90 PHYSIOLOGY OF YEASTS 



cell. This discovery demonstrated that fermentation is able to be pro- 

 duced without the life of the yeast. This made it possible to abandon 

 the vitalistic conception of alcoholic fermentation. 



We have seen at the beginning of this chapter how Buchner ex- 

 tracted his yeast juice. It is definitely settled today that the juice 

 contains a zymase and that its action is not due to particles of pro- 

 toplasm as certain investigators believed in the beginning; when 

 placed in contact with sugar it acts exactly like an enzyme. 



It is not altered and continues to act in the presence of anti- 

 septics (toluol and chloroform). On the other hand its efficiency is 

 not entirely destroyed on filtration through a Chamberland bougie. 

 Finally, Pay en and Persoon have shown that yeast juice precipitated 

 with alcohol gives a powder insoluble in water which possesses all 

 of the properties of the juice. In order to secure this powder, the 

 juice is precipitated by 12 times as much alcohol as there is juice. A 

 mixture of 800 parts of alcohol and 400 parts of ether may also be 

 used. The precipitate is filtered rapidly, washed with ether, and 

 dried over sulfuric acid in a vacuum. 



The investigations of Albert l and those of Rapp have discovered 

 another method of securing alcoholic fermentation away from the liv- 

 ing cell. These investigators have fixed the zymase in the cell by 

 acetone which killed the cell, without altering the enzymes. The 

 method consists of treating the yeast with from 10 to 20 times its 

 volume of alcohol ether or acetone. All of the cells are killed. The 

 yeast at first is rid of its water, is placed on a filter paper, washed 

 with ether, and dried at 45. A white powder is thus obtained made 

 up of dead cells which has " been called zymine or durable yeast 

 (Dauerhefe). The cells which constitute this powder are endowed 

 with the fermenting property like living yeasts and when they are 

 put into a sugar solution, they induce fermentation immediately. 

 When this powder is extracted by the method of Buchner, the juice 

 thus secured possesses the same action as the living cells. 



More recently Lebedeff 2 has obtained a very active zymase by the 

 maceration of the yeast in water. For this, it is sufficient to mac- 

 erate 2.5 to 3 parts of water with 1 part of yeast over a period of 

 time. This is finally filtered through filter paper and a juice collected 

 which is very clear and whose activity excels that secured by any of 

 the other methods. 



The quantity of zymase in living yeasts is variable. It is curious 



1 Albert, K. Herstellung von Dauerhefe mittels Aceton. Ber. d. chem. 

 Ges. 31. 



2 Lebedeff, A. Extraction de la zymase par simple maceration. Comp. 

 Rend. Ac. des Sciences, 152, 1911. 



