ACTION OF FUNGI ON CARBOHYDRATES, ETC. 259 



four sugars it only ferments dextrose. It only induces, there- 

 fore, a feeble alcoholic fermentation in beer-wort. 



Amongst the Torulas there are many which do not secrete 

 invertase, are incapable of fermenting maltose, and only yield 

 about 1 per cent, by volume of alcohol in beer-wort. Other 

 species invert saccharose. In nutritive dextrose solutions 

 the different species induce a more or less vigorous fermenta- 

 tion. 



Monilia Candida, although possessing no inverting enzyme 

 soluble in water, ferments saccharose, maltose, and dextrose. 

 It ferments beer-wort, but at ordinary room temperature it 

 only yields the higher percentages of alcohol at a much slower 

 rate than the Saccharomycetes. 



In milk, various budding fungi have been found. Of these, 

 Grotenfelt and the author have described certain Saccharo- 

 mycetes ; Duclaux, Adametz, Kayser, and Beijerinck several 

 non-Saccharomycetes. They all decompose lactose. Fermi 

 found that certain red and white yeasts exercise a diastatic 

 action. Morris arrived at similar results in experiments with 

 pressed yeast. 



If we now review all these different properties of the 

 Saccharomycetes, we shall see that they fall into two groups : 



I. Those which possess an inverting enzyme and induce 

 alcoholic fermentation. This group is further subdivided 

 into : 



(a) Those which not only ferment saccharose and dextrose, 

 but also vigorously ferment maltose (the six species first 

 described by Hansen, and the yeasts employed in the brewing 

 industry) ; 



(b) Those which ferment saccharose and dextrose, but not 

 maltose (Sacch. Marxianus, Ludwigii, and exiguus). 



II. Those which do not possess any inverting enzyme, and 

 do not induce alcoholic fermentation (Sacch. membrancejaciens). 



The budding fungi which do not form endospores (non- 

 Saccharomycetes) show the most varied characters with refer- 

 ence to the properties of inversion and fermentation. 



I. The great majority do not ferment maltose. Many of 

 these induce a more or less vigorous fermentation in solutions 

 of dextrose and invert sugar. Some Torulas invert saccharose. 



