THE EQUATION OF BUTYRIC FERMENTATION 147 



and whose thread chains are generally stained blue by iodine, is also classified by 

 Beyerinck along with the Granulobacteria. 



117. The Equation of Butyric Fermentation 



is set out in a very simple form in most text-books on chemistry, that for the 

 decomposition of the hexoses (glucose, &c.) being given as follows 



C 6 H ]2 6 = 2H 2 + 2 C0 2 + C 4 H 8 2 , 



or with lactic acid (or its lime salt) as the raw material 

 2C 3 H 6 3 = 2H 2 + 2 CO a + C 4 H 8 2 . 



In the preceding paragraphs we have, however, made the acquaintance of a 

 very large number of bacterial species with divergent methods of action, so that we 

 must at once admit that a general equation for butyric acid fermentation is not to 

 be thought of. All that can be hoped for is the discovery of more accurately 

 defined equations for each of the various species and their characterisation, as 

 e.g., the equation for the fermentation set up by Granulobacler saccharobutyricum, 

 and so on. Nevertheless, even this limitation is not sufficiently strict, as will be 

 evident from what follows. 



L. PERDRIX (I.) examined the fermentative capacity of an anaerobic spore- 

 bearing butyric acid bacterium (closely allied to Botkin's Bacillus butyricus), 

 which he isolated from the water in the Paris mains and named Bacille 

 amylozyme by reason of its property of bringing starch into solution (sacchari- 

 fication). When grown in a meat-broth containing glucose and calcium car- 

 bonate, with exclusion of air, this fission fungus produces acetic acid and butyric 

 acid, in addition to hydrogen and carbon dioxide. The mutual ratio of these 

 four fermentation products changes with the increasing age of the culture. In 

 the first three days it can be approximately expressed by the equation 



S6C 6 H 12 6 + 4 2H 2 = is6H 2 + II4C0 2 + 39C 2 H 4 2 + 36G' 4 H 8 2 , 

 but later on by the equation 



46C 6 H 12 6 + i8H 2 = ii2H 2 + 94C0 2 + I5C 2 H 4 2 + ^SCJJ^Oy 



Finally, the transformation becomes simplified, acetic acid being no longer 

 produced, and the sugar then splitting up very nearly as follows : 



C 6 H 12 O 6 = aH 2 + 2CO 2 + C 4 H 8 2 . 



Similar ratios were established for the fermentation of saccharose and lactose, 

 which is not preceded by inversion. Starch is, as already mentioned, saccharified 

 by the Bacille amylozyme, and is then fermented, amyl alcohol and ethyl alcohol 

 being formed. 



Along with these Schizomycetes must be ranked the Bacillus suaveolens, 

 described by SCLAVO and Gosio (I.), which converts starch into dextrin and 

 glucose, and ferments these with excretion of alcohol, aldehyde, formic acid, 

 acetic acid and butyric acid, which then partly unite to form sweet-smelling 

 esters. Butyric acid bacteria that produce aromatic substances as well are 

 important for the ripening of cheese, being essential for the development of the 

 characteristic odours of the various kinds of cheese. However, in this matter 

 our knowledge is still only in a rudimentary state. E. VON FREUDENREICH (I.) 

 separated from milk a Clostridium fcetidum lactis, which develops, in this 

 medium, an odour resembling that of Limburg cheese, and the same observation 

 was made by H. WEIGMANN (I.). The Bacillus saccharobutyricus, isolated from 



