Malt Extract Agar

Malt Extract Agar

1 L water

20 g agar agar*

20 g malt extract

10 g dextrose

2 g yeast/marmite/yeast flakes (optional)

1 g petone, soybean (optional)


*For liquid cultures use 4 g agar agar instead.


Put water in a pot on stove and add ingredients. 

Heat to near boiling to help dissolve the agar agar. 

Some undissolved components may dissolve/gel during pressure cooking in upcoming steps. 

Stir well before filling heat resistant containers for pressure cooking (flask to pour petri dishes/jars for liquid cultures):  This will ensure any undissolved components are evenly distributed. 

Fill containers half volume max to prevent boil-over. 

One liter will make 4-8 liquid cultures or 20-100 petri dishes depending on size and depth of fill.

Sterilize closed containers of medium for 20 minutes at 121 C at sea level in a pressure canner/sterilizer, according to the manufacturer's instructions.  Overpacked cookers or large volumes will require longer times.  Your goal is to fully sterilize without caramelization. During cooling when the pressure is between 0 and 1 psig move the cooker in front of a HEPA filter air source to finish cooling.