Fungi feed on dead plant and animal remains and decaying organic matter. These fungi break down complex organic compounds into simple inorganic substances. As a result, soil fertility increases. 8 inches of fertile soil can contain a ton of fungi and bacteria.

Vitamin-B is produced from Ashbya gossypii fungus, Vitamin-C from Aspergillus niger and Vitamin-D from yeast.

Yeast cake is made by cultivating Saccharomyces cerevisiae and Candida urtilis fungi through molasses and ammonia mixed culture. Yeast cake is rich in protein. It contains 15% meat.

Aspergillus flavus and Aspergillus oryzae fungi produce digetin, polyzyme and diastase enzymes.

Gibberellin hormone is obtained from the fungus Gibberella fujikuroi. It promotes plant growth.

Citric acid, malic acid, fumaric acid, oxalic acid, gluconic acid etc. are produced from different species of Penicillium. Diastase and oxalic acid from Aspergillus niger, gibberellic acid from Gibberella fujikuroi and invertase enzyme from Saccharomyces are available.

Different types of pesticides are made from fungi. It is used for pest control. Such as Empusa sepulchralis, Isaria ferinosa, Ascherromyces deyroides.

(i) Penicillium and streptomycin (antibiotics) are prepared from Penicillium notatum and Penicillium chrysogenum. Griseofulvin is produced from Penicillium griseofulvum and actinomycetes from Streptomyces griseus. Besides, antibiotics like chloromycin, neomycin, aureomycin etc. are made from fungi.
(ii) Ergot is prepared from Claviceps purpurea. It is used to hasten abortion and stop bleeding after childbirth.
(iii) Steroid drugs are prepared from Aspergillus fungi. It is used to treat arthritis.
(iv) Cyclosporine drug is prepared from Tolypocladium inflatum. Its trade name is Neoral. It is used to transplant human organs.
(v) Mushrooms have the ability to reduce diabetes. Magic mushrooms contain psilocin and psilocybin. Psilocin and psilocybin are the main components of hallucinogens. Hallucinogens relieve the body of depression.

Fungi act as decomposers in ecosystems. They rapidly decompose the dead bodies of plants and animals into organic matter. So they are called transformative. They grow on dead bodies and feed on them. So they are called Saprophage.

Mushrooms containing protein and vitamins are used as human food. There are about 200 species of fungi that are edible to humans. Mushroom (Agaricus, Volvariella), truffle, morel (Morchella) etc. fungi are used as food in different countries of the world including Bangladesh. Edible mushrooms for humans are Agaricus bisporus and Agaricus campestris. Their nutritional quality is good.