Ferments and their actions / by Carl Oppenheimer ; Translated from the German by C. Ainsworth Mitchell.

Date:
1901
Catalogue details

Licence: In copyright

Credit: Ferments and their actions / by Carl Oppenheimer ; Translated from the German by C. Ainsworth Mitchell. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    The velocity of the enzymic decomposition of polysaccharides does not stand in any constant relation to the velocity of alcoholic fermentation, but, on the contrary, this relation varies greatly in different species of yeast.1 Physical Conditions of Alcoholic Fermentation.—Alcoholic fermentation proceeds best at about 25° C., but the optimum temperature varies with the external conditions. Even below 53° 0. the fermentation ceases; in bottom fermentations sometimes as low as 38° 0., though, on the other hand, it still occurs at about 0° C. The optimum tempera- ture differs in the case of top- and bottom-fermentation yeasts.2 Dry yeast resists enormous variations of temperature, from - 113° C. (Bert3) to about 100° C. According to Dumas4 the duration of the fermentation is approximately proportional to the amount of sugar present; according to A. Brown,5 however, this only holds good for con- centrations of 10 to 12 per cent. In the case of higher and lower degrees of concentration less is fermented. Cochin6 has measured the time occupied by it by continuously determining the quantities of carbon dioxide evolved. He found that the fermentation first began after ten to twenty minutes, which was attributed to the slow diffusion through the membranes of the cell. A. Brown 5 then plotted the curve of the evolution of the gas, and found that it differed considerably from the curve of ordinary chemical decompositions. According to Brown (ioc. cit.) and Gayon and Dubourg,7 diffusion plays but a very slight part, if any at all, since the sugar is not fermented in pro- portion to its diffusibility. We cannot deal with the influence of other physical and chemical agents until we come to the biological side of our subject, since this question is inseparable from the consideration of the biological significance of these agents. The Evolution of Heat in Alcoholic Fermentation.—In the simple enzymic processes we had no need to trouble about a consideration of the thermodynamic relations. In that case we had to deal with hydrolytic decompositions, which were also effected by chemical agents, and in which the thermic conditions 1 Hiepe, referred to by Duclaux, Ann. Inst. Past., xi., 348, 1897. 2 A. Mayer, loc. cit., 149. 3 Bert, Comptes Rendus, lxxx., 1579. 4 Dumas, Ann. Chim. Phys. [5], iii., 57, 1874. 5 A. Brown, Joum. Chem. Soc., lxi., 369, 1892. 6 Cochin, Comptes Rendus, cx., 865, 1890. 7 Gayon and Dubourg, Comptes Rendus, cx., 865, 1890.