Production of Citric Acid
Citric acid is a six-carbon tricarboxylic acid, which was first isolated from lemon juice. It is used in the food and beverage industry for various purposes as pharmaceuticals and for other industrial uses. It is an organic carboxylic acid and can be extracted from the juice of citrus fruits by adding calcium oxide to form calcium citrate, which is an insoluble precipitate that can be collected by filtration; the citric acid can be recovered from its calcium salt by adding sulfuric acid. Citric acid is mainly produced by fungal fermentation. Chemical synthesis of citric acid is possible, but it is expensive than fungal fermentation. However, a small amount of citric acid is still produced from citrus fruits in Mexico and South America where they are available economically. There are two very common and practical fermentation processes used: the liquid surface culture and the submerged fermentation process. The second process—submerged culture fermentation—is more popular.