260 MICRO-ORGANISMS AND FERMENTATION. 



and many possess no inverting ferment (Mycoderma cerevisice, 

 Torulas, and Sacch. apiculatus). 



II. The Torula novae carlsbergice, and a few of the species 

 isolated by Will, ferment maltose. One species (Monilia 

 Candida) resembling Torula ferments maltose, as well as both 

 saccharose and dextrose. It contains no inverting enzyme 

 soluble in water. 



The lactose-fermenting Saccharomyces and Torulas demand 

 a special classification. 



When we consider the behaviour of these fungi in the 

 fermentation industries, it is at once seen that it is only in the 

 genus Saccharomyces that species occur which rapidly and 

 vigorously ferment maltose. The yeasts for breweries and 

 distilleries must, therefore, be selected from the true Saccharo- 

 mycetes. The non-Saccharomycetes, the great majority of 

 which cannot ferment maltose, are scarcely capable of playing 

 any important part in these industries ; on the other hand, 

 they may be employed in the manufacture of wines from grapes, 

 currants, and other fruit, since several are able to induce just 

 as vigorous a fermentation in solutions of dextrose and invert 

 sugar as the Saccharomycetes. 



It is, therefore, of the utmost importance that a suitable 

 species should be selected. 



Amongst the carbohydrates synthetically prepared by E. 

 Fischer, isomaltose may be mentioned. For some time it has 

 played a great part in the literature of the subject. As is 

 well known, he discovered this sugar in the products of the 

 reaction at a low temperature of hydrochloric acid on grape 

 sugar, and it received the name of isomaltose because it 

 appeared to have a constitution similar to that of maltose. 

 The sugar is known only in the form of an osazone. Even the 

 existence of Fischer's isomaltose has been questioned, because 

 it was regarded as impure maltose. By a fresh investigation, 

 however, Fischer succeeded in proving biologically that this 

 sugar is sharply distinguished from maltose by the fact that 

 isomaltose is neither fermented by fresh yeast nor split up by 

 the enzymes of yeast, and he asserts that it is only possible to 

 differentiate with certainty between the two sugar species in 

 this way. 



