BIOGRAPHICAL MEMORANDA 



carbon dioxide, acetic acid, ethanol, and glycerol, and had therefore 

 been designated as 'heterofermentative' by Kluyver and Donker to 

 distinguish them from the 'homofermentative' members that yield 

 only lactic acid, could be induced to form acetyl methyl carbinol by 

 cultivating them in fructose solutions. Such a behaviour had been 

 anticipated as a consequence of the fact that the heterofermentative 

 lactic acid bacteria were known to produce mannitol in fructose-, 

 but not in glucose media. This mannitol formation could be considered 

 as a particular case of a phytochemical reduction, and its occurrence 

 would again prevent an equivalent reduction ofacetaldehyde with its 

 consequent condensation to carbinol. 



Thus the sugar fermentations by different organisms had been inter- 

 preted as the net result of a small number of interrelated step reactions. 

 The dynamic nature of these processes had been emphasized by show- 

 ing that the fermentation pattern is not fixed but can be modified as 

 a result of changes in the environmental conditions, and support for 

 at least some of the postulated events had been provided by ingeni- 

 ously contrived experiments. 



But even in the first paper the analysis had already progressed well 

 beyond this point. The impetus to a further extension had been the 

 earlier mentioned investigation of the vinegar bacteria. Ever since 

 1913 Wieland had advocated the idea that the oxidation of ethanol to 

 acetic acid by these organisms should be interpreted as a mechanism 

 involving primarily the transfer of hydrogen atoms from the oxidation 

 substrate, ethanol, and subsequently from its first oxidation product, 

 acetaldehyde (in its hydrated form), to oxygen. The discovery of the 

 various incomplete oxidations performed by A. suboxydans had con- 

 vinced Kluyver that Wieland's theory was equally applicable to these 

 oxidations. Hence, when it appeared that some of the central reactions 

 in fermentations could be regarded as dehydrogenations of inter- 

 mediate products by protoplasm, it logically followed that Wieland's 

 concept could also be invoked to account for these processes, and that 

 the subsequent regeneration reactions of the reduced to the oxidized 

 form of protoplasm, too, were essentially similar in nature. Thus, not 

 only the oxidations characteristic of the acetic acid bacteria, and, by 

 extrapolation, all other biological oxidations, but even the majority 

 of the step reactions in fermentations could be interpreted as specific 



