quality and protein oxidation of salted meat.

The objective of this study was to investigate the effects of different concentrations of sodium nitrite on the quality and protein oxidation of salted meat during 21 days of curing. The salted meat was treated with sodium nitrite at 50, 100, and 150 mg/kg for curing, and salted meat without sodium nitrite was used as a control. The results showed that in salted meat added with sodium nitrite, the carbonyl group, disulfide bond, dityrosine, surface hydrophobicity, and the transformation rate from α-helix to β-sheet were all significantly reduced, whereas the sulfhydryl group content of myofibrillar proteins was significantly increased compared to the control. Meanwhile, the total volatile basic nitrogen and aerobic plate content were significantly decreased, while both the pH and a* value were significantly increased with an increase in nitrite concentration compared to the control group. Importantly, this phenomenon was also observed in salted meat treated with low doses of sodium nitrite (50 mg/kg). In conclusion, the quality of salted beef can be improved by adding low-dose sodium nitrite to inhibit protein oxidation during the curing process. PRACTICAL APPLICATION: A low dose of sodium nitrite inhibited the rate of α-helix to β-sheet transformation of myofibrillar proteins in salted meat, reducing the exposure of hydrophobic groups and decreasing the production of protein oxidation products and TVB-N to improve the quality of salted meat. These results provided a theoretical basis and technical guidance for the application of low-dose sodium nitrite in meat processing enterprises.

Toward a Quantitative Colorimeter for Point-of-Care Nitrite Detection.

This paper reports on a low-cost, quantitative, point-of-care solution for the early detection of nitrite, a common biomarker for urinary tract infections (UTIs). In a healthy individual, nitrite is not found in the urine. However, a subject with a suspected UTI will produce nitrite in their urine since the bacteria present will convert nitrate into nitrite. Traditionally, nitrite is monitored by urinary dipsticks that are either read by eye or using a reflectance spectrophotometer. Both methods provide a semiquantitative positive or negative result at best. In this paper, we described a novel, affordable, portable transmission-based colorimeter for the quantitative measurement of nitrite. A unique permutation of the Griess reaction was optimized for the clinical detection of nitrite in urine and is reported. By using nitrite spiked in a salt buffer, artificial, and human urine samples, the performance of the colorimeter was evaluated against dipsticks read using two commercial dipstick analyzers, Urisys 1100 (Roche Diagnostics) and Clinitek Status+ (Siemens Medical Solutions). The colorimeter was able to detect the clinically relevant range of nitrite from 0.78 to 200 μM in a salt buffer. The detection limit in artificial urine was determined as 1.6 μM, which is ∼16× more sensitive than commercial dipstick reflectance analyzers, enabling the possibility for earlier detection of urinary infections. The colorimeter is assembled using off-the-shelf components (<$80) and controlled by a smartphone application via low-energy bluetooth. It has a built-in color correction algorithm and is designed to enable for a turbidity correction in samples containing bacteria or other cellular debris as well. The mobile application can display the nitrite concentration for a single sample or display the results over a period of time. Tracking urinalysis results longitudinally can help identify trends such as increases in nitrite concentrations over an individual’s baseline and identify possible infections earlier. While the detection of nitrite was showcased here, this portable analyzer can be expanded to other colorimetric-based chemistries to detect a panel of biomarkers, which can improve the overall sensitivity and specificity of the desired assay.

Photodegradation of benzophenones sensitized by nitrite

Benzophenone UV filters (BPs) are a group of contaminants of emerging concern due to their widespread occurrence and adverse effects on aquatic ecosystems. In this study, the transformation of BPs by nitrite sensitized photodegradation was comprehensively investigated. OH and NO2 generated by nitrite photolysis reacted with BPs, forming hydroxylated and nitrated products, respectively. Kinetic modeling revealed that the steady-state concentrations of NO2 were approximately six orders of magnitude higher than those of OH in the UV/nitrite process, although the second-order rate constants of NO2 reactions with BPs were six orders of magnitude lower. With the increase in nitrite concentration, BPs degradation was accelerated, and the contribution of NO2 increased as well. At initial nitrite concentration of 10 μM, the contributions of OH and NO2 to the degradation of 2,4-dihydroxybenzophenone (BP1) were 66.1% and 21.5%, respectively. However, NO2 only contributed a tiny fraction to the degradation of 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid (BP4), due to the presence of an electron-withdrawing sulfonate group in the molecule. Natural organic matter (NOM) inhibited the nitrite sensitized degradation of BPs, due to light screening and radical scavenging effects. This study suggests that BPs can be effectively transformed in sunlit waters in the presence of nitrite, leading to nitrated products.

Differential Effect of Non-Thermal Plasma RONS on Two Human Leukemic Cell Populations.

Simple SummaryAs the number of investigations into the use of non-thermal plasma (NTP) for cancer treatment expands, it is becoming apparent that susceptibility of different cancer cells to NTP varies. We hypothesized that such differences could be attributed to the cell type-dependent interactions between NTP-generated reactive oxygen and nitrogen species (RONS) and the target cells. To test this hypothesis, we examined how two different human leukemic cell lines—Jurkat T lymphocytes and THP-1 monocytes—influence hydrogen peroxide and nitrite content in media after NTP exposure. We also assessed the potential of NTP to enhance immunogenicity in these cells and assayed phagocytosis of NTP-exposed leukemic cells by macrophages. Our results highlight the significance of target-mediated modulation of plasma chemical species in the development and clinical use of protocols involving plasma sources for use in cancer therapeutic application.Non-thermal plasma application to cancer cells is known to induce oxidative stress, cytotoxicity and indirect immunostimulatory effects on antigen presenting cells (APCs). The purpose of this study was to evaluate the responses of two leukemic cell lines—Jurkat T lymphocytes and THP-1 monocytes—to NTP-generated reactive oxygen and nitrogen species (RONS). Both cell types depleted hydrogen peroxide, but THP-1 cells neutralized it almost immediately. Jurkat cells transiently blunted the frequency-dependent increase in nitrite concentrations in contrast to THP-1 cells, which exhibited no immediate effect. A direct relationship between frequency-dependent cytotoxicity and mitochondrial superoxide was observed only in Jurkat cells. Jurkat cells were very responsive to NTP in their display of calreticulin and heat shock proteins 70 and 90. In contrast, THP-1 cells were minimally responsive or unresponsive. Despite no NTP-dependent decrease in cell surface display of CD47 in either cell line, both cell types induced migration of and phagocytosis by APCs. Our results demonstrate that cells modulate the RONS-mediated changes in liquid chemistry, and, importantly, the resultant immunomodulatory effects of NTP can be independent of NTP-induced cytotoxicity.

Correlation of Nitrite and Ammonia with Prevalence of Enterocytozoon hepatopenaei (EHP) in Shrimp (Litopenaeus vannamei) on Several Super-Intensive Ponds in East Java, Indonesia

AbstractEnterocytozoon hepatopenaei (EHP), a microsporidia parasite known to hinder shrimp growth by infecting its hepatopancreas, is recently an emerging infection for Litopenaeus vannamei farms in Indonesia. The present study was conducted to investigate the relationship between nitrite and ammonia concentration with EHP infection in the super-intensive ponds. Shrimps and water samples were collected from six ponds in aquaculture super-intensive ponds with a stocking density of 5,000 shrimps in each pond which is located in Pasuruan, Lamongan, and Tuban Regency, Indonesia. The water sample was taken to the laboratory for the measurement of ammonia and nitrite. The samples of ammonia and nitrite were detected by spectrophotometer, and the PCR was used to detect 18S rRNA of EHP. The PCR analysis that showed two positive samples of L. vannamei, from the ponds with a high concentration of ammonia and nitrite, were infected by EHP. The statistical analysis showed a significant correlation between ammonia and nitrite with the prevalence of EHP infections, where the Pearson correlation (r) was 0.980 and 0.943, respectively. There was a high prevalence of EHP infection with the increase in nitrite concentration and ammonia in pond four and pond six. The concentration of over 1mg/l of ammonia and nitrite could influence EHP infection prevalence in the shrimp farms. Highlight ResearchAmmonia and nitrite concentration influence the prevalence of Enterocytozoon hepatopenaei infection in Super intensive ponds.The estimated prevalence of Enterocytozoon hepatopenaei was 16.7%.PCR amplification analysis was used to detect the 18S ss-rRNA of Enterocytozoon hepatopenaei and 510-bp was obtained.

Pilot Study of Biomarkers of Oxidative Stress and Chlamydia trachomatis in Female Patients with Spontaneous Abortions

The aims of the present study were i. asses the biomarkers of oxi- dative stress including superoxide anion radical, Nitrite measurement and reduced glutathione in female patients with spontaneous abortions Asses the prevalence of C. trachomatis antibodies IgA and IgG in those patients, iii. Correlate the levels of the oxidative biomarkers to the presence of C. trachomatis antibodies. The study included one hundred female patients with 2 or more spon- taneous abortions in addition to one hundred healthy control females with normal gravidity and parity history. Blood samples were obtained from each subject and subjected to laboratory determination of super- oxide anion radical, Nitrite measurement and reduced glutathione by biochemical methods. Determination of specific immunoglobulin A and G (IgA, IgG) was determined by enzyme linked immunosorbent assay (ELISA). The prevalence of IgA and IgG for C. trachomatis in patients was 4% and 8% respectively and, in the control, subjects the prevalence of IgA and IgG were 1% and 2% respectively. The concentration of oxidative stress products was significantly higher in the patients group compared to the control group (P=0.0001). The concentrations of nitrite and reduced glutathione were 27.9± 4.7, 31.4± 1.9 nmol/ml respectively in patients and the concentrations of nitrite and reduced glutathione were 18.9± 2.1 and 27.9± 3.9 respectively in the control group. The concentration of SOD was significantly reduced in the patients group compared to the control group (P=0.0001). The concentration of SOD was 55.1 6.9 in the patients and in the control the concentration was 64.5± 7.7 nmol/ml In the study of oxidative stress markers in the patients with positive serology for C. trachomatis, there was significant increase in nitrite concentrations compared to patients negative for C. trachomatis sero- logical markers (P=0.005). While reduced glutathione concentration had insignificant increase in patients positive for C. trachomatis with reduced SOD compared to patients with negative serology to C. tra- chomatis, P=0.6, P=0.07, respectively. The present study highlights that there was significant increase in oxi- dant stress biomarkers nitrite and reduced glutathione with significant reduction in superoxide dismutase in patients with repeated abortions. The prevalence of IgG to C. trachomatis was significantly prevalent in patients with recurrent abortion compared to control subjects. The nitrite was significantly correlated with positive serology to C. tracho- matis.

Micro-Polluted Surface Water Treated by Yeast-Chitosan Bio-Microcapsules.

Ammonia nitrogen and natural organic matter (NOM) seriously degrade the quality of surface waters. In this study, the optimum preparation conditions of a yeast-chitosan bio-microcapsule of the Candida tropicalis strain, used to treat micro-polluted surface water, were investigated. Fourier transform infrared spectroscopy and scanning electron microscopy were used to characterize the bio-microcapsules. A continuous laboratory-scale reaction apparatus was built to evaluate the engineering applications of the bio-microcapsules and their treatment efficiency for major pollutants in micro-polluted raw water. The yeast-chitosan bio-microcapsules were found to rapidly and effectively remove suspended solids and ammonia nitrogen. Moreover, the bio-microcapsule pre-treatment process was capable of resisting impact loads and fluctuations in water quality. Even at low temperatures (12 °C), the removal rate of ammonia nitrogen still reached 79%. The treatment did not lead to a temporary increase in nitrite concentration, nor to the excessive accumulation of nitrogen. The application of bio-microcapsules is simple; it only requires aeration and certain nutrient substrates, and can be adapted to treat raw drinking water with a poor nutrient substrate, therefore showing promise for future use in engineering applications.

The protective effect of rutin against busulfan-induced testicular damage in adult rats

Here, we studied the protective effect of rutin (RUT) against testicular damage caused by busulfan (BUS) in rats. Adult male Wistar rats were intraperitoneally injected with BUS (4 mg/kg body weight at day 7 and 14), and then treated with RUT (30 mg/kg body weight) by gavage thrice weekly for 60 days. The results showed that BUS-induced increase in 3β-hydroxysteroid dehydrogenase (3β-HSD) was significantly decreased by RUT, whereas 17β-HSD activity and plasma testosterone concentration remained unaffected (p > 0.05). It was also observed that RUT inhibited BUS-induced increase in nitrite concentrations and myeloperoxidase enzyme activities in the plasma and testes (p < 0.05). Similarly, BUS-induced decrease in glutathione and increase in malondialdehyde concentrations in the testes were significantly normalized to control values by RUT. Finally, RUT administration showed some tendency to improve the architecture of the seminiferous epithelium of the rat’s testes after BUS treatment. Overall, RUT inhibited BUS-induced oxidative damage and inflammation in the testis of an experimental rat model.

Plasma lipid peroxidation and antioxidant status in patients with oral precancerous lesions and oral cancer

AbstractObjectiveOral precancerous lesions like oral leukoplakia and oral submucosal fibrosis are very common in north Indian population which often leads to oral squamous cell carcinoma. Chewing of tobacco, pan masala, and betel nut is very common among north Indian women. Reactive oxygen species (ROS) generation is an important outcome of this habit. Imbalance between ROS and antioxidants leads to oxidative stress. The aim of our study was to determine the level of antioxidants in oral precancerous lesions and oral cancer to predict disease susceptibility.MethodThe study group consisted of 120 subjects among which 25 were with histopathologically confirmed oral cancer, 50 with histopathologically confirmed oral precancerous lesions, and 45 were healthy controls. Blood samples were collected for the evaluation of reduced glutathione (GSH) and antioxidant enzymes, catalase, superoxide dismutase (SOD), glutathione reductase (GR) and oxidative stress markers like malondialdehyde (MDA) and nitrite.ResultResults demonstrated a decrease in antioxidant enzymes such as catalase, SOD, and GR in oral precancerous lesion and oral cancer from that of healthy control. An increase in reduced glutathione concentration was observed in oral precancerous lesion and oral cancer as compared to healthy control. Malondialdehyde level was increased significantly in oral cancer. Increase in nitrite concentration was not statistically significant in oral precancerous lesion and oral cancer patients as compared to control.ConclusionOxidative stress and antioxidants have been found to be important indicators in oral cancer and in pre‐malignant lesions which may predict susceptibility of development of oral cancer.

Effect of Tart Cherry Polyphenols on Osteoclast Differentiation and Activity.

Bone is maintained by an intricate balance between bone formation and bone resorption. The presence of inflammation can contribute to an imbalance in bone homeostasis by enhancing differentiation and activity of osteoclasts, the cells that participate in the breakdown of bone. Polyphenols such as flavonoids found in plant-derived foods have been shown to have anti-inflammatory effects in various tissues. Tart cherries are a rich source of such polyphenolic compounds. Using mouse macrophage cells (RAW 264.7), we examined whether tart cherry polyphenols could dose dependently inhibit the proliferation and activity of receptor activator of nuclear factor kappa-B ligand (RANKL) differentiated osteoclasts under inflammatory conditions. Tartrate-resistant acid phosphatase (TRAP) activity and staining of TRAP-positive multinucleated cells, used as indicators of osteoclast differentiation and activity, tended to decrease with tart cherry polyphenols treatment. Osteoprotegerin expression by osteoclasts was decreased in a similar manner. A significant increase in nitrite concentration was observed with the lower doses of tart cherry polyphenols of 50 and 100 μg/mL (P < .05). However, higher doses of tart cherry polyphenols (200 and 300 μg/mL) reduced nitrite concentrations below that of the control that received no tart cherry polyphenols treatment (P < .05). Western blot analyses showed that protein expression of cyclooxygenase-2 (COX-2) followed a similar trend, although results were not statistically significant. On the other hand, tart cherry polyphenols treatments dose dependently increased inducible nitric oxide synthase protein expression, with statistical significance noted at doses of 200 and 300 μg/mL. Overall, our findings suggest that the polyphenols associated with tart cherries potentially inhibit osteoclast differentiation and activity, which may be beneficial to bone health.

Enhanced sludge solubilization and dewaterability by synergistic effects of nitrite and freezing

In this study, nitrite was added into sludge during freezing process to evaluate its role in waste activated sludge (WAS) solubilization and effect on sludge dewatering characteristics. The results showed that the introduction of 100 mg L−1 of nitrite could increase dissolved organic carbon (DOC) concentration from 29.5 to 48.8 mg DOC g−1 VSS under freezing conditions. More DOC was released with the increase of nitrite concentration. Freezing temperature, or freezing speed, also played a role in sludge solubilization. It was found that some readily-biodegradable low molecular weight (LMW) compounds, e.g. LMW protein, LMW polysaccharide, LMW neutrals, building blocks and LMW acids, were mainly released during the freezing process with the presence of nitrite. Interestingly, nitrite could also improve the sludge filterability at the lower nitrite concentration as a result of the increased sludge particle size. However, electrolytes (sodium nitrite) addition effects may mask such enhancement when nitrite concentration was high (800 mg L−1). The rheological characteristics of sludge could be well modeled by Herchel-Bulkley model and the introduction of nitrite into freezing process further increased sludge flowability and decreased sludge viscosity. These results indicated that freezing with the presence of suitable concentration of nitrite could promote sludge solubilization and dewaterability. As such, good liquid and solid separation can be achieved with the recovery of liquid stream as carbon source.

Fate of nitrogen in floating-raft aquaponic systems using natural abundance nitrogen isotopic compositions

Nitrogen is a key nutrient for fish and vegetable productions in aquaponic systems. However, the fate of nitrogen in aquaponic systems has not been fully understood, leading to difficulty in optimizing nitrogen use efficiency (NUE) and plant production. In this study, the fate of nitrogen in floating-raft aquaponic systems with two plant species, pak choi (Brassica rapa L. chinensis) and lettuce (Lactuca sativa longifolia cv. Jericho), and tilapia (Oreochromis sp.) was evaluated using mass balance and natural abundance nitrogen isotopic compositions. Dissolved oxygen (DO) levels associated with hydraulic loading rate (HLR) were found to positively affect nitrite oxidation rate. Increase in nitrite concentration was observed in recirculating water under low DO levels. Nitrite is an intermediate in the dissimilatory reduction of nitrate to N2 gas. Based on progressive enrichment of 15N of nitrate with time in the recirculating water, we estimated total nitrogen loss of up to 46.3% via denitrification. Nitrogen loss via denitrification was reduced by 44–56% when the feed-to-plant ratio was decreased by 30%. Results of this study provide better understanding of nitrogen transformations, which could help in designing and operating efficient aquaponic systems.

Color Developing Capacity of Plasma-treated Water as a Source of Nitrite for Meat Curing.

The interaction of plasma with liquid generates nitrogen species including nitrite (NO−2). Therefore, the color developing capacity of plasma-treated water (PTW) as a nitrite source for meat curing was investigated in this study. PTW, which is generated by surface dielectric barrier discharge in air, and the increase of plasma treatment time resulted in increase of nitrite concentration in PTW. The PTW used in this study contains 46 ppm nitrite after plasma treatment for 30 min. To evaluate the effect of PTW on the cured meat color, meat batters were prepared under three different conditions (control, non-cured meat batter; PTW, meat batter cured with PTW; Sodium nitrite, meat batter cured with sodium nitrite). The meat batters were vacuum-packaged and cooked in a water-bath at 80℃ for 30 min. The typical color of cured meat developed in cooked meat batter treated with sodium nitrite or PTW. The lightness (L*) and yellowness (b*) values were similar in all conditions, whereas, the redness (a*) values of cooked meat batter with PTW and sodium nitrite (p<0.05) were significantly higher than the control. These data indicate that PTW can be used as a nitrite source in the curing process of meat without addition of other nitrite sources.