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PubMed1970

Effect of trace elements on citric acid fermentation by Aspergillus niger.

Citric acid yields of 98.7% (sugar consumption basis) were reached in shaker flasks with mutant UV-ET-71-15 of Aspergillus niger in a resin-treated sucrose medium of the following composition (g/100 ml): sucrose, 14.0; NH(4)NO(3), 0.20; KH(2)PO(4), 0.10; MgSO(4).7H(2)O, 0.025; and (mg/liter): FeSO(4), 0.15 to 0.75; ZnSO(4), 0.10; and CuSO(4), 0.01. Yields of 75% were obtained in medium with resin-treated clarified syrup and 68% with ferrocyanide-treated blackstrap molasses. Optimal conditions included selection of appropriate pellets as inoculum at 3%, pH of 4.5, temperature at 30 C, agitation at 250 rev/min, and fermentation time of 8 days. The mutant tolerated high concentrations of trace elements.

Aspergillus↗

PubMed1983

Quality control of acid phosphatase assay improved by direct reconstitution of lyophilized control materials with citric acid.

Current quality control of assays of acid phosphatase (EC 3.1.3.2) with thymolphthalein substrate is inadequate when certain control-suppliers' instructions are followed for reconstituting and stabilizing human lyophilized control material. If such materials are reconstituted with a citric acid solution, then stored frozen, control vial-to-vial variability is minimized, as are losses of activity in freshly reconstituted controls and losses during room-temperature storage of the control material. Effects of pH of the reconstituting solution on the acid phosphatase activity of human lyophilized controls are also discussed.

Acid Phosphatase↗

PubMed1995

Isotopomer analysis of citric acid cycle and gluconeogenesis in rat liver. Reversibility of isocitrate dehydrogenase and involvement of ATP-citrate lyase in gluconeogenesis.

We conducted an extensive mass isotopomer analysis of citric acid cycle and gluconeogenic metabolites isolated from livers of overnight fasted rats perfused with 4 mM glucose, 0.2 mM octanoate, 1 mM [U-13C3]lactate, and 0.2 mM [U-13C3]pyruvate, in the anterograde or retrograde mode. In both perfusion modes, two distinct isotopomer patterns were observed: (i) those of phosphoenolpyruvate, glucose, malate, and aspartate and (ii) those of citrate, alpha-ketoglutarate, glutamate, and glutamine. Key citric acid cycle parameters and, hence, rates of gluconeogenesis, calculated (Lee, W.-N.P. (1989) J. Biol. Chem. 264, 13002-13004 and Lee, W.-N.P. (1993) J. Biol. Chem. 268, 25522-25526) from our mass isotopomer data did not only vary, but lead to conclusions inconsistent with Lee's citric acid cycle model. Compared to lactate and pyruvate uptake, which sets an upper limit to glucose production, rates of gluconeogenesis calculated (i) with the phosphoenolpyruvate and citrate data were similar, but those calculated (ii) with the glutamate data amounted to only 60%, which is unlikely. All these conclusions are independent of the perfusion modes. We provide evidence that the following processes contribute to the observed labeling discrepancy: (i) the reversibility of the isocitrate dehydrogenase reaction and (ii) an active citrate cleavage pathway for the transfer of the oxaloacetate carbon skeleton from mitochondria to the cytosol. Also, a good fit of our labeling data was obtained with a model of citric acid cycle and gluconeogenesis which we developed to incorporate the above reactions (Fernandez, C.A., and Des Rosiers, C. (1995) J. Biol. Chem. 270, 10037-10042). The following conclusions can be drawn from the calculated reaction rates: (i) about half of the lactate conversion to glucose occurs via the citrate cleavage pathway, (ii) the flux through the reversal of the isocitrate dehydrogenase reaction is almost as fast as that through the citrate synthase reaction, and (iii) the flux through citrate synthase and alpha-ketoglutarate dehydrogenase is 1.6- and 3.2-fold that through pyruvate carboxylase, respectively.

ATP Citrate (pro-S)-Lyase↗

PubMed1996

SR 140333 prevents potentiation by citric acid of plasma exudation induced by histamine in airways.

We here report a model of potentiation by citric acid of airway microvascular leakage induced by histamine and its modification by the tachykinin NK1 and NK2 receptor antagonists, SR 140333 ((S)1-{2-[3-(3,4-dichlorophenyl)-1-(3-iso-propoxyphenylacetyl)p iperidin- 3-yl]ethyl}-phenyl-1-azoniabicyclo[2.2.2]octane, chloride) and SR 48968 (S)-N-methyl-N-[4-(4-acetyl-amino-4-phenylpiperidino)-2-(3,4- dichlorophenyl-butyl]benzamide. Guinea-pigs exposed to an acrosol of citric acid 0.4 M for 1 h developed 24 h later a hyperresponsiveness to histamine-induced microvascular leakage measured by Evans blue dye extravasation. SR 140333, but not SR 48968 (1 mg kg-1 given each once 30 min before citric acid exposure), prevented this potentiation. These results provide further evidence of the role of tachykinin and tachykinin NK1 receptor stimulation on airway hyperresponsiveness and its neurogenic inflammatory component.

Animals↗

PubMed2000

Dialysate made from dry chemicals using citric acid increases dialysis dose.

A new dry dialysate concentrate acidified with citric acid (citrate dialysate) has been used in two separate clinical studies of hemodialysis patients. The first compared a single treatment using this dialysate, with one dialysis using regular standard dialysate acidified with acetic acid (regular dialysate) in a prospective, randomized, crossover study of 74 dialyses. Changes in blood levels of electrolytes and other blood constituents during dialysis were calculated by subtracting postdialysis from predialysis blood concentrations. Compared with acetic acid dialysate, citrate dialysate was associated with significantly greater decreases in total and ionized calcium, magnesium, and chloride levels. Citrate dialysate was also associated with greater increases in serum sodium and citrate concentrations, although their postdialysis concentrations remained within or just outside normal ranges. Changes in other blood constituents were similar with both dialysates. The second study used citrate dialysate exclusively for all dialyses over a 12-week period in 25 patients. Predialysis blood samples were drawn at the start of the study and at 4-week intervals thereafter, and postdialysis blood samples were obtained after the first and last dialysis. Repeated-measure analysis showed that although predialysis blood concentrations of magnesium, potassium, and citrate remained within the normal range, there was a significant declining trend over the course of the study. At the same time, predialysis serum bicarbonate levels increased, and significantly more patients had a predialysis bicarbonate concentration within the normal range at the end of the study than at the start (15 versus 8 patients; P = 0.001, chi-square). In 19 patients (excluding 3 patients for whom the type of dialyzer was changed during the study), the dose of dialysis for the first and last dialysis was calculated by urea reduction ratio and Kt/V. There was a significant increase in both measurements without changes in dialysis time, blood and dialysate flows, or dialyzer used. The urea reduction ratio increased from 68% +/- 5.9% to 73% +/- 5.3% (P < 0. 03), and the Kt/V from 1.23 +/- 0.19 to 1.34 +/- 0.20 (P = 0.01) from the first to last dialysis, respectively. In conclusion, this citric acid dialysate was well tolerated, and intradialytic changes in blood chemistries were similar to those seen with regular dialysate. Using dialysate containing citric instead of acetic acid increases the delivered dialysis dose.

Adult↗

PubMed1993

Acetic, lactic and citric acids and pH inhibition of Listeria monocytogenes Scott A and the effect on intracellular pH.

The effects of acetic, lactic and citric acids and pH on the growth and intracellular pH (pHin) of Listeria monocytogenes Scott A were documented and compared for total acid concentrations ranging from 50 mmol ml-1 to 250 mmol ml-1 for acetic and lactic acids and from 25 mmol ml-1 to 100 mmol ml-1 for citric acid. Initial pH values ranged from 4.7 to 6.0. Although the growth rate of L. monocytogenes Scott A was slower when incubated at 25 degrees C than at 37 degrees C, the relative acid and pH inhibition was identical at both temperatures. As the initial pH values decreased and/or the total acid concentrations increased, the growth rates of L. monocytogenes Scott A decreased. Compared at equal initial pH values and on an equimolar total acid basis, the relative inhibition effect was generally acetic > lactic > citric. When based on initial undissociated acid concentrations, the inhibition effect was citric > lactic > acetic. The effect of differing acid and pH environments on pHin was determined. At equimolar total acid concentrations, the pHin of the cell was changed the least by citric acid and the most by acetic acid. Growth rates were influenced by the pHin and the acid used to adjust the system.

Acetates↗

PubMedDate not supplied

Efficacy of minocycline as a root conditioner in comparison to citric acid and tetracycline. An in vitro evaluation.

This study compared the root surface characteristics produced by Minocycline HCl, Citric acid and Tetracycline HCl. when used as a root conditioner. This study included 5 groups of 10 extracted teeth each with advanced periodontal disease. Diseased root surfaces of group B,C,D and E were planed with Gracy curets and solutions of Citric acid, Tetracycline HCl, Monocycline Hcl and Tween 80 of PH 2.5, were applied to the surface in respective groups with cotton pellets for 5 mts. Group A was not subjected to root planning or application of any root conditioner and was used as a control. The teeth in all five groups were then washed, sectioned processed and examined under scanning electron microscope. These results revealed that the surfaces of acid treated sites differed from each other and with specimens treated sites differed from each other and with specimens treated with root panning alone. The efficacy of Minocycline and tetracycline in the removal of smear layer and exposure of dentinal tubules were comparable and Minocycline HCl though not as effective as Citric acid can probably be recommended in view of its antibactrial activity, anti collagense and substantivity properties.

Acid Etching, Dental↗

PubMed1986

Treatment of localized gingival recessions with coronally displaced flaps and citric acid. An experimental study in the dog.

The present study was designed to examine the effect of citric acid conditioning on the result of healing following treatment of localized gingival recessions with coronally displaced flaps. In 3 beagle dogs, localized gingival recessions were surgically created at the buccal surfaces of canines, premolars and molars. All experimental sites were allowed to accumulate plaque for a period of 6 months. Following preparation of notches in the buccal root surfaces at the level of the gingival margin, buccal and lingual mucoperiosteal flaps were raised. The exposed portion of the root surfaces was scaled and the cementum layer was removed. Another notch was prepared in the root surfaces at the level of the crest of the alveolar bone. Half the number of the roots were treated by topical application of citric acid while the remaining roots were used as non-acid treated controls. The flaps were sutured in a coronally displaced position. After 3 months of healing, the dogs were sacrificed and the jaws removed and placed in fixative. After decalcification, histological sections of the experimental roots and their periodontal tissues were produced. The 2 notches described above were used as reference points in the histological examination. The histological analysis disclosed that new attachment had formed on all test and control roots and extended in some specimens of both groups to a position coronal to the presurgical level of the gingival margin. The amount of new attachment was similar in the 2 categories of roots, demonstrating that citric acid conditioning did not produce additional new attachment.

Animals↗

PubMed1997

Citric acid demineralization of cementum and dentin: the effect of the storage medium.

The purpose of this study was to see if the root surface topography of teeth, stored in saline and subsequently treated with citric acid, differred from the root surface topography of teeth that were treated immediately upon extraction, 12 freshly extracted adult human permanent teeth, with proximal surfaces free of caries and periodontal disease, were treated in succession. The crowns were removed at the level of periodontal attachment, the teeth sectioned buccal-lingually and a treatment area deligniated on each proximal section. The treatment area of 6 teeth was root planed to expose dentin (D) and scaled to remove adherent tissue and leave a cementum surfaces (C) on the other 6 teeth. A coronal-apical groove down the middle of the treatment area divided it into approximately equal parts or experimental regions. One proximal section of each tooth was placed in physiologic saline (S) and treated after 6 weeks of storage while the other proximal section was freshly treated (F). Treatment consisted of applying a 30% citric acid (CA) solution (pH = 1.60) for 5 min. Cotton pellets soaked in the citric acid solution were placed (P) on one half of the experimental area and heavily burnished (B) on the other half. Treatment areas were subsequently prepared for scanning electron microscopy analysis. Assessment was made of (i) the % of surface area tufted, (ii) fibril tufting depth (0.3) and (iii) fibril tufting density (1.3). Similarities were found in the data for both storage methods (F and S) across each application technique (P or B) and each tooth surface (D or C) with respect to the (i) % area tufted and (ii) frequency distribution of tufting depth scores. As for the application techniques, the data for burnishing was greater than placed across each storage method (F or S) and each tooth surface (D or C) for the same two parameters. The results of the study indicated that 6-week physiologic saline storage does not affect root surface demineralization by citric acid, as assessed by SEM.

Adult↗

PubMed1984

The effect of root planing and citric acid applications on flap healing in humans. A histologic evaluation.

Four human teeth and their facial gingival attachment were removed en block 3 months after periodontal flap therapy and citric acid root conditioning and then prepared for histologic evaluation. At the time of periodontal surgery, and prior to citric acid application, the facial root surface was grooved at midline and citric acid was applied only to one-half of each root surface. Tissues were decalcified and histologically prepared as horizontally oriented, step serial sections from the level of the gingival margin to the level of the facial crest. The gingival margins demonstrated reformation of a crevice. The corium at this level showed a mild inflammatory infiltrate. Apical to this level, junctional epithelium adhered to both sides of the root surface and to the central groove. Further apically, supracrestal fiber groups were encountered. No new cementum was noted in these areas. Fiber attachment was present apical to this level. Since no new cementum was seen at this area of attachment, it may represent collagen attachment present prior to periodontal surgery. In the four specimens examined, no differences were seen in the soft tissue closures between the root-planed citric acid-treated root surfaces and root surfaces which received root planing alone.

Administration, Topical↗

PubMed1990

Citric acid production with mixed strains of Aspergillus niger in submerged culture.

Citric acid yield of 8 different strains of Aspergillus niger in pure and mixed cultures was investigated. The yield varied remarkably with the strain and combination of strains. Generally, the yield of citric acid for a given strain was higher in pure than in mixed culture. However, low yielding strains in combination often augmented the yield under mixed culture. The possibility of an additive genic effect is discussed.

Aspergillus niger↗

PubMed1994

Characterization and regulatory properties of a single hexokinase from the citric acid accumulating fungus Aspergillus niger.

A single glucose-phosphorylating enzyme has been detected and purified from the citric acid accumulating fungus Aspergillus niger. The enzyme was formed constitutively, and high activities were formed on glucose and sucrose as carbon sources. Highest activities were formed during growth on high concentrations of glucose or sucrose. The enzyme, purified about 600-fold from cell-free extracts prepared from glucose-grown mycelia, gave a double band in denaturing (SDS)-polyacrylamide gel electrophoresis. Tryptic peptide patterns suggest that the lower molecular weight band was the product of either C- or N-terminal truncation. The specific activity of the enzyme was about 40 and 35 mumol/min and mg protein with glucose and fructose as substrates, respectively. The affinity for glucose was about 10(3)-fold higher than for fructose. The subunit molecular weight was 50,000 and the molecular weight of the native protein was 100,000 by gel permeation chromatography. Of the reaction products ADP, but not glucose 6-phosphate, inhibited hexokinase activity. Citrate inhibited (K1 0.15 mM) non-competitively with respect to both glucose and ATP, which was not due to Mg(2+)-chelation. 2-Deoxyglucose resistant mutant strains of A. niger were isolated which showed decreased growth rate and activity of hexokinase during growth on glucose, while their growth on fructose and hexokinase activities were comparable to the parent strain. They displayed a reduced rate of citric acid accumulation. It is concluded that the synthesis of very high hexokinase activities may counteract citrate inhibition, thereby guaranteeing a high glycolytic flux during citric acid accumulation.

Aspergillus niger↗

PubMed2005

Enhanced phytoextraction: I. Effect of EDTA and citric acid on heavy metal mobility in a calcareous soil.

Phytoextraction, the use of plants to extract heavy metals from contaminated soils, could be an interesting alternative to conventional remediation technologies. However, calcareous soils with relatively high total metal contents are difficult to phytoremediate due to low soluble metal concentrations. Soil amendments such as ethylene diaminetetraacetate (EDTA) have been suggested to increase heavy metal bioavailability and uptake in aboveground plant parts. Strong persistence of EDTA and risks of leaching of potentially toxic metals and essential nutrients have led to research on easily biodegradable soil amendments such as citric acid. In our research, EDTA is regarded as a scientific benchmark with which degradable alternatives are compared for enhanced phytoextraction purposes. The effects of increasing doses of EDTA (0.1,1,10 mmol kg(-1) dry soil) and citric acid (0.01, 0.05, 0.25, 0.442, 0.5 mol kg(-1) dry soil) on bioavailable fractions of Cu, Zn, Cd, and Pb were assessed in one part of our study and results are presented in this article. The evolution of labile soil fractions of heavy metals over time was evaluated using water paste saturation extraction (approximately soluble fraction), extraction with 1 M NH4OAc at pH 7 (approximately exchangeable fraction), and extraction with 0.5 M NH4OAc + 05 M HOAc + 0.02 M EDTA at pH 4.65 (approximately potentially bioavailable fraction). Both citric acid and EDTA produced a rapid initial increase in labile heavy metal fractions. Metal mobilization remained constant in time for soils treated with EDTA, but a strong exponential decrease of labile metal fractions was noted for soils treated with citric acid. The half life of heavy metal mobilization by citric acid varied between 1.5 and 5.7 d. In the following article, the effect of heavy metal mobilization on uptake by Helianthus annuus will be presented.

Biodegradation, Environmental↗

PubMed1991

Citric acid cough threshold and airway responsiveness in asthmatic patients and smokers with chronic airflow obstruction.

The relation between citric acid cough threshold and airway hyperresponsiveness was investigated in 11 non-smoking patients with allergic asthma (mean FEV1 94% predicted) and 25 non-atopic smokers with chronic airflow obstruction (mean FEV1 65% predicted). Cough threshold was determined on two occasions by administering doubling concentrations of citric acid. Seven of the 11 asthmatic subjects and 14 of 25 smokers with chronic airflow obstruction had a positive cough threshold on both test days. Cough threshold measurements were reproducible in both groups (standard deviation of duplicate measurements 1.2 doubling concentrations in asthma, 1.1 doubling concentrations in chronic airflow obstruction). Citric acid provocation did not cause bronchial obstruction in most patients, though four patients had a fall in FEV1 of more than 20% for a short time on one occasion only. No significant difference in cough threshold was found between the two patient groups despite differences in baseline FEV1 values. There was no significant correlation between cough threshold and the provocative concentration of histamine causing a 20% fall in FEV1 (PC20) histamine in either group. Thus sensory nerves can be activated with a tussive agent in patients with asthma and chronic airflow obstruction without causing bronchial smooth muscle contraction.

Adult↗

PubMed1976

Mineral Nutrition of Aspergillus niger for citric acid production.

The mineral requirements of a strain of Aspergillus niger for the production of citric acid in a synthetic medium were studied. It was observed that K2HPO4 and MgSO4. 7 H2O were required at concentrations of 0.1% and 0.02% respectively. The optimum level of each of the trace elements Fe, Mn and Zn was 1.0 mug/ml. NaC1 and CaC12 at lower concentrations had no effect on citric acid production. Trace elements, Cu, Co and Mo, had an adverse effect on the production of citric acid while Ni and V were without effect.

Aspergillus↗

PubMed2005

Reproducibility and validity of a Yan-style portable citric acid cough challenge.

Although many different methods of measuring cough reflex sensitivity have been published, few are simple enough to use outside of a hospital or laboratory environment. The aim of this study was to develop a simple, quick, and portable cough challenge, assess its reproducibility, and compare its results with those measured by an existing established hospital protocol. Twenty-five volunteers performed cough challenges based on an established hospital dosimeter protocol, and, on a separate occasion, by a protocol inhaling citric acid from DeVilbiss 40 hand-held nebulisers (citric acid concentrations of 10-3000 mM). Reproducibility of the hand-held cough challenge was assessed in 11 volunteers. Cough thresholds were consistently higher by the hand-held method than by the hospital dosimeter method. The geometric mean citric acid concentrations causing two coughs (threshold D2) were 3.14 and 2.77 log mM, respectively (p<0.001). The geometric mean (95% CI) difference between the tests was 0.51 log mM (0.18-0.83) of the average of the two values. Cough D2 thresholds attained by the two techniques did, however, show significant correlation (r=0.95, p<0.0001). The coefficient of repeatability for the hand-held method was 0.40 log mM. Administering citric acid from DeVilbiss 40 hand-held nebulisers offers a rapid, portable, and reproducible cough challenge in healthy volunteers. The results correlate well with an existing Mefar dosimeter challenge, but give two to three times greater cough thresholds.

Anticoagulants↗

PubMed1999

In vitro stability of a highly crystalline hydroxylapatite coating in a saturated citric acid solution.

A novel pressurized hydrothermal post-plasma-spray process has been developed to convert the crystalline non-HA and amorphous components of plasma-sprayed hydroxylapatite coatings back into crystalline HA. The process, known commercially as MP-1, was used to produce coatings comprising approximately 96% crystalline HA. The in vitro solubility of the coating in saturated citric acid solution has been measured to simulate the effect of implant detoxification procedures, which use citric acid as a cleaning medium. The MP-1 coating solubility in saturated citric acid solution (pH = 1) was compared to that of coatings with crystalline HA contents ranging from 37.5-82%. All coatings showed an initial sharp rise in coating dissolution, which correlated with crystalline HA content, followed by a steady state dissolution rate. After 60 s at 25 degrees C, the MP-1 coating showed a 65% decrease in solubility compared to a highly amorphous coating (AM-2). All coatings showed very similar steady state dissolution rates, except for AM-2, which was significantly higher. SEM analysis showed that the AM-2 coating surface was degraded substantially more than the other coatings, resulting in partial coating exfoliation. A mechanism of coating dissolution is proposed, in which the initial rapid leaching of soluble phases from the coating leaves behind a porous layer of highly crystalline HA at the coating surface. The stability of this porous crystalline layer leads to steady state, diffusion-limited dissolution of the remainder of the coating. The observed two-regime dissolution profile can be accurately represented by a 2-parameter model, which predicts the initial sharp rise in coating dissolution followed by a slower, steady state loss in coating mass. Model parameters were determined from experimental solubility data, and were shown to correlate with the percentage of crystalline HA in the coatings. The present data suggest that the treated coating is significantly more resistant to degradation from aggressive detoxification procedures such as citric acid burnishing.

Citric Acid↗

PubMed1975

[Relationship of citric acid concentration to various quality indices of the equine ejaculate].

The paper describes the relation of citric acid to other chemical and biological indices of the fertility of stallion sperm. A positive relation was found between citric acid and the density and motility of spermatozoa, to the concentration of ergothioneine, and hemolytic activity, and a negative relation to pH and to the polarographic activity of proteins. Attention is drawn to the important nutritional function of citric acid.

Animals↗