45 8 ENZYMES OF YEAST. 



experiments were valueless, not having been conducted under 

 conditions guaranteeing sterility. 



Other workers proposed a different method of separating the 

 fermentative enzyme from the yeast cell, it being hoped that 

 fermentation would be excited by the cell contents when liberated 

 by the disruption of the cell membrane. Experiments on this 

 line were undertaken by LTJDERSDORFF (I.) and C. Schmidt (at 

 Dorpat), as also by M. Mana-sein. The first-named triturated 

 yeast on a ground glass plate by means of a glass pestle. 

 0. SCHMIDT (I.) consumed six hours in grinding down i grm. of 

 yeast, but failed to obtain any fermentation with the product. 

 M. MANASS^IN (I.) attempted to kill the yeast cells used for the 

 fermentation experiments by the aid of boiling temperature, 

 without destroying the enzyme. 



The fact revealed by all these communications is that the 

 existence of an alcoholic enzyme in beer yeast could not be 

 demonstrated by experiment, but that the presence and repro- 

 duction of living yeast cells are essential to the inception and 

 continuance of alcoholic fermentation. 



Though this state of things apparently controverted the 

 hypothesis of the existence of a fermentative enzyme, further 

 researches and observations contributed to prevent the enzyme 

 theory from stagnating, the chemists, in particular, strongly 

 maintaining the existence of an enzyme. The failure to isolate 

 from yeast an active enzyme capable of decomposing sugar into 

 alcohol and carbon dioxide was generally ascribed to the cir- 

 cumstance that the method of treatment pursued probably altered 

 the composition of the enzyme and rendered it inoperative. Even 

 if alcoholic fermentation had not yet become an accomplished fact, 

 there was no justification for assuming that it would not some 

 day be realised, when a method should be discovered of preparing 

 this enzyme without impairing its activity. 



These opinions on the existence of an alcoholic enzyme 

 necessarily acquired a more stable foundation when P. MIQUEL 

 (VII.), in 1890, succeeded in demonstrating that the fermentation 

 of urea is effected by the intervention of an enzyme, urase, (see 

 vol. i, p. 336), separable from the bacteria present, and not by 

 the vital activity of these bacteria themselves, and when 

 E. FISCHER and P. LINDNER (II.) isolated from Manilla Candida 

 (see p. 445, vo ^ ^-) ^ v triturating the cells with powdered glass, 

 a substance capable of decomposing saccharose in a manner 

 analogous to invertase. The probability of this view was further 

 heightened when E. FISCHER (V.) applied the stereochemical 

 method to enzyme action and showed the previously assumed 

 difference between the chemical activity of the living cell and the 

 action of chemical agencies with regard to molecular asymmetry 

 to be non-existent ; additional confirmation being afforded in 

 course of time by the growing number of communications to the 

 effect that, under certain conditions, the formation of alcohol, 



