168 MICRO-ORGANISMS AND FERMENTATION. 



dextrose solutions the different species induce a more or less 

 vigorous fermentation. 



Manilla Candida, although possessing no enzyme soluble in 

 water, ferments saccharose, maltose, and dextrose. It ferments 

 beer-wort, but at the 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, all of 

 which are able to decompose milk sugar. GROTENFELT and the 

 writer have described some Saccharomycetes ; DUCLAUX, ADA- 

 METZ, KAYSER, and BEIJERINCK several non-Saccharomycetes. 

 Species fermenting milk sugar have never yet been detected 

 in breweries. FERMI found that certain white and red yeasts 

 are capable of exercising 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 sub-divided 

 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) ; 



(6) 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. memlrance- 

 faciens). 



The budding fungi which do not form endospores (non- 

 Saccharomycetes) show the most varied characters with reference 

 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 (Torula 

 forms) invert saccharose, and many possess no invertive 

 ferment (Mycoderma cerevisice, other Torula forms and 

 Sacch. apiculatus). 



