Amount Of Citric Acid Research Articles

Optimization of a bioremediation system of soluble uranium based on the biostimulation of an indigenous bacterial community

High concentrations of uranium(VI) in the Witwatersrand Basin, South Africa from mining leachate is a serious environmental concern. Treatment systems are often ineffective. Therefore, optimization of a bioremediation system that facilitates the bioreduction of U(VI) based on biostimulation of indigenous bacterial communities can be a viable alternative. Tolerance of the indigenous bacteria to high concentrations of U and the amount of citric acid required for U removal was optimized. Two bioreactor studies which showed effective U(VI) removal more than 99%from low (0.0037mgL(-1)) and high (10mgL(-1)) concentrations of U to below the limit allowed by South African National Standards for drinking water (0.0015mgL(-1)). The second bioreactor was able to successfully adapt even with increasing levels of U(VI) feed water up to 10mgL(-1), provided that enough electron donor was available. Molecular biology analyses identified Desulfovibrio sp. and Geobacter sp. among known species, which are known to reduce U(VI). The mineralogical analysis determined that part of the uranium precipitated intracellularly, which meant that the remaining U(VI) was precipitated as U(IV) oxides and TEM-EDS also confirmed this analysis. This was predicted with the geochemical model from the chemical data, which demonstrated that the treated drainage was supersaturated with respect to uraninite > U4O9 > U3O8 > UO2(am). Therefore, the tolerance of the indigenous bacterial community could be optimized to remediate up to 10mgL(-1), and the system can thus be upscaled and employed for remediation of U(VI) impacted sites.

Development and Evaluation of Gastroretentive Atenolol Tablets

The low oral bioavailability of atenolol is primarily because of its poor absorption from the lower gastrointestinal tract. Gastroretentive dosage forms provide an opportunity to deliver the drug with absorption window in the proximal part of the GIT thereby increasing their bioavailability. The objective of this study was to develop a dosage form for atenolol with the objective of increasing the gastric residence and there by its oral bioavailability. Different formulations of floating tablets of atenolol (AT1-AT10) were prepared by varying the composition of hydroxypropyl methyl cellulose (HPMC) K100, lactose and citric acid. The tablets were evaluated for various parameters like friability, weight variation, content variation, floating lag time, total buoyancy and in vitro dissolution. The physicochemical properties of the prepared formulations were found to possess adequate physical integrity. Formulation AT8 showed the lowest floating lag time with 14 h buoyancy. Drug release was found to be dependent on the concentration of HPMC K100 and lactose in the formulation. Further, the increase in amount of citric acid leads to increase in atenolol release rate while reduces the floating time. The findings revealed that the formulation AT8 retarded the atenolol release (~73% in 12 h) and followed zero order kinetics. The in vitro data observed here substantiate the potential of the prepared formulation to provide adequate drug release and buoyancy to improve the bioavailability of atenolol, which necessitate further in vivo studies.

Development of new processed mussel product using local mussel species (Perna viridis)

Perna species (Perna perna and Perna viridis) are commonly found edible mussel species around the margin of territorial sea of Sri Lanka It is seasonal seafood available only in few months per year have being experimentally cultured not commercialized as a processed mussel product yet. In this research, three mussels products (321, 654 and 987) were developed only vary with added citric acid amount (3g, 4g and 5g) and organoleptic properties of three citric acid treated bottle mussel products were investigated; nutritional and shelf-life were determined only for best product. Mussels (Perna viridis) harvesting was done in consecutive three days; extracted mussel flesh was stored under -10 0C. The processed product is having net weight of 115 g of cooked mussel and 85 mL of brine solution. Hot filling was done in all the time and stored in the room temperature. Semi trained 30 sensory panelist were used to determine the organoleptic qualities of the products subjectively and the best product was selected through Friedman non-parametric test. The color and texture sensory attributes were shown only the significant different (P<0.05) such as 0.001 and 0.035 respectively; sensory attributes such as appearance, odor, taste, after taste and overall acceptability have received to the P values which may higher than to the 0.05 significant levels (P > 0.05) such as 0.093, 0.152, 0.099, 0.850 and 0.106 respectively. The product 654 has received the highest sum of rank in all the time and considered as the best product. It having 6 months of expected shelf-life; no quality defects recorded until 20th week of shelf-life and having 73.70%, 16.65% and 2.60% of moisture, crude-protein and crude-fat percentages respectively. DOI: http://dx.doi.org/10.4038/suslj.v13i1.7673Sabaragamuwa University Journal 2014; V. 13 No. 1 pp 57-64

Physical and electrochemical characteristics of carbon content in carbon-coated Li2MnSiO4 for rechargeable lithium batteries

Carbon-coated Li2MnSiO4 powders were synthesized by a citric acid-assisted sol–gel process, and their physical and electrochemical properties were characterized to assess their suitability as a cathode material in lithium-rechargeable batteries. Carbon was coated onto the Li2MnSiO4 particles through the carbonization of polymeric materials that were caused by the addition of citric acid during the sol–gel process. The particle size and electrical conductivity of the Li2MnSiO4 powders were found to be changed by varying the amount of citric acid added during the sol–gel process. XRD analysis showed that the quantity of impurities in Li2MnSiO4 was decreased during the sol–gel process. The carbon coating led to an increase in conductivity and mean particle size by creating an electrical and physical connection between the particles. The discharge capacity of Li2MnSiO4 with over 5 % carbon coating was significantly increased to ~125 mAh g−1 compared to just ~3 mAh g−1 for noncoated material.

The effect of yttrium substitution on the magnetic properties of magnetite nanoparticles

Abstract Superparamagnetic Y-substituted magnetite (Y x Fe 3– x O 4 ,with x =0.00, 0.10, 0.15, 0.20 and 0.40) nanoparticles were synthesized via hydrothermal reduction route in the presence of citric acid. The synthesized nanoparticles were characterized by X-ray diffraction (XRD) analysis, Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), vibrating sample magnetometry (VSM) and gradient field thermomagnetic measurement. The results showed that a minimum amount of citric acid is required to obtain single phase Y-substituted magnetite nanoparticles. Citric acid acts as a modulator and reducing agent in the formation of spinel structure and controls nanoparticle size and crystallinity. Mean crystallite sizes of the single-phase powders were estimated by Williamson–Hall method. Curie temperature measurement of the samples shows that as yttrium content increases, the Curie temperature decreases. Magnetic measurements show that the saturation magnetization of the samples decreases as x increases up to 0.15 and then increases to x =0.20 and finally decreases again for x =0.40.

IR spectroscopy evidence of MoS2 morphology change by citric acid addition on MoS2/Al2O3 catalysts – A step forward to differentiate the reactivity of M-edge and S-edge

Citric acid was used as chelating agent to prepare a series of MoS2/Al2O3 catalysts. CO adsorption followed by infrared spectroscopy characterization (IR/CO) was employed to probe the M-edge and S-edge of MoS2 slabs on these catalysts. Addition of citric acid promotes the growth of S-edge, whereas it inhibits that of M-edge: The morphology of MoS2 is progressively modified from a slightly truncated triangle with predominately M-edge to a hexagon with both M-edge and S-edge with increasing citric acid amount. Such morphology change is of great importance to the catalytic performance as M-edge and S-edge demonstrate different reactivity in hydrodesulfurization (HDS) reactions. Indeed, IR/CO data reveal that sulfur vacancy creation occurs more easily on M-edge, whereas at room temperature, thiophene tends to adsorb more strongly on S-edge. Moreover, parallel between IR/CO study and HDS test shows that S-edge has a higher intrinsic activity than M-edge in thiophene HDS reaction.

Citric Acid Production by Aspergillus niger Cultivated on Parkia biglobosa Fruit Pulp.

The study was conducted to investigate the potential of Parkia biglobosa fruit pulp as substrate for citric acid production by Aspergillus niger. Reducing sugar was estimated by 3,5-dinitrosalicylic acid and citric acid was estimated spectrophotometrically using pyridine-acetic anhydride methods. The studies revealed that production parameters (pH, inoculum size, substrate concentration, incubation temperature, and fermentation period) had profound effect on the amount of citric acid produced. The maximum yield was obtained at the pH of 2 with citric acid of 1.15 g/L and reducing sugar content of 0.541 mMol−1, 3% vegetative inoculum size with citric acid yield of 0.53 g/L and reducing sugar content of 8.87 mMol−1, 2% of the substrate concentration with citric acid yield of 0.83 g/L and reducing sugar content of 9.36 mMol−1, incubation temperature of 55°C with citric acid yield of 0.62 g/L and reducing sugar content of 8.37 mMol−1, and fermentation period of 5 days with citric acid yield of 0.61 g/L and reducing sugar content of 3.70 mMol−1. The results of this study are encouraging and suggest that Parkia biglobosa pulp can be harnessed at low concentration for large scale citric acid production.

Controlling of dielectric parameters of insulating hydroxyapatite by simulated body fluid

Hydroxyapatite (HAp) samples were synthesized under various amounts of citric acid using the sol-gel method. Before and after immersion in simulated body fluid (SBF) for 14 and 28 days, the structural properties of HAp samples were analyzed by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy with energy dispersive X-ray (EDX) spectroscopy and dielectric measurements. The crystallite size (D) was found to be in the range of 25.17-33.06 nm with the crystallinity percent (XC%) of 69.53-86.09. The lattice parameters of a and c were calculated to be in the ranges of 9.373-9.434 Å and 6.828-6.896 Å, respectively. The morphology of the as-synthesized samples was changed with the amount of citric acid and soaking period in SBF. The Ca/P molar ratios indicated a decrease with increasing immersion time, and Ca-deficiency was observed. The relative permittivity (ε') and dielectric loss (ε″) were significantly affected by citric acid content and soaking period in SBF. It was seen that the alternating current conductivity (σac) increased with increasing frequency and the σac values changed with increasing soaking period and amount of citric acid.

Implementation of the Bacillus cereus microbiological plate used for the screening of tetracyclines in raw milk samples with STAR protocol – the problem with false-negative results solved

In antibiotic residue analyses the first step of screening is just as important as the following steps. Screening methods need to be quick and inexpensive, but above all sensitive enough to detect the antibiotic residue at or below the maximum residue limit (MRL). In the case of a positive result, the next step is conducted and further methods are used for confirmation. MRLs stated in European Union Regulation 37/2010 for tetracyclines in raw milk are: 100 µg kg–1 for tetracycline, 100 µg kg–1 for oxytetracycline, 100 µg kg–1 for chlortetracycline and no limit for doxycycline because it is prohibited for use in animals from which milk is produced for human consumption. The current five-plate microbiological screening method for the detection of antibiotic residues in raw milk was found to be simple and inexpensive, but not specific, sensitive and reliable enough to detect tetracycline at MRL in routine raw milk screening procedures. Spiking samples with tetracycline at the MRL level and applying them on Bacillus cereus ATCC 11778 microbiological plates often gave false-negative results, indicating that tetracyclines may have to be inactivated or masked. Tetracyclines seem to bind to a certain component in milk. Consequently, when applying samples to the B. cereus microbiological plate the antibiotic cannot inhibit the growth of B. cereus which disables the formation of inhibition zones on the test plate. After adding the appropriate amount of citric acid into the milk samples, we solved the problem of false-negative results. During the validation 79 samples of milk were spiked with tetracyclines at different concentrations: 100 µg kg–1 for tetracycline, 100 µg kg–1 for oxytetracycline, 80 µg kg–1 for chlortetracycline and 30 µg kg–1 for doxycycline. Concentrations used in the validation matched the requirements for MRLs (they were either at or below the MRLs) stated in European Union Regulation 37/2010. The sensitivity of the validation was 100%.

Hydrothermal synthesis of magnetite particles with uncommon crystal facets

Hydrothermal synthesis of Fe3O4 (magnetite) particles was carried out using organic compounds as morphology control agents to obtain magnetite crystals with uncommon facets. It was established that the morphology of Fe3O4 crystals obtained by hydrothermal treatment of an aqueous solution containing Fe2+ and organic compounds depended on the organic compound used. The shape of the Fe3O4 particles obtained when no additives were used was quasi-octahedral. In contrast, the addition of picolinic acid, citric acid or pyridine resulted in the formation of polyhedral crystals, indicating the presence of not only {1 1 1}, {1 0 0} and {1 1 0} facets but also high-index facets including at least {3 1 1} and {3 3 1}. When citric acid was used as an additive, octahedral crystals with {1 1 1} facets also appeared, and their size decreased as the amount of citric acid was increased. Thus, control of Fe3O4 particle morphology was achieved by a simple hydrothermal treatment using additives.

Deletion of glucose oxidase changes the pattern of organic acid production in Aspergillus carbonarius.

Aspergillus carbonarius has potential as a cell factory for the production of different organic acids. At pH 5.5, A.carbonarius accumulates high amounts of gluconic acid when it grows on glucose based medium whereas at low pH, it produces citric acid. The conversion of glucose to gluconic acid is carried out by secretion of the enzyme, glucose oxidase. In this work, the gene encoding glucose oxidase was identified and deleted from A. carbonarius with the aim of changing the carbon flux towards other organic acids. The effect of genetic engineering was examined by testing glucose oxidase deficient (Δgox) mutants for the production of different organic acids in a defined production medium. The results obtained showed that the gluconic acid accumulation was completely inhibited and increased amounts of citric acid, oxalic acid and malic acid were observed in the Δgox mutants.

Subcritically dried resorcinol–formaldehyde aerogels from a base–acid catalyzed synthesis route

Resorcinol–formaldehyde (RF) aerogels are prepared from a newly developed base–acid catalyzed sol–gel synthesis route. RF-gels synthesized are nanostructured and can be dried under ambient conditions without significant shrinkage. The sol–gel reaction of resorcinol (R) and formaldehyde (F) in water (W) (R/F=0.7, R/W=0.04) is initially catalyzed by Na2CO3 with a molar ratio of resorcinol to catalyst (R/C) of 100. After a specified time after starting the reaction (1–3h), citric acid (1M, 4–20vol.%) is added which initiates the acid catalyzed step and causes a spontaneous gelation. The time of change in pH value by adding acid is of great importance and influences the structure and properties of the material. RF-aerogels consisting of small particles much smaller than 100nm are prepared by applying a long base catalyzed step. Particle size, density, thermal conductivity and surface area are basically independent of the amount of citric acid, but this parameter influences the mechanical resistance. A theoretical model is used to describe the time dependence of catalyst change in the sol–gel process.

Overexpression of the NADP+-specific isocitrate dehydrogenase gene (icdA) in citric acid-producing Aspergillus niger WU-2223L.

In the tricarboxylic acid (TCA) cycle, NADP(+)-specific isocitrate dehydrogenase (NADP(+)-ICDH) catalyzes oxidative decarboxylation of isocitric acid to form α-ketoglutaric acid with NADP(+) as a cofactor. We constructed an NADP(+)-ICDH gene (icdA)-overexpressing strain (OPI-1) using Aspergillus niger WU-2223L as a host and examined the effects of increase in NADP(+)-ICDH activity on citric acid production. Under citric acid-producing conditions with glucose as the carbon source, the amounts of citric acid produced and glucose consumed by OPI-1 for the 12-d cultivation period decreased by 18.7 and 10.5%, respectively, compared with those by WU-2223L. These results indicate that the amount of citric acid produced by A. niger can be altered with the NADP(+)-ICDH activity. Therefore, NADP(+)-ICDH is an important regulator of citric acid production in the TCA cycle of A. niger. Thus, we propose that the icdA gene is a potentially valuable tool for modulating citric acid production by metabolic engineering.

Controlled morphologies and growth direction of WO3 nanostructures hydrothermally synthesized with citric acid

Hexagonal tungsten oxide (h-WO3) nanorods have been synthesized by a hydrothermal process at 180°C using ammonium metatungstate and citric acid as starting materials. The phase constituent, morphology and growth direction of the h-WO3 nanocrystals were characterized by using XRD, SEM, HRTEM techniques. We found that the morphology, size and preferred orientation of the h-WO3 nanocrystals can be controlled by simply adjusting the amount of citric acid. In the absence of citric acid, 2-dimensional (2D) nanoplates or nanosheets 10–20nm thick were formed. With increasing the amount of citric acid, 1-dimensional (1D) nanorods or nanoneedles grew along [002] crystallographic orientation from some certain nanoplate crystallographic planes. The as-synthesized WO3 nanorods were up to 1μm in length and 40–50nm in diameter. It is suggested that the adsorption of carboxyl group on certain crystallographic faces leads to an anisotropic crystal growth and the formation of 1D morphology.

A novel wet-chemical method for preparation of silver flakes

A novel wet-chemical method for the preparation of silver flakes was studied. The well-defined particles were prepared by directly adding FeSO4 solution into AgNO3 solution containing citric acid at an agitation speed of 150 r/min at room temperature. The products were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results show that particles are irregular thin silver flakes. And the sizes of them range from 2 to 10 μm. It is found that citric acid plays an important role in the formation of sliver flakes. There is an optimum amount of citric acid for the preparation of silver flakes by this method. It is also found that high reduction rate is favorable for the formation of silver flakes.

One-pot synthesis of 2,4,5-tri-substituted and 1,2,4,5-tetra-substituted imidazoles catalyzed by poly(4-vinylpyridinium tribromide) (P.V.P.Br3) or citric acid

An efficient, one-pot method for preparation of tri and tetra-substituted imidazoles by condensation of benzil, aldehydes, and ammonium acetate or primary amine in the presence of a catalytic amount of citric acid or poly(4-vinylpyridinium tribromide) (P.V.P.Br3) under solvent-free conditions is reported. The remarkable advantages of this method are the inexpensive green catalyst, mild reaction conditions, simple procedures, and excellent yields of products. .

Controlled Synthesis of Titanium Dioxide Nanocomposites with Different Structures and Morphologies

Pure anatase, pure rutile and the mixed TiO2 crystals with different amounts of rutile and anatase were prepared by a hydrothermal method using Ti (OBu)4 as starting material. The effect of anions on crystal phase and morphology of TiO2 synthesized by the hydrothermal method was investigated, and the relevant mechanism was also discussed. The X-ray diffraction (XRD) results indicate that Cl- ion was in favor of the formation of rutile, while NO3- and CH3COO- were beneficial for the formation of anatase. The hydrothermal conditions have significant effects on the phase component, morphology, and particle size of obtained titania products. Additionally, mixed TiO2 crystals with different amounts of rutile and anatase could be prepared by adjusting the reaction conditions, such as the concentration of Cl- ion, hydrothermal time, the amount of citric acid and the concentration of tetrabutyl titanate.

Screening and Improvement of Local Isolates of <i>Aspergillus Niger</i> for Citric Acid Production

The study involved the screening of fourteen isolates of Aspergillus niger for citric acid production from glucose. The study was aimed at screening and improving local strains of Aspergillus niger with potential for citric acid production. All the isolates screened produced varying amounts of citric acid, the highest was by the isolate designated CP3 which produced 12.81g/l and the least was B11 and O12 which produced 3.42g/l all after 6 days of submerged fermentation. The isolate CP3 was chosen for further studies. Strain improvement studies which was based on exposure of CP3 to ultraviolet irradiation for 10, 30 and 45 minutes increased citric acid yield to 22.20g/l (48.89% increase) by mutant M45 followed by a citric acid yield of 16.22g/l by the 30 minutes mutant (M30) and the least being M10 which produced 13.66g/l in all cases after 6 days of fermentation. The mutant (M45) also yielded higher amount of citric acid (19.64g/l) without methanol as additive compared to the parent strain (CP3) which gave a citric acid of 14.94g/l with the addition of methanol after six days (144h) of fermentation in both cases. Finding from this study showed that all the isolates have potential for citric acid production. Keywords : Isolation, Screening, Improvement, Aspergillus niger , Citric acid

Formulation, characterization and physicochemical evaluation of amoxicillin effervescent tablets.

Background:Amoxicillin is a semisynthetic antibiotic, which is used as an antimicrobial drug. This study was designed to formulate amoxicillin effervescent tablets, aimed at improved patient compliance and increased drug stability.Materials and Methods:In this study, nine effervescent tablet formulations were prepared from amoxicillin trihydrate. The effervescent base was comprised of various amounts of citric acid and sodium bicarbonate. Powders and granules were evaluated for their particle size, bulk density, tapped density, compressibility index, Hausner's ratio and angle of repose. The effervescent tablets were then prepared from powders and granules of acceptable quality by direct compression and fusion methods. The tablets were evaluated for weight variation, friability, pH of solution, carbon dioxide (CO2) content, hardness, effervescence time, thickness, assay, content uniformity, water content and equilibrium moisture content.Results:The results indicated better flowability of granules prepared by fusion method as compared with the direct compression. The percent weight variations of tablets were within the acceptable limit of 0.5%. The friability was less than 1% in all formulations. The solution pH of tablets prepared by direct compression and fusion methods ranged from 4.55 to 5.74 and 4.74-5.84, respectively. The CO2 amounts generated by of fusion method tablets were smaller as compared to the direct compression method. The hardness of tablets was 40.66-56 for direct compression method and 60.6-74.6 for fusion method. The tablets produced by the fusion method had a larger thickness and lower water content than tablets produced by direct compression method.Conclusion:Tablets prepared by the fusion method exhibited superior pre- and post-compression characteristics as compared to tablets prepared by direct compression method.

Development of Better-Quality Assay Method for the Citric Acid and Sodium Citrate in Ophthalmic/Oral Solutions and Their Application to Deformulation Studies

There were several techniques determined for the analysis of citrate and citric acid mixtures in the pharmaceutical dosage forms. Titration methods, photometric and ion chromatographic methods were used for their determination. These methods will restrict too many factors where the accurate quantification of citrate and citric acid is extremely challenging. Citric acid is the natural flavor used as a preservative for many pharmaceutical applications. Deformulation techniques used for the manufacturing of generic drugs require authentic data for their regulatory submissions. Simple accurate and reproducible validated method developed for the determination of citric acid and sodium citrate by titration followed by HPLC analysis. Free citric acid was determined by the titration method and total citric acid was determined by HPLC analysis. After subtracting the free citric acid from total citric acid content, citric acid present in the sodium citrate content was determined. Sodium citrate content was determined by applying sodium correction factor to the subtracted value of the citric acid. The results met all the validation parameters and the method was successfully measured the amount of citric acid and sodium citrate in the marketed ophthalmic/oral solutions.