56 BIOLOGY AND TECHNIQUE 



gether with hydrogen and C0 2 are produced. The chemical 

 mechanism of the fermentation is thus seen to be highly complex. 13 

 Cellulose. Cellulose is fermented by a limited number of bacteria, 

 most of them anaerobes. The chemical process by which this takes 

 place is but poorly understood. 14 



Gelase. An agar-splitting ferment has been found by Gran. 15 

 Invertase. The enzymes which hydrolytically cause cleavage of 

 saccharose into dextrose and levulose are numerous. The chemical 

 process takes place according to the following formula: 



C 12 H 22 O n + H 2 = C 6 H 12 6 -f C 6 H 12 6 

 Saccharose Dextrose Levulose 



Invertase is produced by many of the yeasts. It is one of the most 

 common of the enzymes produced by bacteria, and has been found in 

 cultures of B. megatherium, B. subtilis, pneumococcus, some strepto- 

 cocci, B. coli, and many others. Invertase is usually very susceptible 

 to heat, being destroyed by temperatures of 70 C. and over. A 

 slightly acid reaction of media abets the inverting action of these 

 enzymes. Strong acids and alkalies inhibit them. Inverting enzymes 

 may be precipitated out of solution by alcohol. Antiseptics even 

 in weak concentrations will inhibit their action. 



Lactase. Lactose-splitting ferments are extremely common both 

 among bacteria and among the yeasts. The process is here again a 

 hydrolytic cleavage resulting in the formation of the monosaccharids, 

 dextrose and galactose. 



Maltase. A maltose-splitting ferment has also been found in the 

 cultures of many bacteria, leading to the formation of dextrose. 



Lactic Acid Fermentation. Lactic acid (oxyproprionic acid, 

 C 3 H G 8 ) is one of the -most common substances to appear among 

 the products of bacterial activity, both in media containing carbohy- 

 drates and in those consisting entirely of albuminous substances. 

 In most of these cases, the lactic acid is formed merely as a by- 

 product accompanying many other more complicated chemical 

 cleavages. In some instances, however, lactic acid is produced from 

 carbohydrates, both, disaccharids and monosaccharids, as an almost 



"SpeaJcma-n, Jour, of Biol. Chem., xli, 1920, 319; xliii, 1920, 401. 

 ^OmeliansM, Lafar's "Handb. d. techn. Mykologio, " Bd. iii, Chap. 9. 

 15 Gran, Bergens Museum Aarbog, 1902, Hft. I. 



