PRODUCTION OF CITRIC ACID
Citric acid is a White solid,C3H4OH(COOH)3,soluble in water and slightly soluble in organic solvents, which melts at 153 oC. Aqueous solutions of citric acid are slightly more acidic than solutions of acetic acid. Traces of citric acid are found in numerous plants and animals, because it is a nearly universal intermediate product of metabolism. Large amount of the acid are found in the juice of citrus fruits, from which it is precipitated by the addition of lime; the resulting calcium citrate is treated with sulfuric acid to regenerate the citric acid. Fermentation of sugar by the mold Aspergillus niger is the chief commercial source of the acid. It is added to some foods and beverages to produce pleasant acid flavor; It is also used in medicines, in making blueprint paper, in textile printing, and as a polishing agents for metals. Citric acid is the product of fermentation of numerous organisms.However,certain strains of the fungus Aspergillus niger produce commercially high yield of citric acid from a variety of 2,3,4,5,7 or 12 carbon compounds. Four theories have been proposed for the mechanism of citric acid formation by Aspergillus niger.It would appear that metabolic shunt(induced by environment) is at work, since citric acid is usually not a metabolite that accumulates in the medium but is readily utilized as a carbon source. The culture conditions are minimal for nitrogen and carbon at low pH. Phosphate is usually deficient. Aspergillus niger appears to have more than one systems for the formation of citric since ,it utilizes variety of different length carbon chains under special conditions. Citric acid was originally produced from calcium citrate obtained from cut lemons. Methods for producing citric acid from fungus metabolism were introduced in the United States in 1923.
Mechanism of Citric acid Formation:
Citric acid is one of the principal organic acid produced in the citric (CA) cycle....
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