Action of Accelerating Agents on Living Yeast.

Slator [[1908, 1]] was unable to find any agent which greatly accelerated the rate of fermentation of living yeast. Small concentrations of various inhibiting agents which are often supposed to act in this way were quite ineffective, and phosphates, which produce such a striking change in yeast-juice, were almost without action (cp. p. [124]).

Euler and Bäckström [[1912]], however, have made the important observation that sodium hexosephosphate causes a considerable acceleration although it is itself neither fermented nor hydrolysed under these conditions. The extent of this is evident from the following numbers:—

20 c.c. of 20 per cent. glucose solution. 0·25 g. yeast [Yeast H of St. Erik's brewery].
Without addition.		+ 0·5 g. Na hexosephosphate.
Time. Min.	CO₂.	Time. Min.	CO₂.
46	10·5	37	8
76	17·5	73	19
197	45	188	52·5
347	74·5	321	123
488	95	450	193·5

The observation has been confirmed with English top yeast (Harden and Young, unpublished experiments), but no explanation of the phenomenon is at present forthcoming.

Euler has also found [Euler and Cassel, [1913]; Euler and Berggren, [1912]] that yeast extract, sodium nucleinate and ammonium formate also increase the rate of fermentation of glucose by yeast, but these results have been criticised by Harden and Young [[1913]] on the ground that the possibility of growth of the yeast during the experiment has not been excluded.