On expressed yeast-cell plasma (Buchner's 'zymase') / by Allan MacFadyen, G. Harris Morris and Sydney Rowland.

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

Licence: In copyright

Credit: On expressed yeast-cell plasma (Buchner's 'zymase') / by Allan MacFadyen, G. Harris Morris and Sydney Rowland. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    volume which in m:uiy ctises exceeded th<it given by the Scinie Jiniouiit of juice to which sugar had been added. This auto-fermciitatioii apparently escaped the observation of Buchner, who only incidentally refers to it in one of his papers, and who does not appear to have made any correction for the gas evolved from the jiuce itself in any of his experimental results. The extent to which this fermentatiori occurs may be seen from the subsequent tables (Tables I and II); in one experiment, for instance, 100 c.c. of the fresh juice gave no less than 2‘98 grammes or 1500 c.c. of carbon dioxide. This spontaneous evolution of gas takes place even when the juice is kept at a tempera- tiu-e sufficiently low to maintain it in a solid condition. In all prob- ability 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 from the juice alone, or from its admixtui’e with sugar, by measuring the volume of saturated salt solution which was displaced by the gas ; but later we adopted a modification of Hart’s double titration method, in which the carbon dioxide was absorbed by sodium hydroxide solution, and the amount determined by double titration. In the experiments on the relationship of the carbon dioxide and alcohol formed, we absorbed the carbon dioxide evolved in 33 per cent, podissium hydroxide solution contained in Mohr’s potash bulbs. The alcohol formed iu these experiments was estimated by distillation and determination of the specific gravity of the distillate, the weight of absolute alcohol corresponding to the gravity of the distillate being then 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- fully determined bj' the same methods as those used in the expei iments in the presence of sugar. M'^e employed antiseptics to inhibit the possible action of yeast-cells or other micro-organisms, the nature 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-sugar, this being the concentration which Buchner first considered the most favourable; but we subsequently reduced this to 10 percent., as we found that gi'eater action was obtained with the lesser concentration. In fact, the larger amount of sugar appeared to exercise a retarding influence on the activity of the juice. Ndliirc of ll/’snUs ohtaived.—In Table 1 we give the results of .some of our experiments, in which the gas evolved was measured by the dis-
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