PURE CULTURE FERMENTS IN VINEGAR 305 



of acetic acid bacteria considerably enlarged the field of research, since thence- 

 forward " acetic fermentation " could no longer be spoken of without coupling 

 with it the name of the organism by which it was caused. The species forming 

 the subject of Brown's researches was obtained by him from sour (acetic) beer, 

 and was called Bacterium aceti, though not identical with Hansen's species 

 bearing the same name. Pasteur's discovery that the " acetic acid bacteria " 

 first convert alcohol into acetic acid, and then burn the latter to carbon dioxide 

 and water, was also made by Brown in connection with his B. aceti, but he did 

 not institute any closer examination (more particularly in connection with the 

 ratio of transformation) on this point, so that this theoretically and practically 

 most important question has still to be investigated. 



Methyl alcohol, isobutyl alcohol, and amyl alcohol are not attacked by Brown's 

 B. aceti, but normal propyl alcohol is oxidised to propionic acid. If the nutrient 

 medium (yeast-water) contains dextrose but no alcohol, then gluconic acid is 

 formed, a fact already established by BOUTROUX (I.) in 1880, in connection with 

 another species of bacterium (of questionable purity). Saccharose, lactose, and 

 starch remain unaltered, but mannite is converted into Isevulose, which then 

 remains unchanged. Dulcite is unaffected, whilst glycol is converted into 

 gly collie acid. The behaviour of Bacterium xylinum is approximately the same 

 as in the organism just described. The extensive mucinous envelopes, consisting 

 of cellulose, are produced when the nutrient solution contains dextrose, Isevulose, 

 or mannite J whilst, on the other hand, cane-sugar and starch are useless for 

 this purpose. 



We are indebted to G. BERTRAND (I.) for a beautiful experiment with a 

 fission fungus, not accurately identified, but presumably very closely allied to 

 Bacterium xylinum. Mountain-ash berries, i.e. the fruit of Sorbus aucuparia, S. 

 intermedia, and S. latifolia, contain, in addition to glucose, an alcohol isomeric with 

 mannite, viz., Sorbitol (C 6 H U 6 ). If now the juice of these berries be subjected 

 to alcoholic fermentation (which sets in rapidly and spontaneously), the glucose 

 is decomposed, but not the sorbitol, this latter only being attacked when the 

 above-mentioned fission fungus obtains access into the fermented liquid, which 

 it does through the mediation of a small red fly (Drosophila funebris, Fabricius, 

 I), cellaris, Macquart), known to all fermentation technicists as the "vinegar- 

 fly." This insect haunts places where alcoholic juices (especially fermented fruit- 

 juices) are being stored and converted into vinegar, and there loads itself with 

 acetic acid bacteria, which it then transfers to other localities. The bacterium 

 introduced by these flies into the fermented juice of the mountain-ash berry 

 oxidises the hexavalent alcohol sorbitol to the ketose sorbin (also known as 

 sorbinose or sorbose), according to the equation 



C 6 H 14 6 + = C 6 H 12 6 + H 2 0. 



This affords a convenient method for the production of sorbose. 



"With regard to the fermentative capacity of B. aceti Hansen, and B, Pasteur- 

 ianum, the author, in 1895, published comparative investigations, showing that 

 a sowing of the first- named species on pale lager-beer is able to develop and 

 exert a powerful acidifying effect at 4-4.5 0.; whereas B. Pasteurianum is 

 unable to do this, or to reproduce itself at all, even at 4.5-5 C. 



213. Pure Culture Ferments in the Manufacture of Vinegar. 



Searching investigations into the chemical activity of the different species of 

 acetic acid bacteria would be not only opportune in the interests of science, but 

 also highly important to the practice of the vinegar industry. In this business 

 i u 



