On expressed yeast-cell plasma (Buchner's "Zymase") / by by Allan Macfadyen, M.D., G. Harris Morris, and Sydney Rowland, M.A. ; communicated by Sir Henry E. Roscoe, F.R.S.

  • Macfayden, Allan, 1860-1907
Date:
[1900?]
Catalogue details

Licence: In copyright

Credit: On expressed yeast-cell plasma (Buchner's "Zymase") / by by Allan Macfadyen, M.D., G. Harris Morris, and Sydney Rowland, M.A. ; communicated by Sir Henry E. Roscoe, F.R.S. Source: Wellcome Collection.

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    olume which in many cases exceeded that given by the same amount f juice to which sugar had been added. This auto-fermentation pparently escaped the observation of Buchner, who only incidentally efers to it in one of his papers, and who does not appear to have mde any correction for the gas evolved from the juice itself in any f his experimental results. The extent to which this fermentation ceurs may be seen from the subsequent tables (Tables I and II); in ne experiment, for instance, 100 c.c. of the fresh juice gave no less han 2’98 grammes or 1500 c.c. of carbon dioxide. This spontaneous volution of gas takes place even when the juice is kept at a tempera- ure sufficiently low to maintain it in a solid condition. In all prob- bility the gas which Buchner mentions as‘being evolved on heating ; Zymase ” is due to this cause. In our earlier experiments we determined the carbon dioxide evolved rom the juice alone, or from its admixture with sugar, by measuring he volume of saturated salt solution which was displaced by the gas; >ut later we adopted a modification of Hart’s double titration method, n which the carbon dioxide was absorbed by sodium hydroxide olution, and the amount determined by double titration. In the experiments on the relationship of the carbon dioxide and dcohol formed, we absorbed the carbon dioxide evolved in -33 per rent, potassium hydroxide solution contained in Mohr’s potash bulbs. (The alcohol formed in these experiments was estimated by distillation jmd determination of the specific gravity of the distillate, the weight pf absolute alcohol corresponding to the gravity of the distillate being t-hen found by reference to spirit tables. Control experiments were made in all cases—that is to say, when we were determining the amount of carbon dioxide or of alcohol, formed by any juice from sugar, a corresponding quantity of the juice was placed under identical conditions, but without the addition of any sugar, and the amount of gas evolved or of alcohol formed was care- hilly determined by the same methods as those used in the experiments in the presence of sugar. We employed antiseptics to inhibit the possible action of yeast-cells or other micro-organisms, the natuie of the antiseptics used depending on the object of the experiment. The antiseptics principally employed were sodium arsenite,. toluol, and thymol, all at the rate of 1 per cent. In our earlier experiments we employed 40 per cent, of cane-sugai, this being the concentration which Buchner first considered the most favourable; but we subsequently reduced this to 10 pei cent., as we found that greater action was obtained with the lesser concentiation. In fact, the larger amount of sugar appeared to exercise a retarding influence on the activity of the juice. Nature of Remits obtained.—In Table I we give the results of some of our experiments, in which the gas evolved was measured by the dis-