After the mycelium matures, it gradually changes from white to orange. At this time, the indoor light should be increased to white, and natural scattered light should be used during the day to keep 200 lux. Fluorescent lamp can be used as light source at night, and the daily illumination is not less than 10h, which can promote the color change of mycelium and stimulate the formation of primordium. When the surface of the material bulges to form the original base of millet particles, it is necessary to properly ventilate, supplement fresh air, protect the indoor temperature 18℃-22℃, and raise the relative temperature to 80%-85%. Too high humidity will easily make the culture medium lose water prematurely, which will affect the yield. Cordyceps militaris has strong phototaxis. Therefore, after the fruiting body is formed, the relative direction between the culture bottle and the light source or indoor light source should be properly adjusted according to the situation, so as to ensure the normal growth form of the fruiting body, thereby increasing the yield and forming a rod-shaped subunit (fruiting body) with a slightly swollen orange or orange top. When the fruiting body no longer grows and many small thorns appear at the top, it indicates that it is mature. When harvesting, remove the fruiting body with sterile tweezers, then add a little nutrient solution, repack the bottle mouth, and continue to cultivate for about 20 days to grow the second batch of daughter seats. Air-drying or low-temperature drying the harvested fruiting bodies and selling them. Not for sale, should be sealed and kept in a low temperature and dry place.
Liquid culture
Natural Cordyceps militaris resources are scarce, artificial solid culture cycle is long, and conditions are difficult to control. The chemical composition of Cordyceps mycelium obtained by submerged culture method is close to that of Cordyceps collected from nature, and the substances needed by people can be obtained from fermentation broth, which can also greatly shorten the production cycle.
The optimum growth temperature of Cordyceps mycelium is 20 ~ 25℃, peptone is the best carbon source for mycelium fermentation, and the ratio of carbon to nitrogen is 1∶2 or 1∶3.
The optimum medium composition for fermentation is: 5% rice flour, 1.5% bean cake powder, 1.5% malt powder, 0. 1%KH2PO4 and 0.05% mgso4.7h2o.
The significant order of experimental factors affecting the yield of extracellular polysaccharide from Cordyceps militaris is beet sugar >:; Yeast extract powder >: KNO3 & gtMgSO4 7H2O & gtFeSO4 & gt potassium dihydrogen phosphate. The optimum fermentation parameters of extracellular polysaccharide are: initial pH 500ml, liquid volume in triangular flask 65438+500ml, inoculation amount 6%, temperature 28℃ and period 96h.
The formula of culture medium is: corn flour 4%, soybean flour 0.6%, yeast powder 0.3%, K2HPO40.05%, MgSO40.05%, inoculation amount 3%, pH5.5. It is considered that carbon source has a significant influence on the production of extracellular polysaccharide.
The suitable culture medium for Cordyceps militaris fermentation is composed of sucrose 5.0%, corn steep liquor 3.0%, yeast extract 0.5%, magnesium sulfate 0.05% and potassium dihydrogen phosphate 40.05%. It is considered that sucrose is the best carbon source and yeast extract is the nitrogen source, and the cell yield is the highest.
A variety of carbon and nitrogen sources can be used for the growth of Cordyceps militaris mycelium, and the liquid culture medium with brown sugar carbon source and milk powder as nitrogen sources is the best. The suitable ratio of carbon source to nitrogen source is 2.0~2.5/ 1.0, and the suitable PH is 5.0~6.5.
The composition of the culture medium was determined as peptone 1.5%, magnesium sulfate 40.05%, potassium dihydrogen phosphate 40. 1.05%, vitamin b 1.5 mg/l, 2.4d 2 mg/l. Under the same conditions, the fermentation yield of the optimized culture medium was 4.5 higher than that of the original culture medium. The liquid culture conditions and growth kinetics of Cordyceps militaris were preliminarily obtained, which provided a certain theoretical basis for industrial production.
The ratio of medium can increase the content of cordycepin to 1.2 1%, which is 8. 1 times higher than Czapek medium. John Chai and others concluded that corn flour is the best carbon source, silkworm chrysalis powder is the best nitrogen source, and magnesium sulfate is the best inorganic salt. The optimum medium formula for liquid fermentation is corn flour (20g/ 1000ml), silkworm chrysalis powder (5g/ 1000ml) and magnesium sulfate (0.5g/ 1000ml).