Lentinula edodes (formerly know as Lentinus edodes) is native to East Asia, specifically China. The species has been cultivated for over a thousand years in both China and Japan. Its good flavor and pleasant texture contribute to continued growth in consumer demand and expanding cultivation.
Biology of Lentinula edodes
Lentinula edodes (shiitake) is a saprophyte, colonizing dead hardwoods. In its natural habitat, this species performs the important role of decomposition. Lentinula is not a threat to living trees and there are no restrictions on its cultivation.
The shiitake is a basidiomycete fungus, and produces typical gilled mushrooms that form singly or in clusters on woody substrates. The basidiocarps (mushrooms) are some shade of brown, often with white fibrous filaments, giving sort of a hairy appearance. The caps have white gills and short stems.
Shiitake mushrooms can appear shelf-like but the stems are attached to the center on the underside of the caps in typical mushroom fashion. A veil covers the gills in the early stage of development. The veil tears away as the mushroom expands to leave a trace of ragged white material on the edge of the cap. The spores are white.
Growing Shiitake Mushrooms
Shiitake mushrooms are grown on logs or in bags containing sawdust and woodchips. The most common substrate woods are oak, alder and beech. Which method is better – bags or logs? That depends on whom you ask. Log growers claim log-grown mushrooms taste better. Bag growers counter that there is no difference in taste or quality. Some people might be able to tell the difference – most probably can't.
There are technical advantages and disadvantages to each method. It takes more water to keep the moisture up in a log compared to a bag, and logs are harder to move. Good logs will produce mushroom for years, while bags produce for a few months before they have to be disposed of and new crops started. In either case, the substrates are 100% recyclable.
For log cultivation, freshly cut logs are drilled and wooden dowels that are colonized by the fungus are hammered into the holes. The holes are covered with wax and the logs are kept watered until the mycelium completely colonizes the log. This can take up to a year or more. Then, a series of heavy waterings and cold shocks trigger the appearance of mushrooms over the life of the log.
In bag culture, the substrates are sterilized and then inoculated with shiitake mycelium. The mycelium colonizes the wood particles relatively quickly (14–30 days is typical) and fruiting is initiated by soaking and cold shocking. A maximum of three fruiting cycles can be achieved, with reduced production on succeeding flushes.
Shiitake mushroom kits, both log and bag forms, are available from a number of suppliers, so that small quantities of fresh shiitake mushrooms can be produced by home growers.
Medicinal Value of Shiitake Mushrooms
Of all the mushrooms that have shown promise (or at least been touted) for medicinal purposes, the shiitake is one of the most studied. Research has indicated anti-tumor, anti-viral and cholesterol-lowering activity. For example:
- Lentinan (1,3 Beta-D-glucan), a polysaccharide isolated from Shiitake mushrooms, has shown activity against colon cancer cells.
- Lentinan has also been shown to stimulate the immune system and protect against liver damage.
- Lentin, a protein, has demonstrated antifungal activity, is known to inhibit replication of the human immunodeficiency virus (HIV), and inhibits cell division of leukemia cells.
- Experiments in mice and in vitro have shown promise but the results have generally not carried forward when tested in human clinical trials.
References
Shiitake Mushroom, American Cancer Society, http://www.cancer.org/docroot/ETO/content/ETO_5_3X_Shiitake_Mushroom.asp, (accessed June 6, 2009)
Growing Shiitake Mushrooms, Anderson, S. and Marcouiller, D., Oklahoma Cooperative Extension Service, F-5029
Philip McIntosh - The author holds a B.Sc. in Botany and Chemistry and an M.A in Biology and he has thirty + years of experience in science and industry.
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