kluyver's contributions to microbiology and biochemistry 



triose, pyruvic acid, and acetaldehyde. This not only revealed the fund- 

 amental similarity and interrelations between the diverse fermenta- 

 tions, but it further suggested that these reaction types might also ac- 

 count for some peculiar phenomena, incidentally discovered during 

 studies on fermentations under special conditions, but never before in- 

 tegrated with the normal fermentation patterns. Notably the 'phyto- 

 chemical reductions' belonged to this category. Neuberg had coined 

 this term to designate collectively the reduction of such utterly un- 

 related and 'foreign' substances as, e.g., sulphur, methylene blue, or 

 nitrobenzene, yielding hydrogen sulphide, leuco-methylene blue, or 

 aniline, when the former were added to a sugar solution undergoing 

 fermentation by yeast. It now seemed reasonable to interpret such 

 reductions as the result of alternative regeneration reactions of proto- 

 plasm, the added substances competing with acetaldehyde which nor- 

 mally is exclusively involved in the regeneration process. This concept 

 suggested the general possibility of deliberately steering the fate of a 

 particular intermediate product into channels not ordinarily followed, 

 bv creating special conditions during a fermentation that would inter- 

 fere with the conventional reactions. A direct experimental verifica- 

 tion was provided by experiments that were based on the fact, shown 

 by Neuberg and Reinfurth in 1923, that yeast produces acetyl methyl 

 carbinol if acetaldehyde is added to a fermenting sugar solution. The 

 carbinol is not a normal product of alcoholic fermentation, presum- 

 ably because in this process the sole regenerating reaction involves the 

 quantitative reduction of aldehyde to ethanol. But this should imply 

 that under conditions that bring into play additional regeneration 

 reactions, such as the 'phytochemical reductions', the aldehyde should 

 partly escape reduction; and this fraction should therefore undergo 

 a condensation to carbinol, which in turn might be further reduced 

 to 2,3-butylene glycol. Appropriate experiments with yeast-sugar mix- 

 tures to which methylene blue or sulphur had been added yielded the 

 expected results. Subsequently Kluyver, Donker, and Visser 't Hooft 

 [1925] showed that aeration of a yeast suspension in a sugar solution 

 also gave rise to carbinol production; this result was anticipated be- 

 cause it seemed likely that a regeneration of protoplasm could also be 

 accomplished by a reaction of 'protoplasm-H 2 ' with oxygen. 



Similarly those representatives of the true lactic acid bacteria in the 

 sense of Orla-Jensen that normally produce, in addition to lactic acid, 



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