In the course of cultivation, edible fungus strains will have different degrees of contamination such as green mold, penicillium, Aspergillus, rhizopus, mucor, and bacteria, especially during the high temperature season. In the course of production, due to the infringement of the bacteria, it often leads to a reduction in production or even a loss. Therefore, the search for the cause of bacterial contamination is of great significance for improving the success rate of cultivation and improving economic efficiency. Under normal circumstances, the pollution rate of secondary and tertiary strains is below 5%. If this is beyond this range, we need to find out why. The causes of strain contamination are as follows: (1) Sterilization is not complete: Incomplete sterilization of the culture material can cause contamination with bacteria, and contamination can generally occur within 3-5 days. Incomplete sterilization is also caused by the following reasons: 1 Improper handling of molds: Mycelia and spores of common bacteria can be killed at 100°C, 6-8 hours or 121°C and 0.5-2 hours at atmospheric pressure. At present, edible mushroom culture materials are often sterilized by atmospheric pressure or autoclaved. Atmospheric pressure sterilization is difficult to sterilize cereals, dung and other materials, and it is not easy to fully achieve the effect of sterilization. The effect of autoclaving is much better. When using autoclave sterilization, the key is to drain the cold air from the pan. Otherwise, the saturated vapor pressure cannot be reached in the pan. The sterilization temperature also does not meet the requirements. When sterilizing at normal pressure, the surrounding of the sterilizing chamber is preferably rounded so that the temperature inside the kiln is evenly distributed, and the top of the stove is formed into a round arch so that the condensate flows down the four walls without sterilizing the seed bottle (bags). ). In addition, insufficient steam, low temperature, and atmospheric pressure sterilization are not completely factors. 2 The influence of culture material properties: The type of material needed for seed production, bacterial content in the culture material, water content, and pH can all affect the sterilization effect. When sterilizing, according to the different formulations of culture materials, select the appropriate sterilization time. The selected culture material must be fresh and free of mildew. From the microbiological content before the sterilization of the culture materials, the higher the number of microorganisms, the longer the sterilization time, and vice versa. Therefore, the culture materials must be sterilized promptly after the preparation of the culture materials. The pot is sterilized to avoid the proliferation of microorganisms, resulting in an increase in the amount of bacteria in the material, and it may cause nutrient loss in the material. The thermal conductivity of water is stronger than that of sawdust, dung, etc. If the moisture in the culture is even and suitable, the sterilization effect is good. In the culture medium, "sandwich material" should be avoided (ie, the culture material contains non-absorbent dry material). The steam in the sterilizing pot has weak penetrating power to the sandwich material, and the sterilization dead angle is prone to occur, which can not achieve the purpose of sterilization. In addition, the pH of the culture medium also influences the sterilization effect, and the slightly acidic culture medium has a shorter sterilization time than neutral and alkaline conditions. Improper stacking of 3 strainer bottles (bags): The stacking form of the strainer bottles (bags) in the sterilizing pot can affect the sterilization effect. There must be a certain gap in the discharge so that the steam can circulate and heat up. When sterilizing culture materials in bagged strains, plastic bags are easy to deform and become soft after being heated. If the materials are not loaded tightly, the gaps between the bacteria bags will be reduced when stacked and piled up, which will affect the sterilization effect. The impact of 4 strains of bacteria or strains of the bag: When selecting a seed, it is generally a choice of a strainer bottle or a strainer bag. Plastic bags have a fast heat transfer rate, while glass bottles have a slow heat transfer rate. When using the same sterilization method for the same culture material, the bottle material is slightly longer than the bag material sterilization time. In addition, individual containers that are not tightly sealed or broken can also cause contamination with germs. (2) The inoculation operation is not standardized: the inoculation of the edible fungus requires strict aseptic processing. If the operation is not standardized, contamination of the bacterial culture of the culture material can be easily caused. The contaminated germs are generally the bacteria in the inoculation room, the bacteria on the surface of the bacteria bag, and the surface bacteria of the inoculation personnel. The contamination of culture materials caused by non-standard operation is the growth of bacteria on the surface of the culture material, which usually occurs at the opening of the bacteria bag and the vaccination site. Therefore, we must strictly abide by the aseptic procedure, and the inoculation room should use the "sterile special disinfection king" for strict disinfection. (3) Bacteria with bacteria: The original species used to expand the culture must be pure bacteria, so as to ensure the unity of the species. If the strain itself is not pure, it can cause batch pollution. In the batch of strains produced, the strains contaminated all appear to be contaminated, and the contaminated parts are located in the strain block where contamination occurs earlier and 3-5 times are inoculated. Days can appear. Therefore, we should try to use the best strains of viable strains, suitable strains, and strong resistance to stress. (4) The culture room is not clean: the culture materials are not clean, the air does not circulate, the room is damp, and bacteria can also be infected. The pollution rate in this case is relatively low, but as the incubation time increases, the pollution rate will gradually increase. A lot of pollution appeared later, and it usually appeared after 10 days of inoculation. 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