DISACCHARIDES 



109 



a number of similar disaccharides and glucosides have been 

 synthesized. The two sugars, sucrose and maltose, have, 

 however, so far resisted all attempts at their synthesis by 

 enzymes, although both have been synthesized by chemical 

 means.* 



{b) Fermenting Enzymes. — Contrary to the assertion of 

 Fischer that disaccharides are not attacked by yeasts until 

 they have been hydrolysed by the appropriate enzyme con- 

 tained in the yeast, Willstatter f concluded that both maltose 

 and lactose are directly fermentable, since he was able to effect 

 fermentation of these by distillery yeasts which contained 

 only very little maltase and were entirely free from lactase. 

 The fact that Saccharomyces Marxianus, which is known to 

 be free from maltase, is unable to ferment maltose, he attributes 

 to its not possessing a maltozymase rather than to any 

 deficiency in maltase. 



CANE SUGAR, SUCROSE OR SACCHAROSE. 

 Occurrence. 



Cane sugar is one of the most widely distributed substances 

 to be found in the vegetable kingdom. Besides forming about 

 20 per cent of the juice of the sugar cane, Saccharum officinaruni, 

 and about 10-20 per cent of that of the beetroot, it is found 

 in varying quantities in the wood of m.aple and birch, and in 

 Sorghum saccharatum ; it occurs, moreover, in wheat, maize, 

 barley, in carrots, and in madder root. In most sweet fruits 

 it is found together with a greater or lesser quantity of dextrose 

 and levulose, which may possibly have been formed from it 

 by hydrolysis. It also is found in the leaves of many plants 

 associated with glucose and maltose. The following table, 

 compiled by Kulisch, gives the relative proportions of cane 

 sugar and hexoses found in various fruits. 



Pineapple . 

 Strawberry . 

 Apricot 

 Ripe banana 

 Apple 



* Pictet : " Bull. Soc. Chim.," 1920 

 "Compt. rend.," 1928, 186, 727. 



t Willstatter : " Zeit. physiol. Chem., 



