572 Pflan^enchemie. 



Harden, A. and R. V. Norris. The enzymes ofwashed 

 zymin and dried yeast (Lebedeff). II Reductase. (Bio- 

 chem. Journ. VIII. p. 100-106. Feb. 1914.) 



It has been suggested by Neuberg, Kostytscheff and von 

 Lebedeff, that the reduction of acetaldehyde to ethyl alcohol is 

 an essential step in the process of alcoholic fermentation: while the 

 work of Palladin and of Lvoff has shown that the presence of 

 glucose diminishes the reducing action of zymin on sodium selenite 

 or methylene blue (and vice versa) — one molecule of methylene 

 blue being equivalent to one molecule of glucose. 



On the other band the reduction of selenite or methylene blue 

 by living yeast is accelerated by the presence of glucose (see 

 Grüss 1908). 



The present paper is a record of experiments undertaken to 

 throw further light on the relation of the reducing ferment of yeast 

 to the enzymes concerned in alcoholic fermentation. 



The authors are led to the following conclusions as the result 

 of their experiments. 



1. The presence of a fermentable sugar favours the reduction 

 of selenite by living yeast but has little influence on the reducing 

 power of zymin unless the sugar is present in high concentration 

 (over 25Vo). when inhibition occurs. 



2. Sodium selenite in concentration of 0,58 per 100 c.c. almost 

 totally inhibits the fermentation of glucose by zymin and dried yeast. 



3. When dried yeast or zymin is washed with cold water it 

 loses its power of reducing methylene blue and sodium selenite 

 (and of fermenting sugar). 



4. The power of reducing methylene blue (but not the power 

 of producing alcoholic fermentation) is restored to such washed 

 preparations by the addition of bouillon and many aldehydes e. g. 

 salicylaldehyde, Benzylaldehyde, Anisaldehyde, Isovaleraldehyde 

 (but not Acetaldehyde, Quinol, Pyrogallol &c.). 



5. Addition of the boiled washings to these washed preparations 

 restores both the power of reducing methylene blue and of produ- 

 cing alcoholic fermentation. W. Neilson Jones. 



Harden, A. and S. S. Zilva. The enzy mes ofwashed zymin 

 and dried yeast (Lebedeff). III. Peroxydase, catalase, 

 invertase and maltase. fBiochem. Journ. VIII. p. 217 — 226. 

 June 1914.) 



The results of the experiments recorded in this paper may be 

 summarised, as follows. 



1. Fresh English brewery yeast contains active Peroxydase as 

 shown by its reaction with H2O2 and p-phenylediamine. 



2. When the yeast is dried for 17 hrs at 37° C it no longer 

 gives a Peroxydase reaction. On washing the dried yeast, however, 

 the presence of Peroxydase can be detected. Dried Munich yeast 

 (Schröder) behaves in a similar manner. 



3. The addition of the washings to washed dried yeast (or to 

 milk) inhibits the action of Peroxydase. 



4. Several other substances were found the addition of which 

 to washed, dried yeast inhibits the action of the Peroxydase e. g. 

 Beefbroth, Sodium lactate, Peptone and small traces of acids and 

 alkalies. 



