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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    of arsenious oxide was considerably in excess of the optimum con- centration, although Buchner ascribes the effect to the removal of some of the protective colloids of the juice, owing to the prolonged treatment to which it had been subjected. The extent of the action of arsenite appears from the following re- sults. In one case a rate of 17 c.c. was increased to 7 c.c. by 006 molar arsenite. In another experiment it was found that the optimum con- centration was 0-04 molar arsenite, the addition of which increased the rate three-fold. As in the case of arsenate the optimum concentration and the corresponding maximum rate of fermentation are considerably greater for fructose than for glucose. The relative rates produced by the addition of equivalent amounts of arsenate and arsenite (1 c.c. of 0-3 molar solution in each case to 20 c.c. of yeast-juice) were 27-5 and 3*1, the original rate of the juice being 17. In general the optimum concentration of arsenite is considerably greater than that of arsenate. The inhibiting effects of higher concentrations of arsenite and arsenate also present close analogies, but this most interesting aspect of the question has not yet been sufficiently examined to repay detailed discussion. Buchner [Buchner, E. and H., and Hahn, 1903, pp. 199- 205] suggested that the inhibition was due primarily to some change in the colloidal condition of the enzyme and showed that certain col- loidal substances appeared to protect it, as did also sugar. It seems most probable that the effect is a complex one, in which many factors participate. Nature of the Acceleration Produced by Arsenate and Arsenite. In explanation of the remarkable accelerating action of arsenates and arsenites two obvious possibilities present themselves. In the first place the arsenic compound may actually replace phosphate in the reaction characteristic of alcoholic fermentation, the resulting arsenic analogue of the hexosephosphate being so unstable that it undergoes immediate hydrolysis, and is therefore only present in extremely small concentration at any period of the fermentation and cannot be isolated. In the second place it is possible that the arsenic compound may ac- celerate the decomposition of the hexosephosphate of the juice, and thus by increasing the rate of circulation of the phosphate produce the permanent rise of rate. With this effect may possibly be associated a direct acceleration of the action of the fermenting complex. The experimental decision between these alternative explanations
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