242 MICRO-ORGANISMS AND FERMENTATION. 



become viscous during the alcoholic fermentation. All three 

 species ferment lactose, galactose, cane-sugar, glucose, invert- 

 sugar, and finally maltose, but the last only with great 

 difficulty. In the fermentation of milk-sugar with these 

 yeasts, the resulting liquids are as rich in alcohol as the 

 strongest beers. KAYSER remarks that it may, perhaps, be 

 possible to make practical use of this observation and by 

 means of these fungi convert the large quantities of whey, 

 obtained in the manufacture of cheese, into an alcoholic liquor. 



BELJERINCK has described two yeasts which also ferment 

 milk-sugar, and which must be provisionally regarded as non- 

 Saccharomycetes ; these are " Saccharomyces Kephir" which 

 occurs in kephir-grains and consists of longish cells of varied 

 shape, and forms slightly jagged colonies liquefying gelatine ; 

 and " Saccharomyces Tyrocola" which consists of small roundish 

 cells, and forms snow-white colonies on gelatine. BEIJERINCK 

 found that these two species secrete a particular invertive 

 ferment (lactase) which inverts not only cane-sugar but also 

 milk-sugar ; it does not, however, invert maltose. It is stated 

 that lactase may be prepared as follows : A five per cent, 

 solution of milk-sugar, containing nutrient salts and asparagine, 

 is fermented with kephir-yeast ; the product is filtered and the 

 ferment is precipitated from the filtrate by the addition of 

 alcohol. According to SCHUURMANS STEKHOVEN, however, the 

 enzyme of BEIJERINCK'S kephir-yeast does not invert milk- 

 sugar. 



In Lombardy cheese a unilaterally budding top-fermentation 

 yeast was discovered by BOCHICCIO, which is called Lactomyces 

 inflans caseigrana. It causes blisters on the surface of hard 

 cheese. The growth consists of round, ellipsoidal and oblong 

 cells, and forms whitish colonies on gelatine, with smooth 

 edges. No spore-formation was observed. The fungus 

 coagulates sterilised milk, and partly liquefies the coagulum 

 without any decided formation of acid. In lactose-broth it 

 produces a vigorous fermentation at 25-40 C.; the best 

 temperature for the development is about 30 C., the limit of 

 existence at about 60C. Whey infected with this species is 

 converted into a foaming beverage of a somewhat agreeable 

 taste. 



