BtJCHNER'S ZYMASE OR ALCOHOLASE. 473 



320. Buehner's Zymase OF Aleoholase. 



E. Buchner explained the fermentative effect of expressed yeast 

 juice as being due to the action of an enzyme, which he proposed 

 to call zymase. This was the name applied by BI^CHAMP (VIII.) 

 in 1872, for the enzyme we now term invertase ; whilst other 

 workers regard the word zymase as synonymous with yeast enzymes 

 in general. In order to prevent the misunderstandings likely to 

 arise from this multiplicity of meanings, we will in future refer 

 to the enzyme of alcoholic fermentation as " alcoholase." 



At present nothing definite can be stated with regard to the 

 chemical nature of alcoholase. This enzyme forms a merely 

 insignificant proportion of expressed yeast juice. According to 

 WROBLEWSKI (V.), it is colloidal. Certain other facts speak in 

 favour of its proteid nature, whilst others again indicate a 

 morphological connection. Since the enzyme has not yet been 

 isolated in a pure state, we can only deduce its nature from 

 experiments with yeast juice. The characteristic property is 

 its ability to split up certain sugars compare BUCHNER and 

 MEISENHEIMER (II.). In the dried state it appears to be fairly 

 stable. It is incapable of dialysing through the cell membrane. 

 Under certain conditions it is not destroyed by heating. It is 

 sensitive in variable degree toward chemical reagents, acids being 

 injurious, whereas alkalis in small quantities are beneficial. It 

 is sensitive toward alcohol, but less so toward alcohol-ether or 

 acetone. 



Besides expressed yeast juice we have another preparation of 

 yeast suitable for the study of alcoholase and other yeast enzymes, 

 namely, sterile permanent yeast. Ordinarily, the fermentation 

 technologist applies the term permanent yeast to yeast prepared 

 so as to enable it to be despatched to considerable distances ; but 

 the substance we are now considering must not be confounded 

 with this. Owing to the difficulties in the way of investigators 

 preparing yeast juice themselves, or obtaining it in large quantities 

 for the purpose of further research into the nature of alcoholase, 

 considerable value attaches to a preparation that can be made 

 by any one without any special appliances, arid that is also very 

 stable. Furthermore, permanent yeast presents many advantages 

 over yeast juice as a material for the investigation of fermentation 

 phenomena, inasmuch as the whole of the alcoholase can be 

 recovered from the prepared yeast by a skilled operator. The 

 presence of the uninjured cells give rise to difficulty only in 

 certain investigations, e.g., the extraction of alcoholase; and in 

 such cases the cells must first be opened by trituration with or 

 without sand. 



The basis of the methods of preparing permanent yeast con- 

 sists in the elimination of water, which is effected either by 



