Preparation and use methods of chemical disinfectants commonly used in edible mushroom production

In the spawn production and cultivation of edible mushrooms, sterilization and disinfection are an important link that must be handled well, and using chemical agents for sterilization and disinfection is also an important means. The use of chemical disinfection and sterilization agents can, according to the object to be sterilized, the properties of the agent, equipment and machinery, and environmental conditions, etc., adopt methods such as soaking, rinsing, wiping, spraying, fumigation and dusting to achieve the purpose of sterilization and disinfection. The preparation and use techniques of commonly used disinfectants are introduced as follows:

1. Formalin: Formalin is a solution containing 36-38% formaldehyde. Because it can coagulate proteins and thus has a bactericidal effect, it is an important disinfectant. 5% formalin can kill bacterial spores and fungal spores. It is commonly used to disinfect inoculation boxes (rooms) and culture rooms. Generally, 5-10 milliliters are used per cubic meter of space. When stored for a long time under evaporation or low temperature, it often polymerizes into a white flocculent precipitate; heating it will make the precipitate disappear.

2. Alcohol: The killing ability of alcohol is mainly due to dehydration, which can dehydrate and denature bacterial proteins, causing death; it can dissolve ester secretions and also has a mechanical sterilization effect. 70-75% alcohol is commonly used to disinfect skin and various utensils. Both too low and too high concentrations are not ideal: when too low, the dehydration ability is poor; when too high, because the surface proteins of the bacterial cells are dehydrated and coagulated too quickly, it hinders the penetration of alcohol into deeper layers, the internal structure is not destroyed, and the bactericidal effect is instead reduced. Alcohol is flammable and volatile, so it should be stored sealed and kept away from fire sources. Use 75 milliliters of 95% alcohol and add 20 milliliters of water to mix and prepare 75% alcohol.

3. Phenol: Phenol is also called carbolic acid. It can denature and precipitate proteins and can destroy cell membranes to kill most bacteria. However, it has little effect on fungal spores. Pure phenol is a colorless needle-like crystal with a special odor. A 3-5% phenol solution is commonly used for spray disinfection of inoculation rooms (boxes) or for disinfecting utensils. Phenol is toxic, with a hazard level of Class III (moderate hazard), and is corrosive to the skin; when it contacts the skin, it can be washed with clean water. When preparing, take 50 grams of phenol and add it to 1000 milliliters of distilled water to prepare a 5% phenol aqueous solution, which is a commonly used disinfectant.

4. Lysol: Lysol is a mixture of three isomers of cresol, also known as coal tar soap solution. It is a soap solution containing 50% cresol and is a good disinfectant, with a bactericidal ability four times stronger than phenol. A 1-3% Lysol aqueous solution is commonly used to disinfect skin and various instruments. Use a 3-5% aqueous solution to soak utensils and contaminated materials (about 1 hour) for disinfection. It can also be sprayed to disinfect inoculation boxes (rooms). When preparing, take 30 milliliters of 50% Lysol and add 470 milliliters of water to obtain a 3% Lysol solution.

5. Potassium permanganate. Potassium permanganate is a strong oxidant. A concentration of 0.1% has a disinfecting effect, and a 2-5% solution is effective against spores and can also kill anaerobic bacteria. 0.1% potassium permanganate is commonly used to disinfect the surfaces of utensils, and 1 part of crystalline potassium permanganate can also be poured into 2 parts of formaldehyde solution for fumigation disinfection of inoculation rooms (boxes). Use 5 grams of potassium permanganate per cubic meter.

6. Bleaching powder. Bleaching powder is a white powder with a pungent odor, and its active ingredient is calcium hypochlorite. It dissolves in water and decomposes into hypochlorous acid; when it penetrates into bacterial cells, it can denature proteins, thereby achieving a bactericidal effect. A 2-5% bleaching powder solution is commonly used to scrub the walls and bed walls of inoculation rooms and culture rooms. Because it easily absorbs moisture and carbon dioxide from the air to form hypochlorous acid and thereby lose effectiveness, it should be kept in a sealed container and stored in a dry, cold place.

7. Benzalkonium bromide. Benzalkonium bromide is also called (dodecyldimethylbenzylammonium bromide); it is a light yellow colloidal substance with an aromatic odor. The stock solution concentration is 5%, and it can be diluted to 0.25% when used. It is commonly used for surface disinfection of inoculation boxes and glass utensils, and has a good killing ability against bacteria and viruses. It causes mild irritation to the skin and mucous membranes, and in severe cases may produce a rash.

8. Lime. It is an alkaline substance and can increase the pH value of the culture material or the environment, thereby inhibiting the growth and reproduction of most yeasts and molds and achieving the purpose of disinfection. When used, quicklime can be spread over mold-contaminated areas. It can also be prepared into a 5-10% aqueous solution for spraying, or a 0.5-2% aqueous solution can be used to soak culture materials such as rice straw and wheat straw.

9. Mercuric chloride. Mercuric chloride is also called mercury dichloride. It is highly toxic, with a hazard level of Class I (extremely hazardous). Its bactericidal effect is relatively strong. A 0.1% mercuric chloride solution can kill the vegetative cells of bacteria within a few minutes. A 0.1-0.2% solution is commonly used to disinfect the surfaces of mushroom spawn, spawn water, glass utensils and non-metal instruments. When preparing, take 1 gram of mercuric chloride and add 1000 milliliters of distilled water to obtain a 0.1% mercuric chloride solution. If mercuric chloride contacts the skin, it can be rinsed with a large amount of water and then wet-compressed with a 3-5% sodium thiosulfate solution. Mercuric chloride solution should be stored in brown glass bottles.