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1.
Food Chem ; 367: 130666, 2022 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-34343805

RESUMO

Considering excess nitrites are detrimental to the human body and environment, designing a rapid, sensitive, and real-time quantitative determination for nitrite is of great significance for environmental preservation and public health. In this paper, Co3O4 nanoflowers coupled with ultrafine MoO3 nanoparticles (MoO3/Co3O4) are obtained via a hybrid electrochemical deposition strategy (HED). The as-designed MoO3/Co3O4/CC integrating electrode exhibits superior electrocatalytic properties towards nitrite oxidation, owing to the synergistic effect between MoO3 and Co3O4 caused by the heterostructure of MoO3/Co3O4. The electrode achieved a low response time of 2 s, an excellent sensitivity of 1704.1 µA mM-1 cm-2, and a low limit of detection of 0.075 µM (S/N = 3). Furthermore, the electrode displays promise for nitrite detection in complex food such as water and sausages samples. Our study will provide a significant strategy for the application of bimetallic heterostructure to explore the design of sensing interfaces.


Assuntos
Nanopartículas , Nitritos , Técnicas Eletroquímicas , Eletrodos , Humanos , Água
2.
Food Chem ; 367: 130628, 2022 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-34343807

RESUMO

A spectrophotometric method based on diazo-coupling reaction for nitrite analysis was established and validated, including inter-laboratory validation, linearity, accuracy, precision, the limit of detection (LOD) and limit of quantification (LOQ). The time-saving and high-recovery method was established by examining the filtration step, colorimetric process and concentration range of the calibration curve. This method showed good linearity (r2 > 0.999) in the range of 0.025-1.0 µg/mL. The three-level recoveries were between 86.7% and 108.6%, with the coefficient of variation (CV) below 5.8%. Mean nitrite concentration ranges in processed foods were ND-33.47 mg/kg. The mean nitrite intake was 0.8% of the Acceptable Daily Intake (ADI, 0.07 mg/kg bw/day) for all children and adolescents and 2.8% for the consumer group. The major contributors for all subjects and consumers were ham, sausage and bacon. These results indicated that the improved method was suitable for analyzing nitrite in processed foods and the nitrite exposure levels were safe.


Assuntos
Produtos da Carne , Nitritos , Adolescente , Criança , Dieta , Exposição Dietética , Humanos , Produtos da Carne/análise , Nitritos/análise , República da Coreia
3.
Food Chem ; 367: 130660, 2022 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-34390907

RESUMO

In this work, a quantitative image analysis method based on cyanine dye-upconversion nanoparticles composite luminescent nanoprobe for the detection of nitrite was developed. The nanoprobe was constructed by combining the NaYF4:Yb,Tm@NaYF4 upconversion nanoparticles (UCNPs) and the new cyanine dye IR-790. The upconversion nanoparticles transferred energy to IR-790, resulting in the luminescence quenching, while the luminescence of UCNPs was recovered after adding NO2-. The increase in photons was related to the concentration of NO2-. Under the optimal experimental conditions, the detection range was 0.20-140 µM and the limit of detection was 0.030 µM. The measurement for NO2- can be completed in 29 min. The method has the characteristics of fast response (~0.1 s), low sample consumption (10 µL) and powerful data support (550 frame time series images). Furthermore, the quantitative image analysis method was successfully applied for the analysis of nitrite in environmental water and food samples.


Assuntos
Luminescência , Nanopartículas , Corantes , Nitritos
4.
Food Chem ; 369: 130970, 2022 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-34500207

RESUMO

The excessive uptake of nitrite is perilous and detrimental for human health that prone to cancer disease. Herein, described the synthesis of SiO2/Al2O3/C material through the sol-gel procedure followed by grafting with 3-n propylpyridinium silsesquioxane chloride organic ligand for enhancing electrochemical activity. H-NMR, 13C NMR, and 29Si studies were performed for confirmation of surface functionalization through the grafting technique. The surface morphology was evaluated through SEM and TEM techniques. The material showed an irregular and flakes-like structure that exhibited more compactness and conglomerate structure with no segregation in phase was observed after grafting. The elemental composition was confirmed from EDX analysis. The electrochemical measurements were performed with cyclic voltammetry, electrochemical impedance spectroscopy (EIS), and chronoamperometry. The prepared hybrid inorganic-organic composite Si/C/Al/SiPy+Cl- was applied for the modification of the glassy carbon (GC) electrode and assessed as a sensor for nitrite determination. The sensor showed the low limit of detection (0.01 µM), low limit of quantification (0.08 µM), wide linear response range (0.2-280 µM), and high sensitivity (410 µA·µM-1). It gave a quick response time of <1 s in the presence of 70 µM nitrite. The fabricated sensor showed high sensitivity, chemical stability, and insignificant interference from co-existing species present in sausage meat and food industry discharges. The repeatability of the sensor was evaluated as 2.5 % R.S.D.; for n = 10 at 50 µM nitrite.


Assuntos
Técnicas Eletroquímicas , Nitritos , Carcinógenos , Cloretos , Eletrodos , Humanos , Dióxido de Silício
5.
J Colloid Interface Sci ; 606(Pt 2): 1055-1063, 2022 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-34487928

RESUMO

Ammonia (NH3) plays an important role in agriculture and industry. The industry-scale production mainly depends on the Haber-Bosch process suffering from issues of environment pollution and energy consumption. Electrochemical reduction can degrade nitrite (NO2-) pollutants in the environment and convert it into more valuable NH3. Here, Ni2P nanosheet array on nickel foam is proposed as a 3D electrocatalyst for high-efficiency electrohydrogenation of NO2- to NH3 under ambient reaction conditions. When tested in 0.1 M phosphate buffer saline with 200 ppm NO2-, such Ni2P/NF is able to obtain a large NH3 yield rate of 2692.2 ± 92.1 µg h-1 cm-2 (3282.9 ± 112.3 µg h-1 mgcat.-1), a high Faradic efficiency of 90.2 ± 3.0%, and selectivity of 87.0 ± 1.7% at -0.3 V versus a reversible hydrogen electrode. After 10 h of electrocatalytic reduction, the conversion rate of NO2- achieves near 100%. The catalytic mechanism is further investigated by density functional theory calculations.


Assuntos
Amônia , Nitritos
6.
Sci Total Environ ; 802: 149850, 2022 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-34525707

RESUMO

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.


Assuntos
Nitritos , Poluentes Químicos da Água , Benzofenonas , Ecossistema , Fotólise , Poluentes Químicos da Água/análise
7.
Sci Total Environ ; 806(Pt 1): 150425, 2022 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-34560448

RESUMO

Estuarine and coastal wetlands, which act as large sources of methane (CH4) and undergo substantial loading of anthropogenic nitrogen (N), provide ideal conditions for denitrifying anaerobic methane oxidation (DAMO) to occur. Yet the microbial mechanisms governing DAMO and the main driving factors in estuarine and coastal ecosystems remain unclear. This study investigated the spatiotemporal distribution and associated activity of DAMO microorganisms along a wide swath of China's coastline (latitudinal range: 22-41°N) using molecular assays and isotope tracing techniques. We uncovered significant spatial and seasonal variation in DAMO bacterial community structure, whereas DAMO archaeal community structure exhibited no seasonal differences. The abundance of DAMO bacterial pmoA gene (2.2 × 105-1.0 × 107 copies g-1) was almost one order of magnitude higher than that of DAMO archaeal mcrA gene (8.7 × 104 -1.8 × 106 copies g-1). A significant positive correlation between pmoA and mcrA gene abundances (p < 0.01) was observed, indicating that DAMO bacteria and archaea may cooperate closely and thus complete nitrate elimination. Potential DAMO rates, in the range of 0.09-23.4 nmol 13CO2 g-1 day-1 for nitrite-DAMO and 0.03-43.7 nmol 13CO2 g-1 day-1 for nitrate-DAMO, tended to be greater in the relatively warmer low-latitudes. Potential DAMO rates were weakly positively correlated with gene abundances, suggesting that DAMO microbial activity could not be predicted directly by gene abundance alone. The heterogeneous variability of DAMO was shaped by interactions among key environmental characteristics (sediment texture, N availability, TOC, Fe3+, salinity of water, and temperature). On a broader continental scale, potential N removal rates of 0.1-11.2 g N m-2 yr-1 were estimated via nitrite-DAMO activity in China's coastal wetlands. Overall, our results highlight the widespread distribution of DAMO microbes and their potential role in eliminating excess N inputs and reducing CH4 emissions in estuarine and coastal ecosystems, which could help mitigate global warming.


Assuntos
Metano , Áreas Alagadas , Anaerobiose , China , Desnitrificação , Ecossistema , Nitritos , Oxirredução , RNA Ribossômico 16S
8.
Sci Total Environ ; 806(Pt 1): 150556, 2022 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-34582850

RESUMO

Heterotrophic nitrification bacteria play a critical role in nitrogen cycling and pollution removal. However, the underlying nitrification mechanisms are diverse and have rarely been investigated at the genetic level. In this study, the new heterotrophic nitrifier Pseudomonas sp. strain JQ170 was isolated. Strain JQ170 can utilize ammonia (NH4+-N), nitrite (NO2--N), or nitrate (NO3--N) as sole nitrogen sources, preferring NH4+-N. A ratio of 96.4% of 1.0 mM NH4+-N was removed in 24 h. The optimum pH, temperature, and carbon source for NH4+-N removal were pH 7.0, 30 °C, and citrate, at a C/N ratio of 9-18, respectively. During the NH4+-N removal process, only NO2--N but neither hydroxylamine, NO3--N, nor gaseous nitrogen were detected. A random transposon insertion mutagenesis library of strain JQ170 was constructed. Two NO2--N-production deficient mutants were screened and transposon insertion sites were located in nap genes (which encode periplasmic NO3--N reductase Nap). Further gene knockout and complementation of the napA gene confirmed nap as essential for NO2--N production. The following nitrification processes in strain JQ170 is proposed: NH4+-N to NO3--N in the cytoplasm; then NO3--N to NO2--N in the periplasmic space by Nap; finally, NO2--N secreted out of cells. Overall, this paper provides new insight towards understanding heterotrophic nitrification at the genetic level.


Assuntos
Nitrificação , Nitritos , Aerobiose , Bactérias , Desnitrificação , Processos Heterotróficos , Nitrogênio , Pseudomonas/genética
9.
Sci Total Environ ; 804: 150143, 2022 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-34798727

RESUMO

Sulfide partial denitrification (SPD) is an alternative pathway for nitrite production accompanied with elemental sulfur (S0) production for nitrate removal from wastewater with anammox. In this study, the SPD granular sludge was cultivated for the first time in an upflow anaerobic sludge bed (UASB) reactor to reach the efficacy of maximum nitrate-to-nitrite transformation ratio of 92% and an in-situ maximum NO3--N reduction rate of 2.46 kg-N/m3-d, both much higher than literature results. Mature granules had an average particle size of 2.52 mm and hold smooth surface with excess rod bacteria. The elements Ca and S, and proteins in extracellular polymeric substances contributed to granule structure's stability. Enriched Thiobacillus genus was proposed to accumulate nitrite at moderate HRT (2-6 h). The immobilized functional strains assist efficient partial nitrification reactions to be realized with formed S0 as byproduct.


Assuntos
Nitritos , Águas Residuárias , Reatores Biológicos , Desnitrificação , Nitratos , Nitritos/análise , Nitrogênio , Oxirredução , Esgotos , Sulfetos , Águas Residuárias/análise
10.
Chemosphere ; 286(Pt 3): 131896, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34426268

RESUMO

The completely autotrophic nitrogen-removal over nitrite (CANON) process has merits in energy saving and consumption reducing, thus being considered as an attractive alternative over the common denitrification technology. In this study, the effects of three common heavy metals (Cu2+, Zn2+ and Mn2+) in wastewater to the CANON process were evaluated comprehensively. A central composite design with response surface methodology was utilized to investigate the joint effect of these three metal ions on the nitrogen removal performance of CANON process. In accordance with the determined optimal dosage in batch tests, four bioreactors were established with different amounts of heavy metal dosage in long-term operation, which determined the optimal concentrations for Cu2+, Zn2+ and Mn2+ to be 0.25, 0.81 and 1.00 mg/L, respectively. However, the optimal dosing level determined in batch tests showed no promotion during long-term experiment. This indicated that the actual concentration of heavy metals in bioreactors during long-term operation could be higher than expectation, leading to the difference between short-term tests and long-term experiment. The distribution of metal ions revealed that Mn2+ was mainly absorbed in anammox bacteria cells while Cu2+ and Zn2+ were mostly identified inside AOB cells. Moreover, the addition of heavy metals consistently showed positive effects for the relative abundance of AOB, while only a low level of dosage could promote the abundance of anammox bacteria. Furthermore, a mathematical model was established to simulate the CANON system considering the impacts of heavy metals, which was calibrated and validated using independent dataset in this study.


Assuntos
Nitritos , Nitrogênio , Processos Autotróficos , Reatores Biológicos , Desnitrificação , Zinco
11.
Sci Total Environ ; 803: 150068, 2022 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-34525735

RESUMO

Phenacetin (PNCT), a common antipyretic and analgesic drug, is often used to treat fever and headache. However, the effect of PNCT on nitrifiers in wastewater treatment processes remains unclear. The practicability of attaining partial nitrification (PN) through inhibitor-PNCT was investigated in this study. The optimal treatment conditions of soaking once for 18 h with 2.50 × 10-3 g PNCT/(g MLSS) were applied to the PN stability experiment. The results showed that ammonia oxidation activity recovered quickly after 3 cycles of operation, while nitrite oxidation activity was suppressed steadily. In addition, average ammonium removal efficiency and nitrite accumulation ratio during 138 cycles could reach 94.94% and 85.38%, respectively. Complimentary DNA high-throughput sequencing and oligotyping analysis showed that the activity of Nitrosomonas would gradually surpass Nitrospira after PNCT treatment only once. The decrease of Nitrospira activity was accompanied by the simplification of oligotypes after PNCT treatment, while Nitrosomonas could adapt to PNCT stress by reducing the differences between oligotypes. Metagenomics revealed that the decrease in the number of NXR in the nitrogen metabolism pathways was the key reason for achieving PN. The potential mechanisms might be that the dominant nitrite-oxidizing bacteria and complete ammonia oxidizers were bio-killed by PNCT.


Assuntos
Metagenômica , Fenacetina , Amônia , Reatores Biológicos , Nitrificação , Nitritos , Nitrogênio , Oxirredução
12.
J Colloid Interface Sci ; 607(Pt 2): 1313-1322, 2022 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-34583036

RESUMO

A highly sensitive electrochemical sensor was developed through a one-pot green synthesis method for nitrite detection based on the electrochemical technique. Xylan-based carbon quantum dots (CQDs) were used as green in situ reducing agent to prepare CQDs capped gold nanoparticles (Au@CQDs). MXene of good electrical conductivity was used as the immobilized matrix to fabricate Au@CQDs-MXene nanocomposites with the advantages of good electrical conductivity and electrocatalysis. An electrochemical sensor for nitrite monitor was obtained by loading the Au@CQDs-MXene on a glassy carbon electrode. The sensor presents high sensitivity, good stability, wide linear range, and excellent selectivity due to the high catalytic activity of AuNPs and CQDs, the large specific surface area of MXene, and exceptional electrical conductivity of AuNPs and MXene. Under the optimal condition, the linear detection range of the sensor was from 1 µM to 3200 µM with a detection limit of 0.078 µM (S/N = 3), which was superior to most reported sensors using differential pulse voltammetry (DPV) method. Furthermore, this sensor was successfully applied to detect nitrite in tap water and salted vegetables with satisfactory recoveries. This modified electrocatalytic sensor shows a new pathway to fabricate nitrite detection sensor with feasibility for practical application.


Assuntos
Nanopartículas Metálicas , Nanocompostos , Pontos Quânticos , Carbono , Técnicas Eletroquímicas , Eletrodos , Ouro , Limite de Detecção , Nitritos
13.
J Sci Food Agric ; 102(1): 147-155, 2022 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-34057213

RESUMO

BACKGROUND: Bacterial community successions were surveyed during the processing stages of sugar production using high-throughput sequencing methods. Furthermore, the correlation between bacterial community and nitrate/nitrite content in beet sugar processing were investigated. RESULTS: In an analysis of the V3-V4 region of the 16S rDNA gene, 254 122 effective sequences were obtained from samples, which included sugar beet, cossettes, diffusion juice, second-phase diffusion juice, light juice and thick juice. The results showed that dominant genera included Pantoea, Pseudomonas, Leuconostoc and Burkholderia. Moreover, significant changes in bacterial communities were observed in samples. Regarding the relevant nitrogen metabolic potential, this study revealed communities with the ability for nitrate and nitrite metabolism. Furthermore, a shaking experiment involving diffusion juice and second-phase diffusion juice was performed, and results showed that the nitrate level declined 73% and 98% in 36 h, respectively. These results suggested that the bacterial communities contribute to nitrate and nitrite transformation. CONCLUSION: This study illustrated that the bacterial communities and their specific effects on the formation of nitrate and nitrite during beet sugar processing. The results presented the basic concept involving the nitrate- and nitrite-forming pathways directly related to the mechanism of bacterial community growth. This study could facilitate an understanding of the correlation between nitrite content and microorganisms to guide beet sugar manufacturers regarding the control of nitrite and nitrate content. © 2021 Society of Chemical Industry.


Assuntos
Bactérias/metabolismo , Beta vulgaris/química , Nitratos/análise , Nitritos/análise , Tubérculos/microbiologia , Açúcares/isolamento & purificação , Bactérias/classificação , Bactérias/genética , Bactérias/isolamento & purificação , Beta vulgaris/microbiologia , Biotransformação , Manipulação de Alimentos , Sequenciamento de Nucleotídeos em Larga Escala , Nitratos/metabolismo , Nitritos/metabolismo , Tubérculos/química , Açúcares/química
14.
Food Chem ; 372: 131356, 2022 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-34818750

RESUMO

An electrochemical sensor based on stearyl trimethyl ammonium bromide - functionalized niobium carbide@multi-walled carbon nanotubes (Nb2C@MWCNTs-STAB) for signal amplification was successfully constructed for sensitive detection of nitrite (NO2-). Niobium carbide@multi-walled carbon nanotubes (Nb2C@MWCNTs) with high electrical conductivity and water dispersibility were first prepared in a one-pot hydrothermal synthesis, after which cationic STAB was added to overcome the negative surface charge on the Nb2C@MWCNTs. The electrostatic attraction between Nb2C@MWCNTs-STAB and NO2- was improved by the STAB, which enhanced the sensitivity of the constructed sensor for NO2-. Under optimized conditions, Nb2C@MWCNTs-STAB/GCE exhibited excellent analytical performance for detection NO2- with two wide liner ranges (0.1-100 µmol L-1 and 100-2000 µmol L-1) and a limit of detection of 0.022 µmol L-1. Nitrite recovery tests in milk and spinach samples showed recoveries in the range of 89.82-104.52%. The NO2- residues in ham and pickled vegetable (cedrela sinensis) samples were analysed using the presented sensor and a spectrophotometric method, with no significant difference found between the results of the two methods.


Assuntos
Nanotubos de Carbono , Técnicas Eletroquímicas , Eletrodos , Limite de Detecção , Nióbio , Nitritos
15.
Chemosphere ; 287(Pt 2): 132148, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34509756

RESUMO

Nitrate/nitrite-dependent anaerobic methane oxidation (n-DAMO) is an important process linking nitrogen and carbon cycle. It is recently demonstrated that n-DAMO archaea are able to couple n-DAMO to dissimilatory nitrate reduction to ammonium (DNRA). In this work, a mathematical model is developed to describe DNRA by n-DAMO archaea for the first time. The anabolic and catabolic processes of n-DAMO archaea, n-DAMO bacteria and anaerobic ammonium oxidation (Anammox) bacteria are involved. The different impacts of exogenous and endogenous nitrite on DNRA and n-DAMO microbes are considered. The developed model is calibrated and validated using experimental data collected from a sequencing batch reactor (SBR) and a counter-diffusion membrane biofilm bioreactor (MBfR). The model outputs fit well with the profiles of nitrogen (N) dynamics and biomass changes in both reactors, demonstrating its good predictive ability. The developed model is further used to simulate the counter-diffusion MBfR incorporating n-DAMO and Anammox process to treat sidestream wastewater. The simulated distribution profiles of N removal/production rates by different microbes along biofilm depth reveal that DNRA by n-DAMO archaea plays an important role in N transformation of the integrated n-DAMO and Anammox process. It is further suggested that the counter-diffusion MBfR under the investigated conditions should be operated at proper hydraulic retention times (HRTs) (i.e. 6h and 8h) with exogenous NO2- in the range of 0-10 mg N/L or at HRTs >3h with the absence of exogenous NO2- in order to achieve dischargeable effluent.


Assuntos
Compostos de Amônio , Anaerobiose , Reatores Biológicos , Desnitrificação , Metano , Nitratos , Nitritos , Nitrogênio , Oxirredução
16.
Bioresour Technol ; 343: 126066, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34626765

RESUMO

In this study, the fluctuating profiles of physicochemical and microbial characterizations along different filling heights of continuously up-flow solid-phase denitrification (SPD) columns packed with polycaprolactone (PCL) were investigated. It was found both the PCL filling area and non-filling area made significant contributions to treatment performance and denitrification mainly occurred near the bottom of the filling column. Nitrate displayed a high proportional removal (≥98.7%) among all the cases except the one with the lowest filling ratio (FR30) and highest NLR (3.99 ± 0.12 gN/(L·d)), while nitrite and ammonium displayed a weak accumulation in final effluents (nitrite ≤ 0.40 mg/L; ammonium ≤ 0.98 mg/L). The intensity of PCL hydrolysis in the top substrate was stronger than those in the middle or bottom. Both dissimilatory nitrate reduction to ammonium (DNRA) and microbial lysis contributed to ammonium accumulation, and nitrate was mainly removed via traditional denitrification and DNRA. JGI_0000069-P22_unclassified and Gracilibacteria_unclassified might contribute to denitrification.


Assuntos
Compostos de Amônio , Desnitrificação , Nitratos , Nitritos , Nitrogênio , Poliésteres
17.
Bioresour Technol ; 343: 126116, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34653622

RESUMO

A heterotrophic nitrification- aerobic denitrification (HNAD) bacterium, Acinetobacter junii ZHG-1, was isolated, meanwhile, the optimal conditions for the strain were evaluated, moreover, the influence mechanism of the C/N ratio on the HNAD process was investigated from the perspective of electron transport and energy level. The increasing of C/N ratio enhanced the reduced/oxidized nicotinamide adenine dinucleotide (NADH/NAD+) ratio, NADH concentration, electron transport system activity (ETSA), ATP content, as well as enzymes activities, consequently, the HNAD performance of the strain can be improved, however, when the C/N ratio was higher than 30, the activities of enzymes relating to the HNAD process and the ETSA had reached the maximum, which might limit the further improvement of the nitrogen removal with the increasing of C/N ratio. As the interaction between different biochemical reactions in HNAD process, more efforts should be devoted to the influent mechanism of different environmental factors on the HNAD process.


Assuntos
Desnitrificação , Nitrificação , Acinetobacter , Aerobiose , Processos Heterotróficos , Nitritos , Nitrogênio
18.
Sensors (Basel) ; 21(22)2021 Nov 12.
Artigo em Inglês | MEDLINE | ID: mdl-34833600

RESUMO

Nitrification is a common issue observed in chloraminated drinking water distribution systems, resulting in the undesirable loss of monochloramine (NH2Cl) residual. The decay of monochloramine releases ammonia (NH3), which is converted to nitrite (NO2-) and nitrate (NO3-) through a biological oxidation process. During the course of monochloramine decay and the production of nitrite and nitrate, the spectral fingerprint is observed to change within the wavelength region sensitive to these species. In addition, chloraminated drinking water will contain natural organic matter (NOM), which also has a spectral fingerprint. To assess the nitrification status, the combined nitrate and nitrite absorbance fingerprint was isolated from the total spectra. A novel method is proposed here to isolate their spectra and estimate their combined concentration. The spectral fingerprint of pure monochloramine solution at different concentrations indicated that the absorbance difference between two concentrations at a specific wavelength can be related to other wavelengths by a linear function. It is assumed that the absorbance reduction in drinking water spectra due to monochloramine decay will follow a similar pattern as in ultrapure water. Based on this criteria, combined nitrate and nitrite spectra were isolated from the total spectrum. A machine learning model was developed using the support vector regression (SVR) algorithm to relate the spectral features of pure nitrate and nitrite with their concentrations. The model was used to predict the combined nitrate and nitrite concentration for a number of test samples. Out of these samples, the nitrified sample showed an increasing trend of combined nitrate and nitrite productions. The predicted values were matched with the observed concentrations, and the level of precision by the method was ± 0.01 mg-N L-1. This method can be implemented in chloraminated distribution systems to monitor and manage nitrification.


Assuntos
Água Potável , Nitrificação , Amônia , Nitritos , Oxirredução , Abastecimento de Água
19.
Braz Dent J ; 32(2): 27-36, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34614058

RESUMO

The objective of this 9-month clinical study is to assess the impact of one-stage full-mouth disinfection (FMD) on salivary nitrite levels and systemic biomarkers and its correlation with total subgingival bacterial load in obese and non-obese patients with periodontitis. In total, 94 patients (55 obese and 39 non-obese) were initially evaluated, seven were lost during follow-up, resulting in 87 individuals at the end of the study. Outcomes were assessed at baseline, 3, 6, and 9 months post periodontal treatment by FMD. Salivary nitrite levels were determined using Griess reagent. Blood samples were collected to determine C-Reactive Protein (CRP), alkaline phosphatase and fasting blood glucose. Real-time PCR was used to determine the total subgingival bacterial load. FMD protocol resulted in increased salivary nitrite levels at 6- and 9-months post-treatment in the non-obese group (p<0.05). In obese individuals, FMD treatment led to an increase in salivary nitrite levels at 6 months (p<0.05); however, at 9 months, the nitrite levels returned to baseline levels. For both groups, the highest nitrite values were observed at 6 months. In addition, in both groups, FMD was associated with a decrease in biomarkers related to systemic inflammation and cardiovascular diseases, such as CRP (p<0.05) and alkaline phosphatase (p<0.05), and had no impact on the fasting blood glucose. This study demonstrates that obese patients with periodontitis present similar salivary nitrite levels when compared with non-obese individuals. FMD protocol resulted in increases in salivary nitrite levels and was associated with a positive impact on systemic biomarkers, regardless of obesity status.


Assuntos
Nitritos , Periodontite , Biomarcadores , Desinfecção , Humanos , Obesidade/complicações
20.
PLoS One ; 16(10): e0258368, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34644318

RESUMO

Effective treatment of respiratory infections continues to be a major challenge. In high doses (≥160 ppm), inhaled Nitric Oxide (iNO) has been shown to act as a broad-spectrum antimicrobial agent, including its efficacy in vitro for coronavirus family. However, the safety of prolonged in vivo implementation of high-dose iNO therapy has not been studied. Herein we aim to explore the feasibility and safety of delivering continuous high-dose iNO over an extended period of time using an in vivo animal model. Yorkshire pigs were randomized to one of the following two groups: group 1, standard ventilation; and group 2, standard ventilation + continuous iNO 160 ppm + methylene blue (MB) as intravenous bolus, whenever required, to maintain metHb <6%. Both groups were ventilated continuously for 6 hours, then the animals were weaned from sedation, mechanical ventilation and followed for 3 days. During treatment, and on the third post-operative day, physiologic assessments were performed to monitor lung function and other significative markers were assessed for potential pulmonary or systemic injury. No significant change in lung function, or inflammatory markers were observed during the study period. Both gas exchange function, lung tissue cytokine analysis and histology were similar between treated and control animals. During treatment, levels of metHb were maintained <6% by administration of MB, and NO2 remained <5 ppm. Additionally, considering extrapulmonary effects, no significant changes were observed in biochemistry markers. Our findings showed that high-dose iNO delivered continuously over 6 hours with adjuvant MB is clinically feasible and safe. These findings support the development of investigations of continuous high-dose iNO treatment of respiratory tract infections, including SARS-CoV-2.


Assuntos
Anti-Infecciosos/administração & dosagem , Óxido Nítrico/administração & dosagem , Administração por Inalação , Animais , Citocinas/análise , Citocinas/sangue , Avaliação Pré-Clínica de Medicamentos , Hemodinâmica , Hemoglobina A/análise , Pulmão/metabolismo , Pulmão/patologia , Masculino , Metemoglobina/análise , Azul de Metileno/administração & dosagem , Modelos Animais , Nitratos/análise , Nitritos/análise , Suínos
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