A critical study of the conditions under which zymase and its associated co-enzyme bring about alcoholic fermentation

Zymase, the enzyme of yeast discovered in 1896 has since been proved by Harden and Young to consist of two parts, (1) zymase proper, an enzyme-like body possessed of high molecular complexity, non-diffusible and thermo-labile, and (2) a readily diffusible, thermo-stabile, relatively simple, chemical complex, which, for lack of a better term, has been designated as the co-enzyme of zymase.

Harden and Young separated the bodies in question by diffusion, but owing to the paucity of their materials and the destructive effect exerted by secondary causes during the lengthy process involved, it was found impossible to obtain any clear insight into the conditions of physico-chemical equilibrium obtained in this reaction. Buchner's dauerhefe, that is to say, a preparation of pressed yeast precipitated by an excess of acetone or alcohol ether, can be prepared in large quantities and exhibits a high degree of resistance to the action of destructive enzymes. We therefore directed our attention to the preparation of dauerhefe containing as large a zymase content and as small a co-enzyme content as possible, our object being to study the effect exerted by a preparation of this nature upon fermentable sugars, when used in conjunction with varying proportions of a boiled yeast extract containing co-enzyme. It was found possible to produce a preparation of acetone dauerhefe which in itself alone possessed no fermentative activity whatsoever, but which when used in conjunction with a suitable quantity of boiled yeast extract, exhibited an unusually active fermentation, 2 grams mixed with 6 grams of sugar and 20 c.c. of extract producing from 1 to 2 grams of CO₂ in the course of 8 to 10 days.