ALCOHOLIC FERMENTATION OF MILK 479 



Other Peptonizing Bacteria. A number of other organisms fre- 

 quently found in milk, which coagulate the casein and subsequently 

 peptonize or liquefy it, have been described by Duclaux. These 

 are the Tyrothrix or Bacillus tenuis, Tyrothrix or Bacillus distortus, 

 Tyrothrix or Bacillus geniculatus and several others of the same family. 

 These organisms are aerobic and facultative anaerobic, spore forming, 

 motile or immobile rods. Tyrothrix geniculatus peptonizes the casein 

 without preceding precipitation. 



It is generally believed that the bacteria of the Bacillus subtilis 

 group play an important role in the ripening of cheese; also the 

 different species of tyrothrix described by Duclaux. 



CHROMOGENIC BACTERIA IN MILK. 



Fluorescent and chromogenic bacteria sometimes impart a par- 

 ticular color to milk. The former kind sometimes produce a green 

 fluorescent pigment. The Bacillus cyanogenus, a motile, Gram- 

 negative, non-sporogenous bacterium, produces a bluish to brownish- 

 red pigment. The Bacillus violaceus, a water bacterium, sometimes 

 gets into milk and produces a violet color, as does also the Bacillus 

 membranaceus amethystinus. Sarcina rosacea stains cream pinkish, 

 while the Bacillus prodigiosus may produce in cream a more decidedly 

 red color. Bacillus lactorubefaciens stains the whole milk red and 

 makes it slimy, Bacillus mycoides roseus gives it a rust-brown color, 

 Bacterium synxanthum stains it yellow. 



ALCOHOLIC FERMENTATION OF MILK. 



Under certain conditions yeast cells, or saccharomyces, are found 

 in milk. They possess the faculty of forming alcohol from lactose. 

 The enzyme which brings about this fermentation is called lactose, 

 and is not identical with the yeast enzyme known as zymase, which 

 splits monosaccharids into alcohol and carbon dioxide. Most of the 

 microorganisms which form alcohol from lactose are not true yeast 

 cells, or saccharomyces, but belong to the nearly related family known 

 as Torula. The principal generic difference between yeast cells and 

 torula is that the former form spores, but the latter are asporogenous , 

 The most important organisms which form alcohol in milk from milk 

 sugar are the following: 



Saccharomyces lactis acidi of Grotenfeld acidulates milk, coagulates 

 it, and forms some alcohol; Saccharomyces Freudenreich and Jensen, 

 Saccharomyces fragilis of Joergensen, and Torula lactis of Adametz. 

 The latter is a torula which was discovered by Weigmann. It forms 

 in milk from lactose 51.2 per cent, by weight of alcohol, 34.4 per 

 cent, of carbon dioxide and 3.6 per cent.of butyric acid. The so-called 



