All the foregoing preparations exhibit the same general properties as yeast-juice, as regards their behaviour towards the various sugars, antiseptics, etc.
When zymin is mixed with sugar solution without being previously ground, it exhibits a peculiarity which is of some practical interest. The time which elapses before the normal rate of fermentation is attained and the total fermentation obtainable vary with the amount of sugar solution added, the time increasing and the total diminishing as the quantity of this increases. This phenomenon appears to have been noticed by Trommsdorff [[1902]], and a single experiment of Buchner shows the influence of the same conditions [Buchner, E. and H., and Hahn, [1903], p. 265, Nos. 700–1]. Harden and Young have found that when 2 grams of zymin are mixed with varying quantities of 10 per cent. sugar solution the following results are obtained:—
| Volumes of Sugar Solution | Total Gas Evolved in | ||||
|---|---|---|---|---|---|
| 1 | 2 | 3 | 4 | 22·5 hours. | |
| 5 c.c. | 15·7 | 31·6 | 44·8 | 56·5 | 233·3 |
| 10 | 2·2 | 10·5 | 23 | 31·8 | 202·3 |
| 20 | 0·9 | 2·4 | 13·6 | 23·7 | 125·5 |
| 40 | 1·4 | 1·7 | 2·3 | 2·9 | 56·3 |
This behaviour appears to be due to the removal of soluble matter essential for fermentation from the cell, which is discussed later on. It follows that when zymin is being tested for fermenting power, a uniform method should be adopted, and all comparative tests should be made with the same volumes of added sugar solution. Ground zymin appears to begin to ferment somewhat more slowly than unground (2 grm. to 12·4 c.c. of sugar solution in each case), but eventually produces the same total volume of gas [Buchner and Antoni, [1905, 1]].
CHAPTER III. THE FUNCTION OF PHOSPHATES IN ALCOHOLIC FERMENTATION.
In the course of some preliminary experiments (commenced by the late Allan Macfadyen, but subsequently abandoned) on the production of anti-ferments by the injection of yeast-juice into animals, the serum of the treated animals was tested for the presence of such antibodies both for the alcoholic and proteoclastic enzymes of yeast-juice, and it was then observed that the serum of normal and of treated animals alike greatly diminished the autolysis of yeast-juice.
As the explanation of the comparatively rapid disappearance of the fermenting power from yeast-juice had been sought, as already mentioned (p. [20]), in the hydrolytic action of the tryptic enzyme which always accompanies zymase, the experiment was made of carrying out the fermentation in the presence of serum, with the result that about 60 to 80 per cent. more sugar was fermented than in the absence of the serum [Harden, [1903]].
This fact was the starting-point of a series of attempts to obtain a similar effect by different means, in the course of which a boiled and filtered solution of autolysed yeast-juice was used, in the hope that the products formed by the action of the tryptic enzyme on the proteins of the juice would, in accordance with the general rule, prove to be an effective inhibitant of that enzyme. This solution was, in fact, found to produce a very marked increase in the total fermentation effected by yeast-juice, the addition of a volume of boiled juice equal to that of the yeast-juice doubling the amount of carbon dioxide evolved [Harden and Young, [1905, 1]]. This effect was found to be common to the filtrates from boiled fresh yeast-juice and from boiled autolysed yeast-juice, and was ultimately traced in the main, not to the antitryptic effect which had been surmised, but to two independent factors, either of which was capable in some degree of bringing about the observed result.