Basics of sterile working

The first thing you have to learn when cultivating mushrooms at home is that you have to work sterile. You just have to work extremely clean. The spores, the mycelium and the mushrooms themselves are very vulnerable to contamination. Contamination will generally have dramatic consequences for the development of the mycelium and eventually for the mushroom itself. During the cultivation process it’s important to pay close attention to sterility to avoid these contaminations, and always work as clean as possible. The 5 most common sources of contamination are:

  1. The cultivator
  2. The surroundings
  3. The instruments
  4. Spores or the mushroom’s mycelium
  5. The substrate

1. The cultivator You yourself are a big source of bacteria. Your skin, hair, breath, and clothes are all risky. So make sure you are clean when you get down to business. Take a shower and wash your hands and arms thoroughly with a disinfecting soap. Wear gloves, a mouth mask, and clean clothes when you’re going to work.

2. The surroundings It is of utmost importance to have clean surroundings. There is an incredible amount of bacteria in the air and they are all capable of ruining your work. Clean your working space thoroughly with a disinfectant. It is best to choose the smallest space possible. For example, a closet is very good. Also a bathroom or a kitchen. Be sure not to have a draft in your working space, so close all the doors and windows. If necessary close cracks with tape. After cleaning the room, be sure to leave for about 5 minutes, so the disinfectant can do its job. Warning: space should be thoroughly cleaned with a disinfectant. But be careful. 

Large quantities of disinfectants in the air can be bad for your health! So pay attention to the amount you use. If you can’t find a good, clean spot in your house or you just want better results, you might consider constructing or purchasing a glovebox. Or even better, a laminar flow hood:

– glove box A semi-sterile closed space. Relatively cheap.

– Laminar flow hood A sterile space using a HEPA-filter. For the cultivator who does not want to compromise.

3. The instruments Obviously all instruments should be sterilized before being used. Especially the instrument which will come in contact with the substrate or agar media should be impeccably clean. Heat these with a lighter or a gas-burner till they start to glow red and let them completely cool off. Always keep in mind that if you touch something it is no longer sterile. You will have to re-sterilize it. Some instruments can also be sterilized in a pressure cooker. Warning: disinfectants are inflammable! Be extremely careful when you use fire to sterilize in a disinfected space. 

4. Spores or the mushroom mycelium You can take all the precautions in the world to work sterile, but if the thing that will serve as inoculant isn’t sterile, all your work will have been in vain. The spores or the mycelium are the basis. Especially at this stage then, sterility is of utmost importance.

5. The substrate The last source of contamination is also the biggest source. The substrate. The substrate which will serve as a feeding ground for the mycelium and the mushrooms, such as rye, vermiculite, rice flour, and straw contain millions of bacteria. Therefore the substrate should always be sterilized in a pressure cooker. Sometimes the pasteurization of the substrate is also enough.