1915] Joseph Samuel Hepburn i39 



tained in a tall glass cylinder, was completely frozen with a mixture 

 of ice and rock salt, and the frozen mass permitted to thaw slowly 

 but completely. During liquefaction, the juice separated into two 

 layers ; a colorless Upper layer, consisting of almost pure water, and 

 a deeply reddish-brown lower layer, the conc. press-juice. The 

 Upper layer possessed but slight fermentive power and the lower 

 layer a fermentive power considerably greater than that of the orig- 

 inal press-juice, the conc. juice at the very bottom of the lower 

 layer being the most active. Sucrose was used as Substrate in these 



tests. 



Ahrens (8) concentrated yeast press-juice, in order to increase 

 its zymase content, by cooling to a temp. not lower than — 2° C, 

 while stirring. Ice crystals, which contained but slight quantities of 

 the constituents of the juice, separated and were removed by rapid 

 filtration with the aid of pressure. The zymase was in the filtrate. 

 In Order to attain a still greater concentration of the enzyme, in some 

 of the experiments, the filtrate was cooled and the entire procedure 

 just outlined was repeated several times. 



Macfadyen (9) subjected yeast-cell plasma to the temp. of liquid 

 air, —182° to —190° C, for a period of 20 hr. After this ex- 

 posure, the zymase remained unchanged in its power to produce 

 alcohol and carbon dioxid. 



Invertase (sucrase) retains its activity after exposure to the 

 temp. of solid carbon dioxid; for the yeast-cell plasma, obtained by 

 Buchner (7) by means of carbon dioxid snow, produced alcoholic 

 fermentation of sucrose during incubation at 22° C. 



Pozerski (5) held Solutions of invertase, prepared from beer 

 yeast and from Aspergillus niger, at the temp. of liquid air (app. 

 — 191° C.) for 45 min. The enzyme completely retained its power 



to invert sucrose. 



Maltase (glucase) retains its activity after repeated exposure 

 to a temp. as low as — 2° C. The yeast press-juice, concentrated by 

 the process of Ahrens (8) and incubated at a temp. of 5° to 18° C, 

 with a wort prepared from starch paste and kiln-dried malt, induced 

 alcoholic fermentation of the latter. 



DiASTASE. Pozerski (5) studied the action of liquid air (temp. 

 app. — 191° C.) on Solutions of diastase. Two varieties of the 

 enzyme were used, salivary diastase contained in filtered mixed 



