Citric-Acid Fermentation

oxidation of carbohydrates, certain alcohols, and organic acids into citric acid by the action of the fungi of the genera Aspergillus and Penicillium. In addition to citric acid, the fermentation process also yields small quantities of gluconic acid and oxalic acid. At the onset of the fermentation process, the fungus produces pyruvic acid from the carbohydrates. The pyruvic acid is then converted into oxala-cetic acid. The enzyme citrate synthase together with coenzyme A condenses the oxalacetic acid with acetate to form citric acid. The industrial production of citric acid is based on the fermentation of a saccharose or molasses solution by the action of Aspergillus niger. A 70- to 75-percent citric-acid yield is produced based on the amount of sugar used.