INTRODUCTION:

The fleshy fungi of class Ascomycetes and Basidiomycetes are generally termed as mushroom. Mushrooms also known as toadstool are part of fleshy, spore-bearing fruiting body of a fungus, typically produced above ground on soil or on its food source. Mushrooms are found in various shapes, sizes and color. The mushroom are defined as “a macro fungus with a distinctive fruiting body, large enough to be seen with the naked eye and to be picked up by hand” (Chang and Miles, 1991).

There are 38,000 different varieties of mushrooms in which 300 mushroom species are edible, but only 30 have been domesticated and 10 are grown commercially. Annually, 61.16 lakh of mushroom is cultivated throughout the world (Narayanasamy et al., 2008). Mushroom farming first started in America in 1896 in Kennett Square, Pennsylvania, which is called the “mushroom capital of the world”. Nearly half the nation’s button mushrooms are produced here. California and Florida are the second and third leading producers of mushroom.

Some mushrooms are poisonous and some are edible. The common cultivated mushrooms are white button mushroom (Agaricus bisporus), Shitake (Lentinula edodes), Enoki (Flammulina velutipes), and Oyster (Pleurotus ostreatus). Mushrooms have been widely used since ancient times, not only as foods or food-flavoring materials but also for medicinal or functional purposes. Edible mushroom are highly nutritious and can be compared with eggs, milk and meat (Oei, 2003). It contains high quality of proteins, has high fibre value, vitamins and minerals, which is easily digested and it has no cholesterol content (Isikhuemhen and Okhuoya, 1999). They have an ability to maintain the blood cholesterol at the optimum level. They have been used in folk medicine throughout the world since ancient times. Attempts have been made in many parts of the world to explore the use of mushrooms and their metabolites for the treatment of a variety of human ailments. The potential of medicinal mushrooms is enormous but mostly untapped. It can evolve into a successful biotechnological industry for the benefit of humankind.

From different varieties of mushroom the Volvariella volvacea is an edible tropical mushroom that is a popular ingredient in dishes of many countries. Volvariella volvacea is also important for the treatment of different diseases in human as is evident from the biochemical analysis of the fruiting bodies of these mushrooms (Jones and Janardhanan, 2000). The nutritional value of these mushrooms depends on the type of the agricultural waste used for its production. The cultural, economic and nutritional value of V. volvacea has recently attracted attention as functional health promoter and in development of drugs and nutraceuticals. There is very little documentation and report on the amount of mushroom produced, harvested, chemical composition and therapeutic properties which can help in establishing the market value chain of mushroom dynamics of this mushroom in our country.

In this article, general state of knowledge in the area of cultivation, chemical composition, and nutritional value and therapeutics properties of V. volvacea has been reviewed.

Volvariella volvacea

The different varieties of Volvariella found worldwide are V. bombycine, V. coesiotincta, V. gloiocephala, V. hypopithys, V. iranica, V. jamaicensis, V. lepiotospora, V. peckii, V. sathei, V. speciosa, V. surrecta,V. volvacea. Amongst all these species Volvariella volvacea is commonly used for edible purpose. It is commonly known as paddy straw mushroom (because it grows best on paddy straw) or straw mushroom or Chinese mushroom (because artificial cultivation of this mushroom first started in China having a white cap and long stem (Chang, 1969). It is also known as Tributary mushroom or “Nanhua mushroom”. The name Nanhua came from the Nanhua Temple of Chaohsi in northern Kwangtung Province, China.

Volvariella volvacea is also known for its unique aroma and texture, and grows well between 28 and 35°C (Chang, 1978. It widely grows in tropical, subtropical regions and temperate regions of both the eastern and the western hemispheres by using agricultural wastes (rice straw, cotton wastes) as growth substrates (Ahlawatet et al., 2008, Shaffer, 1957). According to Zoberi (1972), this species grows naturally on dead leaves, dead wood, animal droppings, on trees and waste stumps. In addition to rice straw, Volvariella volvacea also grows on water-hyacinth, palm oil bunch wastes, pericarp wastes, banana leaves, and cotton waste (Chang, 1974). Straw mushroom is characterized macroscopically by pink colored spores, free lamellae, an exannulate stipe and volvate base.

This mushroom is the easiest to grow, in as little as 4 days, and is adapted to areas with high temperatures (30-36 °C) due to which it are also known as warm mushroom. Volvariella volvacea shows significant pharmacological properties like anti-tumor, immunosuppressant and immunomodulatory (Kishida et al., 1998).They are not as popular amongst the consumers as button, oyster, or shiitake mushrooms, but still accounts for 6 percent of the world’s production (Buswell and Chen, 2005). In India, Su and Seth (1940) first cultivated straw mushroom; however, scientific cultivation using spawn was successfully demonstrated by Thomas et al. (1943).

Cultivation of Volvariella volvacea

Volvariella volvacea is a tropical fungus that requires relatively high temperatures for vegetative growth and fruiting. It is cultivated on straw bed in the open field or by the use of wooden frames. It is the oldest and commonly used technique but it gives very low mushroom yield (10-15% of dry substrate). It is because straw alone is not sufficient as a composting material as it does not contains sufficient nutrients and has a slow rate of decomposition.

Some extra cellular enzymes (pectinolytic enzymes) like cellulases, hemicellulases and lignases play key role in the developmental stages of Volvariella sp. To trigger the enzyme production for higher growth, specific nutrients might be essential. Stamets (2001) reported that the substrate must contain essential macro elements (potassium, calcium, phosphorous, magnesium, nitrogen and sodium) for crop production. Generally these essential nutrients are added to the substrate to stimulate fruit body formation and development.

Therefore, straw mushrooms presently are grown in some other materials such as cotton waste (Rajapakse, 2011), cocoa bean shell, and sawdust-Gliricidia mixture (Belewu, 2003; Belewu and Lawal, 2003), sugar cane bagasse, dried banana leaves (Oei, 2003), oil farm bunch waste etc. Growing on these substrates has resulted in significant increase (2 or 3 fold) in the biological efficiency and more stable production yield. Ukoima et al. (2009) found that palm fiber wastes significantly influenced the growth and yield of Volvariella volvacea fruiting bodies as compare to rice husk and sawdust wastes. Thiribhuvanamala et al. (2011) reported that the oil palm bunch waste in combination with rice straw or alone recorded significantly higher yields of paddy straw mushroom.

Tripathy et al. (2011) had studied the effect of various lignocelluloses waste on mycelia growth and the yield of Volvariella species. They reported that the highest yield of Volvariella volvacea was obtained from wheat grain with rice bran.

Thevasingh et al. (2007) worked on the effect of some edible mushroom extracts on fruiting body of formation of Volvariella volvacea. They reported that the aqueous extract of Pleurotus ostreatus when added in culture media, resulted in a faster growth and dense mycelia of straw mushroom compared with control. Similarly when the diluted extract of Pleurotus ostreatus was sprayed on fully colonized moist cotton waste of straw mushroom three to four times then the yield of early mature fruiting bodies was increased upto 40% compared to control.

Chemical composition

The chemical composition of mushrooms determines their nutritional value and sensory properties. Volvariella volvacea contains 90% water, high amount of protein, fibers (chitin), vitamins (large amount of vitamin C, and also all water soluble vitamins like riboflavin, biotin and thiamine), fats (5.7%), carbohydrates (56.8%), amino acids (all essential amino acids like alanine, arginine, glycine, serine etc.), unsaturated fatty acids, essential minerals (potassium, sodium and phosphorus) and has low calorific value (Chang and Buswell, 1996; Jiskani, 2001; Buigut, 2002; Ouzouni et al., 2009).

Octavalent carbonate alcohols and carbonyl compounds are also present in this mushroom which is responsible for the aroma. It does not play any essential role in nutrition but they stimulate the appetite and give mushroom dishes a characteristic flavor. The aroma of mushroom also depends on the content of amino acids, nucleotides, some other elements, such as nitrogen, phosphorus, potassium, sulfur, iron and zinc and also on the auto-oxidation of unsaturated fatty acids (Grzybowski, 1978).

Secondary metabolites

Volvariella volvacea is good source of polypeptides, terpenes, steroids (Shwetha and Sudha, 2012) and phenolic compounds such as flavonoids, phenolic acids, and tannins which contribute to high antioxidant capacity. Hung and Nhi (2012) reported the nutritional composition and antioxidant activity of five popular mushrooms. They found that the free phenolics are higher in the Volvariella volvacea which are the major contributor to the antioxidant activity. According to Ames et al. (1993) antioxidant activity provide protection against the risks for chronic angiogenic diseases such as cardiovascular diseases, arthritis, chronic inflammation and cancers. Ram kumar et al. (2012) reported highest levels of antioxidants; catalase, superoxide dismutase, glutathione peroxidase, peroxidase, glutathione-S-transferase and glutathione reductase in mycelial mats and dried straw mushroom. Kalaiselvan (2007) reported high level of antioxidative substances (variegatic acid and diboviquinone) due to calcium carbonate activity in Volvariella volvacea.

Therapeutic activity

Cochran (1978) reported that the protein extract of Volvariella volvacea contain cardio-toxic proteins called volvatoxin and flammutoxin, which inhibit respiration in certain tumour cells. It also contains protein that contains glycans and polysaccharides, having anti tumor property (Zhang et al., 1994). Methanol and water extracts of Volvariella volvacea were found to have rich antioxidative activities which help in the prevention of cardiovascular diseases, cancer, (Cheung et al., 2003), neuro-degenerative diseases (Joseph et al., 1999), inflammation, and problems caused by cell and cutaneous aging (Ames et al., 1993).

CONCLUSION:

It is strongly believed that detailed information as presented in this review on the phytochemical and various biological properties of Volvariella volvacea might provide detailed evidence for its use in different medicines. The fruiting bodies have been used in traditional medicine for decades and the studies done yet have authentified the practice. But the therapeutic properties yet known as per its biochemical components are not satisfactory and thus, more clinical and pathological studies must be conducted to investigate the unexploited potential of this mushroom.

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Received on 20.12.2013 Accepted on 15.01.2014

Asian J. Pharm. Tech. 2014; Vol. 4: Issue 2, Pg 110-113