96 PHYSIOLOGY OF YEASTS 



It ought to have intermediary products. Quite recently, Wohl and 

 also Buchner, 1 Boy en-Jensen, and Fernbach 2 have admitted that this 

 intermediate product may be dioxyacetone with the formula CH 2 OH- 

 CO-CH 2 OH. 



This compound, under certain rare conditions, is able to yield lac- 

 tic acid. But, more often, this dioxyacetone will give alcohol and 

 carbon dioxide directly. Alcoholic fermentation then acts in two 

 phases: in the first, the glucose is transformed into dioxyacetone, and 

 in the second phase, a dioxyacetonase will change the dioxyacetone 

 into alcohol and carbon dioxide. Zymase will then in reality be made 

 up of two enzymes acting successively. 



Buchner and Meisenheimer have been able to obtain fermentation 

 of dioxyacetone (2 per cent solution) by yeast juice. Lebedeff 3 quite 

 recently obtained good results when making yeast juice ferment a 

 5 per cent solution of dioxyacetone. All of these facts are very in- 

 teresting, but it still remains true that the demonstration of the 

 formation of dioxyacetone during fermentation has not been accom- 

 plished. Its existence is, then, purely theoretical. We have cited the 

 work of Harden 4 and Young, who have demonstrated that zymase is 

 composed of two elements, one a dialyzable and thermostabile, the 

 other not dialyzable and destroyed at 100 C. This last does not 

 possess any fermenting function. If one adds to it the coenzyme, fer- 

 mentation will result immediately. 



But another agent has been found which will activate yeast juice 

 which has no or little activity; it is the phosphates of either sodium 

 or potassium. If a little soluble phosphate is added to yeast juice 

 a brisk liberation of CO2 results. This exists for a time proportional 

 to the quantity of phosphate added, then it slows up and fermenta- 

 tion goes on as before. If phosphate is added again the phenomenon 

 is repeated. One is thus able to reproduce it a number of times. The 

 addition of phosphates then has the same effect as the addition of 

 a coenzyme or the boiled inactive juice alone. 



Such are the facts which the investigations of Harden and Young 

 and Lebedeff have established. An ingenious conception of the 

 mechanism of alcoholic fermentation has thus been formed. 



1 Buchner, E. La fermentation alcoolique des sucres. Rev. g. des Sciences, 

 21, 1910. 



2 Fernbach, A. Sur la degradation des hydrates de carbonne. C. R. Acad. 

 des Sciences, 150, 1910. 



3 Lebedeff, A. Sur le mecanisme de la fermentation alcoolique. Comp. 

 Rendu Acad. Sciences, 153, 1911; Ueber Hexosphosphorsauerester. Biochem. 

 Zeitschr. 27, 1910. 



4 Harden, A. Recherches recentes sur la fermentation alcoolique. Ann. 

 de la Brasserie et de la Distillerie, 14th Year, 1911. 



