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Economic Importance of Fungi

Economic Importance of Fungi

Fungi are beneficial to us, directly or indirectly, in many ways. They keep our environment clean by removing organic debris; they provide food, medicines and several other useful products, and they play an important role in many industries.

Fungi as Food

Fungi have been used as food since times immemorial and esteemed as delicacies. The fructifications of several mushrooms and morels (e.g. Agaricus bisporus, Amanita vaginata, Boietus edulis, Clavatia gigantean, Lentinus edodes, Morchella, Pleurotus, Volvaria, Volvariella volvacea) are used as food. Agaricus campestris is cultivated in many areas of north and south India and Morchella esculenta is grown in Punjab and Kashmir. Mushroosm are preferred for food because of their fairly large protein contents (21-30%). They are also rich in vitamins, carbohydrates, minerals and amino acids.

Yeast is an important source of vitamin B and vitamin D. Saccharomyces, Endomyces, Rhodotorula and Torulopsis are particularly rich in proteins and hence they are mixed in incomplete livestock.

Similarly, a popular food, ‘Sufu’ is produced from species of Mucor and Antimucor.

Some foods like soybeans and cassava although rich in nutrients can not be easily digested by man. These are made easily palatable by fermenting fungi. Soybeans are fermented by species of Rhigopus (e.g. R. oligosporus, R. oryae and to prepare tempeh, a food which is more digestible and tasty. Similarly, ‘Incaparina’ foods developed by the Institute of Nutrition of Central America and Panama, consist of corn (26%), cotton seed flour (38%), sorghum (26%), food yeast (3%) and minerals and vitamins. Nothern Utilisation Research and Development Division of USDA has developed protein cake by combining wheat, barley, oats, rice and soybean flour cooked and fermented with the help of Rhizopus oligosporus. This cake is rich in niacin and riboflavin. Single-cell protein (SCP), obtained from yeast, species of Aspergillus, Penicillium, Fusarium, Neurospora and Candida is a complete substitute for conventional protein foods.

Fungi as Medicine

Several fungi are used in the production of medicines.

  1. Ergot:

    Ergot is prepared from the sclerotia of Claviceps purpurea. It contains some alkaloids which are used to induce uterine contraction for abortion, in the treatment of menstrual disorders and to check haemorrhages. However, excess of ergot leads to serious convulsions or a gangrenous condition that may result in loss of limbs.

  2. Ephedrine:

    It is synthesized from benzaldehyde by the action of yeast and is used in the treatment of asthama and nasal troubles.

  3. Steroids:

    Steroids are complex organic compounds, effective against rheumatoid arthritis, allergic, dermatologic and other diseases. They are also used as anaesthetic and antifertility agents. Steroids are adrenal cortical and gonadal hormones and their derivatives. Their extraction from biological system is highly expensive. A wide variety of fungi have the capacity of synthesizing many steroids, for instance, cortisone is prepared by fermentation of plant glycosides by Rhizopus nigricans and Aspergillus niger.

  4. Vitamins:

    Vitamins are accessory micronutrients, which are required by living organisms for their proper growth. Several yeasts, including Saccharomyces Cerevisiae, are good source of vitamin B-complex. Ergosterol a precursor of vitamin D, is synthesized from some molds and yeasts. Eremothemium ashbyii is a rich source of vitamin B12, whereas vitamin A is extracted from Rhodotorula gracilis.

  5. Antibiotics:

    Antibiotics are metabolic substances produced by some living organisms which are injurious to other living beings. Alexander Fleming, in 1944, for the first time extracted the wonder drug penicillin from Penicillium notatum. Since then several other antibiotics have been extracted from fungi.

Several fungi are active against human pathogens; for instance, spread of Candida albicans is prevented by the extract of Tricholoma saponaceum. Mushrooms like Lentinus edodes, Flammulina velutipes, Agaricus bisporus, Volvariella volvacea, and Boletus edulis possess antitumour properties. Many edible mushrooms (e.g. Lentinus edodes, Agaricus bisporus) have the ability to lower blood cholesterol.

Fungi in Production of Organic Acids

Biochemical activities of several fungi are utilized in the commercial production of organic acids.

  1. Citric acid:

    It is produced by fermenting sucrose and molasses by Aspergillus niger and A. wentii. Citric acid is used in soft drinks and other foods and medicinal preparations. It is a superior sequestering agent and is used in the manufacture of ink, dyeing, electroplating and leather tanning.

  2. Itaconic acid:

    It is produced by fermentation of sugars by Aspergillus itaconicum and A. terreus. It is widely used in the manufacture of alkyl resins, synthetic fibres and plasticizers.

  3. Gluconic acid:

    It is produced by fermenting sugars by Aspergillus niger and Penicillium purpurogenum. It is used in pharmaceutical, food, textile, leather and photographic industries.

  4. Kojic acid:

    It is produced by fermentation of sugars by Aspergillus oryzae. It possesses insecticidal and antibiotic properties and is used in the preparation of pyridines, ethers, esters, azodyes, etc.

  5. Gallic acid:

    It is synthesized by the hydrolysis of gallotannin present in gall nuts by Penicillium glaucum and Aspergillus gallomyces. It is used in the manufacture of inks and dyes.

  6. Fumaric acid:

    It is obtained by fermentation of sugars by Rhizopus stolonifer. It is used in the manufacture of alkyl resins and wetting agents.

Besides, several species of Mucor and Rhizopus are used in the production of lactic, oxalic and succinic acids.

Fungi in Industry

  1. In brewery:

    Alcoholic fermentation with the help of fungi is the basis of brewing industries. Wine is produced by fermenting rice with Aspergillus oryzae. This method is popular in Japan and many European countries. Saccharomyces cerevisiae is used in the production of beer.

  2. In baking industry:

    Fermentation of carbohydrates by Saccharomyces cerevisiae produces ethyl alcohol and CO2.

C6H12O6 (in presence of yeast) →2C2H5OH + 2CO2

Carbon dioxide liberated in this process is used in the preparation of several bakery products such as breads and cakes.

  1. In cheese industry:

    Some species of Penicillium (e.g. camembertile, P. rocqueforti, P. candidum) are used for maturation of cheese. They impart specific flavours to cheese.

Fungi in Enzyme Production

Many intra and extracellular enzymes are found in fungi and some are extracted on commercial scale.

  1. Invertase:

    The yeast Saccharomyces cerevisiae is used for extraction of the enzyme invertase. This enzyme hydrolyses sugars into glucose and fructose and is used in confectionery and paper industry.

  2. Zymase:

    The enzyme zymase obtained from Saccharomyces cerevisiae in used in the preparation of ethyl alcohol by fermentation of carbohydrates.

C6H12O6 (in presence of zymase) ——-> 2C2H5OH + 2CO2

  1. Amylase:

    Aspergillus niger and oryzae are used in the production of the enzyme amylase. This enzyme is used in alcohol industry in the manufacture of dextrinized starch and in medicines.

  2. Cellulose:

    Trichoderma reesli is used in the production of the enzyme cellulose, which is used in the preparation of cheese and in saccharification of cellulosic and lignocellulosic wasters together with recycling of hydrolysate for the production of single cell protein, microbial biomass, vitamins (like â-carotene), etc.

Fungi are also used in the production of several other important enzymes like lipase, pectinases, glucose oxidase, proteases and lactase.

Fungi in Agriculture

Fungi play an important role in agriculture in various ways.

  1. As scavengers:

    The ratio of carbon dioxide in the atmosphere is maintained by decomposition of plants and animals debris by fungi and bacteria. In the absence of these scavengers, the surface of the earth would have covered with the accumulating remains of dead animals and plants.

In acidic soils the activity of bacteria becomes very slow and under such conditions decomposition is mainly carried by saprophytic fungi. The enzymes secreted by these fungi decompose complex organic substances into their inorganic components and thus increase soil fertility.

  1. In biological control:

    Fungi play an important role in biological control of diseases, for instance, Trichoderma lignorum suppresses the growth of root rot fungus, Pythium and the growth of Rhizoctonia solani can be checked by Penicillium vermiculatum and Rhizoctonia oryzae. Gliocladium roseum is used to control Sclerotinia diseases. Trichoderma harzianum is used to control blight of tomato and peanuts caused by Sclerotim rolfsii. Fungal pathogens play an important role in nature in the reduction of weeds. The strategy of using fungal plant pathogens in biological control involves a classic tactic and a bioherbicide tactic. The first approach involves the introduction of a foreign plant pathogen, while the later envisages the development of endemic pathogens and using them as microbial weed killers (bioherbicides). Pathogens are multiplied in vitro and applied as herbicides so that each individual weed plant is heavily inoculated with infectious propagules. For instance, Septogloeum gillis, Wallrothiella arecuthdoii and Colletotrichum gloeosporioides have the ability to attack mistletoes (Arecuthobium) at all stages of development. Similarly, the growth of the weed, Eupatorium adenophorum can be controlled by Cercospora eupatorii and Colletotrichum destructive can be used as a biocontrol agent for dodder. Several fungi are also utilized for controlling soil borne organisms like amoeba and nematodes. For instance, Nematophthora gyrophila is capable to control effectively Heterodera avenae, a cereal cyst nematode.

  2. Importance as mycorrhiza:

    A symbiotic relationship between fungal hyphae and roots of higher plants is known as mycorrhiza. Several fungi, like species of Rhizoctonia, Phoma, Tricholoma, Boletus, Phallus, Scleroderma and Amanita, form mycorrhizal relationships with higher plants. The fungal partner of the mycorrhiza obtains food from the roots of higher plant and in return it supplies mineral elements to the other partner. Mycorrhiza are important organs of water adsorption for the plants growing in dry conditions and plays a dominant role, particularly in the uptake of less-mobile plant nutrients.

  3. In soil aggregation and soil fertility:

    Some fungi, such as specie of Absidia, Aspergillus, Cladosporium, Chaetomium, Mucor, Penicillium and Rhizopus, have soil binding properties. The mucilaginous substances secreted by them are helpful in soil aggregation. Yeasts (such as species- of Rhodotorula and Saccharomyces) and several phylloplane fungi have nitrogen fixing capabilities, thus increasing soil fertility. In a forest ecosystem the natural mushroom flora greatly helps in bio-degradation of woody wastes. The ultimate end product in the form of humus is quite useful for the growth of other plants.

  4. As growth hormones :

    Gibberellin, produced by Gibberella fujikuroi, is an important plant hormone. It is used to accelerate growth of many crops. The hormone trisporic acid is obtained from Mucor mucedo and Choanephora trispara.

  5. As insecticides:

    Many insect pests can be controlled by the use of fungi Aschersonia aleyrodis, Beauveria bassiana, Cordyceps melonthae Empusa sepulchralis, Fusarium oxysporum and Metarhizium anisopliae. Some soil fungi (e.g. Trichoderma viride, Fusarium roseum f. sp- cereal, Rhizopus nigricans) act as ‘soil nibblers‘ since they attack and kill some roots but do not cause excessive damage. Their overall effect is to promote more fibrous root development and to increase total area of root absorption.

Fungi as Test Organisms

Several fungi are used as important research tools for the study of various fundamental biological processes. They grow very fast and require a short period to complete their life cycle. Furthermore, experimentation with fungi requires less space and inexpensive equipments. For instance Neurospora has become these days an ideal material for genetical studies and Physarum polycephalum is a very good material for the study of DNA synthesis, morphogenesis and mitotic cycle.

Neurospora crassa is used as a test organism to detect the presence and quantity of vitamin B in a given sample. Aspergillus niger is used for the detection of trace elements like zinc, nickel and copper, even when they are present in very minute quantities. Several fungi such as species of Aspergillus, Absidia, Mortierella, Penicillium, Torulopsis, Endomyces, Rhodotorula are capable of synthesizing fats and fatty substances. Many alkaloids are also produced by fungi; for instance, fumigaclarin is produced by Aspergillus fumigatus and Claviceps purpurea produces a number of important alkaloids like ergotinine, ergotinic acid, ergobasine and ergotetrine. Several fungi which possess coloured spores and mycelium are utilized as dyes. A red pigment obtained from Monascus purpureus is used for colouring rice and Cercosporina kikuchii produces a reddish-violet novel pigment, neocercosporin. A similar maroon pigment is obtained from Aspergillus fumigates. A brown pigment atromentin is obtained from Paxillus atromentosus and a yellow pigment citrinin from Penicillium citrinum. Some Basidiomycetes like Armillaria mellea show bioluminescence, thus their fruiting bodies are used as ornamentals and path markers during night.

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