THE CHEMICAL PROCESSES IN PLANT RESPIRATION 13I 



The formation of such important amounts of aldehyde is 

 really due to the fact that the acetaldehyde is removed from the 

 system of coupled reactions in the form of the bisulphite com- 

 pound. Consequently the active hydrogen does not reduce 

 the acetaldehyde but reduces an unidentified substance to 

 glycerine. Neuberg and his coworkers^ have shown that all 

 aldehydes studied by them could be reduced by yeast. 



An accumulation of acetaldehyde also results from the 

 random choice of active hydrogen by suitable acceptors,^ 

 whereat the greater part or even all of the acetaldehyde is 

 changed to acetic acid and alcohol or to ethyl acetate by the 

 Cannizzaro reaction. The same process takes place if alcoholic 

 fermentation proceeds in a weakly alkaline medium.^ The 

 more recent discovery of Abderhalden,^ that a fermentation of 

 sugar to acetaldehyde and glycerine by yeast takes place in the 

 presence of animal charcoal, is very interesting. 



Such varied proofs of the formation of acetaldehyde by 

 alcoholic fermentation, and its liability of reduction to ethyl 

 alcohol by yeast hardly leaves room for any doubt but that 

 acetaldehyde is an intermediate of alcoholic fermentation. 

 Kostychev^ has already assumed that acetaldehyde comes from 

 pyruvic acid. Grab^ showed that pyru\dc acid is probably 

 formed as follows in alcoholic fermentation: he proved that the 

 addition of /3-naphthylamine to fermenting yeast juice effects 

 the formation of methyl naphtho-cinchoninic acid. The 

 process cannot be explained except by the reaction of naph- 

 thylamine, pyruvic acid and acetaldehyde, for the following 

 reaction is characteristic of pyruvic acid:^ 



1 Neuberg, C. und Steenbock. Biochem. Z. 52: 494- I9i3; 59= 188. 1914; Neuberg, 

 C. urd F. Nord. Ibid. 67: 24. 1914; Neuberg, C. und Schwenk. Ibid. 71: 114. 1915; 

 Mayer, P. und C. Neuberg. Ibid. 71: 174. 1915; and others. 



- Kostytschew, S. Z. f. physiol. Chem. 83: 93- I9i3- 



3 Wilenko, G. Z. f. physiol. Chem. 98: 255. 1917; 100: 225. 1917; Oelsner, A. und 

 A. Koch. Ibid. 104: 175. 1919: Neuberg, C. und J. Hirsch. Biochem. Z. 100: 304. 

 1919; Neuberg, C, J. Hirsch und E. Reinfurth. Ibid. 105: 307. 1920. 



< Abderhalden, E. Fermentforschung. 5: 89, 255. 1921-22; 6: 162. 1922; Abder- 

 halden, E. und Fodor. Ibid. 5: 138. 1919; Abderhalden, E. und S. Glaubach. Ibid. 6: 

 143. 1922; (however see Warburg, loc. cit. for consideration of the possible effect of impuri- 

 ties in the charcoal]. 



5 Kostytschew, S. Ber. d. chem. Ges. 45: 1289. 1912; Z. f. physiol. Chem. 79: 130. 

 1912. [C/. F. F. Nord. Chem. Rev. 3 : 41-79. 1926 for an English resume of the chemistry 

 of fermentation in which acetaldehyde is given a prominent place.] 



8 Grab, M. v. Biochem. Z. 123: 69. 1921. 



' Dbbner. Ann. d. Chem. 242 : 291. 1887; 281:1. 1894- 



