24S MICRO-ORGANISMS AND FERMENTATION. 



that of invertase, according to Kjeldahl, is 52-53 C. In a 

 similar way, a lactose-cleaving enzyme (lactase) and an enzyme 

 resembling invertase were isolated from Monilia. 



At the same time, Hans and Eduard Buchner were 

 endeavouring to prepare a juice by a treatment of the yeast 

 cells similar to that adopted by Emil Fischer i.e., by grinding 

 the wall of the cells, hoping to apply it to therapeutic experi- 

 ments. To preserve the juice, it was mixed with sugar, and 

 E. Buchner thus observed that a vigorous development of gas 

 took place in the mixture. A further examination showed 

 that the gas was carbon dioxide, and that alcohol was simul- 

 taneously produced in the juice. This was the basis of the 

 extended researches which led to the discovery of the alcohol 

 enzyme, which was successfully separated from the living cell 

 (communicated first in 1897). 



Buchner's process is as follows : Fresh washed and 

 strongly pressed yeast is ground with quartz and kieselguhr 

 in a mortar. The cells are torn and broken open by the 

 sharp sand, and the liquid absorbed by the kieselguhr. In a 

 few moments the whole mass cakes together to form a dough. 

 This is wrapped in a strong press cloth, and subjected to 

 very high pressure in a hydraulic press, up to 90 kilogrammes 

 per square centimetre. For every kilogramme of yeast about 

 500 c.c. of clear yellow or yellowish-brown juice is obtained. 

 When the juice is mixed with a solution of saccharose, grape 

 sugar or maltose, a strong frothing takes place within a few 

 minutes, due to the development of carbon dioxide, and at 

 the same time almost the same quantity of ethyl-alcohol is 

 produced. By the addition of minute quantities of alkalies 

 (potassium carbonate, disodium phosphate, etc.), the process 

 of fermentation is quickened. 



It can be shown that the fermentation is not caused by 

 living cells remaining in the juice, for it is possible to add 

 strong antiseptics like chloroform, thymol, or toluol.* which 

 would arrest every living function of the cells, or again the 

 juice may be filtered free from germs through a porcelain 

 filter, without destroying its activity. It might be supposed 



* On the other hand, n>ercuric chloride destroys the fermentative power of 

 the juice. 



