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BACILLI WHICH CAUSE FERMENTATION. 



3. Hueppe's 

 aerobic 

 butyric acid 

 bacillus. 



Action on 

 milk. 



Bacillus butyricus (Hueppe). 



Hueppe was able to isolate large bacilli from milk which 

 was sterilised sufficiently to prevent the lactic fermenta- 

 tion, but in which the casein became precipitated later, 

 the reaction of the medium being at first unaltered, and 

 later slightly alkaline ; these organisms resembled mor- 

 phologically those described by Prazmowski, but were 

 much less sensitive to oxygen. They grew in nutrient 

 jelly, and led to rapid liquefaction of it, and no precautions 

 with regard to the removal of oxygen were necessary. 

 These bacilli are unable to cause directly the fermentation 

 of milk sugar, and only form butyric acid when the milk 

 sugar has been either dehydrated by other bacteria or 

 when lactates are present. They also cause coagulation 

 of the casein like the rennet ferment, and then they split 

 up the casein, and produce peptone, leucine, tyrosine, 

 ammonia, and substances with a bitter taste. The 

 coagulum of casein, which is at first precipitated from 

 sterilised milk by the butyric acid bacilli, presents, after 

 about 8 days, an appearance as if its edges were being 

 eaten away, and it gradually disappears almost entirely. 



Bacillus caucasicus. 

 (Dispora caucasica, the ferment of kephyr.) 



Organisms of An intoxicating drink has been repeatedly obtained 



kephyr. from milk by alcoholic fermentation, as for example in 



the preparation of koumis from the milk of mares by 



the inhabitants of the Kirghiz steppes, and also in the 



preparation of kephyr from the milk of cows, as has been 



done from ancient times in the Caucasian highlands. 



In these cases the alcoholic fermentation appears to be 



always occasioned by a torula; as, however, the milk 



sugar of milk cannot undergo the alcoholic fermentation 



directly, something must be added to it which is able to 



transform the milk sugar into fermentescible glucose. 



The course of This transformation is carried out in an energetic manner 



fernSatior ^ tlie ordinary lactic acid bacteria, and thus an alcoholic 



fermentation of milk may be set up by the combined use 



of lactic acid bacteria and yeast cells. But the lactic 



