Supplies

• Petri dishes
• Malt extract (barley malt sugar)
• Agar agar powder
• Nutritional yeast
• Peptone

 

Process

• Add dry ingredients to media bottle and pour hot water over
  • For 20 100 mm plates: 
    • 12 g malt extract 
    • 12 g agar agar powder
    • 1.2 g nutritional yeast
    • 0.6 g peptone
    • 600 mL water
  • For 20 90 mm plates:
    • 10 g malt extract 
    • 10 g agar agar powder
    • 1 g nutritional yeast
    • 0.5 g peptone
    • 500 mL water
• Shake / stir
• Add lid and loosen a quarter turn, then put a piece of tinfoil over the lid
• Pressure sterilize for 25 minutes at 15 psi (turn stove off after 20 mins, open valve at 0 psi if using All American)
• Once the pressure in the cooker comes back down to zero and the bottle is just cool enough to handle, proceed to the next step
• Sterilize the outside of the bag of sterile petri dishes.
• Cut open the bag in a still air box or in front of a flow hood.
• Make stacks of 10 with the petri dishes. 
• Starting from the bottom and picking up the whole stack on top, begin pouring the dishes.
• Leave the dishes in the box to cool.
• Seal the outside of the petri dishes with parafilm to store.