NATURE 



385 



THURSDAY, AUGUST 27, 1903. 



ALCOHOLIC FERMENTATION. 

 Die Zymase gar ung Untersuchungen iiber den Inhalt 

 der Hefezellen und die biologische Seite des 

 Gdrungsproblems. By Eduard Buchner, Hans 

 Buchner, and Martin Hahn. Pp. viii + 416. 

 (Miinchen : Oldenbourg.) Price 12 marks. 



IN the preface to this book, written by Profs. Eduard 

 Buchner and Martin Hahn, credit is given to the 

 late Prof. Hans Buchner for the general scheme of 

 arrangement which has been carried out after his 

 death by the other authors. 



There are four parts to the treatise; the first, by 

 Prof. Eduard Buchner, entitled " Uber die Zymase- 

 garung," occupies nearly three-quarters of the entire 

 I book, and deals with the important researches of this 

 \ author and others on the soluble ferment first separ- 

 ated by him from yeast-cells and called zymase, the 

 I ferment which induces alcoholic fermentation of 

 * sugar. 



I His original papers on the subject have appeared in 

 ' contributions to scientific journals since the end of 

 1896, and are now presented in book form. 



After a brief historical review of the development 

 of" ideas on the subject of alcoholic fermentation, and 

 a comparison of Liebig's and Pasteur's theories with 

 regard to this process, he discusses the nature of 

 " zymase," which he brings into the category of the 

 enzymes, or soluble ferments. A very full and com- 

 plete account is given of the method of preparing 

 " active " yeast-juice, the main steps of which are now 

 familiar to all students of the subject. Especial stress 

 is laid on the powdering of the yeast-cells with quartz 

 sand in order to break up the cell-membranes. With- 

 out this, no amount of pressure avails for getting 

 active juice from the cells, while, after breaking the 

 cells, comparatively little pressure will give some 

 active juice, increase of pressure increasing both the 

 activity and the yield. The activity of yeast-juice, 

 i.e. its capacity for inducing the alcoholic fermentation 

 of sugar, varies with different species of yeasts ; no 

 conclusion as to richness in zymase can be drawn 

 directly from observed variations in activity, as yeast- 

 juice contains, besides several previously discovered 

 ferments, one, endotryptase, which digests and 

 destroys zymase, and this is present in very variable 

 amounts in the different yeasts. Juices also of very 

 different activity are obtained from different batches of 

 the same variety of yeast. These differences are partly 

 explained by the action of endotryptase on zymase. 



The method of determining the " activity," depen- 

 dent as it is on these conflicting factors, is fully de- 

 scribed, and consist^ in the estimation of the quantity 

 of carbon dioxide formed in a given time under 

 ' standard conditions. 



When the juice is collected in fractions, the first 

 fraction that is pressed out shows least activity, and 

 the activity increases with successive fractions to the 

 last, so that methods which give a small yield may 

 also give juice of relatively small activity. The most 

 active juice is much less active than fresh yeast, and 

 NO. 1765, VOL. 68] 



the explanation is that in fermentation with the latter 

 there is always a fresh production of zymase. The 

 so-called self-fermentation of yeast-juice is fully dis- 

 cussed, and shown to be a function of the glycogen 

 content. Some interesting results are recorded in th« 

 fermenting of sugars other than glucose. For in- 

 stance, glucose and fructose are fermented equally 

 fast by the yeast-juice, whereas fresh yeast ferments 

 glucose the more quickly. The author explains this 

 as due to the fructose having a lower rate of diffusion 

 into the yeast-cell. Similarly, glycogen was fer- 

 mented by yeast-juice obtained from yeast which, in 

 the fresh state, did not ferment this carbohydrate, the 

 explanation being that the glycogen cannot diffuse 

 through the cell-membrane. The experimental proof 

 that the juice can ferment glycogen is an interesting 

 confirmation of what has been induced theoretically, 

 viz. that any cell which can synthesise glycogen must 

 be capable also of hydrolysing it, at least intra- 

 cellularly. It explains the phenomenon of "self- 

 fermentation," and accords with the new theory of 

 the reversible action of ferments. 



The discussion on the mode of action of antiseptics 

 is interesting, but not always convincing. As regards 

 chloroform, the hypothesis is adopted that living cells 

 are subdivided into separate workshops by partitions 

 of cholesterin (Overton), which the author thinks may 

 be injured by the drug and thus allow of a mingling 

 of substances which ought to be kept apart. He gives 

 the impression that chloroform is a substance almost 

 inert towards ferments, for which, therefore, some 

 mechanical action on living cells is to be sought. 

 Qhloroform is, however, certainly not without action 

 on ferments, and affects some much more than others ; 

 the maltase of yeast, for instance, is distinctly affected 

 by it, and it may be that some ferment essential to. 

 cell-growth and multiplication is extremely sensitive 

 to it. It is difficult to estimate at all quantitatively 

 from his experiments the sensitiveness of zymase to 

 such antiseptics, on account of the unknown factor of 

 their action on endotryptase. This also applies to the 

 experiments on the action of added alcohol ; expt. 4256 

 especially suggests that the alcohol has no negligible 

 effect on endotryptase. The experiments with 

 arsenites are interesting, and give food for reflection 

 to physiologists and physicians alike. 



The quantitative fermentation of cane sugar in con- 

 centrated solution by zymase was attempted, but the 

 yield of COj and alcohol was always less than the 

 calculated amount, and the author considers and dis- 

 cusses several possible explanations of the pheno- 

 menon. In this connection he touches on cases of 

 zymo-hydrolysis where incompleteness has been traced 

 to the action of the hydrolytic products, but does not 

 clearly distinguish between a direct paralysing action 

 of one of the products on the enzyme, such as was 

 found by Taumann in the hydrolysis of amygdalin by 

 emulsin, and a slowing down due to mass-action of 

 the products, a consequence of the reversible nature 

 of enzyme-action, and occurring only on the approach 

 of chemical equilibrium in the system on which the 

 enzyme acts. The fermentation residue was examined 

 for cane sugar with a negative result, but not for a 

 reversion sugar. The author, however, hopes to 



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