Revolution of Greenhouse Cordyceps Stroma

Cordyceps is known as “legendary treasure of the East”. Cordyceps, in Chinese called “Winter Worm, Summer Grass 冬蟲夏草”, belongs to the family of fungus (Cordyceps sinensis (Berk.) Sacc. Clavicipitaceae). As the name implies, Cordyceps is a caterpillar in Winter which evolves into a “grass” in summer. The fungus is parasitic on the larva of the bat moth (Hepialus armoricanus Oberthur, Hepialidae). The parasitic fungus invades the body of caterpillar when it is hibernating during winter and consumes its soft tissue. Finally, the caterpillar dies. During summer, the stroma which is about 3-5 cm long, grows from the head of the larva.

It is occasionally found growing on other moth species as well. The normal range of this fungus is above 2000 meters elevation, and it has been found as high as 6,000 meters. There are also many other species of the genus Cordyceps. About 250 species of the Cordyceps are distributed worldwide, about 65 of them in China, 100 in Japan, and about 70 in Korea.

Artificial Cultivation of Cordyceps

- 1980s : 

Asexual reproduction. Production of Cordyceps mycelium, mainly in China, using artificial medium as host. The mycelium is cultivated in huge tanks using liquid fermentation method. It is sold in the market as capsules or wine or drinks only.

ii. Mid 1990s:

Sexual reproduction using silkworm as hosts. Scientists in Japan and Korea used silkworm puma as host to cultivate the stroma (or the fruit body) of Cordyceps.

iii. Latest Development :

Direct cultivation of Cordyceps stroma.  Involves sexual reproduction with specially formulated  medium which replaces the bat-moth caterpillar. The fruit body cultivation is based on organic medium developed by scientists. This is the most advanced stage of cultivation which engages the highest level of technology application. Only a small number of quality strains can be successfully cultivated into stroma.

The cultivation process is very complicated but the following basic environmental parameters must be controlled and regulated precisely.

·    Change of temperature is necessary in the cultivation process as the Cordyceps bacterium prefers relatively low temperature, about 15-20 C, and form sclerotium at a degree between 10-20 C, and stroma at 14-25 C.

·    Humidity conditions should be controlled at 80-90% for growth, stroma formation and releasing of spores.

·    Different lighting conditions are required at  different growth stages. 

·    Stroma growth takes place between pH 5.0~ 6.5 acidity and grows fast at pH 6.0~ 6.3.

Stroma of Cordyceps

Cordyceps stroma or "fruit body" is the mushroom part of the Cordyceps. The stroma grows from the head of the caterpillar corpse (which has been replaced by organic medium) when the Cordyceps becomes mature. In fact, the stroma is equivalent to the fruit on the fruit tree, and the mycelium of the caterpillar corpse (which has been replaced by the organic medium in our  stroma cultivation process) serves to provide nutrition to the fruit. In fact, the most effective and potent elements are concentrated inside the fruit body.

Findings:

1. Anti-hyperglycemic Activity of the fruiting body (stroma) of Cordyceps The results revealed that fruiting body, not carcass, of Cordyceps attenuated the diabetes-induced weight loss, polydipsia and hyperglycemia.

2.Inhibitory effects on aortic cholesterol deposition Water extracts from fruiting body of cultured Cordyceps sinensis exert beneficial effects on the formation of the atherosclerotic lesion.

3.Antioxidant activity Extracts of cultured Cordyceps sinensis posses potent antioxidant and anti-lipid peroxidation activities and inhibit accumulation of cholesteryl ester in macrophages via suppression of LDL oxidation

Culture Methods

In looking at the variations in quality from different strains and producers of Cordyceps, one must wonder what is it that causes this to be so. After all, a tomato is a tomato, no matter where it is grown. Yet with Cordyceps, even the same strain (CS-4) grown by different growers turns out to be entirely different from a standpoint of active ingredients. There are two different methods used today in the cultivation of Cordyceps.

(i) Mycelium Cultivation through Liquid Culture

Liquid culture or Fermentation, in which the organism is introduced into a tank of sterilized liquid medium, which has been formulated to provide all of the necessary nutritional components for rapid growth of the mycelium. After growth in the liquid medium, the mycelium is harvested by straining out of the liquid broth and dried and ground into fine powder. Essential bio-active extra-cellular compounds such as Cordycepin produced during the growth process are discarded with the spent both. In other words, mycelium products lack many unique metabolites produced by Cordyceps that have potent medicinal effects. It is estimated by researchers that as much as 90% of the bioactive compounds that are produced by the Cordyceps are discarded after the mycelium is harvested. The majority of Cordyceps product available in capsule or liquid forms is liquid cultured mycelium.
(ii) Stroma Cultivation through Solid-Substrate Culture

The second method of cultivating Cordyceps uses some type of sterilized solid nutrient source, usually a cereal grain or mixture of grains, for inoculation. Cultivation period is much longer on solid material but in this way, it is possible to capture all the unique compounds, which is naturally lost when cultivated by liquid or fermentation technique.

However, it is important to note that the quality potential of Cordyceps cultivated under solid substrate may also vary among different cultivators. The final quality of cultivated Cordyceps is determined by the following factors:

i.  the particular strain chosen for cultivation

ii. the substrate composition

iii. the culture parameters, e.g. temperature and oxygen content

iv. the length of time that it is grown. Optimum harvesting period is crucial to the potency of the stroma. Longer harvesting period implies higher costing as another round of cultivation could have taken place. Stroma that has been harvested too early is usually cream coloured. At the optimum harvesting period, it should be golden-orange in colour. Therefore, it is important for customers to demand independent analytical reports on the chemical compounds in order to ensure quality and value.