182 GENERAL MICROBIOLOGY 



ENZYMIC REACTIONS OF WELL KNOWN FERMEN- 

 TATION PROCESSES 



A. Beer or bread fermentation by Saach. cerevisice. 



I. starch + water +hydroly tic enzyme = maltose. 



2(C 6 Hi O 6 ) + xH 2 O + amylase = zCi 2 H 22 O u . 



II. (a) maltose + water +hydrolytic enzyme = 2 mols. dextrose. 



(from yeast) 

 Ci 2 H 22 On + H 2 O + maltase =2C 6 H 12 6 . 



III. dextrose + enzyme producing intra- = alcohol + carbon 



molecular change dioxide. 



(from yeast) 



C 6 H 12 O 6 + yeast zymase = 2CH 3 CH 2 OH+2CO 2 . 



This same yeast, and other yeasts also, can ferment saccharose 

 (.cane sugar) corresponding to II above, as follows: 

 II. (6) saccharose -f- water -j-hydroly tic enzyme = d-dextrose + 

 fj (from yeast) d-levulose. 



Ci 2 H 22 On + H 2 O + sucrose =C 6 H ;2 O 6 +C 6 Hi 2 06. 



Both of these simple sugars can be fermented to alcohol 

 and CO2 according to III above. 



Comparatively few yeasts can attack lactose (milk sugar) , 

 e.g., Sacch. kefir (p. 369, Marshall), Sacch. fragilis, Sacch. 

 tyricola, etc. (See p. 106, Guilliermond's Les Levures.) 

 The reactions are similar to II (a) above, as follows : 



(c) lactose + water+hydrolytic enzyme = d-dextrose +d-ga- 



(from yeast) lactose. 



Ci 2 H 22 On + H 2 + lactose = C 6 H 12 O 6 +C 6 Hi 2 O 



Both simple sugars are changed to alcohol and CO 2 according to 

 III above. 



B. Glucoside decomposition, by molds, bacteria and yeasts. 



General reaction, 



glucoside + water -f hydroly tic enzy me = sugar -f- aldehydes, acids, etc. 

 Specific reaction, 



amygdalin-f- water -f emulsin = dextrose + benzaldehyde + hy- 

 drocyanic acid. 



C 20 H 27 OnN + 2H 2 O + emulsin* = 2C 6 H 12 O 6 + C 6 H 6 CHO+HCN. 

 * Emulsin is a mixture of four different enzymes, 



