ALCOHOLIC FERMENTS. 241 



TORULA- YEASTS FERMENTING MILK-SUGAR. 



DUCLAUX found a yeast-fungus in milk which induces 

 alcoholic fermentation in a solution of lactose. This fungus 

 appears to be most closely related to the Torula species. 

 The cells are 1*5 to 2 '5 /x in diameter, and almost spherical. 

 According to DUCLAUX'S experiments, this yeast is more 

 aerobic than the ordinary alcoholic yeasts. Even with strong 

 aeration of the liquid, the whole of the milk-sugar is used up 

 in the alcoholic fermentation. In a 5 per cent, solution of 

 milk-sugar 2 - 5 per cent, of alcohol was formed in eleven days 

 at 25C. The most favourable temperature for the fermenta- 

 tion of a neutral solution is 25 to 32 C., whilst at 37 to 

 40 C. the fermentation ceases. Small quantities of acid have 

 a retarding influence on the fermentative activity of this yeast. 



ADAMETZ likewise describes a budding-fungus which fer- 

 ments milk-sugar (" Saccharomyces lactis"). Since this fungus 

 does not yield endogenous spores by HANSEN'S method, it is 

 classed in the group of non-Saccharomycetes. The cells are 

 of about the same size as those of Saccharomyces cerevisice, and 

 are spherical and elliptical. The colonies grown on peptone- 

 gelatine are round, with slightly jagged borders, and are of a 

 dark brown colour. A puncture-cultivation in wort-gelatine 

 yields a dull, flat mass on the surface and a vigorous growth 

 in the punctured channel, and from this numerous offshoots 

 penetrate into the gelatine. In sterilised milk this fungus 

 induces fermentation phenomena within 24 hours at 50 C., 

 in 48 hours at 38 C., and in about four days at 25 C. In 

 this fermentation the milk-sugar is alone decomposed. 



Both of the species mentioned above have been more closely 

 investigated by KAYSER, together with a new species which 

 likewise ferments lactose and belongs to the non-Saccharomy- 

 cetes. All three yield colonies on gelatine, which are more 

 widely spread than those of beer- and wine-yeasts; in the 

 middle of the colonies there is a thick portion, while the 

 border resembles mycelium. In milk and in neutral liquids, 

 when sufficiently aerated, they induce an appreciable fermen- 

 tation at 25 to 30 C. The milk does not coagulate or 



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