Causes of contamination of miscellaneous bacteria in the production of edible fungi

At present, it is the critical period for mushroom farmers to produce high-temperature mushroom strains. In order to improve the success rate and economic benefits of cultivation, it is necessary to prevent miscellaneous bacteria pollution when producing strains. The causes of strain pollution are as follows:

1. Incomplete sterilization: incomplete sterilization of culture materials will cause miscellaneous bacteria pollution, which can occur in 3-5 days, while incomplete sterilization is caused by the following reasons:

1. Sterilization did not reach the specified pressure and temperature: the mycelium and spores of general miscellaneous bacteria could be killed after 1-2 hours, pressure 1 MPA, temperature 121 ℃ or atmospheric pressure 100 ℃, 6-8 hours. When using high pressure sterilization, the key is to drain the cold air in the pot, otherwise, even if the specified pressure and temperature are reached, all the miscellaneous bacteria can not be killed. When using atmospheric pressure sterilization, it is best to build a circle around the sterilization chamber so that the temperature in the stove is uniform and the top of the stove is arched, so that the condensed water flows down along the four walls without dampening the bacteria bottle (bag). In addition, insufficient steam and low temperature are also the factors of incomplete atmospheric pressure sterilization.

2. The influence of the properties of culture materials: the types of materials needed for seed production, the content of bacteria, water content and acidity-alkalinity can affect the effect of sterilization. When sterilizing, the corresponding sterilization time should be selected according to the different formula of the culture material. After the preparation of the culture material, it must be sterilized in time to avoid a large number of microorganisms, resulting in an increase in the content of bacteria in the material, and will cause nutritional loss in the material. The moisture in the culture material should be uniform and suitable, so that the sterilization effect is good. The "sandwich material" should be avoided in the culture material (the culture material contains dry material that does not absorb water). The steam in the sterilizing pot has weak penetration ability to the sandwich material, and it is easy to appear the dead corner of sterilization, which can not achieve complete sterilization. In addition, the acidity and alkalinity of culture materials also affect the effect of sterilization, and the sterilization time of acidic medium is shorter than that of neutral and alkaline medium.

3. Improper stacking of strain bottles (bags): the stacking form of bacteria bottles (bags) in the sterilization pot can affect the effect of sterilization. There should be a certain gap in the discharge to facilitate the flow and heating of steam. When sterilizing the culture material in the strain bag, because the plastic bag is easy to deform and soften after being heated, if the loading is not tight, the gap between the bacteria bag will be reduced when stacked, which will affect the effect of sterilization.

Second, the inoculation operation is not standard: the inoculation process of edible fungi needs strict aseptic operation, if the operation is not standard, it is easy to cause miscellaneous bacteria pollution of culture materials. Miscellaneous bacteria are generally in the air of the inoculation room (tent), the surface of the bacterial bag, and the body surface of the vaccinator. The characteristic of culture material pollution caused by non-standard operation is that it occurs at the opening of bacterial bag or inoculation point. Therefore, it must be vaccinated in strict accordance with aseptic operating procedures, and strict disinfection should be carried out before inoculation.

Third, carrying miscellaneous bacteria in the original species: the original species used for expanded reproduction must be pure bacteria, so as to ensure the oneness of the bacteria. If the original species itself is not pure, it can cause batch pollution. It is characterized by concentrated pollution of a batch of bacteria after inoculation, and the contaminated site is in the inoculation site, which can appear 3-5 days after inoculation. Therefore, we must adopt the excellent original seed with strong vitality, suitable bacterial age and strong stress resistance in seed production.

Fourth, the culture room is not clean: the culture room is not clean, the air is not ventilated, the room is damp, and it can also be infected with miscellaneous bacteria. In this case, the contamination rate is relatively low, but with the extension of culture time, the contamination rate will gradually increase. A large amount of pollution appeared relatively late, usually 10 days after inoculation.