Semi-Defined Food

Brewer's Yeast80grams
Yeast Extract20grams
MgSO4 x 6H2O0.5grams
CaCl2 x 2H2O0.5grams
Propionic acid6milliliters
10% p-Hydroxy-benzoic acid methyl ester in 95% ethanol10milliliters
Distilled Wateradd to above to make 1 liter
*adjust agar concentration according to the gel strength of your agar
  1. Stir, one at a time, each ingredient except propionic acid and p-hydroxy-benzoic acid methyl ester into most of the water. Add additional water to bring the total to 1 liter.
  2. Bring mixture to a boil and turn off heat source.
  3. Cool to 60oC.
  4. Add p-hydroxy-benzoic acid methyl ester, stirring constantly.
  5. Add propionic acid just before dispensing.
  6. Dispense when the temperature of the mixture is between 40o and 60oC. The medium will separate if it is too hot when poured.
  7. Store at 8oC until ready to use.
The amount of agar should be determined empirically for your brand and lot of agar. We buy agar from MoorAgar, Inc., 6923 Woodley Ave., Van Nuys, CA 91406