Agar is a naturally gelatinous powder derived from marine red algae. It is used in the cultivation and study of moulds, bacteria and fungi. Malt extract is a sugar derived from barley grain. It contains minerals and vitamins that have a variety of uses. In mushroom growing, malt extract, light malt extract, dried malt extract are essentially all the same.
When mixed with agar and water, then sterilised and poured, under sterile conditions, into a petridish, ME (malt extract) is used to propagate mushroom cultures from cloned tissue, spores and even liquid cultures.
Once grown out, the agar (with the culture now grown into/on it) can be transferred to sterile grain, master slant, liquid culture or in some cases, directly onto a substrate.
When mixed with just water, ME (malt extract) can be used to make a LC (liquid culture) broth. Once sterilised a culture can be added to the broth and allowed to grow out and eventually become a liquid culture.
Due to the nature of ME, it is very sensitive to moisture/humidity. If, for some reason, your ME arrives with any clumps, don’t worry. This is normal and will dissolve in hot water just fine.
Although there are dozens of agar recipes for growing mushrooms, I would recommend making MEA. In order to prepare agar for mushroom cultivation purposes use the following instructions for a basic MEA (Malt Extract Agar).
Step 1: Mix 20g of agar powder and 20g of ME (Malt Extract) in 1000ml of hot water.
Step 2: Stir until dissolved then decant contents into a PC (pressure cooker) safe container.
Step 3: PC your mix for 15 minutes at 15psi, once 15 minutes are up, remove your PC from the heat and allow to cool. Do not force vent your PC, it will cause your agar to boil over inside your PC.
Step 4: Once cool enough to handle the container, in a SAB (Still Air Box) or In front of a Flow-hood pour your agar into sterile petri dishes.
Step 5: Once your petri dishes have solidified wrap with Parafilm or Micropore Tape and store in a cool, dark environment until required.
This recipe should make between 20 and 30 plates depending on how thick you pour the agar.
*Please note, this malt extract or agar are not for human consumption.