4 66 ENZYMES OF YEAST. 



that BUCHNER and RAPP (I.), by using a Chamber-land filter, 

 obtained a yeast juice that was perfectly devoid of cells, but 

 exhibited active fermentative power despite the entire absence of 

 germs. 



319. Changes set up in Expressed Yeast Juice by 

 External Physical or Chemical Influences, or 

 by Living 1 Organisms. 



The influence of temperature "on alcoholic fermentation with 

 expressed yeast juice was investigated by E. BUCHNER (X.), who 

 found that the fermentative power was maintained longest at 

 5-7 C., but that fermentation commenced soonest at 28-3oC., 

 the absolute maximum effect being obtained with a temperature 

 of i2-i4 0. In repeating these experiments, MACFADYEN, 

 MORRIS and ROWLAND (I.) observed that the fermentative 

 efficiency is increased at higher temperatures ; but they left the 

 time factor out of consideration, confining their experiments to a 

 period of only forty-eight hours. 



Desiccated yeast juice, on the other hand, will stand higher 

 temperatures without loss of fermentative power. Thus, 

 according to BUCHNER and RAPP (VI.), yeast juice that has been 

 dried very carefully may be heated to 85 C. for eight hours 

 without suffering any considerable loss of power, and even at 

 97 G. the fermentative power is not entirely destroyed. BUCHNER 

 (VIII.) states that the precipitate obtained with alcohol and 

 ether (see p. 471) continues to excite fermentation after being 

 heated to T05-no C. for four hours; and the same authority 

 (V.) says that the permanent yeast (to be described later on) does 

 not entirely lose its power when heated to 110 0. for six hours 

 in the air, or to 100 C. for eight hours followed by heating for 

 ten hours at no C. in a current of hydrogen, though it is 

 destroyed by exposure to 140- 145 C. for an hour. 



On the basis of existing knowledge it might be presumed, 

 a priori, that the dialysis of the fermentative enzyme through 

 animal membranes would be difficult, if feasible at all ; and as a 

 matter of fact, BUCHNER and RAPP (II. and IV.) have established 

 that the enzyme cannot be extracted from the living yeast by 

 lixiviafcion, nor can any considerable proportion be obtained by 

 dialysis through parchment paper. Similar results were obtained 

 by R ALBERT (I.) with sterile permanent yeast, no fermentative 

 enzyme being extractable with the aid of water or sugar solution 

 unless the cell membranes had been previously destroyed. 

 According to the newer researches of HARDEN and YOUNG (III.) 

 and BUCHNER and ANTONI (II.) the juice is apparently inoperative 

 at the end of forty-eight hours after having been dialysed through 

 Martin's gelatin filter or in Giirber's apparatus at o C., though 

 when united with the concentrated dialysate or with scalded press 



