I have previously covered the use of a microwave oven to sterilize the plastic containers that are used for the process but in this article I am going to provide you with a new insight on using it to sterilize the media itself.
The procedure is essentially very simple. You merely place the container of your selected liquid media into your microwave oven and heat it to just below boiling which should be approximately 4 minutes. What could be easier? Keep firmly in mind that should you forget and allow the media to boil for more then several seconds you will have one heck of a mess to clean up in your microwave.
Several major variables that will affect your procedure are the amount of the media that you will be sterilizing and the maximum power output from your particular microwave. It will more then likely be necessary for you to do a bit of experimenting at first by using different power settings and time for your particular containers. You could fill your vessels with water during your experimental stages in place of actual media. It is usually a lot cheaper using a mixture of water, a little agar, 2 percent sucrose and some tomato juice when doing your tests. The tests if accomplished properly can teach you a lot of valuable information that relates to the problem of contamination and how you best can eliminate it.
You will want to be especially careful if your microwave oven has what is known as “hot spots”. In this case you may need to move your media round slightly to ensure that it sterilizes all of the intended media. You may actually end up increasing your heating time but however you look at it you are still saving a lot of time over the conventional pressure cooker method. A very useful item that you may decide to purchase for use in your microwave is the microwave pressure cooker called the "Micro-Go-Round". It is a microwave turntable made by Nordic. This does an excellent job of microwave tissue culture sterilization. If you are using baby food jars it can sterilize the media right in the jars.
Although this will work well for the home lab you would not want to use it if you eventually go professional as it is simply too small. The unit is 7 inches in diameter and 4 inches high. That’s about 87 cubic inches of useable space. Unfortunately as I mention you could not place too many Petri dishes or tissue flashes in this little marvel. You could place a small plastic rack of some sort in the bottom of it and include a bit of water in order to generate some steam which would exceed 100 degrees C.
Do not place a cap on your containers nor use any sort of aluminum foil as a cover. You can easily use some plastic caps on your culture tubes or a single hole stoppers on culture flasks.
You may be interested in knowing that the process has a tendency to work very well. Media that has been sterilized in this manner has not become cloudy as a result of bacteria and it shows no signs of developing mold even after several weeks of sitting.
The truth of the matter is that you may perhaps contaminate your project as a result of handling your explants as opposed to the media itself being contaminated.
Copyright @ 2009 Joseph Parish