Mold

Certain types of cheeses are ripened by mold fungi. Indeed, the molds responsible for this action have taken their names from the cheeses they affect. Camembert is ripened by Penicillium camemberti, and Roquefort is by Penicillium roquefortii.

The Penicillium mold has another important use, namely the production of antibiotics. Two species have been used for the production of penicillin, the first antibiotic to be discovered: Penicillium notatum and Penicillium chrysogenum. The Penicillium species can grow on different substrates, such as plants, cloth, leather, paper, wood, tree bark, cork, animal dung, carcasses, ink, syrup, seeds, and virtually any other item that is organic.

A unique characteristic of Penicillium species is their capacity to survive at low temperatures. The growth rate of Penicillium is greatly reduced, but not to the extent of its competition, so as the temperature rises the Penicillium is able to rapidly grow over new areas. However, this period of initial growth can be slowed by the presence of other, competing microorganisms. Most molds will have been killed by the cold, but various bacteria may still be present. By releasing a chemical into the environment capable of destroying these bacteria, the competition is removed and growth of the Penicillium can carry on. This bacteria killing chemical is what we now recognize as penicillin. The anti-bacterial qualities of penicillin were originally discovered in 1929 by Sir Sanford Fleming.

Since Flemming's pioneering observations, the careful selection of the Penicillium cultures has increased the yield of antibiotic many hundred fold since the first attempts of commercial scale production during the 1930s.

Other molds are used in various industrial processes. For example, Aspergillus terreus is used to manufacture icatonic acid, which is used in plastics production. Other molds are used in the production of alcohol. For example, Rhizopus, which can metabolize starch into glucose, directly ferments the glucose to give alcohol. Other molds are used in the manufacture of cheeses, flavorings and chemical additives for foods.

In times past, the involvement of mold in cheese making was more happenstance than by design. Often, a cheese was just left in a place where mold production was likely to occur. However, in modern production cheeses are inoculated with a pure culture of the mold (some past techniques involved adding a previously infected bit of cheese). Some of the mold varieties used in cheese production are domesticated, and are not found in the wild. In cheese production, the cultures are frequently checked to ensure that no mutants have arisen, which could produce unpalatable flavors.