Whether the sterilization of the medium is thorough or not directly affects the scientific research data, and there are many factors affecting the sterilization of the medium. In addition to the type and quantity of the bacteria in the medium, the length of sterilization and the temperature are also determined by the following points. Nutritional retention When the microorganisms are killed by moist heat sterilization, the nutrients of the medium are also damaged, especially amino acids and vitamins. For example, at 121 ° C, only 20 min, 59% of lysine and arginine and other basic amino acids were destroyed, and a considerable amount of methionine and tryptophan were destroyed. Under the action of heat, some nutrients may also react with each other due to heat, resulting in a change in the amount of original nutrients in the medium, thus affecting the quality of the medium. Microbial heat resistance The thermal resistance of bacterial spores is large and the time required for sterilization depends on reducing the bacterial spores to the specified number of times. pH value The pH value has a great influence on the heat resistance of microorganisms. Microorganisms are the least likely to die when the pH is between 6.0 and 8.0. When pH<6.0, microorganisms are more likely to die. At this time, PH easily infiltrates into the cells of the microorganisms, thereby changing the physiological response of the cells and causing them to die. Therefore, the lower the pH of the medium, the shorter the time required. Composition of the medium High-concentration organic matter composed of oils, sugars, and proteins surrounds the cells in the form of a thin film that affects heat conduction. High concentrations of salts and pigments impair heat resistance and sterilization is relatively easy. For example, E. coli dies in water heated to 60-65 ° C. It takes 70-6 minutes to heat in 10% sugar solution for 4-6 minutes, and it takes 30 minutes to die in 30% sugar solution. Generally, it is best to use 115 ° C for 30 minutes when the sugar content is high; the general medium can be selected from 121 ° C for 20 minutes. foam The air in the foam forms an insulating layer that makes it difficult for heat to penetrate and kill the bacteria. Granule The particles are small, easy to sterilize, and the particles are large, so it is difficult to sterilize. For medium containing a small amount of larger particles and crude fiber, the medium can be removed by a coarse filtration method (which should not affect the quality of the medium), and the agglomeration of the medium may result in incomplete sterilization of the medium. Is the air in the sterilizer drained? This is the main point that affects the relationship between temperature and pressure. When the same pressure is reached, if the air is not discharged, that is to say it is not pure steam sterilization, the temperature at this time may not meet the requirements. Will seriously affect the sterilization effect Fingerprint Tripod Turnstile,Full Height Turnstile,Automatic Flap Swing Tripod Turnstile,Full Height Swing Tripod Turnstile Shenzhen Bio Technology Co., Ltd , https://www.hfsecuritytech.com
Factors affecting the sterilization effect of the medium
Prev Article
How to choose a medium for growing orchids