i 18 



Action of Dissolved Substances upon the Autofer mentation 

 of Yeast. 



By Arthur Harden, F.E.S., and Sydney G-. Paine. 

 (Received October 17, — Read December 7, 1911.) 

 (From the Biochemical Department, Lister Institute.) 



During experiments upon the permeability of the yeast-cell it was found 

 that, when yeast was immersed in a molar solution of sodium chloride, and 

 allowed to stand at air temperature, the amount of gas produced by auto- 

 fermentation was considerably greater than that given by a water control. 



The production of carbon dioxide by autofermentation of yeast is 

 brought about by the action of at least two enzymes. The reserve material 

 of the cell, for the most part glycogen, is first converted by a glycogenase 

 into a sugar, which in turn is fermented by zymase with the production of 

 alcohol and carbon dioxide. As the rate of autofermentation is con- 

 siderably less than that produced by the same yeast in presence of excess 

 of sugar, it follows that the rate of autofermentation is controlled by the 

 rate of production of sugar within the cell, in other words, by the rate of 

 action of the glycogenase. An increase in the rate of autofermentation, 

 therefore, indicates greater activity of this enzyme within the cell. In 

 order to investigate the action of solutions of various salts upon the rate 

 of autofermentation of yeast, this was ascertained by measuring the volume 

 of carbon dioxide evolved during successive intervals of time by means of 

 the apparatus described by Harden, Thompson, and Young (1). The yeast 

 employed was prepared from top-yeast as obtained from the brewery by 

 pressing out the wort in a small hand press, it having been demonstrated (2) 

 that practically the whole of the interstitial liquid can be removed in this 

 way. A certain weight of such pressed yeast was carefully weighed into 

 each of the fermentation flasks, and treated with a certain volume of the 

 various liquids under experiment, controls being made with water. The 

 liquids were saturated with carbon dioxide at 25°, the temperature of the 

 water- bath. 



1. Effect of Sodium Chloride and other Salts upon the Autofermentation 

 of Yeast. 



When yeast was immersed in molar sodium chloride solution the rates 

 of evolution of gas during the first six successive intervals of 20 minutes 



