Addition Of Sodium Nitrate Research Articles

Effects of hydrogen peroxide and sodium nitrate on microwave-assisted polyethylene oxidative degradation in the presence of nitric acid

Polyethylene (PE) upcycling has been challenging due to the chemical robustness of non-activated C-C and C-H bonds. One promising strategy is oxidative degradation, in which a strong oxidizing agent, usually nitric acid, oxidizes PE to produce a mixture of organic acids (C4 to C7 diacids and acetic acid). However, current research focuses on how to utilize the obtained organic acids as feedstock (e.g. for plasticizer and gaseous hydrocarbon synthesis) rather than improving the process itself. In this study, we evaluated the effects of adding hydrogen peroxide and sodium nitrate at 200 °C, considering possible PE oxidation mechanisms in the presence of nitric acid. Hydrogen peroxide can partially replace nitric acid, thereby reducing the required amount of nitric acid in the process. This is because, at sufficient nitric acid concentrations, hydrogen peroxide accelerates PE oxidation, while nitric acid simultaneously prevents the overoxidation of the resulting organic acids by hydrogen peroxide. When a nitric acid/hydrogen peroxide solution (1:1 mol/L) was employed for 3 h, the carbon efficiency and total organic acid concentration were 35.6 % and 14.0 g/L, respectively. Furthermore, the addition of sodium nitrate improved overall reaction efficiency through the Baeyer-Villiger type oxidation, which involves a nucleophilic attack on the protonated carbonyls by the nitrate ions. When a nitric acid/sodium nitrate solution (1.5:0.5 mol/L) was employed for 1.5 h, the carbon efficiency and the organic acid yield increased to 39.0 % and 15.3 g/L, respectively. Finally, the potential for upcycling waste PE was also demonstrated using both HNO3/H2O2 and HNO3/NaNO3 conditions, producing organic acids from waste linear low-density polyethylene (LLDPE) and high-density polyethylene (HDPE). This study comfirms the potential to reduce the amount of nitric acid used in the microwave-assisted upcycling of waste PE, an aspect that had been previously overlooked. This reduction can contribute to a more environmentally friendly transformation of the proposed process, facilitating the conversion of waste PE into valuable chemicals.

Removal of polycyclic aromatic hydrocarbons (PAHs) from produced water using the microalgae Chlorella vulgaris cultivated in mixotrophic and heterotrophic conditions

Chlorella vulgaris was cultivated for 15 days in 10 different treatments under mixotrophic and heterotrophic conditions, using wastewater from oil and poultry industries as the culture medium. The blends were made with produced water (PW), sterilized produced water (PWs), sterilized poultry wastewater (PoWs), sterilized seawater (SWs), and the addition of sodium nitrate to evaluate cell growth in treatments and the removal of PAHs. The heterotrophic condition showed more effective removal, having an initial concentration of 3.93 μg L−1 and a final concentration of 0.57 μg L−1 of total PAHs reporting 83%, during phycoremediation of (PW) than the mixotrophic condition, with an initial concentration of 3.93 μg L−1 and a final concentration of 1.96 and 43% removal for the PAHs. In the heterotrophic condition, the blend with (PWs + SWs) with an initial concentration of 0.90 μg L−1 and a final concentration of 0.32 μg L−1 had 64% removal of total PAHs compared to the mixotrophic condition with 37% removal having an initial concentration of 0.90 μg L−1 and a final concentration of 0.56 μg L−1. However, the best result in the mixotrophic condition was obtained using a blend of (PWs + PoWs) that had an initial cell concentration of 1.18 × 105 cells mL−1 and reached a final cell concentration of 4.39 × 105 cells mL−1, an initial concentration of 4.76 μg L−1 and a final concentration of 0.37 μg L−1 having a 92% total removal of PAHs. The biostimulation process increased the percentage of PAHs removal by 45% (PW) in the mixotrophic condition. This study showed that it is possible to allow an environmental remediation strategy that significantly reduces effluent toxicity and generates high value-added biomass in contaminated effluents rich in nutrients and carbon, based on a circular bioeconomy model.

Effects of nitrogen addition on greenhouse gas fluxes during continuous freeze-thaw cycles in a cold temperate forest.

Both nitrogen (N) deposition and soil freeze-thaw cycles (FTCs) induce pulses of greenhouse gas (GHG) emissions in cold temperate zones due to changes in soil carbon (C) and nitrogen (N) turnover. However, the combined effects of N addition and FTCs on GHG fluxes have received little research attention, particularly in boreal forests. We conducted a laboratory incubation experiment using intact soil cores from Rhododendron dauricum-Larix dahurica plots to investigate the GHG flux response to these combined effects. We separated the soil samples into seven groups (no, low, medium, and high sodium nitrate addition and low, medium, and high ammonium chloride addition) and exposed each group to continuous FTC conditions. The N2O and CO2 emissions were eventually stimulated by the FTCs, while CH4 uptake was inhibited by FTCs but responded differently under different N addition treatments. All the treatments had substantially increased N2O emissions compared to the control. However, the soil respiration rate significantly increased only with medium sodium nitrate addition, and high levels of N addition (regardless of form) inhibited CH4 uptake. These findings demonstrate that FTCs and N addition (in various forms and levels) have considerable effects on GHG emissions in temperate forest ecosystems. Moreover, dissolved organic carbon (DOC), microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), and inorganic nitrogen in soil are potential factors that drive GHG emissions and are necessary considerations in predicting future feedback effects of GHG emissions on climate change.

Physiological and Gene Expression Response of Interspecific Hybrids of Fraxinus mandshurica × Fraxinus americana to MJ or SNP under Drought

Drought affects the growth and production of Fraxinus tree species, such as the precious woody plant Fraxinus mandshurica. Based on interspecific hybrid F1 combinations, D110 plants of F. mandshurica × F. americana with strong drought resistance were selected for this study. To further reveal their heterosis mechanism under drought, in this study, an analysis was conducted pertaining to the physiological indexes and gene expression of related key gene changes in materials of 5 yr D110 seedlings and their female and male parental controls (D113 and 4–3) in response to drought, as well as to the addition of sodium nitrate (SNP, a donor of nitric oxide) and methyl jasmonate (MJ, a donor of jasmonate) signal molecules after drought. The results showed that under drought stress, hybrid D110 plants performed significantly better than their parents, especially compared to D113, in plant growth (the plant height growth was 29.48% higher), photosynthesis (the net photosynthetic rate was 38.4% higher), peroxidation (the increase in MDA content was 71.77% lower), defense enzyme activity (SOD and POD activities were 36.63% and 65.58% higher), hormone contents (ABA, IAA and GA were 33.9%~51.2% higher) and gene expression (the LHY and TOC1 rhythmic genes were 131.97%~165.81% higher). When an exogenous additive agent (SNP or MJ) was applied after drought, the negative effects of drought on growth were effectively alleviated (the tree height growth of D110 increased from 22.76% to 22.32% in comparison to drought conditions); meanwhile, the height growth of D110 plants was significantly higher than that of their parents. Further results of physiological indexes and the expression of related key gene changes in response to SNP or MJ also indicated that D110 plants can recover faster from drought than their parents after application of SNP or MJ. This article provides new ideas for revealing the heterosis mechanism of the drought resistance of interspecific F1 hybrids and supplies effective measures for improving drought resistance in F. mandshurica.

Effect of Hydrogen-Consuming Compounds on In Vitro Ruminal Fermentation, Fatty Acids Profile, and Microbial Community in Water Buffalo.

The present study aimed to investigate the effect of hydrogen-consuming compounds on ruminal methane (CH4) production, in vitro fermentation parameters, fatty acids profile, and microbial community in water buffalo. Different sodium nitrate to disodium fumarate ratios [2:1 (F), 1:1 (S), 1:2 (T)]were studied in vitro by batch culture technique in the presence of linoleic acid. Results revealed that the dominant bacterial communities were not affected with sodium nitrate and disodium fumarate, whereas CH4 production and Verrucomicrobia, Succiniclasticum, norank_f__Muribaculaceae, and Prevotellaceae_UCG-003 were reduced (P < 0.05). However, ruminal pH, unsaturated fatty acids/saturated fatty acids (UFA/SFA) and Campilobacterota, Selenomonas, Succinivibrio, Oribacterium, Christensenellaceae_R-7_group, Campylobacter, Shuttleworthia, Schwartzia, and Prevotellaceae_YAB2003_group were increased (P < 0.05). Total volatile fatty acids (TVFA) and Spirochaetae, Fibrobacterota, Verrucomicrobia, Fibrobacter, Treponema, and Prevotellaceae were decreased in F (P < 0.05), but cis-9, trans-11CLA, acetate/propionate and Proteobacteria, Campilobacterota, Selenomonas, Succinivibrio, and Campylobacter were increased in F (P < 0.05). The highly selected bacterial genera in F were Campylobacter and Succinivibrio. The disodium fumarate, enhanced (P < 0.05) the TVFA, propionate, total bacteria, Butyrivibrio proteoclasticus, and Atypical butyrivibrio. The concentrations of C18:3n3, C20:3n6, C21:0, C22:2n6, and C22:1n9, as well as the populations of total fungi, protozoa, methanogens, Butyrivibrio hungatei in T were higher (P < 0.05). The highly selected bacterial genera in T were Fibrobacter and Treponema. Conclusively, the addition of sodium nitrate and disodium fumarate can reduce the CH4 production and optimize ruminal fatty acid composition. Furthermore, disodium fumarate can alleviate the adverse effect of sodium nitrate on the rumen fermentation.

Value-added utilization of silicon and iron in copper smelting slag

ABSTRACT The methodology enhanced by synergic catalyzation with sodium nitrate and ultrasonic irradiation under alkaline leaching condition at atmospheric pressure was proposed, for separating silicon and iron in acid leaching residue of copper smelting slag. And the preparation of white carbon black from the alkaline leachate obtained was conducted for utilizing the silicon in the copper smelting slag, as well as the alkaline leaching residue can be used as raw materials with high quality for iron making. The effects of leaching temperature, sodium hydroxide concentration, ultrasonic power, stirring speed, liquid-solid ratio, leaching time and additional amount of sodium nitrate on silica leaching rate were studied. The leaching kinetics of SiO2 from the acid leaching residue of copper smelting slag was also studied. The results showed that under the optimal leaching conditions of temperature 130°C, sodium hydroxide concentration 20 wt.%, ultrasonic power 315 W, stirring rate 500 rpm, liquid-solid ratio 6 mL/g, leaching time 60 min and sodium nitrate addition 2.5 g, the leaching rate of SiO2 reached 94.5 wt.%. Among 90 ~ 130°C, the leaching process was controlled by diffusion and consistent with Johnson Mehl Avrami. The quality of white carbon black prepared was of meeting grade A in Chinese national standard.

Optimal Nitrate Supplementation in Phaeodactylum tricornutum Culture Medium Increases Biomass and Fucoxanthin Production.

Phaeodactylum tricornutum is a model diatom with numerous potential applications in the industry, including the production of high-value carotenoid pigments such as fucoxanthin. This compound is a potent antioxidant currently extracted mainly from brown macroalgae. Fucoxanthin exhibits several biological properties with well-known beneficial effects in the treatment and prevention of lifestyle-related diseases. P. tricornutum offers a valuable alternative to macroalgae for fucoxanthin production as it has a specific productivity that is 10-fold higher as compared with macroalgae. However, production processes still need to be optimised to become a cost-effective alternative. In this work, we investigated the optimal supplementation of nitrate in a cultivation medium that is currently used for P. tricornutum and how this nitrate concentration affects cell growth and fucoxanthin production. It has previously been shown that the addition of sodium nitrate increases productivity, but optimal conditions were not accurately determined. In this report, we observed that the continuous increase in nitrate concentration did not lead to an increase in biomass and fucoxanthin content, but there was rather a window of optimal values of nitrate that led to maximum growth and pigment production. These results are discussed considering both the scale up for industrial production and the profitability of the process, as well as the implications in the cell’s metabolism and effects in fucoxanthin production.

Sodium nitrate as a methanogenesis suppressor in earthen separator microbial fuel cell treating rice mill wastewater.

The microbial fuel cell (MFC) is one of the sustainable technologies, which alongside treating wastewater, can generate electricity. However, its performance is limited by factors like methanogenesis where methanogens compete with the anode respiring bacteria for substrate, reducing the power output. Thus, sodium nitrate, which has been previously reported to target the hydrogenotrophic methanogens, was used as a methanogenic suppressor in this study. The performance of MFC with and without sodium nitrate was studied during the treatment of rice mill wastewater. A significantly higher power density and coulombic efficiency (CE) were noted in the MFC with sodium nitrate (MFCT) (271.26 mW/m3) as compared to the control MFC (MFCC) (107.95 mW/m3). Polarization studies showed lower internal resistance for the MFCT (330 Ω) as compared to MFCC (390 Ω). Linear sweep voltammetry and cyclic voltammetry indicated a higher electron discharge on the anode surface due to enhancement of electrogenic activity. Considerable reduction (76.8%) in specific methanogenic activity was also observed in anaerobic sewage sludge mixed with sodium nitrate compared to the activity of anaerobic sewage sludge without any treatment. Due to the inhibition of methanogens, a lower chemical oxygen demand (COD) and phenol removal efficiency were observed in MFCT as compared to MFCC. The COD balance study showed an increase in substrate conversion to electricity despite the increase in nitrate concentration. Therefore, selective inhibition of methanogenesis had been achieved with the addition of sodium nitrate, thus enhancing the power generation by MFCs.

The kinetics of tempeh wastewater treatment using Arthrospira platensis.

The microalga Arthrospira platensis (Spirulina) was used for tempeh wastewater treatment. Microalga growth and the kinetics of chemical oxygen demand (COD) degradation under different light intensities (2,100 and 4,300 lux), tempeh wastewater concentrations (0, 0.5, 1, 1.5% v/v), and sodium nitrate concentrations (0, 0.75, 1, 2, 2.5 g/L) were studied. Improved cell growth in wastewater indicated that mixotrophic growth was preferred. The addition of sodium nitrate up to 2 g/L increased COD removal. The highest COD removal was 92.2%, which was obtained from cultivation with 1% v/v tempeh wastewater, 2 g/L sodium nitrate, 2,100 lux, and the specific growth rate of 0.33 ± 0.01 day-1. The COD removal followed a pseudo-first-order kinetic model with the kinetic constant of 0.3748 day-1 and the nitrate uptake rate of 0.122 g/L-day. The results can be used to design a pilot-scale tempeh wastewater treatment facility using A. platensis for tertiary treatment. Based on the kinetic model, a 20 m3 reactor can treat tempeh wastewater to reduce the COD from 400 to 100 ppm in 4 days and produces approximately 32.8 kg of dried microalgae.

Thermogravimetric Study of Oxidation Firing of Rhenium- and Osmium-Containing Lead Sludge

Results are provided for thermal and thermogravimetric studies of lead sludge in the presence of and without oxidizing agents in order to determine the thermally active part of the charge composition. It is shown that during oxidation firing of lead sludge the process begins with charge dewatering and organic compound decomposition, and rare metal oxidation commences after complete destruction of organic compounds. Addition of sodium nitrate or calcium hypochlorite oxidizing agents provides complete oxidation of rhenium and osmium in the range of 400–650°C with the subsequent extraction of osmium into sublimate and concentration of rhenium in the form of perrhenate compounds in the ash. In this case decomposition of organic substances proceeds in parallel with oxidation reactions of rare metals without affecting their oxidation.

Nitrogen Optimization on Rhamnolipid Biosurfactant Production from Pseudoxanthomonas sp. G3 and Its Preservation Techniques

Biosurfactant is a microbial bioproduct that is used to reduce the surface tension, and can acted as emulsifier, dispersant, and anti-adhesive. Optimization of biosurfactant production needs to be done, not only to increase its production quantity, but also to reduce overall production cost. This study aims to determine the most suitable and optimum concentration of nitrogen source for biosurfactant production and its preservation techniques. The biosurfactant was produced by Pseudoxanthomonas sp. G3 using minimal salt medium with 2% light crude oil as carbon source and different nitrogen sources in the form of urea, sodium nitrate, and ammonium nitrate. The activity of biosurfactants were measured by emulsification index (E24), interfacial tense (IFT), oil drop assay, and dry weight. Potassium sorbate 0.2% (w/v) was used as preservative agent. The results showed that biosurfactant production using sodium nitrate as a nitrogen source provides the highest activity and yield. The E24 value was 76.63% and the clear zone diameter observed was 0.875 cm. The overall decreased in IFT was 35.4% and the biosurfactant dry weight was 0.45 gL-1. Microbial contamination occurred after 3 weeks of storage in the treatment without the addition of preservative. It also showed that the activity of biosurfactants (emulsification and IFT) were gradually decreased during storage. In conclusion, the optimum biosurfactant production by Pseudoxanthomonas sp. G3 was obtained by the addition of sodium nitrate 0.3% (w/v). Meanwhile, the most effective biosurfactant preservation method was by adding potassium sorbate which was stored at 4 ℃.

Effect of Adding Sodium Nitrate without or with some Feed Additives in Growing Rabbit Diets on: 1. Growth Performance and Economic Efficiency

Ninety, 7 weeks of age weaning New Zealand White (NZW) rabbits with similar average live body weight (745 g) were used in this study. Rabbits were randomly distributed into 10 equal groups (each group contains 9 animals) and housed in separate cages (3 rabbits in each). The experimental groups were fed randomly on one of the 10 formulated experimental diets used. Sodium nitrate addition for these diets was at two levels. The first level was 0.0 % of the total mixed diet for diet 1 (R1), diet 2 (R2), diet 3 (R3), diet 4 (R4) and diet 5 (R5), while the second level was 2 % of the total mixed diet for diet 6 (R6), diet 7 (R7), diet 8 (R8), diet 9 (R9) and diet 10 (R10). The diets R1 and R6 were without feed additives, while the four feed additivees which were used, sodium sulphate (0.2 % of the total mixed diet), bentonite (clay) (2.0 % of the total mixed diet, yeast (0.25 % of the total mixed diet) and prebiotic (0.2 % of the total mixed diet) for diets R2, R3, R4 and R5 respectively and also, in diets R7, R8, R9 and R10 respectively. The main results showed that live body weight was higher with feeding on R1, R4. R5, R9 and R10 (1199, 1104.0, 1149, 1114 and 1142 g, respectively) than feeding on the other experimental diets. The average daily gain from 7 to 14 weeks were higher when feeding on the control without NaNO3 (R1) (24.48 g/h/d) or added yeast or prebiotic as shown in R4 or R5 (22.54 and 23.46 g/h/d, respectively) and with feeding on NaNO3 with added yeast or prebiotic (R9 or R10) (22.73 and 23.32 g/h/d, respectively) than the others R2 or R3 or R6 or R7 and R8 diets, being 21.87, 20.69, 22.09, 20.10 and 22.38 g/h/d, respectively. The average DMI from 7 to 14 weeks of age when feeding the experimental diets was ranged from 89.96 g/h/d with feeding on R7 to 93.55 g/h/d with feeding on R6. The average feed conversion ratio (FCR) from 7 to 14 weeks was the highest when feeding on R2, R3, R4, R6, R7, R8 and R9 (4.25, 4.49, 4.09, 4.25, 4.33, 4.02 and 4.09 g DMI/g DG, respectively), while the lowest ratio values were with feeding on R1 and R10 (3.81 and 3.99 g DMI/g DG, respective). The relative economic efficiency from R1 of the experimental diets were 76.16, 63.73, 77.25, 68.73, 76.77, 58.29, 76.01, 78.04 and 66.37 % for R2, R3, R4, R5, R6, R7, R8, R9 and R10, respectively. Conclusively, the present study showed that the live body weight was higher with feeding on diet without NaNO3 or without feed additives (R1) or with added yeast (R4) or prebiotic (R5) or with NaNO3 and with added yeast (R9) or prebiotic (R10). In general, feeding these feed additives need some trials to adjust the economic efficiency.

Research Note: Evaluation of dietary administration of sodium chlorate and sodium nitrate for Histomonas meleagridis prophylaxis in turkeys

Histomoniasis is currently a re-emerging disease of major significance for many commercial turkey and broiler breeder production companies because of the unavailability of drugs or vaccines. The protozoa Histomonas meleagridis (HM) requires the presence of enteric microflora to promote the disease. The objectives of this research note were to evaluate the effect of dietary administration of sodium chlorate (SC) and sodium nitrate (SN) in vitro and in vivo for HM prophylaxis in poults. A total of 128 day-of-hatch female poults obtained from a commercial hatchery were wing-tagged and randomly assigned into 1 of 4 experimental groups: negative control (NC), positive control, dietary inclusion of SC (3,200 ppm) and SN (500 ppm). Poults from groups SC and SN started on their respective diets on day 12. All groups, except the NC, were challenged with 2 × 105 HM on day 19. Controls were fed a basal diet, identical to the treatment diets but not supplemented with SC or SN. Body weight gain (BWG) was determined weekly, starting on day 1 until day 28, and postchallenge morbidity and mortality were recorded. On day 28 of age, all surviving poults were lesion scored for hepatic and cecal lesions. Ceca and distal ileum were collected on day 28 for bacterial recovery on selective media for total aerobic, lactic acid bacteria, or gram-negative bacteria. The addition of SC and SN in the in vitro growth of HM greatly reduced the growth of the protozoa after 20 h of incubation when compared with the control nontreated group (P < 0.05). However, dietary supplementation of SC and SN had no effect against HM in vivo, as was demonstrated by BWG, the severity of lesions in the liver and ceca or bacterial recovery of treated poults when compared with the positive control group.

Green Synthesis of Reduced Graphene Oxide with in situ Decoration of Metal Nanoparticles for Charge Storage Application

Abstract In the present work, Carbon based 2-D layered (GRM’s) Graphene Related Materials (Graphene Oxide (GO) and Reduced Graphene Oxide (rGO)) have been synthesized. Where GO was composed using lucrative one step Chemical Method (Modified Hummer’s Method) without the addition of Sodium Nitrate, the GO was then simultaneous reduced with added nitrates of Silver and Copper(in-situ) using green reducing agent (NaOH + Al foil). For confirmation the obtained rGO decorated with Metal or Metal Oxides of Ag and Cu, GO and rGO is analysed by XRD, EDAX, SEM and FTIR. Further, by Dip Coating the working electrode of the synthesized material on Copper foil was prepared for Cyclic Voltammetry measurements the results signify the promising application of GRM’s (Metal decorated rGO) in energy storage applications

Effect of sodium nitrate concentration on biomass and oil production of four microalgae species

ABSTRACTThe chemical composition of the culture medium is essential for microalgae growth, and to increase the production of biomass and oil. This work studied the influence of sodium nitrate concentration on microalgae growth, biomass production and oil recovery in Chlorella vulgaris, Nannochloropsis oculata, Tetraselmis chui, and Tetraselmis tetrathele. Microalgae were cultivated in mediums with the addition of sodium nitrate varying from 25 to 75 mg/L. The increase of sodium nitrate increased the biomass production of N.oculata (from 0.4 to 2.2 g/L) and C.vulgaris (from 1.4 to 3.4 g/L) and had limited influence on the growth of T.tetrathele, while no change was observed on the growth of T.chui. The oil to biomass ratio increased with nitrogen limitation, with N.oculata presenting the highest oil to biomass ratio. Chlorella vulgaris presented the highest lipid productivity (0.15 g/L.day), while T.chui was the only microalgae that presented its highest productivity at low sodium nitrate concentration.

Effect of the Addition of Sodium Nitrate in a Total Mixed Ration with Fermented Tofu Waste on Methane Production from the Rumen Fluid

Effect of the Addition of Sodium Nitrate in a Total Mixed Ration with Fermented Tofu Waste on Methane Production from the Rumen Fluid

Preparation and Characterization of Macro Porous Glass-Ceramics as Bioactive Scaffold Material

Bioactive glass and glass-ceramics have a huge interest in biomedical application due to their high biocompatibility and bioactive property. In this study, macro porous glass-ceramic based on 51.26% SiO2 - 36.56% CaO - 11.83% P2O5 and 42.11% SiO2 - 18.42% CaO - 29.82% Na2O - 9.65% P2O5 (in mol%) were prepared via sol-gel synthesis and powder sintering method. Sodium nitrate was used as the precursor for sodium oxide (Na2O) composition in the sol-gel glass. Effect of sodium nitrate addition on the sintered glass (glass-ceramic) properties were studied. The stabilized gel-glasses obtained were compacted into pellets and sintered at 1000 °C for 3 hours. It was found that, Na-contained glass-ceramic (Na-GC) crystallized at 71.5% due to increase in sodium-related crystalline phases. Na-GC showed 72.98% of apparent porosity and densified at 27.02% with macro porous structure with pore sizes in the range of 22.4 μm to 302 μm. The macro porous structure of Na-GC was obtained due to the foaming effect occurred during sintering. Flux effect occurred during sintering also resulted in relatively high compressive strength of Na-GC at 21.53 MPa. The macro porous Na-GC also proved to be bioactive as apatite-like structures were deposited on its surface after immersed into SBF solution for 14 days. The prepared macro porous Na-GC has high potential to be used as a scaffold material in biomedical application due to combination of suitable macro-pore size range, bioactive and has sufficient mechanical strength.

Sol Gel Synthesis and Preparation of Macroporous Glass: Effect of Sodium Nitrate Addition

Sol Gel Synthesis and Preparation of Macroporous Glass: Effect of Sodium Nitrate Addition

Exogenous silicon alleviates cadmium toxicity in rice seedlings in relation to Cd distribution and ultrastructure changes

Silicon (Si) has inhibitory effects on cadmium (Cd) toxicity in rice, but the effects of Si-containing materials on the chemical properties of hydroponic media have been ignored. The increased pH value and introduction of excess cations when utilizing alkaline reagents may disguise the true function of the Si. Thus, the present study investigated Si-alleviated effect on Cd toxicity in rice seedlings by eliminating the aforementioned interferences. The hydroponic cultivation of rice seedlings was carried out to demonstrate the inhibiting effects of exogenous Si on Cd accumulation and distribution. The chlorophyll and carotenoid contents in leaf cells under Cd stress were also measured. Transmission electron microscopy was used to investigate ultrastructural changes in rice mesophyll cells, chloroplasts, and mitochondria under different Cd-stressed and Si-amended conditions. The alkalinity of the Si source was neutralized with nitric acid, and discrepancies in Na+ levels was eliminated by the addition of sodium nitrate to different treatments. Toxicity symptoms were observed in rice seedlings under Cd (5 mg L−1) treatment after 35 days, and the biomass, and chlorophyll and carotenoid contents, were lowered. The levels of these indices increased after adding 120 mg L−1 Si. The bioconcentration and translocation factor values indicated that Si reduced Cd accumulation in rice plants and also decreased the ratio of Cd translocation from roots to shoots, which effectively alleviated the Cd toxicity. The positive effects of Si were mainly reflected in the recovery of grana lamellae and membrane structures in chloroplasts, and restored membrane morphology and increased numbers of cristae in mitochondria. Exogenous Si reduced Cd uptake in rice seedlings, especially in shoots, and inhibited Cd transport into aboveground parts. In addition, Si restored the functions of chloroplasts owing to a decrease in lipid peroxidation. The application of Si indicated that Cd toxicity is alleviated partly because of the improvement in chloroplast biosynthesis and the diminution of Cd bioavailability.

Nitrate Sensing and Metabolism Inhibit Biofilm Formation in the Opportunistic Pathogen Burkholderia pseudomallei by Reducing the Intracellular Concentration of c-di-GMP.

The opportunistic pathogen Burkholderia pseudomallei is a saprophytic bacterium and the causative agent of melioidosis, an emerging infectious disease associated with high morbidity and mortality. Although melioidosis is most prevalent during the rainy season in endemic areas, domestic gardens and farms can also serve as a reservoir for B. pseudomallei during the dry season, in part due to irrigation and fertilizer use. In the environment, B. pseudomallei forms biofilms and persists in soil near plant root zones. Biofilms are dynamic bacterial communities whose formation is regulated by extracellular cues and corresponding changes in the nearly universal secondary messenger cyclic dimeric GMP. Recent studies suggest B. pseudomallei loads are increased by irrigation and the addition of nitrate-rich fertilizers, whereby such nutrient imbalances may be linked to the transmission epidemiology of this important pathogen. We hypothesized that exogenous nitrate inhibits B. pseudomallei biofilms by reducing the intracellular concentration of c-di-GMP. Bioinformatics analyses revealed B. pseudomallei 1026b has the coding capacity for nitrate sensing, metabolism, and transport distributed on both chromosomes. Using a sequence-defined library of B. pseudomallei 1026b transposon insertion mutants, we characterized the role of denitrification genes in biofilm formation in response to nitrate. Our results indicate that the denitrification pathway is implicated in B. pseudomallei biofilm growth dynamics and biofilm formation is inhibited by exogenous addition of sodium nitrate. Genomics analysis identified transposon insertional mutants in a predicted two-component system (narX/narL), a nitrate reductase (narGH), and a nitrate transporter (narK-1) required to sense nitrate and alter biofilm formation. Additionally, the results presented here show that exogenous nitrate reduces intracellular levels of the bacterial second messenger c-di-GMP. These results implicate the role of nitrate sensing in the regulation of a c-di-GMP phosphodiesterase and the corresponding effects on c-di-GMP levels and biofilm formation in B. pseudomallei 1026b.