Citric Acid Fermentation Presentation PDF

Citric Acid Fermentation Chemical Formula: CH2COOH | C (OH)-COOH | CH2COOH Citric acid was first isolated from lemon juice and crystallized as a solid by Sheele (1784). It is found as a natural constituent of citrus fruits, pineapple, pears, peaches, figs and othe...

Citric Acid Fermentation Chemical Formula: CH2COOH | C (OH)-COOH | CH2COOH Citric acid was first isolated from lemon juice and crystallized as a solid by Sheele (1784). It is found as a natural constituent of citrus fruits, pineapple, pears, peaches, figs and other fruits and tissues (natural citric acid). Wehmer (1893) was first described citric acid as a product of mold fermentation.  Organisms: Aspergillus niger, A. japonicas, A. wentii, A. clavatus, Mucor piriformis, Paecilomyces divaricatum, Penicillium citrinum, P. luteum, Uslulina vulgaris. Only, strains of Aspergillus niger appear to be of industrial importance.  Production of Citric Acid: 1)By Surface Culture Method: Media: Currie medium (1917): Currie (1917) found that the most favorable medium for producing citric acid contained the following: Sucrose 125-150g/l NH4NO3 2- 2.5g/l KH2PO4 0.75- 1.0 g/l MgSO4.7H2O 0.20- 0.25g/l pH 3.4- 3.5 (HCl).  Doelger and Prescott medium (1934): Sucrose 140g/l NH4NO3 2- 2.3g/l K2HPO4 1.00 g/l MgSO4.7H2O 0.23g/ l pH 1.6- 2.2 (HCl). Temperatura 26- 28oC, incubation period 10days.  2)By Submerged Culture Method: The molds: A. wentii and A. niger. Sucrose 150 g/l Temperature 28- 35oC Urea 1.0g/l pH 2 (HCl) MgSO4.7H2O 0.5g/ l KH2PO4 0.08 g/l KCl 0.15g/l MnSO4.4H2O 0.02g/l ZnSO4.7H2O 0.01g/l  Production of Citric Acid from Cane Molasses: Molasses 180g/l NH4NO3 2.25g/l KH2PO4 1.00 g/l MgSO4.7H2O 0.25g/ l pH 2.3 (HCl). Treatment of molasses with cation-exchange or potassium ferrocyanide reduced the amount of ash and resulted in improved yield.  Fermentation Procedures: Production of citric acid by the shallow-pan method (surface method) is completed in 7-10 days and about of 60% of sugar used in the medium may be recovered as citric acid. At the completion of the fermentation, the solution is drained off and the mat is pressed to remove any acid contained in it. Calcium citrate is then precipitated from a hot neutral solution of Ca(OH)2. By treating the precipitate with an equivalent of sulfuric acid, the citric acid is liberated and is recovered by separating it from the calcium sulfate Citric acid + Ca(OH)2 Ca citrate +H2SO4 CaSO4 + C6H8O7 Citric acid  Mechanism of Citric Acid Formation: 1) Euler Theory: Euler 1909 suggested that pyruvic acid was formed from glucose which decomposed into acetaldehyde and carbon dioxide. Three molecules of acetaldehyde condensed and product was oxidized to citric acid. 3C6H12O6 6 CH3CO-COOH 6 CO2 + 2 C6H8O7  2) Raistrick and Clark Theory: Raistrick and Clark (1919) suggested that hexose is broken down into α and γ– diketoadipic acid, which then hydrolyzed to acetic acid and oxalacetic acid, these two acids combined together to form citric acid. CHO COOH COOH COOH | | | | CHOH CHOH C=O C=O | | | | CHOH +3/2 O2 CHOH -2 H2O CH2 + H2O CH2 | | | | CHOH CHOH C=O COOH | | | Oxalacetic CHOH CHOH CH2 acid | | | CH2OH COOH COOH CH3 α,γ– | Glucose Saccharic diketo COOH acid Acetic adipic acid acid C6H8O7 Citric acid  3) Butkewitsch Theory: Butkewitsch (1924) proposed a scheme in which glucose was directly oxidized to citric acid. C6H12O6 + 3/2 O2 C6H8O7 + 2 H2O Glucose Citric acid  4) Gudlet Theory: Gudlet (1935) proposed that glucose split into a 4- carbon molecule (succinic acid) and a 2 carbon compound (acetaldehyde).  COOH COOH COOH | | | CH2 CH CH2 | || | C6H12O6 +H2O CH2 -H2 CH + H2O CHOH -H2 | | | COOH COOH COOH Succinic Fumaric Malic Acid Acid acid + + CH3-CHO + CH3-COOH ½ O2 Acetaldehyde Acetic acid COOH | CH2 | C(OH) | COOH Citric | CH2 acid | COOH