Which fungus was used in the first mass production of citric acid?

Aspergillus niger was used in the first industrial mass production of citric acid. This common black mold became a valuable manufacturing organism because selected strains can convert inexpensive sugars into large quantities of citric acid.

The breakthrough came in 1917, when American food chemist James Currie identified efficient citric-acid-producing strains. Pfizer began industrial-scale production using the method in 1919, two years later. This replaced reliance on citrus fruit and helped secure supplies when World War I disrupted imports of calcium citrate from Italy.

Modern production feeds A. niger with carbohydrate sources such as sucrose, glucose, molasses, corn steep liquor, or hydrolyzed corn starch. The mold releases citric acid into the liquid culture. Manufacturers then remove the fungal biomass and recover the acid through chemical processing, traditionally involving calcium citrate and sulfuric acid.

A common mix-up is Penicillium: a Penicillium mold was reported to produce citric acid in 1893, but Aspergillus niger became the organism associated with successful industrial production. Citric acid is now widely used in foods, drinks, medicines, and cleaning products.