Fermentation by Living Yeast.
Much important information as to the nature of the processes involved in fermentation has been acquired by the direct experimental study of the action of living yeast on different sugars.
This phenomenon has formed the subject of several investigations from the kinetic point of view, and its general features may now be regarded as well established.
The difficulty, which must as far as possible be avoided in quantitative experiments of this sort with living yeast, is the alteration [p128] in the amount or properties of the yeast, due to growth or to some change in the cells. This has been obviated in the work of Slator [[1906]] by determining in every case the initial rate of fermentation, so that the process only continues for a very short period, during which any change in the amount or constitution of the yeast is negligible. The method has the further advantage that interference of the products of the reaction is to a large extent avoided. The pressure apparatus already described (p. [29]) was employed by Slator, the rate of production of carbon dioxide being measured by the increase of pressure in the experimental vessel.