ALCOHOLIC FERMENTS. 167 



produced turbidity : in weakly fermented Danish high-fer- 

 mentation beers there occurred Torula species with the 

 same properties. 



PICHI has recently detected disease-yeasts in wine. 



Just as mould-fungi exhibit a different behaviour towards 

 the various carbohydrates (see Penicillium, Mucor, Monilia), 

 so the different Saccharomyeetes and allied fungi have been 

 shown by HANSEN'S comprehensive investigations to exhibit 

 pronounced characteristics in the same direction. In addition 

 to the true Saccharomyeetes we shall review Mycoderma cere- 

 visice, Sacch. apiculatus, the Torula forms, and Monilia. 



HANSEN studied the behaviour of a large number of yeasts 

 towards the four carbohydrates saccharose (cane-sugar), maltose, 

 lactose, and dextrose. 



His six species of Saccharomyeetes (Sacch. ceremsice 1., Sacch. 

 Pastorianus I., II., and III., Sacch. ellipsoideus I. and //.) 

 behave as follows : They all develop invertase ; they convert 

 cane-sugar into invert-sugar, which they then ferment ; they 

 ferment maltose and dextrose, but not lactose. All the bottom- 

 yeasts used in practice show the same behaviour towards these 

 four sugars. 



Sacch. Marxianus, Sacch. Ludwigii, and Sacch. exiguus do not 

 ferment maltose and lactose ; they invert saccharose and 

 ferment nutritive solutions of invert-sugar and dextrose. 1 



Sacch. membranwfaciens and Mycoderma cerevisice can neither 

 invert nor ferment these four carbohydrates. 2 



Sacch. apicidatus does not invert saccharose, and of the four 

 sugars mentioned, it only ferments dextrose. It therefore only 

 induces a feeble alcoholic fermentation in beer-wort. 



Amongst the Torula forms examined by HANSEN there are 

 many which do not secrete invertase, do not ferment maltose, 

 and only yield about 1 per cent, of alcohol (by volume) in 

 beer-wort. Other species invert saccharose. In nutritive 



1 According to EMIL FISCHER, maltose is not fermented directly, but is first 

 inverted by a particular enzyme. Thus, most known species of Saccharo- 

 myeetes contain both the enzyme inverting cane-sugar and that inverting 

 maltose. In the three species, S. Marxianus, S. Ludwigii, and S. exiguus, on 

 the other hand, only the enzyme which inverts cane-sugar is found. 



2 According to LASCHE'S experiments, some species of Mycoderma present in 

 beer are capable of inducing alcoholic fermentation. 



