Alcoholic fermentation / by Arthur Harden.

  • Arthur Harden
Date:
1932
Catalogue details

Licence: In copyright

Credit: Alcoholic fermentation / by Arthur Harden. Source: Wellcome Collection.

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    (/) Effect of Varying Concentration of Yeast-Juice. This subject, which is of considerable importance with reference to the question of the protoplasmic or enzymic nature of the active agent in yeast-juice, has been examined in some detail by Buchner [Buchner, E. and H., and Hahn, 1903, pp. 158-65] and by Meisenheimer [1903] for juices from bottom yeast, by Harden and Young [1904] for those from top yeast, and by Lebedev [1911, 4] for maceration extract, the results obtained being in substantial agreement. Dilution of yeast-juice with sugar solution, so that the concentra- tion of the sugar remains constant, produces a small progressive diminution in the total fermentation, which only becomes marked when more than two volumes are added, and this independently of the actual concentration of the sugar. Dilution with water produces a somewhat more decided diminution, which, however, does not exceed 50 per cent, of the total for the addition of three volumes of water. The effect on maceration extract is somewhat greater but of the same kind. The autofermentation of juice from top yeast is scarcely affected by dilution with four volumes of water. On the whole, therefore, yeast-juice may be said to be only slightly affected by dilution even with pure water, and the effect of the latter can in no way be regarded as comparable with the poisonous effect which it exerts on living protoplasm, as suggested by Macfadyen, Morris, and Rowland [1900]. (g) The Effect of Antiseptics on the Fermentation of Sugars by Yeast-Juice. Buchner has paid special attention to the effect of antiseptics on the course of fermentation by yeast-juice [Buchner and Rapp, 1897 ; 1898, 2, 3 ; 1899, I ; Buchner and Antoni, 1905, I ; Buchner and Hoffmann, 1907 ; Buchner, E. and H., and Hahn, 1903, pp. 169-205 ; see also Albert, 1899, 2 ; Gromoff and Grigorieff, 1904 ; Duchacek, 1909] in order (1) to obtain evidence as to the possibility of the active agent in yeast-juice consisting of fragments of protoplasm and not of a soluble enzyme, and (2) also to provide a safe method of avoiding contamination, by the growth of bacteria or yeasts, of the liquids used, which were often kept at 250 for several days. The results of these experiments as far as they bear on these two points are briefly sum- marised in the following table, in which the effect of each substance on the total fermentation produced is noted :—
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