Page 232 - Chemical and process design handbook

Speight_Part II_C 11/7/01 3:08 PM Page 2.172

CITRIC ACID

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Citric acid (melting point: 153 C, density: 1.665) is one of our most ver-
satile organic acids and is used as an acidulant in carbonated beverages,
jams, jellies, and other foodstuffs. Another large outlet is in the medicinal
field, including the manufacture of citrates and effervescent salts.
Industrially citric acid is used as an ion-sequestering agent buffer and in
the form of acetyl tributyl citrate, as a plasticizer for vinyl resins.
Except for small amounts produced from citrus-fruit wastes, citric acid
is manufactured by aerobic fermentation of crude sugar or corn sugar by a
special strain of Aspergillus niger,

C H O + H O + 3O → 2C H O + 4H O
12 22 11 2 2 6 8 7 2
sucrose citric acid
2C H O + 3O → C H O + 4H O
6 12 6 2 6 8 7 2
dextrose citric acid
The submerged process for the manufacture of citric acid (Fig. 1)
involves coordinated sequences of biochemical conversions with the aid of
A. niger and various unit operations and chemical conversions.

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