BIOGRAPHICAL MEMORANDA 



Furthermore, the butane diol fermentation could also be modified 

 so as to yield acetyl methyl carbinol instead of the glycol as a major 

 end product. Scheffer, in Kluyver's laboratory, had shown that this 

 can be accomplished by a proper aeration of Aerobacter cultures in 

 sugar media; this apparently prevents the reduction of the primarily 

 formed carbinol to a large extent, so that under these conditions it can 

 accumulate in significant amounts during the fermentation. Now, 

 acetyl methyl carbinol had been noted as a regular component of 

 wine vinegar by Visser 't Hooft [1925a, 1925b, 1925Tb] in Kluyver's 

 institute ; and he had also shown that its concentration in vinegar can 

 be used as an excellent index of the quality of this condiment. Even 

 more important was the fact that, in 1927, Kluyver and co-workers 

 had identified the substance principally responsible for the character- 

 istic and delicate flavour of high-grade butter as diacetyl, which also 

 appears to be an important flavouring ingredient of many another 

 food product [Kluyver, Van Niel and Derx, 1929a, 1929b]. The ready 

 convertibility of acetyl methyl carbinol into diacetyl, either by means 

 of a purely chemical oxidation or, even better, with the aid of A. suboxy- 

 dans, thus emphasized the potential usefulness of the butylene glycol 

 fermentation for several different purposes. 



When, after the first decade of Kluyver's directorship of the Delft 

 laboratory, the most important microbial sugar fermentations had 

 been surveyed, he could begin to pay special attention to the metab- 

 olic activities of various moulds, also briefly mentioned in the inau- 

 gural address. These often lead to the production of organic acids, 

 notably gluconic, fumaric, and citric acids, although the fundamental 

 mechanism whereby these substances are formed were not clearly 

 understood. It could thus be expected that a better comprehension of 

 this type of metabolism might permit the industrial microbiologist to 

 use conditions which improved the yield of these particular com- 

 pounds, or which might be conducive to making the production of 

 some other substances, sometimes formed in very small quantity, 

 economically feasible. Apart from this the insight gained into metab- 

 olic reactions generally might be considerably increased by such a 

 study of oxidative processes. 



From the beginning it was evident that a commercially useful 

 aspect of mould metabolism is that which is characterized by an in- 

 complete oxidation of the substrate. Furthermore, the large number 



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