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Citric acid

About: Citric acid is a research topic. Over the lifetime, 17745 publications have been published within this topic receiving 277125 citations. The topic is also known as: citrate & H3cit.


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Journal ArticleDOI
TL;DR: Determinations of activity at substrate and effector concentrations resembling the conditions that occur in vivo support the hypothesis that the apparent insensitivity of the enzyme to citrate during the accumulation of citric acid in the fungus is due to counteraction of citrate inhibition by NH4+.
Abstract: Phosphofructokinase (EC 2.7.1.11) from a citric acid-producing strain of Aspergillus niger was partially purified by the application of affinity chromatography on Blue Dextran--Sepharose and the use of fructose 6-phosphate and glycerol as stabilizers in the working buffer. The resulting preparation was still impure, but free of enzyme activities interfering with kinetic investigations. Kinetic studies showed that the enzyme exhibits high co-operativity with fructose 6-phosphate, but shows Michaelis--Menten kinetics with ATP, which inhibits at concentrations higher than those for maximal activity. Citrate and phosphoenolpyruvate inhibit the enzyme; citrate increases the substrate (fructose 6-phosphate) concentration for half-maximal velocity, [S]0.5, and the Hill coefficient, h. The inhibition by citrate is counteracted by NH4+, AMP and phosphate. Among univalent cations tested only NH4+ activates by decreasing the [S]0.5 for fructose 6-phosphate and h, but has no effect on Vmax. AMP and ADP activate at low and inhibit at high concentrations of fructose 6-phosphate, thereby decreasing the [S]0.5 for fructose 6-phosphate. Phosphate has no effect in the absence of citrate. The results indicate that phosphofructokinase from A. niger is a distinct species of this enzyme, with some properties similar to those of the yeast enzyme and in some other properties resembling the mammalian enzyme. The results of determinations of activity at substrate and effector concentrations resembling the conditions that occur in vivo support the hypothesis that the apparent insensitivity of the enzyme to citrate during the accumulation of citric acid in the fungus is due to counteraction of citrate inhibition by NH4+.

92 citations

Journal ArticleDOI
TL;DR: In this article, the efficacy of roasting process by incorporation of lemon juice and/or citric acid on the reduction of AFB1 in contaminated pistachio nuts (AFB1 at two levels of 268 and 383 nng/g) was investigated.

92 citations

Journal ArticleDOI
TL;DR: The results show that growth and agglomeration of calcium oxalate crystals are separate processes which are differently modulated by various compounds, and provide a possible explanation for the pathogenetic role of citrate in hypocitraturic renal stone disease.

92 citations

Journal ArticleDOI
Vielma, Ruohonen, Lall1
TL;DR: The bioavailability of dietary P can be improved by fine grinding the bone in fish meals, and dietary acidification by citric acid significantly increased whole-body iron in a linear fashion.
Abstract: Juvenile rainbow trout Oncorhynchus mykiss (Walbaum) were fed six low-phosphorus (P) diets supplemented with two different sizes of ground fish bone-meals (fine, 68 μm or less; coarse, 250–425 μm) and a coarse bone-meal diet containing four levels of citric acid (0, 4, 8 or 16 g kg−1 diet) to investigate the effects of pH and bone particle size on P bioavailability The basal diet provided 34 g P kg−1 and bone-meal increased P contents to 54–60 g P kg−1 Coarse bone-meal diets supplemented with 0, 4, 8 or 16 g kg−1 of citric acid had pH values of 60, 57, 54 and 50, respectively Weight gain and whole-body water, protein and lipid contents were not influenced by bone-meal supplementation Supplementing the basal diet with both coarse and fine bone-meal significantly increased whole-body ash content Fish fed no bone-meal were hypophosphataemic compared with fish fed with either fine or coarse bone-meals Phosphorus in fine bone-meal had higher availability than P in coarse bone-meal Bone-meal supplementation significantly decreased whole-body manganese content from 89 μg g−1 in fish fed no bone-meal to 23 and 45 μg g−1 in fish fed with fine and coarse bone-meals, respectively The concentration of magnesium increased but zinc concentration was not affected by bone-meal supplements Citric acid increased whole-body ash content but the influence of citric acid on the body P content was not significant (P = 007) Dietary acidification by citric acid significantly increased whole-body iron in a linear fashion The bioavailability of dietary P can be improved by fine grinding the bone in fish meals

92 citations

Journal ArticleDOI
TL;DR: It is suggested that ligands with high affinity for Fe (e.g. EDTA) can prevent Fe from binding tannin and can remove Fe already bound.

92 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023725
20221,540
2021441
2020597
2019678
2018823