BIOGRAPHICAL MEMORANDA 



investigated to some extent belongs in the realm of vitamin require- 

 ments by yeasts, the impure maltose being the source of such sub- 

 stances. That Kluyver did not further pursue the problem can easily 

 be understood if it be remembered that the main object of the thesis 

 was the development of a satisfactory method for quantitative sugar 

 determinations. And, although the problem posed by the experiments 

 of Rose, of Lindner and Saito, and of Kita had to be disposed of in 

 order to provide a solid foundation for an interpretation of the sugar 

 fermentation data, it was certainly not necessary for Kluyver to at- 

 tempt a chemical characterization of the impurities that exerted so 

 marked an effect on yeast growth ; it was quite sufficient to show that 

 maltose itself could not be assimilated under conditions where glucose 

 is not. 



This much may be granted. But it does not account for a curious 

 omission in rounding out this investigation, and it is interesting to 

 speculate on the significance of this fact. Kluyver had demonstrated 

 that recrystallized maltose is not assimilated, and that the original 

 preparation contained an alcohol-precipitable impurity; he had as- 

 cribed to this impurity the striking effect of maltose on yeast growth. 

 Now it must be evident that a simple experiment could have provided 

 direct support for this hypothesis; it would have consisted in testing 

 the growth of yeasts that responded in the characteristic fashion to the 

 impure maltose also in asparagine media with glucose, supplemented 

 with the flocculent precipitate. There is, however, no indication in 

 Kluyver's publication that this logical experiment was ever perform- 

 ed. Does this imply that he had overlooked so obvious and simple a 

 check? Not necessarily; it is at least equally probable that the experi- 

 ment was carried out but, contrary to expectation, had yielded neg- 

 ative results. On the basis of present-day knowledge of yeast nutrition 

 such a negative result could be predicted with a high degree of proba- 

 bility, because it is almost certain that vitamins of the B-group were 

 involved as growth factors for the yeasts under investigation. It is 

 quite reasonable to suppose that these substances were present in the 

 impure maltose. Evidence to this effect is also furnished by the fact 

 that Kluyver failed to observe an improvement of yeast growth in 

 Hayduck's medium with glucose to which o. i per cent 'Witte' peptone 

 had been added. Now the B vitamins would not have been found in 

 the alcohol-precipitable fraction; hence this material, too, would have 



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