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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: In this paper, the root-induced changes in the soil affecting phosphate solubility were measured, and the extent to which the observed excretion of citrate and rootinduced pH changes could account for the observed phosphorus solubilization and uptake was assessed using a mathematical model.
Abstract: Rice (Oryza sativa) plants were grown with their roots sandwiched between thin layers of phosphorus-deficient soil from which they were separated by fine mesh, and root-induced changes in the soil affecting phosphate solubility were measured. The concentrations of low molecular weight organic anions in the thin layers, particularly citrate, increased in the presence of the plants. Apparent rates of citrate excretion from the roots, calculated from the quantities in the soil and rates of decomposition calculated with a first order rate constant measured independently, varied from 337–155 nmol g−1 root f. wt h−1 over the course of plant growth, equivalent to 2–3% of plant d. wt. Rates of excretion were similar for NH4+ and NO3−-fed plants. The soil pH decreased from its initial value by up to 0.6 units for the NH4+-fed plants and increased by up to 0.4 units for the NO3−-fed ones. The contribution of organic anion excretion to the pH changes was small compared with that of the inorganic cation-anion balance in the plants. The extent to which the observed excretion of citrate and root-induced pH changes could account for the observed phosphate solubilization and uptake was assessed using a mathematical model. Previous work had shown that phosphate solubilization by rice in this soil could not be explained by enhanced phosphatase activity in the rhizosphere, and the roots were not infected with mycorrhizas. The model allows for the diffusion of the solubilizing agent (citrate or H+) away from the roots, its decomposition by soil microbes (citrate only); its reaction with the soil in solubilizing phosphate and diffusion of the solubilized phosphate to the roots. The model contains no arbitrary assumptions and uses only independently measured parameter values. The agreement between the measured time course of phosphorus uptake and that predicted for solubilization by citrate was good. Root-induced acidification by NH4+-fed plants resulted in additional solubilization, the acidification enhancing the solubilizing effect of citrate. However, the final phosphorus uptake by NH4+-fed plants was no greater than that of NO3−-fed plants, presumably because the acidification inhibited plant growth. The mechanism of solubilization by citrate involved formation of soluble metal-citrate chelates rather than displacement of phosphate from adsorption sites.

150 citations

Journal ArticleDOI
TL;DR: A new method to detect cross-linking of starch by CA in solution-cast films by molecular weight measurements and quantify di-ester content within starch films by using a modification in the method of complexometric titration with copper(II)-sulfate is described.

150 citations

Journal ArticleDOI
TL;DR: In several of the strains cultured in media containing a low glucose concentration, unicellular morphology was observed, while at high glucose concentrations mycelia were predominant, indicating lipid degradation even for the genetically modified strains.
Abstract: The biochemical behavior of wild-type or genetically modified (presenting decreased expression of intracellular acyl-CoA oxidases) Yarrowia lipolytica strains cultivated on commercial glucose was studied. Flask nitrogen-limited cultures were performed favoring the production of organic acids (and potentially the accumulation of lipid). Nitrogen depletion induced secretion of citric acid, while intracellular lipid was not produced in high quantities. Maximum total citric acid up to 49 g/L (yield 0.85 g/g glucose) was produced. In some of the wild-type strains, an increase of glucose in the medium also induced noticeable production of acetic acid. Increasing the amount of added glucose led to an increase in the total lipid quantity (%) produced, although in the stationary growth phase the concentration of lipid declined, indicating lipid degradation even for the genetically modified strains. Total lipid amount did not exceed the value of 14%, while neutral fractions increased with increase in glucose concentration. In all cases, the total microbial lipids and major lipid fractions were composed of C16 and C18 (principally unsaturated) fatty acids. Finally, in several of the strains cultured in media containing a low glucose concentration, unicellular morphology was observed, while at high glucose concentrations mycelia were predominant.

149 citations

Journal ArticleDOI
TL;DR: In this article, a packed-bed bioreactor consisting of jacket and four stages with dimensions of 100×16 cm 2 was constructed and operated for solid state fermentation and the operation of this bioreacter was optimised using Taguchi statistical method of analysis.

149 citations

Journal ArticleDOI
TL;DR: The role of citric acid in a simulated body fluid (SBF) was examined with the main focus on its induction ability of hydroxyapatite (HAp) nucleation on a bioinert collagen membrane, especially strong chelation ability ofcitric acid with the calcium ion.

149 citations


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