464 ENZYMES OF YEAST. 



saccharose furnish up to 30 c.c. of gas, after ninety minutes at 

 28 C ; that is to say, two and a half times the volume of the 

 original liquid. Other workers observed greater fluctuations in 

 the fermentative power. Thus, WROBLEWSKI (III.) obtained 

 i 8-10 c.c. of carbon dioxide from 3.5 c.c. of juice, 14 c.c. of water 

 and 3.5 c.c. of a 60 per cent, solution of saccharose. The results 

 obtained by MACFADYEN, MORRIS, and ROWLAND (I.) with top- 

 fermentation yeast are so irregular that as these workers admit 

 no clear information is obtainable therefrom. More favourable 

 results were obtained by HARDEN and YOUNG (I.) with similar 

 fermentation yeast. BUCHNER and ANTONI (I.) found that fer- 

 mentation with expressed yeast juice goes on with equal power 

 in an atmosphere of oxygen or hydrogen. Expressed juice has 

 been prepared in Munich from bottom-fermentation yeast by 

 BUCHNER and RAPP (I.-VI1L); in Berlin by Buchner, Albert, 

 Spitta, Meisenheimer and Antoni from the bottom yeast of three 

 different breweries; by LANGE (II.) from pressed yeast; by 

 R. GREEN (III.) from Saccharomyces cerevisice (Hansen); by 

 TAKAHASHI (I.) from Sak6 yeast ; by WROBLEWSKI (I., II., IV., Y.) 

 from commercial yeast and wine yeast, pure cultures of beer 

 yeast and Okoci distillery yeast ; by MACFADYEN, MORRIS and 

 ROWLAND (I.) and by HARDEN and YOUNG (I.) from top-fermentation 

 yeast. 



Before proceeding to describe the other peculiarities of ex- 

 pressed yeast juice, it may be mentioned that, up to the present, 

 all the observations on the extent to which the fermentative enzyme 

 are influenced by various factors have been made with the juice 

 alone and not with the pure enzyme itself. Consequently, the 

 degree to which the results obtained has been affected, one way 

 or the other, by the other constituents of the juice, must be left 

 out of consideration. 



Influences of this kind come into play during the storage of 

 the expressed juice. BUCHNER and RAPP (I.) observed that the 

 juice loses its efficiency in proportion to the length of time and 

 increasing temperature of storage ; and the same peculiarity was 

 also noticed by R. Albert and by MACFADYEN, MORRIS and 

 ROWLAND (I.). Storage in ice affords the best means of pre- 

 serving the fermentative power of the juice. The loss of power 

 is ascribed by E. BUCHNER (III.) to extensive alterations, such 

 as are set up by the autodigestion of the juice (see chapter Ixvi.) ; 

 but another cause might be traced to the gradual development 

 of an acid reaction, AHRENS (I.) having found that, in the course 

 of a night, the acidity increases from 0.305 per cent, to 0.81 per 

 cent, (expressed as lactic acid). 



Both the digestive action and the production of acid may be 

 largely prevented by desiccation (see p. 463). As a matter of 

 fact, the stability of the dried juice is considerable, for, according 

 to BUCHNER and RAPP (VI. and VIII.) no appreciable diminution 



