ALCOHOLIC FERMENTS. 177 



Haiisen found this species in pressed yeast. Its behaviour 

 towards the sugars is similar to that of the last species, though 

 it develops a greater fermentative activity in solutions of 

 saccharose and dextrose. In wort, it also yields only small 

 quantities of alcohol. It does not ferment maltose solutions. 

 It inverts saccharose. 



Experiments of a practical nature, which were conducted 

 by Hansen, have shown that this species does not produce any 

 disease in beer, even when present in considerable quantities 

 either at the beginning or end of the primary fermentation, 

 or when it is added after storage of the beer. 1 



.Some other species examined by Hansen can likewise 

 ferment saccharose and dextrose, but not maltose and lactose. 



Saccharomyces Joergensenii, described by Lasche, also 

 belongs to the group of the Saccharomycetes, which may be 

 termed Sacch. exiguus. The growth consists of small round 

 and oval cells. The optimum temperature for spore-formation 

 is 25 C., the temperature limits being 8 and 30 C. At tem- 

 peratures above 30 C. the growth rapidly dies. A true film- 

 formation was not observed ; in old cultures only a very feeble 

 yeast ring was formed, and this consisted of round and oval 

 cells. In gelatine it yields colonies which resemble those of 

 low-fermentation brewery yeast. Wort-gelatine becomes slowly 

 liquefied. The streak-culture is dirty grey in appearance, with 

 smooth edges. This species ferments saccharose and dextrose, 

 but not maltose. When it is mixed with cultivated yeasts and 

 grown in wort, it consequently becomes suppressed and cannot 

 therefore produce any disease in beer. 



SACCHAROMYCES MEMBRAN^EFACIENS. HANSEN. 



This peculiar species, which occupies a special place amongst 

 the Saccharomycetes, when grown in wort, yields a strongly- 

 developed light grey, wrinkled film, which very quickly covers 



1 This is of special interest, as Sacch. exiguus was formerly regarded 

 as a disease-producing species. 



N 



