Showing papers on "Citric acid published in 1981"

Dentin permeability: Effects of smear layer removal

Abstract: The results of this study permit the following conclusions: 1. The use of dilute (6%) citric acid for very short time intervals permits sequential removal of the smear layer on human dentin. 2. Acid-etching for as little as 5 seconds removes much of the smear layer and exposes the orifices of dentinal tubules. 3. Dentin permeability increased rapidly during acid-etching with 6% citric acid, reaching a maximum value after only 15 seconds of etching. 4. The production of a smear layer on dentin during restorative procedures establishes a protective diffusion barrier. Removal of the smear layer by acid-etching increases the permeability of dentin which, under some conditions, must be regarded as a liability.

Nifedipine-containing solid preparation composition

Abstract: A novel nifedipine-containing solid pharmaceutical preparation composition comprising a mixture of nifedipine and at least one 1st(a) substance selected from polyvinyl pyrrolidone, methyl cellulose, hydroxypropyl cellulose and hydroxypropylmethyl cellulose; a mixture of nifedipine, at least one 1st(b) substance selected from polyvinyl pyrrolidone, urea, citric acid mannitol, succinic acid, methyl cellulose, hydroxypropyl cellulose, hydroxypropylmethyl cellulose and amino acid, and at least one 2nd substance selected from a surface active agent, polyethylene glycol, propylene glycol, glycerol, a glycerol fatty acid ester and a vegetable oil; or a mixture of nifedipine, the 1st(b) substance, the 2nd substance and calcium lactate. The composition of this invention can increase the bioavailability of nifedipine and makes it possible to provide a nifedipine-containing pharmaceutical preparation which has small bulk and can be easily administered.

Acidophilic, heterotrophic bacteria of acidic mine waters.

Abstract: Obligately acidophilic, heterotrophic bacteria were isolated both from enrichment cultures developed with acidic mine water and from natural mine drainage. The bacteria were grouped by the ability to utilize a number of organic acids as sole carbon sources. None of the strains were capable of chemolithotrophic growth on inorganic reduced iron and sulfur compounds. All bacteria were rod shaped, gram negative, nonencapsulated, motile, capable of growth at pH 2.6 but not at pH 6.0, catalase and oxidase positive, strictly aerobic, and capable of growth on citric acid. The bacteria were cultivatable on solid nutrient media only if agarose was employed as the hardening agent. Bacterial densities in natural mine waters ranged from approximately 20 to 250 cells per ml, depending upon source and culture medium. Ferric hydrates and stream vegetation contained from 1,500 to over 7 × 106 cells per g.

Itaconic acid fermentation by a yeast belonging to the genus Candida.

Abstract: Many yeasts were isolated from natural sources in the tropics and subtropics by enrichment culture technique, using medium which contained a surfactant. The medium was acidified with citric acid. A strain S–10 belonging to the genus Candida was found to produce itaconic acid. Under suitable conditions in shake culture, a mutant derived from this strain produced the acid at about 35 % yield on the basis of glucose supplied.

Aconitase activity, citrate oxidation, and zinc inhibition in rat ventral prostate

Abstract: Aconitase activity and citrate oxidation were determined in mitochondrial preparations from rat ventral prostate. Aconitase activity in prostate mitochondria was approximately 10% of the activity observed in kidney preparations. The prostate aconitase activity was completely inhibited by the addition of 1.0 mmol/l zinc and kidney aconitase was inhibited by approximately 50%. The presence of 1.0 mmol/l zinc also markedly inhibited the formation of isocitrate from cis-aconitate. The reduction of NADP by citrate was markedly inhibited (approx. 95%) by 1.0 mmol/l zinc as compared with a 70 and 40% inhibition of aconitate--and isocitrate--stimulated reduction, respectively. These results indicate that zinc might be a strong inhibitor of aconitase activity with an inhibitory effect on isocitrate dehydrogenase also. The effect of 1.0 mmol/l zinc on citrate oxidation was studied by determining 14CO2 production from 6-14C-citrate. 14CO2 was significantly inhibited by zinc. These results further corroborate the conclusion that citrate accumulation in prostate might be the result of limited citrate oxidation which results from a combination of low aconitase activity and possibly zinc inhibition.

Bacitracin and protease production in relation to sporulation during exponential growth of Bacillus licheniformis on poorly utilized carbon and nitrogen sources.

Abstract: Growth of Bacillus licheniformis in a chemically defined medium containing glucose and ammonium chloride yielded a doubling time of 1.00 h. Examination of the culture during exponential growth revealed a lack of heat-resistant spores together with a complete absence of detectable concentrations of bacitracin or extracellular serine protease. Replacement of glucose as the sole carbon source by glycerol, pyruvic acid, citric acid, or lactic acid resulted in doubling times of 1.13, 2.00, 3.16, and 3.95 h, respectively. Bacitracin, protease, and heat-resistant spores were produced during exponential growth in amounts related to these doubling times. A qualitatively similar pattern was observed when ammonium chloride was replaced by sodium nitrate, alanine, or glutamic acid which gave doubling times of 1.65, 1.77, and 1.90 h, respectively. Protease, but not bacitracin, concentrations were substantially higher when the growth rate was restricted by use of poor nitrogen rather than poor carbon sources. The relationships between bacitracin production, protease production, and the sporulation process are discussed.

Citric Acid Fermentation by Aspergillus niger on Low Sugar Concentrations and Cotton Waste

Abstract: The possible use of cotton waste as a carbohydrate source of citric acid production by Aspergillus niger was examined. No citric acid was produced when A. niger was grown on cotton waste as a sole carbon source. In two-stage fermentations, however, mycelium obtained from surface cultures in cotton waste medium yielded more citric acid when transferred to sucrose-containing media than when directly inoculated to sucrose-containing media. It is concluded that cotton waste can be used for saving sucrose and for increasing yields of citric acid fermentation by A. niger.

Cosmetic for making skin soft

Abstract: PURPOSE:A cosmetic for making the skin soft having weak acidity of pH of the skin, safe in skin science, having improved preserving properties of corneum, flexibility, capable of keeping softening effect for extremely long time, comprising a specific hydroxy acid and a basic amino acid. CONSTITUTION:The titled cosmetic obtained by blending a hydroxy acid having 2-18C in the molecule with a basic amino acid in a molar ratio of (1:0.5)- (0.5:1), preferably (1:0.7)-(0.7:1). The concentration of a mixture of the hydroxy acid and the basic amino acid in the cosmetic is 1-10wt%. Glycolic acid, lactic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid, hydroxycaprylic acid, citric acid, tartaric acid, etc. may be cited as the hydroxy acid. Lysine, alginine, histidine, ornithine, etc. may be cited as the basic amino acid.

Monitoring Bacterial Metabolites in Cultured Buttermilk by High Performance Liquid Chromatography and Headspace Gas Chromatography

Abstract: A commercial buttermilk culture was added to Grade a skim milk. Samples were analyzed hourly for a total of eighteen hours. Headspace gas chromatography measured changes in acetaldehyde, acetone, ethanol, and diacetyl concentrations. High performance liquid chromatography measured changes in orotic, citric, pyruvic, lactic, uric, acetic, and propionic acid concentrations. Consumption of orotic acid and citric acid substrates was noted. Production of diacetyl, ethanol, pyruvic, lactic, acetic, and propionic acids was observed. Acetaldehyde concentration increased initially and then decreased as ethanol was formed. Acetone and uric acid concentrations remained constant during fermentation. In addition, chemical changes occurring during refrigeration were measured after seven days. Acetaldehyde, ethanol, and acetic acid increased in concentration; diacetyl, orotic, citric, pyruvic, lactic, and propionic acids decreased in concentration. Also, a headspace gas chromatographic test was done for the quantitation of acetoin.

Method for retarding gelation of bicarbonate-carbonate-zeolite-silicate crutcher slurries

Abstract: Gelation and setting of desirably miscible and pumpable crutcher slurries comprising sodium carbonate, sodium bicarbonate, zeolite and sodium silicate in an aqueous medium are retarded and often prevented by the addition to such medium of a citric material, such as citric acid and/or water soluble citrate, and magnesium sulfate. Alternatively, magnesium citrate may be employed. The addition of the citric material and magnesium sulfate (or magnesium citrate) appreciably lengthens mixing time available before setting of the mix, increasing it over such times for similar crutcher mixes not containing any anti-gelling material, or including citric material as an anti-gelling component but not incorporating magnesium sulfate. The improved workability of the crutcher mix permits the making of higher solids content crutcher slurries, thereby resulting in significant energy savings and improvements in production rates when the crutcher slurries are subsequently spray dried to free flowing inorganic base bead form, from which commercially acceptable detergent compositions may be made, as by post-spraying with a nonionic synthetic organic detergent in liquid state.

Malate dehydrogenase isoenzymes in Aspergillus niger

Abstract: The accumulation and excretion of citric acid by Aspergillus niger is a notable example of fungal 'over-flow' metabolism, and for 30 years has been the world's primary source of citric acid. However, the biochemical information available on this process has to date not permitted its elucidation, but recently certain regulatory steps of A. niger energy metabolism have been investigated with respect to citric acid accumulation [ 1-4]. Malate dehydrogenase (EC 1.1.1.37) isoenzymes of A. niger were investigated because of the key role of oxaloacetate in the accumulation of citric acid [5]. They are involved in a shuttle mechanism which transports reduced NADH across the mitochondrial membrane and thereby generates mitochondrial oxaloacetate. On the other hand, there is a very active pyruvate carboxylase (EC 6.4.1.1), located intramitochondrially [6], whose activity in vivo has been shown to be strongly correlated with citric acid accumulation [7]. The present paper reports some molecular and regulatory properties of two malate dehydrogenase isoenzymes from A. niger. 2.1. Organism and conditions for growth

Preservation of green plant tissues

Abstract: A process for preserving green colored plant tissues and in particular coniferous needles, holly and low fiber leaves such as mosses, lichens and ferns in which selected leaves are immersed in a solution comprising (by volume) 35-45% water, 20-30% 2-propanol, 5-12% propionic acid, 5-10% sulphurous acid, 5-10% formalin, 2.5-5% formic acid, 1-5% ethylene glycol, and optionally minor amounts of compounds selected from the group consisting of cupric sulphate, cupric chloride, 20-20-20 fertilizer, citric acid, DBE, magnesium sulphate, acetic acid, cupric acetate, cupric nitrate, sodium phosphate, sodium sulfite, butylated hydroxytolulene and glycerol, for a sufficient time to exchange the naturally occurring water in the tissues with the "chemical water" of the solution and thereby permanently retain and biologically fix the green color of the leaves.

Role of malate synthase in citric Acid synthesis by maturing cotton embryos: a proposal

Abstract: Cotton embryos from 34 to 54 days after anthesis were analyzed for organic acids, and enzymes associated with organic acid metabolism. During this developmental period, embryos accumulated citrate. Malate synthase activity appeared at 46 days after anthesis and increased rapidly to 54 days. Of other enzymes examined, only citrate synthase activity increased during this period. As isocitrate lyase activity was absent from cotton embryos during maturation, an alternative source of glyoxylate would be required for in vivo malate synthase activity. Of several metabolic sources tested, glycine was converted to glyoxylate via a transamination reaction.Halves of 50-day (mature) cotton embryos incorporated radioactivity from [1-(14)C]acetate, [1-(14)C]glyoxylate, and [1-(14)C]glycine into organic acids. Embryo halves incubated with [(14)C]glyoxylate plus [(3)H]acetate synthesized double-labeled malate and citrate. Radioactive citrate isolated from 50-day cotton embryos incubated with [1-(14)C]acetate was degraded; label was distributed as follows: 55% in C(1), 33% in C(5), and 12% in C(6). Taken together, these data strongly suggest participation of malate synthase in citrate production in vivo.Separation of organelles by sucrose density gradient sedimentation revealed that malate synthase, malate dehydrogenase, and citrate synthase were compartmentalized together only in the peroxisome fraction (1.24 grams per milliliter). Peroxisomes isolated from 50-day embryos, when incubated with glyoxylate and [(3)H]acetyl-CoA, synthesized labeled malate and citrate, but only radioactive citrate accumulated. Incubations with glycine plus alpha-ketoglutarate, in place of glyoxylate, also resulted in synthesis of radioactive citrate.A metabolic scheme illustrating the participation of cotton embryo peroxisomes in citrate synthesis is proposed. This scheme suggests a function for plant peroxisomes not previously elucidated. The ontogenetic and metabolic relationship between these organelles and glyoxysomes active in gluconeogenesis during postgerminative growth remains to be examined.

A preliminary study of w/o/w emulsions with a view to possible food applications

Abstract: A study was made of the influence of various additives on the stability and low shear viscosity of water-in-olive oil-in-water emulsions. The additives were glucose, sucrose, acetic acid, citric acid, ascorbic acid, sodium chloride and sodium acetate, Glucose and sucrose increased viscosity for some time until a constant value was reached. With the other additives an initial increase in viscosity was followed by a decrease and a corresponding decrease in stability. These observations are explained in terms of the osmotic pressure gradient between the inner and outer water compartments, and the effect of additives on the physical state of the emulsifier films adsorbed at the interfaces between the two water compartments and the oil phase.

Effects of yeast strains and environmental conditions on formation of organic acids in must during fermentation

Abstract: The effects of yeast strains and environmental conditions on the formation of organic acids during fermentation were examined with pasteurized Koshu grape musts. Twenty strains of yeast influenced considerably the formation of succinic and acetic acids by fermentation. Succinic acid was formed in quantity by Saccharomyces cerevisiae IAM 4274 and Sacch. bailii NISL TK-1, and acetic acid by Candida krusei IAM 4801. Hansenula anomala IAM 4721 produced much citric acid in addition to acetic acid. Formation of succinic and acetic acids was affected by fermentation temperature, sugar concentration, and pH of the must and the yeast strain used, while lactic and citric acid levels in the finished wines were not influenced by these factors.

Process for the extraction of organic acids from aqueous solution

Abstract: Organic acids, such as citric acid, malic acid and lactic acid. can be extracted from aqueous solutions thereof by contacting such solutions with a mixture of a water immiscible amine and a water immiscible organic acid dissolved in a suitable water immiscible solvent.

Conjugated compound of calcium citrate and calcium malate and its preparation

Abstract: PURPOSE:To obtain the titled conjugated compound useful for wide application of food fields, having improved water-soluble tendency of calcium citrate, coexisting slightly water-soluble calcium citrate with calcium malate. CONSTITUTION:A substance comprising conjugated compound of water-soluble calcium malate, and calcium citrate, linked in a weight ratio of calcium malate : calcium citrate of at least 2:3, obtained by dissolving not more than 70wt% citric acid and not less than 30wt% malic acid in water, followed by adding calcium hydroxide or calcium carbonate to neutralize the solution, or by dissolving not more than 70wt% sodium citrate and not less than 30wt% sodium malate in water, adding calcium chloride in an amount equimolar with the solution, followed by separating the resulting crystalline deposit. USE:Usable for foods requiring transparency, especially as nutritive calcium for drinks, rice, etc.

Effect of magnesium citrate on the in vitro adsorption of aspirin by activated charcoal.

Abstract: The objective of this study was to determine if magnesium citrate solution given concurrently with activated charcoal would affect charcoal's in vitro ability to bind aspirin. Aspirin and charcoal were mixed in simulated gastric fluid and simulated intestinal fluid, and then magnesium citrate solution was added in proportions simulating those encountered clinically. Results indicate that no clinically significant interaction occurs between magnesium citrate and activated charcoal in either fluid, and that these two agents can be given simultaneously without decreasing the binding capacity for aspirin.

Continuous process for production of citric acid

Abstract: A process for the production of citric acid by Aspergillus niger in a single-stage continuous culture is presented. The citric acid is produced under nitrogen limiting conditions. The process has been investigated in the dilution rate range 0.05 to 0.20 h−1 and the citric acid concentration increases rapidly with decreasing dilution rate. Citric acid production is greatly affected by the medium composition and operational parameters. The continuous process represents a considerable increase in productivity from the batch process.

Triazines and related products. Part 23. New photo-products from 5-diazoimidazole-4-carboxamide (Diazo-IC)

Abstract: Photolysis of Diazo-IC in dilute aqueous solution affords products which differ according to the pH of the medium. At pH 1, or pH 7.4–12 the product is 2-azahypoxanthine (2): in the intervening pH range the product is 4-carbamoylimidazolium-5-olate (3). In the dark only 2-azahypoxanthine is formed. Photolysis of Diazo-IC in concentrated solution containing citric acid (1 mol equiv.) at pH 2.5 affords a maroon imidazolylazoimidazolium olate (8) and 2-azahypoxanthine.

Citric acid fermentation in whey permeate

Abstract: Acid-whey permeate was used for the production of citric acid by Aspergillus niger. The fermentation proceeded in 2 phases: a growth phase when citric acid was not accumulated, followed by an acidogenic phase when citric acid accumulated and mold growth was greatly reduced. Optimal production of citric acid occurred after 8-12 days at 30 degrees. Maximum citric acid yields were influenced by the initial lactose concentration and reached 10 g/l when the lactose concentration in the acid-whey permeate was adjusted to 15%. MeOH at 2-4% markedly increased the production of citric acid. Fermentation of acid-whey permeate by a mutant strain (A. niger 599-3) was more reproducible, and yields of citric acid were substantially improved. The amount of citric acid produced by A. niger 599-3 was 18-23 g/l after 12-14 days, depending on the lactose content of the whey permeate. Throughout the fermentation, galactose was apparently co-metabolized with glucose.

Germination of Aspergillus niger in a high citric acid yielding medium

Abstract: Numerous papers have dealt with the fermentation technology of citric acid production by Aspergillus niger but relatively few have described morphological properties of the mould during the fermentation. Manganese deficiency which induced good citric acid yields and affected the morphology of pellets was described by Clark et al. [1]. Recently impaired germination in Mn 2+ deficient medium was reported by Kisser et al. [2]. The present paper describes unusual germination in the form of spherical cells in A. niger during early stages of development in a high citric acid yielding medium. The appearance of spherical bulbous cells and later changes in morphology indicated some correlation to dimorphism found in some other fungi [3]. In Aspergillus dimorphism was found in A. parasiticus [4] in a Mn 2+ deficient medium and some similarity to this phenomenon has been described in A. niger where giant cells developed at elevated temperature [5].

Biosynthesis of citric acid in relation to the activity of selected enzymes of the Krebs cycle in Aspergillus niger mycelium

Abstract: The activities of ACH1, NAD-ICDH, NADP-ICDH and CS were determined in cell extracts of high and low citric acid-producing strains of A. niger, cultivated on molasses medium by the surface or submerged method. A high differentiation in the activities of the enzymes studied was found to occur at various accumulation stages of citric acid and during its decomposition by moulds. During intensive citric acid synthesis, the activity of ACH and that of both dehydrogenases decreased significantly (though they did not disappear completely) compared to their initial activities during the growth period of the mycelium. CS activity, however, was maintained at almost the same level over the whole fermentation period or increased slightly, particularly in the case of low citric acid-producing strains. The relationships between the activities of these enzymes were reversed during citric acid decomposition by moulds.

Prevention of the Green-Gray Discoloration in Cooked Liquid Whole Eggs

Abstract: The prevention of the green-gray discoloration of cooked liquid whole eggs was studied. Acidic chelating agents were added to raw liquid whole egg samples at pH 8.50. Samples were cooked at 100°C for 20 min, held over a steam bath for 60 min, and then measured for color. Results show the following approximate optimum concentrations will prevent the discoloration at p = 0.05: acetic acid, 0.19%; citric acid, 0.17%; Na2EDTA, 0.029%; lactic acid, 0.27%; malic acid, 0.22%; monosodium phosphate, 0.34%; propionic acid, 0.26%; and succinic acid, 0.27%. It was also found that the average maximum pH attained by raw liquid whole eggs when stored at 3°C for 21 days was 7.93 ± 0.19. A taste panel indicated that there were no significant differences in overall acceptability with the Na2EDTA and the monosodium phosphate treatments. The citric acid treatment was not significantly different from the control in flavor acceptability. Other treatments were judged to be inferior to the control.

Protein binding effects on salivary excretion of phenobarbital in dogs

Abstract: The salivary excretion of phenobarbital was investigated by collecting parotid saliva (Pr) and mandibular-sublingual saliva (MS) separately after intravenous administration in beagle dogs. (1) The alterations in the proportions of saliva secreted by the different glands were produced by salivation stimulants such as citric acid, ascorbic acid, sodium chloride and sodium glutamate. (2) The phenobarbital concentrations in both Pr amd MS were lower than those in plasma. The drug concentrations in MS were significantly lower than in Pr with stimulus of 10% citric acid of 15% sodium chloride (p less than 0.05). There was a significant correlation between phenobarbital concentration in each saliva and plasma specimen ( p less than 0.05). (3) The stimulation with 10% citric acid produced higher saliva /plasma drug concentration ratios (S/P ratios: 0.923 +/- 0.175 for Pr, 0.633 +/- 0.073 for MS) than that with 15% sodium chloride (S/P ratios: 0.597 +/- 0.071 for Pr, 0.509 +/- 0.067 or MS). (4) The S/P ratios were hardly influenced by salivary flow rates, at least under the experimental conditions examined in this study. (5) The increased S/P ratios were observed with higher salivary pH and then the equation of Matin et al. 3) seemed to hold for the average values of salivary pH and S/P ratio. (6) The stimulation with 10% citric acid produced higher protein concentration in saliva and higher S/P ratio than that with 15% sodium chloride following alternate stimulations in the same dog.