The fermentation industry is mostly pure breed cultivation, and the production process can only have production bacteria, and no other bacteria are allowed.
Ensure pure breed fermentation, sterilize the culture medium, air system, feed material, fermentation tank, and pipeline system before inoculating the production strain, and disinfect the environment.
Disinfection: Using physical or chemical methods to kill all pathogenic microorganisms (surfaces) in materials, containers, and environments can generally only kill nutrient cells and cannot kill bacterial spores.
Sterilization: To kill or remove all microorganisms using physical or chemical methods. Sterilization: Using filtration methods to remove microorganisms or spores from air or liquid. Category: Thermal sterilization method, radiation sterilization method, chemical sterilization method, filtration sterilization method.
1. Dry heat sterilization concept: Heating in equipment under the action of infrared or electric heating, mainly used to sterilize dry materials, utensils, etc.
Method: Commonly used in an oven, the temperature inside the oven is maintained at 160-170 degrees Celsius for 1-2 hours. Attention: Do not exceed 180 degrees, do not place sterilized objects too tightly, cool down slowly, and only open the oven door when the temperature drops below 80 degrees. Disadvantages: The penetration power of dry heat is weak, and microorganisms are subjected to much stronger forces in dry heat than in humid heat. The required sterilization temperature is relatively high and the time is long. Flame sterilization: using flames to directly kill microorganisms. The sterilization of vaccination needles, rings, etc. has limited application scope.
2. The concept of moist heat sterilization: By utilizing the heat released by steam, the chemical bonds, especially hydrogen bonds, within proteins, nucleic acids, and enzyme molecules in microbial cells are disrupted, causing irreversible denaturation and microbial death. Thermal resistance: The lethal time of microorganisms under certain conditions. Scope: Widely used for sterilization of production equipment and culture media.
Compared to dry heat sterilization, sterilization is more effective at the same temperature. Reason: (1) Under humid and hot conditions, bacterial cells absorb water and proteins are more likely to coagulate. Due to the increase in moisture content, the required solidification temperature decreases (2) the penetration power of humid and hot steam is greater (3) humid and hot steam has latent heat. Types of moist heat sterilization: boiling sterilization, pasteurization, intermittent sterilization, high-pressure steam sterilization, etc.
Boiling method: Put the item to be disinfected into water and boil it (100 degrees). Boiling time: 15-20 minutes, kill microbial nutrient cells. 1-2 hours, kill the spores, add sodium carbonate or carbolic acid (0.5%). Object: Suitable for disinfection of food or equipment. The object to be disinfected by the pasteurization method is heated at 60-62 ° C for 30 minutes or at 70 ° C for 15 minutes to kill pathogenic bacteria and some microorganisms. Object: Foods such as milk, beer, yellow wine, soy sauce, etc. Characteristic: It does not damage the nutritional value, color, aroma, and taste of certain foods. Example: Sterilization of beer. Intermittent sterilization method uses repeated atmospheric steam sterilization to kill microbial nutrients and spores. Method: The items to be sterilized are heated to 100 ℃ in a sterilizer and maintained for 30-60 minutes. They are then removed, cooled, and incubated in a 37 ℃ constant temperature incubator for 1 hour. The next day, they are treated using the same method. Three times in total. Object: Substances that are not suitable for high-pressure sterilization. Such as sugar gelatin milk culture medium, etc. High pressure steam sterilization mainly uses sealed high-pressure steam sterilization pots. Widely used.
Method: Maintain a pressure of 0.1 MPa and a temperature of 121 degrees Celsius for 15-30 minutes. Attention: After sterilization, slowly reduce the pressure.
Advantages and disadvantages of wet heat sterilization: easy steam source, strong steam penetration, thorough sterilization, high latent heat of steam, adjustable pressure.
Disadvantage: The equipment cost is high and cannot be used for sterilization of materials that are afraid of moisture.
2、 Radiation sterilization method
Concept: Using high-energy electromagnetic radiation and particle radiation to kill microorganisms. Ultraviolet radiation is the most commonly used. Applicable: Vaccination room, ultra clean workbench, sterile culture room, and material surface. Attention: Ultraviolet radiation has low penetration rate and can only be used for surface sterilization. Exposure to a 30W ultraviolet lamp for 30 minutes can achieve sterilization effect. Usually used in conjunction with chemical reagents. Principle: Break the DNA chain of microorganisms, disrupt the connection between ribose and phosphate, cause hydrogen bond breaks within or between DNA molecules, and lead to microbial death.
3、 Chemical sterilization method
Concept: The method by which chemicals directly act on microorganisms to kill them. Scope: Disinfection of small equipment and hands in production workshops, sterile rooms, laboratories, and before inoculation. Method: Soak, add, wipe, spray, etc. Principle: Chemical substances can easily react with certain components in microbial cells. Such as protein denaturation, inactivation of proteins, disruption of cell membrane permeability, and killing of microorganisms. Attention: Not suitable for sterilization of culture media, suitable for sterilization of local spaces or instruments.
4、 Filtration sterilization method
Concept: Using the principle that bacteria cannot pass through dense porous filter materials to remove microorganisms from gases or liquids. Scope: Commonly used for sterilizing gas and thermally unstable drug solutions or raw materials. Mainly used for sterilizing heat-resistant biological products such as serum, antibiotics, and air. Equipment: The equipment used is a filter with tiny pores. The commonly used filters include membrane filters (0.45 μ m and 0.22 μ m pore sizes), ceramic filters, asbestos filters (i.e. Seitz filters), sintered glass filters, etc.
The filtration sterilization method is divided into absolute filtration and deep filtration. Absolute filtration: It means that the filter holes of the filter medium are smaller than the solid particles, trapping the particles. Deep filtration: The filter holes of the medium are not necessarily smaller than the solid particles. It intercepts the particles through the tortuous channels within the filter layer.
