Effect of Ethanol upon Fermentative Activity of Zymin

Abstract

In studies on the effect of the composition of the medium upon the cell-free alcohol fermentation by zymin, it was soon evident that the zymin is very sensitive to relatively low concentrations of ethanol. In Table I are given quantitative data on the effect of various concentrations of ethanol upon the relative rates of fermentation based upon the production of carbon dioxide. There are also given the data obtained by Rahn 1 for yeast. An analysis of the latter data shows a linear relation between the concentration of alcohol and the relative rate of CO₂ production, up to a concentration of about 10%. From this point there is a slow and practically constant rate even in the presence of as high as 14%. There is a linear relationship for the zymin up to about 1.8% alcohol from which point there is also evident the low but continuous fermentation. The equations for the linear portions of the curve are

Relative rate for yeast = 100— 2.1 X % ethanol.

Relative rate for zymin = 100—22.5 X % ethanol.

It is at once evident that the zymin is much more sensitive to the alcohol than is the yeast. Harden 2 reports that there is a 0-20% diminution of the fermentative activity of yeast juice in the presence of a 6% ethanol and a 75% decrease for 14% ethanol. In the preparation of zymin there is evidently removed some factor which protects against alcohol. The addition of the extracted material did not decrease the sensitivity. Experiments, the details of which will be published later, show that while the addition of phosphate gives the expected increase in activity there is no decrease in sensitivity toward ethanol; the addition of the appropriate concentration of ammonium chloride not only increases the fermentative activity, with or without the addition of phosphate, but very materially decreases the sensitivity toward ethanol.