Yeast Growth in Pure Medium 



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Can yeast grow in a chemically pure medium? 

 By CASIMIR FUNK AND LOUIS FREEDMAN 



[From the Research Laboratory of H. A. Metz, New York City.] 



Reports have lately appeared that yeast can grow on a medium 

 composed of known ingredients, viz. : 50 grams cane sugar 

 (Domino brand), 2 grams KH 2 P0 4 , 2.35 grams (NH 4 ) 2 S0 4 , 

 0.25 gram CaCl 2 and 0.25 gram MgS0 4 , dissolved in a liter of 

 distilled water. It was claimed that on the above medium, which 

 we will call medium O, yeast could be grown in sufficient quan- 

 tities to serve as a source of vitamine B in animal feeding experi- 

 ments. 



We have attempted to grow yeast on the above medium but 

 have found it difficult to obtain sufficient yeast by this method. 

 It grew very slowly in the incubator and hardly at all at room 

 temperature. The yields were very small; for example, 1800 c.c. 

 of nutritive solution distributed in twelve flasks gave, after grow- 

 ing for a month, 1.5 grams of dried yeast, whereas on addition 

 of 1 c.c. autolyzed yeast to each flask, 900 c.c. in six flasks gave 

 in four days 3 grams of product. Whereas the yeast in the first 

 case developed a brown pigment and presented a spore-like 

 shrunken appearance, in the second case the cells were colorless 

 and in active budding. 



In sub-culturing the yeast obtained on medium O, by intro- 

 ducing 5 c.c. into each of a series of flasks containing fresh 

 media, the yield remained almost constant. This excluded the 

 cause of the growth as being due to vitamine D introduced with 

 the seeding, and suggested the possibility of an impurity in the 

 medium. It therefore became necessary to investigate more 

 carefully the purity of one or more of the three constituents of 

 the medium, namely, salts, water and cane sugar. 



Each one of the salts used as well as the cane sugar was dis- 

 solved separately in distilled water, shaken out with fullers earth 

 and the filtrate evaporated to dryness. The distilled water of the 

 laboratory was redistilled three times in an all-glass apparatus. 

 The salts, sugar and the water were used to make up the neces- 



