Alcoholic fermentation / by Arthur Harden.

  • Arthur Harden
Date:
1932
Catalogue details

Licence: In copyright

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

    106/258 page 96
    [see Neuberg and Kerb, 1913, 1] the universal presence of the enzyme in yeasts capable of producing alcoholic fermentation and the extreme readiness with which the fermentation of pyruvic acid takes place create a strong presumption that the decomposition of pyruvic acid actually forms a stage in the process of the alcoholic fermentation of sugar. This presumption is raised almost to a certainty by the work of Neuberg on the fixation method of fermentation in the presence of sulphites, which is discussed in Chapter VII. Ehrlich’s alcoholic fer- mentation of the amino-acids (p. 169) provides another function for carboxylase—that of decomposing the ^-ketonic acids produced by the deamination of the amino-acids. It must be remembered in this connection that carboxylase is not specific in its action, but catalyses the decomposition not only of pyruvic acid but also of a large number of other a-ketonic acids, including many of those which correspond to the amino-acids of proteins and are doubtless formed in the character- istic decomposition of these amino-acids by yeast. A comparison of the conditions of action of carboxylase and zymase has revealed many interesting points of difference, and there can be no doubt that carboxylase is an independent enzyme. Neuberg and Rosenthal [1913] have observed that the fermentation of pyruvic acid by maceration extract commences much more rapidly than that of glucose, and interpret this to mean that in the fermentation of glucose a long preliminary process occurs before sufficient pyruvic acid has been produced to yield a perceptible amount of carbon dioxide. The pyruvic acid fermentation is less affected by antiseptics [Neuberg and Karczag, 1911, 4 ; Neuberg and Rosenthal, 1913, 1914 ; Neuberg, 1915, 1] ; amounts of chloroform and of many other anti- septics [Neuberg and Ivanov, 1914] sufficient to stop the glucose fer- mentation brought about by yeast or dried yeast are usually without effect on the fermentation of the pyruvates either alone or in presence of boric or arsenious acid. Further, the action of carboxylase is not affected in the same way as that of zymase by solutions of emulsin or taka-diastase, boiled or unboiled [Lvov, 1912; Palladin, Gromov, and Monteverde, 1914] or by salts [Harden and Henley, 1921, 2]. The carboxylase, moreover, persists much longer than the zymase in macer- ation extract, when this is preserved in presence of antiseptics or at low temperatures [Neuberg and Rosenthal, 1914; Neuberg, 1915, 1] and in dried yeast [Neuberg, 1913, 3]. Extraction with methyl alcohol renders dried yeast incapable of fermenting sugars, but scarcely affects the carboxylase [Palladin, Gromov, and Monteverde, 1914].
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