Studies on the fermentative activity of yeast zymin

In a summation of the experimental work presented herein, the following points are believed significant: (1) The fermentation of dextrose by maceration extract of yeast is stimulated by ammonium chloride and magnesium sulfate. (2) The activity of zymin preparations will vary greatly depending upon the source of the yeast and upon the length of time the yeast is stored at 5°C. (3) Mixtures of zymins of different activities gives a resultant activity which is lower than the theoretical activity of the mixture. (4) The washing of a fresh yeast which normally would yield a zymin of low activity produces considerably higher activity. (5) Zymins respond differently toward ammonium chloride, and the differences range from definite inhibition to stimulation as high as 80 percent. There also is a fairly good correlation between the activity of a zymin and the degree of stimulation by ammonium chloride. The less active a zymin is, the more than zymin is stimulated by ammonium chloride, and the higher the optimum concentration of ammonium chloride will be. (6) In a series of studies with methyl ammonium chlorides, stimulation is observable which is similar to that observed with ammonium chloride, but the degree of stimulation is progressively less according to the following series: NH4+ CH3NH3 + (CH3)2NH2+ (CH 3) NH+. (7) The effect of magnesium sulfate appears to be rather consistently the same regardless of the activity of the zymin. (8) A substance was separated from a zymin of low activity which had an inhibitory effect on the activity of more active zymins. Its action was, in turn, strongly depressed by small concentrations of ammonium chloride. (9) The effects of magnesium sulfate and ammonium chloride were inhibitory in the fermentation of sodium hexosediphosphate. (10) The effects of both salts were also inhibitory in the fermentation of dihydroxyacetone. (11) The salts were inhibitory in the fermentation of sodium pyruvate. However, in the presence of ethanol, ammonium chloride protected the system from the toxic effect of ethanol, and therefore a stimulation occurred