FERMENT A TION 2 1 7 



them can oxidize glucose into gluconic acid, mannite into laevulose, sorbite into 

 sorbose. In addition, certain acetic acid Bacteria are known to be able to form 

 oxalic acid from sugar and many other organic compounds — though scarcely 

 from alcohols (Banning, 1902). Sugar is further a good source of carbon for 

 acetic acid Bacteria and can be used for growth purpose -■> along with an appro- 

 priate source of nitrogen ; many acids also, e.g. acetic acid, serve as food-stuff, 

 while alcohol is employed only as a fermentable substance. 



Although acetic acid Bacteria do not make any further use of that acid, 

 another widely distributed organism occurs in nature — known as Saccharomyces 

 mycoderma — which does do so, and by the three consecutive activities of yeast, 

 of acetic acid Bacteria and of Mycoderma, the sugar is finally transformed into 

 the same end products which arise from it in respiration in the normal plant. 



The decompositions described are not the only ones which sugar and 

 related carbohydrates undergo owing to the action of microbes in nature ; 

 very often lactic acid or fatty acids arise. Bacteria which produce lactic acid 

 as a by-product have been described by the dozen, but only a few form this acid 

 in such quantity that we may speak in this case of lactic acid fermentation. 

 If, as in the case of Bacillus lactis acidi, the entire fermentation consists 

 simply in the splitting of one molecule of glucose into two molecules of 

 dextro-lactic acid, or, as in Bacillus acidificans longissimus, into two molecules 

 of laevo-lactic acid, there is no question of fermentation in the old sense of the 

 term, since no energy is released in the process and its significance can lie only 

 in the exclusion of associated organisms. There are other lactic acid Bacteria, 

 however, which give rise to other fermentation products. 



Butyric acid is the only one of the fatty acids which arise during the 

 fermentation process which we need speak of here. Animal anaerobes produce 

 fatty acids also as fermentative products, e. g. propionic acid in Ascaris (Wein- 

 LAND, 1901, Zeit. f. Biol. 24, 55). Butyric acid may be derived from sugar 

 as well as from lactic acid, and indirectly from the polysaccharides starch, inulin, 

 dextrin, &c. ; its development is due for the most part to the influence of 

 anaerobic Bacteria, as to which much more or less accurate information has been 

 accumulated. These forms are very like each other morphologically, and also 

 resemble Bacillus hutylicus above described. According to Beijerinck (1894) 

 the latter is characterized by producing butyl-alcohol only, and never but3nic 

 acid, whUe Bacillus saccharo-butyricus (Granulobacfer, Beij.), which occurs in 

 similar situations to B. butylicus, develops from butyric acid, in addition to 

 butyl-alcohol, large quantities of carbon-dioxide and hydrogen. Grimbert 

 (cited by Duclaux, Trait6 de Microbiol, vol. IV) has described a bacterium 

 named Bacillus orthobuiylicus, which, in addition to these bodies, forms acetic 

 acid also, as does a bacterium studied by Perdrix (cited by Duclaux), termed 

 by him ' bacille amylozyme '. In the cases which have been accurately investi- 

 gated it has been shown that the proportion of fermentation products is by no 

 means constant ; thus in the case, e. g., of ' bacille amylozyme ', at the beginning 

 the amount of carbon-dioxide is far less than that of hydrogen, though, later 

 on, both occur in about equal quantities ; so too at the beginning of fermentation 

 only acetic acid is formed, but not in the later stages. No explanation has as yet 

 been given of the causes of these variations, nor of the appearance of such varied 

 products ; we must wait for the future to provide us with an explanation of how 

 the active enzymes are to be found and isolated ; especially if it be shown that 

 several different zymases occur in one and the same organism, whose activities 

 are affected in a variety of ways by external conditions. 



As we have already said, polysaccharides, such as starch, can be used up by 

 certain butyric acid Bacteria ; some also are able to attack cellulose, e. g. the 

 bacterium studied by Omelianski (1902) in Winogradsky's laboratory, 

 a bacillus of very small diameter (0-2 /a) which forms spherical spores in terminal 

 swellings, but which gives no blue reaction when treated with iodine. It may be 



