Sterilize with high pressure steam. First add water (about 300ml) to the specified water level in the pot, then put it into the sterilization bucket, and fix the lid of the pot to prevent air leakage.Then put the sterilization pot on the boiler or electric stove, close the exhaust valve to heat, when the pointer of the pressure gauge reaches 4.9x10*Pa (0.5 kgf/cm2), open the exhaust valve to discharge the cold air in the pot, after the pressure drops to "0", close the exhaust valve. The sterilization effect is better if it is repeated again. After that, the pointers of the thermometer and pressure gauge gradually rise. When the pressure in the autoclave reaches 9.8x10 Pa (1 kgf/cm2), adjust the fire source to maintain the pressure at 9.8x10 Pa for 30 to 40 minutes. Then turn off the heat source, wait for the pressure to naturally drop to 0, open the exhaust valve, discharge the water vapor, use the waste heat to bake the newspaper and tampon, and take it out after half an hour. In a clean room, it should be placed on an inclined plane. The length of the inclined plane is generally about 1/2 of the length of the test tube, and should not exceed 3/5 of the length. It is better to place the inclined surface in bundles, and the condensed water on the surface of the inclined surface is less. If the room temperature is too low, condensed water will easily appear on the slope, which is not good for inoculation and bacterial growth. You can cover several layers of clean gauze on the inclined surface to keep warm, so that it slowly solidifies, and the condensation water will be greatly reduced. After the mother culture medium is ready, if it cannot be used up for a while during production, it can be stored in the refrigerator for about 20 days.