THEORIES OF FERMENTATION. 249 



that the fragments of protoplasm torn from the cells could be 

 regarded as carriers of this power, and that the enzyme itself 

 had not been separated. This cannot, however, be the case, 

 for if the juice is treated with precipitants like alcohol-ether 

 or acetone, the active substance is thrown down, and this, 

 along with other precipitated substances, on drying, forms an 

 amorphous and very stable powder which, on treatment with 

 water, can once more be employed as an exciter of fermentation. 



It has since been shown that high pressure is not essential. 

 R. Albert has recently shown that by treatment of yeast with 

 alcohol-ether, or, better still, with acetone in such a way 

 that all the cells are destroyed, a very active powder can 

 be prepared (zymin). The yeast is partially dried and 

 soaked for a quarter of an hour in acetone (ten times its 

 volume). It is then spread on filter paper to dry, washed 

 with ether, and dried at 45 C. The preparation takes the form 

 of a white powder. The powder, which consists of dead cells, 

 that are still whole, produces almost immediate fermentation 

 in a sugar solution. If it is washed with water, the water 

 does not acquire any fermentative power. If, however, the 

 cells are first disintegrated, it is possible by simple suction 

 with a water pump to obtain a juice from which a precipitate 

 is thrown down by means of ethyl alcohol, which can be dis- 

 solved in water and immediately produces a vigorous fer- 

 mentation in a sugar solution. Whilst yeast that has been 

 killed in the usual way does not retain any alcohol enzyme, 

 it is possible by this method to fix the enzyme so that it 

 remains intact in the dead cells. 



These remarkable observations only permit of one explana- 

 tion, viz., that living yeast cells are not essential for the 

 production of fermentation, and that it is possible to separate 

 an active enzyme from the disintegrated yeast cells which is 

 soluble in water, and is much more resistant to antiseptics and 

 other strong influences than the living cells, a property that 

 it possesses in common with other enzymes. This substance, 

 which is contained in pressed-yeast juice, Buchner named 

 zymase (alcoholase). 



Buchner declares in very interesting fashion that this 

 discovery proves that both Pasteur and Liebig were correct 



