Describe the role of certain fungi in industrial production.

The industrial uses of fungi are many and varied. In fact the fungi form the basis of many important industries. There are a number of industrial processes in which the biochemical activities of certain fungi are harnessed to good account.

A brief sketch of some of the most important of these processes is given below:

(i) Alcoholic fermentation:

It is the basis of two important industries in India or rather all over the world. These are brewing and baking. Both are dependent on the fact that the fermentation of sugar solutions by yeasts produces ethyl alcohol and carbon dioxide.

In brewing or wine making industry alcohol is the important product. The other by-product which is carbon dioxide was formerly allowed to escape as a useless thing.

Now carbon dioxide is also considered a valuable by-product. It is collected, solidified and sold as “dry ice”. In the baking or bread- making industry CO₂ is the useful product.

It serves two purposes:

(i) Causes the dough to rise.

(ii) Makes the bread light.

The other by-product, which is alcohol, is incidental. The yeasts secrete the enzyme complex called zymase which brings about conversion of sugar into alcohol. Many excellent yeast strains are now available.

The yeasts lack diastase. So they cannot break starch into sugar. There are a number of fungi popularly known as the moulds. They secrete a whole range of enzymes and thus bring about fermentation of complex carbohydrates.

In producing industrial alcohol moulds are employed as starters to bring about scarification of the starch. At the second stage yeast is employed to act on the sugar.

Although mould can complete the conversion to sugar but the yield is better if yeast is employed for the second stage. The moulds commonly used for purpose of scarification are Mucor racemosus, M, rouxii and some species of Rhizopus Aspergillus flavus is used in the production of African native beer.

(ii) Enzyme preparations:

Takamine on the basis of his intensive study of the enzymes produced by Aspergillus flavus-oryzae series has introduced in the market a few products of high enzymic activity. These are Digestin, Polyzime, Taka diastase, etc. They are used for dextrinization of starch and desiring of textiles.

Cultures of Aspergillus niger and A. oryzae on trays of moist, sterile bran yield a well-known amylase which contains two starch splitting components.

Invertase is extracted from Saccharoymces cerevisiae. It has many industrial uses. It hydrolyses sucrose to a mixture of glucose and fructose.

(iii) Preparation of organic acids:

The important organic acids produced commercially as the result of the biochemical activities of moulds are oxalic acid, citric acid, gluconic acid, gallic acid, fumaric acid, etc.

Oxalic acid is the fermentation product of Aspergillus niger. Citric acid is made by mould fermentation. Many species of Penicillium are used for the purpose. The acid is produced on a commercial scale and is cheaper than the acid made from the citrus fruits.

The gluconic acid is prepared from sugars. The moulds chiefly employed for this purpose are some species of Penicillium and Aspergillus.

Gallic acid is prepared on a commercial scale in Europe and America. The details of the method employed, however, are not known. It may be a modification of Calmete’s process.

Calmette (1902) obtained the gallic acid as the fermentation product of an extract of tannin by Aspergillus gallomyces.

(iv) Gibberellins:

These are plant hormones produced by the fungus Gibberella fujikuroi which cause a disease of rice accompanied by abnormal elongation. Gibberellins are used to accelerate growth of several horticultural crops.

(v) Cheese Industry:

Certain fungi popularly known as the cheese moulds play an important role in the refining of cheese. They give cheese a characteristic texture and flavor.