You can sterilize microbial growth media containing at least 10% salt by boiling on a hot plate, on a stovetop, or in a microwave. Use a hot plate with a magnetic stirrer if one is available. A stir bar will prevent ingredients from settling and burning on the bottom of the container, as well as sudden boil-overs.
- Cover your container. If you are using a microwave, cover your container with plastic wrap, and make a small hole in the opening to allow steam to escape. If you are using a hot plate or stovetop, cover your container loosely with aluminum foil.
- To ensure that the media is properly sterilized, boil it for at least 15 minutes.
Tip: Sterilize water by placing a water-filled bottle (with the cap on loosely) in a boiling water bath for 15 minutes. Place something under the bottle so it does not directly contact the bottom of the pot. The containers in the photo below are sitting on top of metal canning rings.
CAUTION: Agar-based media tends to foam easily and suddenly, so watch it carefully. Swirl often to mix until all ingredients are dissolved. Use thick oven mitts to help protect your hands from a potential boil-over.