KLUYVER S CONTRIBUTIONS TO MICROBIOLOGY AND BIOCHEMISTRY 



plete disappearance of the gas. Pertinent tests revealed that this phe- 

 nomenon, again encountered only with Sch. pombe, was associated with 

 the development of an alkaline reaction in the fermented samples. The 

 alkali production could then be traced to the hydrolysis of urea by the 

 yeast. Thus it was ascertained that this species is unique among yeasts 

 in that it can ferment malic acid and possesses a strong urease activ- 

 ity as well. 



The numerous experiments carried out in preparation for the develop- 

 ment of the method of biochemical sugar determinations had revealed 

 several regularities in the fermentation patterns of different yeasts. 

 These can be summarized as follows: 

 /. Under anaerobic conditions yeasts can ferment only certain hexoses 



and oligosaccharides; pentoses, for example, are not fermented. 

 2. A yeast that can ferment any sugar is always capable of fermenting 



glucose, fructose, and mannose. 

 j. A sucrose-fermenting yeast can also ferment rafhnose, and vice versa. 

 4. A maltose-fermenting yeast does not ferment lactose, nor can a lac- 

 tose-fermenting yeast ferment maltose. 

 But although these regularities had consistently turned up in the ex- 

 tensive series of tests, they did not appear to have general validity. 

 There were a number of reports in the literature indicating a contrary 

 behaviour of certain yeast species. None of these reports was, however, 

 based on studies carried out with the Van Iterson-Kluyver apparatus ; 

 and in his preliminary investigations Kluyver had become acutely 

 aware of the shortcomings - as well as of the merits - of different me- 

 thods for establishing the fermentative properties of yeasts. In order to 

 be in a sound position to evaluate the contradictory reports, Kluyver 

 therefore secured strains of all the yeasts for which a behaviour had 

 been claimed different from what he had observed, and these cultures 

 were subjected to a careful scrutiny, using a variety of methods. The 

 results will be discussed in some detail because this will provide an 

 opportunity to call attention to certain aspects of Kluyver's scientific 

 attitude. 



The relationship between the fermentation of glucose, fructose and 

 mannose by yeasts had been previously noticed. To Kluyver the situa- 

 tion seemed readily explicable in view of the closely similar stereo- 

 chemical configuration of these sugars and the ease with which they 



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