Basic knowledge and techniques of edible fungi

Edible fungi are excellent green foods that are "natural, nutritious, and healthy"; they are ecological projects that utilize straw, purify the environment, require little investment, have quick results, use less arable land, and require three-dimensional cultivation and efficient production; they also have large consumption and broad domestic and foreign markets, making them a promising biological industry in the 21st century.

In order to develop edible fungus production faster and better, and to enable urban and rural professionals and agricultural technicians who are interested in developing the edible fungus business to master this practical technology as quickly as possible and rely on science and technology to embark on the road of hard work and wealth, this brief information has been specially compiled for reference by beginners.

The cultivation value of edible fungi

Edible fungi refer to large edible fungi, such as mushrooms, shiitake mushrooms, straw mushrooms, oyster mushrooms, fungus, ganoderma, hericium, etc. They are different from plants. They do not have chlorophyll and cannot use photosynthesis to form nutrients. Instead, they survive by saprophytic or parasitic means. There are no less than 850 known edible fungi in my country, more than 60 of which can be cultivated artificially, and more than 20 of which are in production scale.

1. Nutritional value:

Edible fungi are rich in nutrition and delicious, and are known as "mountain treasures". Generally, they contain about 4% protein (fresh mushrooms), which is 4-12 times higher than that of vegetables and fruits. One pound of dried mushrooms has a protein content of 20-25%, which is equivalent to the content of 2 pounds of lean meat, 3 pounds of eggs, and 12 pounds of milk. And it is rich in 8 essential amino acids, vitamins, and mineral elements for the human body.

2. Medicinal value:

Edible fungi contain steroids, triterpenes, organic germanium and polysaccharides, which have significant effects on regulating human functions, improving immunity, anti-tumor, lowering blood pressure, lowering blood lipids and cholesterol, anti-virus, prolonging life and anti-aging. It is a health food.

3. Ecological value:

Edible fungi can directly use cellulose, hemicellulose and lignin in crop straw to convert into edible fungi protein for humans. The world can produce 200 billion tons of organic matter every year, but only 1% is starch, fat, protein, and the vast majority is fiber, lignin, etc. If edible fungi are used for conversion, it can support the survival of more than 10 times the population, reduce pollution, and promote ecological balance. It is an important part of the development of two-dimensional agriculture (plants, animals) to three-dimensional agriculture (animals, plants, microorganisms).

Edible fungi require environmental conditions

The environmental conditions required for the growth and development of edible fungi are mainly nutrition, temperature, moisture, air, light, pH and other factors.

1. Nutrition: Generally, there are three types: saprophytic, symbiotic, and facultative parasitic.

① Saprophytic type: decompose dead grass and dead wood to obtain nutrition, such as straw mushrooms, oyster mushrooms, shiitake mushrooms, etc. 

② Symbiotic type: must grow on living trees, such as pine mushrooms and boletus.

③ Facultative parasitic type: such as honey fungus, which can grow on dead wood and invade Gastrodia elata to grow.

The nutrients are mainly: Carbon source: fiber, lignin, starch, sugar, etc., which are decomposed under the action of acid for edible fungi to absorb.Nitrogen source: comes from protein, amino acids, urea, ammonia, nitrates, etc. Inorganic salts: Among them, phosphorus, potassium, and magnesium are the most important.

2. Temperature: Edible fungi have three temperature requirements in their life:

① Mycelium growth stage. The mycelium growth range of most edible fungi is 5-33℃, and the optimum temperature is 20-25℃. Generally, mycelium is not resistant to high temperature, but straw mushroom grows well at 40 degrees.

② Fruiting body differentiation stage: generally lower than mycelium. 

Divided into low temperature type: the optimum temperature is below 18 degrees, such as oyster mushroom, shiitake mushroom, etc.; mushrooms are produced in autumn, winter and early spring. Medium temperature type: the optimum temperature is 20-24 degrees, such as coprinus comatus, tremella, etc., which are mostly produced in spring and autumn. High temperature type: the optimum temperature is above 24 degrees, such as straw mushroom and high temperature oyster mushroom, which are mostly produced in summer. 

③ Fruiting body development stage: higher than mycelium, but lower than differentiation stage.

3. Water: The water content of culture medium is very important. During cultivation, air humidity is also critical.

The water content of the culture medium is generally about 60%, and the air humidity is generally 85-95%.

4. Air: Edible fungi are aerobic fungi, and ventilation conditions must be met.

5. Light: Generally, they are cultivated under shading conditions, dark conditions are required for fungi to grow, and scattered light is required for fruiting body development, otherwise deformed mushrooms will appear.

6. pH: (PH value)

Most edible fungi prefer acidic environments, and the optimal pH value for mycelium growth is 5-5.5. If it is greater than 8, it will be affected. Due to the relationship between sterilization and the acidification of the material, the culture medium should be slightly higher than the required value for mycelium when mixing ingredients.

Basic equipment for edible fungus production

Edible fungus production includes seed production and cultivation. There are many seed production equipments, which have a development process from simple to complex, from rough to fine, and finally to serialized and modernized production; cultivation requires places and mushroom houses, and also has a scale and procedures, which need to be gradually invested and developed.

1. Sterilizer: There are two types: high-pressure sterilizer and normal pressure sterilizer. High-pressure sterilization at a pressure of 1.1 kg/cm2 for 30 minutes can kill the bacteria in the inclined test tube; sterilization at a pressure of 1.5 kg/cm2 for 1 hour can kill the bacteria in the culture medium such as cotton seed shells and sawdust in the mushroom bottle. If conditions permit, you can purchase a portable medical sterilizer, which can sterilize 50-60 test tubes or 10 mushroom bottles at a time. Normal pressure sterilizer: It is made of bricks and cement. Put the sterilized material on the steamer. Just boil the water and keep it for 6-8 hours; simmer for 1-2 hours after stopping the fire; it is generally used for production seed disinfection. At present, simple disinfection uses steamer intermittent disinfection. Boil the water and keep it for 1-1.5 hours, stop the fire and cool it down for 30 minutes, then boil it with high heat and keep it for 1-1.5 hours, and the disinfection is completed. Microwave disinfection can be done with medium and high-grade, and disinfection can be completed in 10 minutes. Intermittent disinfection can also be adopted.

2. Inoculation box: All strain transfer, separation, and propagation must be carried out in the inoculation box; it must be tightly closed and easy to operate. Generally, the simple inoculation box is 50 cm high, 47 cm wide, and 82 cm long; a 30×32 cm glass is installed on the upper side of the long side for observation, and two holes with a diameter of 14 cm are left below. The holes are equipped with 33 cm long cloth sleeves, and the cuffs are tied with elastic bands. A lamp is installed in the box, and an ultraviolet lamp is installed if conditions permit. Open inoculation is often used in large-scale production, which requires the purchase of an inoculator and inoculation in a sterile wind area.

3. Constant temperature box: There are special ones and homemade ones. The homemade wooden box can be made of double-layer boards, filled with sawdust for insulation, and several specifications of light bulbs can be installed in the box for adjustment. Now there are also ovens for modification, and the insulation effect is generally very good. 

4. Culture room: It is required to be dry, clean, ventilated, and have scattered light. The strains must be disinfected before entering the room. There should be multi-layer culture racks in the room, and a heating furnace is also required. The iron pipe is led to the outside for exhaust. There should be a fan in summer to facilitate cooling.

5. Seed making tools

Balance: 500g ordinary balance Measuring cup: used to measure the volume of water, there are two types of 500 and 1000 ml    Small funnel: Test tube: generally uses 20×200 mm specifications    Strain bottle: Strain bag: high temperature resistant polyolefin film, specifications are different    Alcohol lamp: Inoculation knife, shovel, needle, tweezers, cotton, gauze, etc.

6. Disinfectants: Formaldehyde: used for space fumigation, 2 ml per cubic meter

Potassium permanganate: prepared into 0.1% solution, used for material surface disinfection, or 5 grams of potassium permanganate plus 10 ml of formaldehyde mixed fumigation disinfection. Sanisol, bleaching powder, carbendazim, lime, etc. are all standing disinfectants. 

7. Mushroom shed construction:

The construction of mushroom sheds requires shade, keeping the shed three parts sunny and seven parts shady, only scattered light, no direct sunlight; secondly, ventilation, air outlet, heat preservation and moisture retention, easy to operate, manage and harvest. The main forms are:

①. Small plastic shed: The arched small plastic shed is generally 1.0-1.5 meters wide, which should be determined according to the width of the mushroom bed. The shed is made of thin bamboo poles or bamboo pieces, with a spacing of 0.3-0.6 meters between each other, and covered with a film. The small shed has a good warming and moisturizing effect and is a kind of outdoor simple mushroom shed.

②. Semi-pit shed: Semi-pit shed is a more suitable shed designed according to local conditions and with simple means. The main structure and characteristics are: ⑴ It can be east-west or north-south, generally 50 meters long and 6 meters wide, with bamboo poles supporting the two ribs in the middle, and bamboo or bamboo pieces arched into an arc. ⑵ The surrounding walls are made of earthen walls, the ground inside the shed is dug about 30 centimeters below the ground, the surrounding walls are about 50 centimeters high, and the ridge shed in the middle is about 2 meters high. ⑶ Use iron wire to reinforce the frame, cover it with agricultural film, compact the soil around it, and cover it with straw for shade. This type of greenhouse is inexpensive, has heat preservation and moisture retention, uniform scattered light, good ventilation performance, and is easy to operate. 

③. Solar greenhouse: This is a greenhouse that uses sunlight as energy. It has good heat preservation performance, is generally more than 10℃ higher than the outside world, and the temperature difference is not large. Its back wall is made of earth wall or double bricks, and the front is composed of pillars, beams, etc. The shed is covered with film and straw curtains, and the back wall should have ventilation holes.

In addition, there are steel frame greenhouses with large cultivation areas and fast temperature increase, but a layer of sunshade nets must be added, and straw curtains must be covered in winter to keep warm.

Measures to reduce bacterial contamination in edible fungus production

Controlling bacterial contamination is a very important link in the development of edible fungus production. The so-called miscellaneous bacteria refer to all microorganisms that inhibit or hinder the normal growth of edible fungi other than edible fungi grown on culture media and non-specific cultured edible fungi, collectively referred to as miscellaneous bacteria. General measures to reduce miscellaneous bacterial contamination:

1. Clumped and agglomerated culture materials should be broken up, and the culture materials should be fermented or treated with lime water first.

2. The cotton plugs used to culture the mother and original species should not absorb moisture and be contaminated. The tightness should be moderate. Too looseness will easily lead to the entry of bacteria. 

3. During high-pressure sterilization, attention should be paid to the relationship between pressure, temperature and time. Secondary exhaust should be mastered. The mother species test tube should be sterilized for no less than half an hour, and the original species should be sterilized for no less than 1 hour. Normal pressure sterilization should be carried out for no less than 10 hours after reaching the timing temperature.

4. During inoculation, it is necessary to strictly follow the aseptic operation requirements, and the procedures should not be reduced to minimize the source of pollution.

5. The culture room should be ventilated and dry, and disinfected in time.

6. To prevent the contamination of bacteria, the principle of prevention first and drugs as a supplement should be implemented to reduce pollution, increase production, reduce costs, improve quality, and ensure the safety and health of consumers.

7. Common bacteria: Common Alternaria (red bread mold) in high temperature seasons, green Trichoderma, white at the beginning, then green, root mold is white at the beginning, then grayish white to black; Penicillium hyphae are broom-shaped, and there are Aspergillus, Mucor and Coprinus. The fundamental way to prevent it is to strictly operate every link, discover the disease in time after it occurs, and take measures to prevent its spread and harm.