KLUYVER S CONTRIBUTIONS TO MICROBIOLOGY AND BIOCHEMISTRY 



An extensive study of the properties of a large number of yeast 

 strains led to the selection of a limited group exhibiting the most de- 

 sirable patterns of sugar fermentation. It included two new isolates, 

 described in the thesis as Torula monosa and T. dattila, n. sp. ; like the 

 other members of the small collection both had been found to ferment 

 rapidly and completely glucose, fructose, and mannose. But T. monosa 

 appeared to be incapable of fermenting any other sugar, whereas T. 

 dattila could also ferment sucrose. The additional strains were chosen 

 because they could ferment one or more of the following sugars be- 

 sides the above-mentioned ones: galactose, maltose, lactose, melibiose, 

 and raffinose. 



For each of these strains the quantitative relationships between car- 

 bon dioxide production and amount of fermentable sugar were next 

 determined ; thus it was established that there existed a linear propor- 

 tionality between these quantities over a wide range of carbohydrate 

 concentrations, and that the absolute value of the relationship showed 

 slight but consistent differences between the individual cultures. In 

 this manner the requisite calibration data were obtained; once these 

 were available it was possible to compute the quantity of fermented 

 sugar from the amount of carbon dioxide evolved. Consequently the 

 quantity of glucose, fructose, and mannose combined could be esti- 

 mated from the amount of carbon dioxide produced by T. monosa; 

 sucrose from the extra carbon dioxide formed by T. dattila; maltose 

 from that evolved by Saccharomyces cerevisiae; and other sugars in like 

 manner from the results of fermentations with other yeasts. 



During this investigation it was further established that the raffi- 

 nose-fermenting yeasts can be divided into two categories ; one group 

 produces from the trisaccharide an amount of gas that corresponds 

 closely with two molecules of carbon dioxide per molecule of raffinose, 

 whereas the other liberates three times as much. The members of the 

 former category, in contradistinction to these of the latter, were shown 

 to be incapable of fermenting melibiose. Even closely related yeast 

 types, such as bottom- and top-yeast, both classified as S. cerevisiae, can 

 be readily distinguished on this basis; only the former ferments raf- 

 finose completely. 



The simplicity of the method, coupled with its great specificity, 

 made it eminently suitable for the purpose of quantitative determina- 

 tions of individual sugars in mixtures. Kluyver specifically studied a 



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