BIOGRAPHICAL MEMORANDA 



number of applications ; he showed, for example, that it can be used 

 to distinguish sharply between commercial jams and preserves pre- 

 pared with the addition of sucrose, and of potato- or corn-sugar, re- 

 spectively. This rests on the fact that the latter materials, produced 

 by an enzymatic hydrolysis of starch, contain a high and reasonably 

 uniform percentage of maltose, so that from the quantities of carbon 

 dioxide produced by T. monosa (sucrose and maltose negative), T. dat- 

 tila (sucrose positive, maltose negative), and S. cerevisiae (sucrose and 

 maltose positive), respectively, the amounts of hexoses, sucrose, and 

 maltose can be computed. A similar application was later developed 

 by Den Dooren de Jong for the determination of lactose in bread; 

 this permitted a ready detection of falsification of 'premium bread' 

 which, according to the Dutch pure food laws, must be prepared 

 with the addition of a specified minimum amount of milk to the 

 dough. The constant lactose content of milk, together with the 

 inability of baker's yeast to ferment this sugar, imply that the quan- 

 tity of lactose in 'premium bread' is rigorously determined by the 

 amount of milk added. The simple and specific estimation of lactose 

 by the fermentation method thus provides an accurate check. It may 

 be mentioned that in his thesis Kluyver had already hinted at the ap- 

 plication of lactose-fermenting yeasts for the analysis of milk products. 

 Kluyver used his method also for the determination of the specific 

 sugars present in glucosides ; in leaves after periods of photosynthesis 

 or storage in darkness; in germinating seeds and various other plant 

 products; and in urine and blood. During these studies two unusual 

 features of one particular yeast were discovered. The established pro- 

 duction of carbon dioxide from pyruvic acid by yeasts led Kluyver to 

 investigate the possibility that other acids, especially those generally 

 encountered in fruits, might also yield carbon dioxide under the in- 

 fluence of certain yeasts. In these experiments it was found that 

 Schizosaccharomyces pombe does, in fact, decompose malic acid under 

 anaerobic conditions, provided a fermentable sugar is simultaneously 

 present. The fermentation of malic acid can then be expressed by the 



equation: 



C 4 H 6 5 -> 2 C0 2 +C 2 H 5 OH 



In experiments on the fermentations in sugar-containing urine samples 

 by various yeasts the observation was made that an initial carbon di- 

 oxide production was occasionally superseded by the eventually com- 



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