16 LABORATORY MANUAL OF MICROBIOLOGY 



MEDIA FOR YEASTS 

 Medium 24 

 Sucrose Peptone (Hansen's) Solution 



Sucrose or maltose 50 . gm. 



Peptone 10.0 gm. 



Monopotassium phosphate (KH2PO4) 3.0 gm. 



Magnesium sulphate (MgS04-7H20) 2 . to 5 . gm. 



Distilled water 1,000. cc. 



Medium 25 

 Sucrose — Malt Extract Agar 



Agar 15.0 gm. 



Sucrose 50 . gm. 



Malt extract (desiccated) 10. gm. 



Distilled water 1,000.0 cc. 



Medium 26 

 Malt Extract Broth 



Malt (finely ground) 250 . gm. 



or 



Malt extract (desiccated) 15.0 gm. 



Water 1,000.0 cc. 



Incubate for 1 hour at 65°C. and test for starch; when the 

 latter is still present, incubate for a longer time. Filter through 

 a hand press, cook for 2 to 3 hours. Again filter and make up 

 to 1 liter. For a soUd medium add 1.2 to 1.5 per cent of agar. 



Medium 27 

 Fresh Yeast Infusion 



Yeast (fresh-pressed cakes, starch-free) 100.0 gm. 



Water 1,000.0 cc. 



The 1-pound cake of starch-free pressed yeast will be found 

 useful. Steam for 3 to 4 hours with occasional stirring. Steri- 

 lize in deep layers and allow to stand for 1 week. If undisturbed 

 the yeast cells will settle to the bottom and leave a clear straw- 

 colored liquid above. This clear infusion should be siphoned 

 off and the reaction adjusted to pH 6.6 to 6.8. Yeast extract 

 prepared in this way contains only a trace of fermentable carbo- 



