74 



CARBON NUTRITION 



300 



200 



&0 



E 

 x: 



Dp 

 <D 



100 



Glucose + 

 fructose 



Time, days 



Figure 1. The growth of Schizolhecium longicolle on disaccharides and on equiva- 

 lent mixtures of their constituent hexoses. From tabular data of Lilly and Barnett 

 (116). 



2. The rate of growth of a lactase-rich mycelium on lactose is 

 demonstrably higher than that of a lactase-poor mycelium (112). 



3. Fungi which cannot use a disaccharide have been shown to use 

 its constituent monosaccharides (Figure 1). That is, the only bar to 

 utilization appears to be inability to convert the compound sugar to 

 hexoses. 



It is often held that direct utilization of oligosaccharides, without 

 prior splitting of the glycosidic bond, occurs in fungi. Data cited in 

 support of this claim include (1) quantitative superiority of a di- 

 saccharide to its constituent monosaccharides (78, 82), (2) differences 

 in metabolic processes during disaccharide and monosaccharide utiliza- 

 tion (52, 145), and (3) utilization of a disaccharide by intact cells at a 

 pH at which the corresponding hydrolytic enzyme is inactive in vitro 

 (141). All of these phenomena, however, can be explained without 

 recourse to the hypothesis of direct utilization; some of the problems 

 as they have been studied in yeast are reviewed by Hestrin (83, 84). 



