Showing papers on "Citric acid published in 1982"

Sustained release pharmaceutical composition of solid medical material

Abstract: Sustained release pharmaceutical compositions of a solid medical material which contains an amorphous solid medical material, polyethylene oxide, and at least one basic substance selected from the group consisting of hydroxypropylmethyl cellulose, hydroxypropyl cellulose, methyl cellulose, polyvinyl pyrrolidone, carboxyvinyl polymer, hydroxypropylmethyl cellulose phthalate, cellulose acetate phthalate, methyl meta-acrylate meta-acrylic acid copolymer, polyvinylacetal diethylaminoacetate, dimethylaminoethyl meta-acrylate meta-acrylic acid copolymer, 2-methyl-5-vinylpyridinemethyl acrylate meta-acrylic acid copolymer, citric acid, urea, succinic acid and amino acid, and may further contain one basic substance selected from the group consisting of a surface active agent, polyethylene glycol, propylene glycol, glycerin, a glycerin fatty acid ester and a vegetable oil (first embodiment); and in the case where the solid medical material in nicardipine, the composition may consist only of the amorphous nicardipine or a salt thereof without the above compound (second embodiment).

Effects of salts on activated carbon adsorption of fulvic acids

Abstract: Calcium, magnesium, and sodium significantly influenced the adsorptive capacity of activated carbon for fulvic acids from three sources, including a natural groundwater supply. Adsorptive capacity was evaluated as a function of salt type, salt concentration, and pH and was most sensitive to changes in low concentrations of salt. Chloride, sulfate, bicarbonate, and phosphate exhibited no observable effect on the adsorption of fulvic acid. Calcium significantly influenced the adsorption of peat fulvic acid by an activated carbon column, the addition of calcium greatly enhanced adsorption, and the withdrawal of calcium from a loaded column resulted in substantial desorption. Salts enhanced the adsorption of dihydroxybenzoic acid but had variable effects on the adsorption of EDTA, citric acid, and aspartic acid.

Chromosomal mutation for citrate utilization by Escherichia coli K-12.

Abstract: A mutant strain of Escherichia coli K-12 that utilizes citrate as a sole source of carbon and energy was isolated. Citrate utilization arose as the consequence of two mutations in genes citA and citB, which are linked to the gal operon. The mutant strain expresses a semiconstitutive citrate transport system, and it utilizes both citrate and isocitrate as carbon and energy sources. It is capable of utilizing cis- and trans-aconitate, but only if it is preinduced by growth on citrate.

Anti‐bacterial effect of citric acid treatment of periodontally diseased root surfaces In vitro

Abstract: This investigation examined whether citric acid may exert an anti-bacterial effect against plaque deposits present on root surfaces in vitro. Aerobic and anaerobic blood-agar plate cultures were prepared from plaque samples obtained from the proximal root surfaces of 20 periodontally diseased human teeth following extraction. Ten teeth were exposed to saturated citric acid (pH 1) for 3 min, followed by rinsing in sterile 0.85% saline and plaque samples were then obtained immediately adjacent to those sites sampled initially. Controls consisted of using sterile water instead of citric acid on a further five teeth. The numbers of colonies present on pre- and post-treatment culture plates were counted al 24 h. The results indicated that citric acid application reduced, in all instances, the numbers of colonies grown from post-exposure plaque samples as compared to pre-exposure samples. No colonies were detected in 55% of aerobic and 30% of anaerobic cultures of acid-treated root surface samples. For aerobic cultures, citric acid exposure reduced the number of colonies grown from >104 to 104 to <100 was found in 80% of surfaces sampled. The findings indicate that citric acid exerts anti-bacterial activity against microbial plaque deposits present on periodontally diseased root surfaces in vitro.

Proteolysis during fermentation‐like incubation of cocoa seeds

Abstract: Proteolysis in cocoa seeds was studied by fermentation-like anaerobic incubation to determine whether post-mortem proteolysis depends only on temperature and acidity. In acetone dry powder incubation, autolytic release of α-amino nitrogen is optimal at pH 4.0-4.5 and is higher at 55°C than at 45°C. Proteolysis increases with acidification. However, in seed and seed fragment incubation, acetic acid is more effective than citric acid under similar conditions. Further, a first incubation at a low temperature (40°C) in contrast to a high temperature (50°C) favours post-mortem proteolysis during a subsequent incubation of cotyledon tissue at 50°C in an acetic solution, whereas it does not with cotyledon dry powder in the same solution. This effect of pre-incubation temperature in seeds is diminished in the presence of a high concentration of acetic acid. It does not depend on microorganisms, on exudation or on interaction of proteins and polyhydroxyphenols. Since increased proteolysis after incubation at 40°C correlates with structural changes in protein vacuoles and with water uptake by the intact seeds, a causal relationship is indicated.

Formation of gluconic acid at low pH-values by free and immobilized Aspergillus niger cells during citric acid fermentation

Abstract: A recently developed immobilization method, characterized by the adsorption of the mycelia onto a glass-carrier in a fixed-bed reactor, was applied for citric acid production by Aspergillus niger ATCC 9142, and compared with conventional culture techniques.

Photochemical reduction of iron. II. Plant related factors

Abstract: Photochemical reduction of ferric iron induced by ultraviolet (UV) and blue radiation is enhanced by certain di‐ and tri‐carboxylic acids. Iron photoreduction proceeds according to the following relative rates in Fe3+‐organic acid solutions containing the major plant acids listed: tartaric >oxalic>citric> malic>aconitic > fumaric ≥succinic≥FeCl3 (control). Any sensitized ferric to ferrous photoreduction occurring in plant foliage exposed to sunlight or artificial light would make iron more available to the tissues for metabolism. Iron is translocated within plants primarily complexed with citric acid (Tiffin, 1972). Citric acid is decarboxylated during Fe‐citrate photoreduction‐oxidation. Ferric iron photoreduction is thus accompanied by citrate degradation. In plant foliage, the fate of ferric citrate taken up the stem depends upon many plant‐related factors. Chelated iron is translocated predominately to actively growing regions where enzymatic reactions largely determine the immediate fate. In...

Characterization of ATP citrate lyase from Chlorobium limicola.

Abstract: ATP citrate lyase (EC 4.1.3.8) from Chlorobium limicola was partially purified. It was established that the consumption of substrates and the formation of products proceeded stoichiometrically and that citrate cleavage was of the si-type. ADP and oxaloacetate inhibited enzyme activity. Oxaloacetate also inhibited the growth of C. limicola.

Citric acid production with alginate bead entrappedAspergillus niger ATCC 9142.

Abstract: Aspergillus niger ATCC 9142 mycelium was entrapped in calcium alginate beads and employed in an air-lift completely stirred reactor for continuous production of citric acid. Maximum yield obtained from 10% (w/v) sucrose was 12 g dm-3 with about 40% fermentation efficiency. Maximum rate of production 70 mg g-1 h-1 was about five times that obtained in classical batch fermentation.

Equilibrium and Structural Studies of Silicon(IV) and Aluminium(III) in Aqueous Solution : 4. A Potentiometric Study of Polynuclear Aluminium(III) Hydroxo Complexes with Gallic Acid in Hydrolyzed Aluminium(III) Solutions.

Abstract: The thesis is a summary and discussion of eight papers. During the last decades, precipitation has become increasingly acidic due to the extensive use of fossil fuels. In areas of poorly buffered bedrocks, e.g. Scandinavia, northeastern United States, this phenomenon has resulted in elevated amounts of Al(III) being leached into streams and lakes. Recent findings reveal that these elevated Al-concentrations could cause fish death and decreasing forest production.In the present thesis, the importance of taking naturally occurring substances into consideration when discussing Al(III) in natural waters, is emphasized. On the basis of a chemical characterization of relevant ligand classes in a natural water, the complex formation between Al^+, hydroxide ions and the inorganic ligand carbonic acid, the low-molecular weight organic ligand citric acid and the high-molecular weight model substances gallic acid, 1,2-dihydroxynaphtha-lene-4-sulfonate, 1,2-naphthoquinone-4-sulfonate, pyrocatechol and salicylic acid were investigated. The investigations were performed as series of Potentiometrie titrations and data were processed by means of the least-squares computer program LETAGROPVRID using a technique called pqr-analysis, permitting an unbiased search for complex model (and corresponding equilibrium constants) to be made. In most systems studied, the complexation at high ligand excesses can be described by a series of mononuclear complexes AIL-AIL^. Tentatively, the whole series consists of octahedrally coordinated (water and ligand oxygens) AI(III). At lower ligand excesses, the significance and in some cases even predominance of ternary mono- and polynuclear hydroxo complexes is demonstrated. In two of the systems, binary aluminium hydroxo species are evaluated.The potential importance of the substances with respect to Al-com-plexation in natural waters are indicated in a number of model calculations. The solubility of the clay mineral kaolinite is calculated as a function of -lg[H+] and ligand concentration. It is shown that citric acid, gallic acid, 1,2-dihydroxynaphthalene-4-sulfonate, pyrocatechol and salicylic acid contribute quite significant to the total solubilities, even at very low concentrations.As a complement and background to the equilibrium studies, the corrosion rate for one of the naturally occurring Al-bearing minerals, corundum, is reported. In this investigation, performed with a leach-ant solution of ground-water composition, an experimental technique was employed which made it possible to divide the corrosion into chemical and mechanical losses.

The response of seven prostatic fluid components to prostatic disease.

Abstract: 282 human prostatic fluid samples have been investigated for their pH value, zinc, and citrate concentration and their acid phosphatase, leucine aminopeptidase, diamine oxidase, and beta-glucuronidase activities. The results have been analysed in terms of the clinical status of the patients. Significant differences between patient categories were found with all but diamine oxidase and beta-glucuronidase. These differences were mainly found between men with apparently healthy prostates and prostatitis patients; the pH being raised and the acid phosphatase, leucine aminopeptidase, zinc and citrate being reduced. The diagnostic value of these parameters was evaluated, each could be used to classify correctly 90% of patients from these 2 groups. Zinc, citrate and leucine aminopeptidase showed no age relationship and were better than acid phosphatase and pH in discriminating between BPH and prostatitis. Evidence was also found for a return of normal secretory function sometime after an episode of prostatitis. Zinc and citrate are likely to be the most useful parameters for clinical evaluation.

Iron transport in Mycobacterium smegmatis: Uptake of iron from ferric citrate.

Abstract: In mycobacterial growth medium 40 to 400 microM citrate was required to solubilize 2 microM 55Fe. This solubilized 55Fe was taken up into both iron-deficient and iron sufficient washed cell suspensions of Mycobacterium smegmatis and Mycobacterium bovis BCG. Although the 55Fe was taken up into the cell, the citrate was not. The uptake system with M. smegmatis was not inhibited by electron transport inhibitors, uncouplers of oxidative phosphorylation, or thiol reagents and was saturable with iron at approximately 35 microM. The system was independent of the iron transport systems already known to exist in M. smegmatis: i.e., the two exochelin routes of assimilation as well as the mycobactin-salicylate system. It was not induced by the presence of 400 microM citrate in the growth medium, nor did the presence of citrate in the medium affect the production of either exochelin or mycobactin.

Trace metal-citric acid complexes as inhibitors of calcification and crystal formation.

Abstract: At high citrate:metal ratios the small polyvalent metals Fe3+, Be2+, Al3+, and Cr3+ interact with citrate to form potent inhibitors of both calcium uptake by a calcifiable matrix and crystal formation from a metastable solution of calcium phosphate. These unique metal-citrate complexes are effective inhibitors at 0.2-30 × 10−6M, with iron (III) citrate being the most potent. The inhibitor effects of mixtures of the metal-citrate complexes are additive. These observations define a new role for citrate and indicate how certain trace elements may, by interaction with citrate, be important determinants in the control of calcium salt deposition in vivo. The possible pertinence of these observations to the deposition of calcium salts within the kidney and to the prevalence of idiopathic calculi in various geographic areas is now under investigation.

Nutzung von Paraffinen und anderen Nichtkohlenhydrat-Kohlenstoffquellen zur mikrobiellen Citronensäuresynthese

Abstract: This article reviews the developments achieved in citrate and isocitrate accumulation with non-carbohydrate substrates by microorganisms presented as well in academic publications as in patents. The efficiency of citrate and isocitrate overproducing microorganisms and of mutants obtained thereof with respect to different carbon sources (n-alkanes, triglycerides, organic acids, etc.) is discussed. The influence of environmental conditions (media, pH etc.) and biochemical mechanisms which lead to metabolic overflow are emphasized. The kinetics of fermentation processes are discribed, calculations concerning carbon balances are involved. The production of by-products and the conversion of isocitrate to citrate is considered. The production of citric acid by yeasts which utilize different carbon sources may be economically feasible and an accession to the practized molasse-Aspergillus-process.

Malic and Citric Acids in Pickling Cucumbers

Abstract: The content of major organic acids in pickling cucumbers has been determined. Malic acid was found to be the major organic acid in commercial size pickling cucumbers. The concentration among a group of six cultivars ranged from 0.2–0.3% on a fresh weight basis. Malic acid was present in all parts of the fruit. The highest concentration was in the outer 3 mm of the mesocarp, followed by the endocarp, the inner mesocarp, and the exocarp. During enlargement and maturation of cucumbers, citric acid became the principal organic acid, reaching levels in excess of 1% on a wet weight basis in the endocarp. This large accumulation of citric acid is the probable cause of the decline in endocarp pH during fruit maturation.

Utilization of paraffins and other noncarbohydrate carbon sources for microbial citric acid synthesis

Abstract: This article reviews the developments achieved in citrate and isocitrate accumulation with non-carbohydrate substrates by microorganisms presented as well in academic publications as in patients. The efficiency of citrate and isocitrate overproducing microorganisms and of mutants obtained thereof with respect to different carbon sources (n-alkanes, triglycerides, organic acids, etc.) is discussed. The influence of environmental conditions (media, pH etc.) and biochemical mechanisms which lead to metabolic overflow are emphasized. The kinetics of fermentation processes are described, calculations concerning carbon balances are involved. The production of by-products and the conversion of isocitrate to citrate is considered. The production of citric acid by yeasts which utilize different carbon sources may be economically feasible and an accession to the practized molasse-Aspergillus-process.

Citric acid production in chemically defined media by Aspergillus niger

Abstract: The effect of changing the composition of a chemically defined medium on citric acid production by Aspergillus niger was investigated. High and reproducible amounts of citric acid were obtained with deionized commercial sugar solutions, proper phosphate concentrations, low initial pH values and suitable amounts of copper as growth inhibiting agent. Comparison of high and low yielding process parameters showed that under high yielding conditions, (deionized sugar, Cu++ addition) besides more citric acid, less mycelium and less mycelial lipids were formed; the consumption of sugar, nitrogen and phosphorus was related to the amount of biomass.

Acid-catalysed condensation of isoprene with phenols. Formation of 2,2-dimethylchromans

Abstract: A novel method of nuclear isopentenylation which gives exclusively 2,2-dimethylchromans has been achieved by the direct condensation of phenols, viz. resorcinol, quinol, pyrogallol, and phloroglucinol, with 2-methylbuta-1,3-diene(isoprene) in the presence of orthophosphoric acid as catalyst. Condensation of 2-methylbut-3-en-2-ol with phenols in the presence of aqueous citric acid has been reinvestigated.

Polyethylene terephthalate compositions having improved crystallization rate and surface appearance

Abstract: Compositions comprising polyethylene terephthalate and an additive to promote crystallization rate and improve surface appearance selected from the group consisting of monomeric esters of citric acid and epoxidized esters of unsaturated aliphatic carboxylic acids. Compositions comprising polyethylene terephthalate, poly (C4 -C6) terephthalate, and a surface appearance and crystallization rate improving additive selected from the group consisting of monomeric esters of citric acid, organic esters of an aromatic carboxylic acid of 7 to 11 carbon atoms containing at least one carboxyl group per aromatic nucleus and an alcohol, oligomeric polyesters, and epoxidized esters of unsaturated aliphatic carboxylic acids.

The interrelationships between acid phosphatase, aminopeptidase, diamine oxidase, citric acid, beta-glucuronidase, pH and zinc in human prostatic fluid.

Abstract: Biochemical analysis of 328 human prostatic fluid samples were performed. The urea concentration of 69 samples was similar to that of serum and not indicative of significant contamination with urine. The pH of normal fluids was acidic (mean pH = 6.7). The interrelationships between zinc, citrate, acid phosphatase aminopeptidase, beta-glucuronidase, diamine oxidase and pH were investigated by factor analysis. Two significant factors were extracted, the first accounted for 89% of their common variance and the second for 11%. Zinc, citrate, acid phosphatase and aminopeptidase were positively and pH was negatively related to factor one. Beta-glucuronidase was positively related to factor two and diamine oxidase was largely independent of both factors. It was concluded that variables related to factor one share a common secretory control and mechanism, that some other mechanism operates in the case of beta-glucuronidase and that diamine oxidase may not be a true secretory product of the prostate.

Indirect Androgenic Control of Citrate Accumulation in Rat Ventral Prostate

Abstract: Androgenic control of citrate metabolism was studied by measuring the conversion of (2-14C)acetate or (6-14C)glucose to (14C)citrate and 14CO2 in the ventral prostate of the rat. The decarboxylation of (2-14C)acetate showed that androgen preferentially increased (14C)citrate oxidation, probably to meet the increased energy demands of cellular synthetic reactions. This led to the decreased accumulation of (14C)citrate from (2-14C)acetate. On the other hand, both the production of (14C)citrate and the formation of 14CO2 from (6-14C)glucose were decreased by castration and increased by testosterone, this being mainly due to the androgenic control of pyruvate dehydrogenase. These changes were more marked and rapid than those in oxygen consumption, in (2-14C)acetate oxidation, or in the total content of prostatic citrate that was maintained by testosterone. Glucose as the main source of citrate in testosterone-treated rats can thus be replaced by alternative substrates in castrated rats. The rate of citrate accumulation could be more dependent on the number of secretory cells than their hormonal activation.

Influence of intraluminal constituents on zinc absorption by isolated, vascularly perfused rat intestine.

Abstract: An isolated, vascularly perfused rat intestine system was utilized to compare the influence of a variety of potential zinc-binding compounds on zinc absorption. Citric acid, cysteine, reduced glutathione, histidine, methionine, picolinic acid and tryptophan were added to the lumen perfusate at 110 microM. Two lumen perfusate pH values (4.2 and 6.6) were compared. The influence of EDTA at pH 6.6 was also investigated as was the influence of citric acid, histidine, picolinic acid and tryptophan additions to the lumen perfusate at 550 microM. Of the substances tested only EDTA significantly enhanced the transfer of zinc from the lumen to the portal circulation. These results suggest these potential zinc chelators, exclusive of EDTA, do not promote zinc absorption by the intestine in this system.

Extraction of aluminum from fly-ash by commercial and microbiologically-produced citric acid

Abstract: Aluminum extraction from two aluminum-rich fly-ashes by commercial and microbiologically-produced citric acids was tested. Up to 12% Al2O3 of the total was extracted by a 21 hrs1 shaking treatment at 60° C. Extraction efficiency is considerably affected by extracting acid concentration and extraction temperature. The extraction efficiency of microbiologically-produced citric acids was only slightly lower than that of commercial citric acid of equal molarity.