Introduction to physical methods of disinfection and sterilization of Ganoderma lucidum

Disinfection and sterilization are two different concepts. Disinfection kills or removes some microorganisms, such as pathogenic microorganisms, microbial nutrients, etc., by physical or chemical methods, but has no effect on spores or spores, so it is partial and surface; while sterilization kills or removes all microorganisms by physical or chemical methods, so it is complete and thorough.

I. physical methods

1. Dry heat sterilization is generally used for articles that remain dry after sterilization.

The main results are as follows: (1) Burning sterilization directly burns microorganisms with flame. Sterilization is simple, thorough, rapid and reliable, but the scope of application is limited. Commonly used for inoculation tools, test tube mouth, bottle mouth, cotton stopper and so on. For glass and porcelain products, they should be fully dried before burning to avoid cracking.

(2) dry and hot air sterilization using oven hot air for baking sterilization, gradually heating up to 140160 ℃ during operation, and keeping it for 2-3 hours can achieve the purpose of sterilization. It is fast and convenient, but it is only suitable for metal and glassware, but not for culture medium.

two。 Due to the strong penetration of hot and humid steam, the efficacy of wet-heat sterilization is high.

(1) High-pressure steam sterilization is also called pressure sterilization. It is sterilized according to the principle that the steam temperature is proportional to the steam pressure, that is, when the pressure increases, the boiling point also increases. If the pressure is 0.103 MPA and the temperature is 121 ℃, it can kill all the vegetative bacteria and spores in the liquid medium for 30 minutes. Therefore, it can greatly shorten the sterilization time, and is one of the most effective and widely used sterilization methods. In the scientific research and production of Ganoderma lucidum, the inclined medium, sterile water, utensils and inoculation tools are often sterilized with a pressure of 0.103 MPA for 30 minutes, while the media with large volume and poor heat conductivity, such as sawdust, bran bran and cottonseed shell, need to be sterilized by 0.137 MPA for 1.5-2 hours.

Before using the pressure cooker, in addition to carefully reading the operating instructions, we should also pay attention to the following problems.

① needs to add water before use, first add water to the pot before each use, the amount of water to reach the water level mark as the degree. Do not burn in the air or add insufficient water, or burn dry midway to cause an explosion.

② correctly stack materials into the pot sterilization medium, materials, etc., need to leave gaps when stacking, so that steam smooth, if the stack is tight, it will hinder steam penetration, the temperature inside and outside the material is uneven, resulting in "dead corner", resulting in incomplete sterilization.

③ exhaust cold air heating sterilization open the exhaust valve, so that the pot of cold air out, when the water boil there is a large amount of steam flushing out, and then close the exhaust valve. If cold air is left in the sterilizer, it expands soon after being heated, and the pressure rises, resulting in a difference between pressure and temperature, that is, high pressure and low temperature, forming pseudo vapor pressure, resulting in incomplete sterilization.

After ④ sterilization and natural hypobaric sterilization, it is allowed to slowly reduce temperature and decompression. If the exhaust pressure is too fast, negative pressure occurs in the pot, and the pressure in the bottle bag is instantly higher than the pressure in the pot, resulting in the swelling and breaking of the material bag, or contamination and shedding of the cotton plug. ⑤ to prevent cotton plug wet sterilization when the cotton plug is wet by condensed water, it loses the purpose of filtering bacteria and leads to mold growth at the same time. In order to prevent dampness, the cotton plug should face outward or upward to avoid contact with the pot wall and be wet by the condensation water flowing down the peripheral wall. you can also wrap a film on the bottle mouth or cover it with a small plastic bag.

(2) Atmospheric steam sterilization is widely used in production, such as steam cage, iron bucket, soil steam stove, steam furnace and so on. During sterilization, the bottles and bags are placed on the grid in the pot with a certain gap, and 100 ℃ is kept for 8 hours or more. The end of sterilization should not be opened until the temperature drops below 70 ℃, otherwise it is easy to cause the material bag to be thinned and scrapped. The deficiency of atmospheric pressure sterilization is that it takes a long time to sterilize, consumes a lot of energy, and water is easy to dry or need to add water frequently.

(3) intermittent sterilization was heated to 100 ℃ each time and kept for 1 hour, then cultured at a certain temperature (30-37 ℃) for 24 hours to promote spores to germinate into vegetative cells, and then boiled for the second time, so that all microorganisms and spores could be killed for 3 times.

(4) boil disinfect and boil utensils and articles in water for 15 minutes, microbial nutrients can be killed, if 2% Kaiser 5% carbolic acid is added to the water, spores can also be killed, and 1% baking soda can increase the boiling point of the water, accelerate the death of spores, and prevent metal instruments from being rusted by boiling.

(5) Pasteur disinfection is also called Bath effect or low temperature disinfection. That is, 60-70 ℃ after a certain period of time, kill pathogenic microorganisms and bacteria nutrients. Culture material heap fermentation is the use of this principle to kill the harmful microorganisms, but it takes longer.

3. Filtration and sterilization A method of removing microorganisms by the retention of filter materials. It is commonly used for air filtration and sterilization of some heated liquids that are volatile or change their properties. The air purifier and fermentor air filter in edible mushroom equipment, and the cotton plug and mask in seed production are also simple forms of air filtration.

4. Ultraviolet sterilization its germicidal effect is to promote cytoplasmic degeneration, resulting in the death of bacteria. Secondly, under the irradiation of ultraviolet light, the air produces ozone (03), which also has bactericidal effect. The strongest bactericidal effect is at the wavelength of 250nm and 260nm, and the wavelength of the UV lamp sold in the market is 253.7 nm. There are differences in the tolerance of various microorganisms to ultraviolet rays, such as fungal spores have the strongest tolerance to ultraviolet rays, bacterial spores take the second place, and microbial nutrients are the weakest. Ultraviolet radiation belongs to low-energy electromagnetic radiation, and its penetration is very poor, so it is generally limited to object surface and air sterilization.