Pressure cooker (sterilization)

Here is a more DIY approach to sterilization of media/equipment,etc that can be done at the BioFabLab.
This approach is simpler and usually faster than using the larger autoclave machines in RUC's laboratories (also less scary if you're just starting off).

There are two types of pressure cookers in the BioFabLab: the smaller kitchen variety used for most of the video, and the larger Hawkins Big-Boy models. Specific information on the latter is given in the last section of the video, as well as in this manual (which can be found online or in the Kitchen Lab).

In general the pressure cooker sterilization procedure is as follows:

  1. If you are sterilizing a sample in a container (eg: agar) make sure it doesn't fill the container by more than two-thirds. Cover the top with aluminium foil and keep it down with a piece of autoclave tape.

  2. Fill the bottom of the pressure cooker with water to the depth of 1-2cm (not enough to start covering the base of the sample). This should be de-ionised water, which can be gotten from the green taps without any hot/cold symbols in the Classic Lab.
    Place a separator in the bottom of the pressure cooker so that the sample sits just on top of the water layer and is not in direct contact with the cooker's base. In the video, we just used a spoon.

  3. Seal the pressure cooker and place it on a hot.plate at high heat. Make sure the pressure valve is completely open.

  4. When steam begins to come out of the pressure valve opening, close it fully and turn the heat down to medium (approx. half the max). Leave it this way for the required sterilization time (usually 30min-1hr).

  5. When the time is up, switch off the hot plate and remove the pressure cooker so it can cool down for approx. 10-15min.
    Then, gradually open the pressure valve until steam has stopped coming out. With the Hawkins Big-Boy, this can be done by lifting the pressure cap slightly using a fork.
    It is now safe to open the lid and remove the sample. Careful, it will be hot.