kluyver's contributions to microbiology and biochemistry 



2. The formation of acetic acid from carbon dioxide and hydrogen 

 by Clostridium aceticum, which Wieringa [1936, 1940] had discov- 

 ered during a study of the utilization of hydrogen gas by micro- 

 organisms under anaerobic conditions. 



3. The assimilation of carbon dioxide during the fermentation of 

 glycerol by propionic acid bacteria, observed by Wood and Werk- 

 man. This observation led to the recognition that many cell types 

 can catalyze such a process in which carbon dioxide is condensed 

 with a three-carbon compound, resulting in the formation of four- 

 carbon dicarboxylic acids ; this has become the basis on which the 

 production of succinic acid in various fermentations is best explained. 

 This, too, must have come as a complete surprise to Kluyver who 

 until then had defended the thesis that the formation of succinic 

 acid during the anaerobic decomposition of sugars and related com- 

 pounds could only be attributed to an initial cleavage of hexose 

 into a two- and a four-carbon fragment, a possibility first suggested 

 by Virtanen. The reasoning followed by Kluyver is of sufficient 

 general interest to warrant a brief discussion. 



Kluyver started from the premise that there were only two alternative 

 mechanisms that could account for the formation of succinic acid ; in 

 addition to the one suggested by Virtanen and mentioned above, 

 there was the reaction proposed by Thunberg and Wieland which 

 involved a condensation of two molecules of acetic acid with the 

 simultaneous elimination of two hydrogen atoms : 



HOOC • CH 3 + H 3 C • COOH -> HOOC • CH 2 • CH, • COOH+ 2H 



This mode of formation had, however, been ruled out by the following 

 argument. If the primary degradation of a hexose molecule invariably 

 yields two triose moieties, then all products with two carbon atoms 

 and their derivatives should be accompanied by an equimolar amount 

 of one-carbon products which, in fermentations, are generally rep- 

 resented by formic acid and carbon dioxide. Now, the results of 

 quantitative analyses of fermented sugar solutions invariably showed 

 that, whenever succinic acid was encountered among the products, 

 there was a marked deviation from the required ratio of two- and 

 one-carbon products in favour of the former. This was considered 

 sufficient to dismiss the Thunberg- Wieland mechanism as a possible 

 source of the dicarboxylic acid. 



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