Which Agar recipe should I choose?
When I first decided to start using agar. I wanted to know which recipe would be the best. My initial research didn’t yield much useful information. Many people said just pick one and see if you like it, and to keep trying different recipes until you find one that you like. But, choosing an Agar recipe isn’t like picking your favorite flavor of ice cream. Each one is formulated differently for a reason. Below are three recipes, and a description of each to help you choose the best recipe for your specific needs.
Water Agar: This recipe has no nutrients in it at all. It provides water, but not food. This lack of nutrients means that is very resistant to contamination. Without food, the contamination cannot grow. However, this also means there are no nutrients for mycelium to feed on either. So, it’s not used to growing out spores or liquid cultures.
It is used to isolate clean mycelium from a sample that is already strong and healthy, but potentially contaminated.
A good example of this would be a cuttings of a wild foraged mushroom. The cutting would be placed on the water agar and the healthy mycelium would use already stored energy to spread out searching for food. By allowing it to spread out over a clean surface, you will be able to take a clean sample of tissue and transfer it to a more nutritious agar like malt extract agar, without transferring any contaminates.
Malt Extract Agar (MEA): This agar is a good agar to start spores and tissue samples on. It is mildly nutritious, so it will allow mycelium to grow. But, if your plate or sample is contaminated. The contamination will grow also. However, the agar is only mildly nutritious. So, it will grow slower and will not be as healthy. This will buy you some time to transfer good tissue away from any contaminates. But, don’t expect huge fluffy webs of mycelium to be bursting from your petri dish like all the photos you might see online.
Malt Yeast Agar (MYA): This is the most nutritious agar of the three. Use this recipe once you are sure you have a clean sample of mycelium to work with. Clean mycelium will grow beautifully on this mixture. It will grow thicker and healthier, resulting in strong mycelium. However.. If your sample is not clean, or it is contaminated during transfer. The contamination will grow like wild fire and you can kiss your plate goodbye.
And now for the recipes….
Water Agar
This recipe makes 500ml of Water Agar.
(Approximately 25-30, 100mm petri dishes)
| Ingredient | Amount |
|---|---|
| Water | 500ml |
| Agar | 10 grams |
Malt Extract Agar (MEA)
This recipe makes 500ml of Malt Extract Agar (MEA)
(Approximately 25-30, 100mm petri dishes)
| Ingredient | Amount |
|---|---|
| Water | 500ml |
| Agar | 10 grams |
| Malt Extract | 7.5 grams |
Malt / Yeast Agar (MYA)
This recipe makes 500ml of Malt Yeast Agar (MYA)
(Approximately 25-30, 100mm petri dishes)
IMPORTANT: Nutritional Yeast is typically sold in flake form. The flakes will need to be ground into a fine powder prior to mixing into your recipe. A simple mortar and pestle or coffee grinder will do the trick.
| Ingredient | Amount |
|---|---|
| Water | 500ml |
| Agar | 10 grams |
| Malt Extract | 7.5 grams |
| Nutritional Yeast Powder | 0.25 grams |
This concludes our overview on agar choice, and recipes.
If you are ready to prepare and sterilize your agar, or you want to learn more about the next steps involved.
See our guide on preparing and sterilizing agar.
If you want to brush up on best practices for pouring agar, see our guide to pouring agar.
NOTES ON COLORED AGAR
I personally use a few drops of food coloring mixed into the agar solution prior to sterilization. I mix the food coloring into the liquid agar solution at the same time as mixing in the other ingredients of the recipe. I use the coloring to easily identify what recipe is in each plate, without having to label each one. I color the MEA Red, the MYA Blue, and leave the Water Agar as is (un-colored). The digestive enzymes released by the mycelium will break down dye as the mycelium grows across the plate. So, do not expect the color to last if you are using food coloring to dye your plates.
Not all types of food coloring will survive the sterilization process, and some food coloring actually contains sugars or other ingredients that you do not want in your agar. So, avoid fancy, or organic food coloring and select the simple and cheap dye only types. The ingredients listed on the box will only show the dyes used. Such as Red #40, Yellow #5, Blue #1, etc.
As far as selecting colors for your agar, Do not use green. Several types of contaminates are green in color. So, using green agar will make it difficult to see them and deal with them appropriately.