Agar plates are a nutritious gel that is contained in a sterile container. Agar Agar is the ingredient used to set the liquid but it in itself has no nutritional value so some form of sugar needs to be added to the recipe to feed the growing mycelium.
The idea is that the mycelium will be grown on a flat 2-dimensional surface as apposed to when growing in Liquid Culture which is 3-dimensional. When viewing the mycelium on an agar plate it is much easier to notice any growing infections and easy to isolate healthy mycelium.
What are Agar plates used for?
Learning to make and work with Agar plates is one of the most important aspects of mycology. Agar plates are used for the following procedures :
- Growing out spore prints.
- Cleaning contaminated mycelium by transferring the cleanest parts over and over until you are left with contam free plates.
- Isolating the fastest / healthiest growing parts of your mycelium.
- Cloning mushroom tissue.
- Testing liquid culture to make sure it is viable and contam free.
- Making grainspawn.
- Long term storage of your mycelium (in particular making agar slides lets you store mycelium for up to a year or two).
What recipe should I use ?
There are many different recipes and methods to make agar plates, the most common recipe is MEA (Malt Extract Agar). These plates come out almost see through and are probably the best for beginners (and are most used by experienced growers too). Other recopies include Potato Dextrose, Soy Flour, Oatmeal, Dextrose, adventurous budding mycologists have even experimented using dog food.
It may be beneficial for mycelium to be grown / exposed to multiple food sources so some growers alternate two different types of plates in between transfers.
How to make MEA Liquid
Per 500ml clean water
10g Agar Agar
10g Light Malt Extract
1g Brewers yeast (optional)
Find a suitable glass bottle with a plastic screw on lid. Make sure the lid and bottle has been cleaned with jik and water solution (probably not necessary as it is going to be sterilized but best to be careful).
In a separate clean jug mix the dry ingredients and the water (it helps if the water is hot and it’s best to add the dry ingredients to the hot water to get it to dissolve better).
Once incorporated pour the mixture into the glass bottle and screw on the lid (you need to leave the lid slightly unscrewed to release any built up pressure when pressure cooking).
Wrap the lid in tinfoil.
Place bottle upright in pressure cooker and cook for 45 minutes at 15psi (make sure bottle is secure and cant fall over).
Pouring the plates
Prepare your still air box by wiping down all surfaces.
Get everything ready : Alcohol, petri dishes, gloves, parafilm cut in strips, scissors.
Once the bottle of MEA has cooled put it in your still air box. You want to be able to handle it but it shouldn’t cool down too much or it will start to set.
Wipe down your gloves, the MEA bottle and your packed of plates with alcohol.
Cut the bottom of your plates and stand them up as the come on top of each other (the lid on top). These plates come sterile in a pack of 10, once the bag is open sterile techniques should be used.
The easiest way is to pick up the lid from the first plate with the other 9 plates on top, pour in your agar about a third to half way up the plate. Put the lid back and repeat until each plate is filled.
Wait for these to cool and set, then wrap them with parafilm (parafilm is a stretch porous tape that seals the sides of the petri dishes).
You may get some condensation on the lid especially if the MEA was very hot when you poured it. With practice you will eliminate this and the plates can still be used, just when stored turn them upside down so any excess moisture is on the lid side.
500ml is enough for about 20 x 65mm petri dishes.
We recommend keeping your plates at room temp for a few days to check if there is any contamination, if not then store in the fridge.
There are other methods to making agar such as fist fulling heat resistant containers with your MEA liquid and then sterilising those which may be easier for beginners, we advise you to do your own research – there are loads of youtube videos.