64 MICRO-ORGANISMS AND FERMENTATION. 



ing to Lindner, all other organisms are suppressed. It has 

 been proved chemically that the acid, which is abundantly 

 produced, consists for the most part of lactic acid. When a 

 malt-mash or malt-rye mash is maintained at 41 C., the 

 Pediococcits develops vigorously, and the rod-shaped lactic 

 acid bacteria are suppressed. In a neutral malt-extract 

 solution, the Pediococcus is killed after five minutes' exposure 

 to 62 C. In gelatine it does not thrive well; it is only in 

 puncture-cultivations in neutral malt-extract gelatine, that 

 very vigorous white colonies are formed below the surface. 

 This species appears, on the whole, to thrive better when the 

 air is excluded. 



The Saccharobacillus Pastorianus described by Van 

 Laer, which occurs in the form of rods of different lengths, 

 produces a characteristic disease (" tourne ") in beer, which 

 manifests itself as follows : the liquid gradually loses its 

 brightness, and when it is agitated filaments of a silky lustre 

 rise from the bottom, and the beer assumes a disagreeable 

 odour and taste. The bacillus, in cultures, develops both in 

 the presence of free oxygen and when this is excluded. In 

 nutrient liquids it ferments the carbohydrates, and amongst 

 them the saccharoses, without previously inverting them. 

 Amongst the fermentation-products lactic acid, acetic acid, 

 and alcohol, are especially mentioned. The acids produced 

 cause the precipitation of nitrogenous compounds in the 

 liquid, and these, mixed with the bacilli, produce the 

 above-mentioned clouds, consisting of lustrous filaments. 



Besides the investigators mentioned, several others have 

 likewise carried out researches in this field ; as, for instance, 

 Pasteur's co-operator Duclaux. Grotenfelt has recently 

 described some species which must doubtless be regarded as 

 new ones ; at any rate he could not identify them with those 

 described by Hueppe and Marpmann* Some species were 

 observed to yield alcohol in addition to lactic acid by the 

 decomposition of sugar ; he expresses the belief that these 

 species take part in the formation of the aroma of butter. 



