Sour Dough Medium Recipe

1. Dissolve the following in 700ml of distilled water
   • 6g Casein peptone, tryptic digest
   • 0.3g Tween 80
   • 15ml Fresh yeast extract
     • Autoclave a 20% suspension of commercial baker´s yeast in distilled water for 30 min at 121°C
     • Allow the suspension to settle overnight at 2 to 8°C
     • Decant and further clarify the supernatant by centrifugation if necessary
     • Adjust to pH 6.5
     • If not to be used within a 2-3 days the extract should be frozen or freeze-dried immediately
   • 3g Yeast extract
   • 20g Maltose
2. Adjust pH to 5.6 with HCl.
3. Bring to 1000ml with distilled water
4. Autoclave to sterilize