Alcoholic fermentation / by Arthur Harden.

  • Arthur Harden
Date:
1911
Catalogue details

Licence: In copyright

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

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    solution. Not a single bubble of gas was evolved. A similar result was obtained in a repetition of the experiment by Schmidt in Liebig’s laboratory [1847, 234], the grinding being continued in this case for six hours, but the natural conclusion that living yeast was essential for fermentation was not accepted, on the ground that during the lengthy process of trituration in contact with air the yeast had become altered and now no longer possessed the power of producing alcoholic fer- mentation, but instead had acquired that of changing sugar into lactic acid [see Gerhardt, 1856, 113, p. 545]- Similar experiments made in 1871 by Marie von Manassein [1872, 187 ; 1897, 188], in which yeast was ground for six to fifteen hours with powdered rock crystal, yielded products which fermented sugar, but they contained unbroken yeast cells, so that the results obtained could not be considered decisive [Buchner and Rapp, 1898, 63], although Frau von Manassei'n herself drew from them and from others in which sugar solution was treated with heated yeast, but not under aseptic con- ditions, the conclusion that living yeast cells were not necessary for fermentation. Quite unsuccessful were also the attempts made to accomplish the separation of fermentation from the living cell by Adolf Mayer [1879, 192, p. 66], and, as we learn from Roux, by Pasteur himself, grinding, freezing, and plasmolysing the cells, having in his hands proved alike in vain. Extraction by glycerol or water, a method by which many enzymes can be obtained in solution, gave no better results [Nageli and Loew, 1878, 201], and the enzyme theory of alcoholic fermentation appeared quite unjustified by experiment. Having convinced himself of this, Nageli [1879, 200] suggested a new explanation of the facts based on molecular-physical grounds. According to this view, which unites in itself some of the conceptions of Liebig, Pasteur, and Traube, fermentation is the transference of a state of motion from the molecules, atomic groups, and atoms of the compounds constituting the living plasma of the cell to the ferment- able material, whereby the equilibrium existing in the molecules of the latter is disturbed and decomposition ensues [200, p. 29]. This somewhat complex idea, whilst including, as did Liebig’s theory, Stahl’s fundamental conception of a transmission of a state of motion, satisfies Pasteur’s contention that fermentation cannot occur without life, and at the same time explains the specific action of differ- ent organisms by differences in the constitution of their cell contents. The really essential part of Nageli’s theory consisted in the limitation of the power of transference of molecular motion to the living plasma.
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