238 UTILIZATION OF CARBOHYDRATES 



The Cannizzaro reaction in step (c), whereby in the presence of alkaH two molecules 



of aldehyde are reduced and oxidized, respectively, into a molecule each of acid and 



of alcohol, has been termed "dismutation" by Neuberg. 



This third type of fermentation is virtually that worked out by Harden' for B. coli 



many years ago. Harden believed that at least three separate and distinct enzymatic 



processes were involved; the first of these results in the change of glucose to lactic 



acid: 



C6H..06=2CH3 . CHOH • COOH . 



The second was responsible for a second molecule of glucose being broken down into 

 a molecule each of alcohol and acetic acid, and two molecules of formic acid: 



C6H:.Oo+H,0 = C.H50H+CH3 • COOH+2H • COOH . 



The third reaction involved the cleavage of formic acid by the enzyme formiase into 

 carbon dioxide and hydrogen : 



2H-COOH = 2H.+ 2CO. . 



The production and subsequent cleavage of formic acid by micro-organisms seems 

 to be a point of much discussion. Schade- and others believe that the fermentation 

 of glucose by yeast involves the production of formic acid, but this view has been 

 unacceptable to many subsequent observers, partly on the ground that the yeast 

 plant cannot decompose formates with the evolution of gas.^ On the other hand, there 

 is much evidence that formic acid is produced under widely differing conditions during 

 the utilization of glucose for energy and that this formic acid may or may not be 

 decomposed subsequently into CO2 and Hj. The enzyme "formiase" is found in the 

 press juice from muscles^ and especially in cultures of certain bacteria. ^ According to 

 Clark,* one of the chemical differences between bacteria that produce gas from fer- 

 menting sugars, and those that produce acid but no gas under parallel conditions, is 

 the presence of formiase in the enzyme armamentarium of the former and its absence 

 among the latter. According to this view, most of the common bacteria produce 

 formic acid during fermentation. Gas-forming bacteria, as the members of the para- 

 typhoid-colon-proteus-mucosus-capsulatus groups, and many anaerobes, which pos- 

 sess formiase in their enzyme equipment, are able to transform formic acid more or 

 less completely into CO, and H2. Many if indeed not a decided majority of bacteria 

 that do not produce gas also produce formic acid, but it accumulates in the culture. 

 This is certainly true of the typhoid bacillus,^ cultures of which, grown in the presence 



' Harden, A. : loc. cit. 



2 Schade, H.: Biochem. Ztschr., 7, 299. 1908. 



3 See Thomas, K.: Conipt. rend. Acad, de Sc, 136, 1015. 1903. 



t See Stoklasa; J.: Ber. d. dent. Chem. Gesellsch., 38, 607. 1905; Battelli, F.: Compt. rend. Acad, 

 de Sc, 138, 651. 1904. 



s See Pakes, W. C. C, and Jollyman, W. H.: /. Chem. Soc, 79, 386, 459. 1901; Franzen, H., and 

 Greve, G.: Ztschr. f. physio! . Chemie, 64, 169. 1910. 



* Clark, W. M.: Science, 38, 669. 1913. 



'See Franzen, H., and Egger, F.: Ztschr. physiol. Chemie, 79. i77- 1912; 83, 226. 1913. 



