ENZYMIC REACTIONS 183 



C. Fat decomposition, by a few molds, yeasts and bacteria. 

 Only microbial method of fat decomposition. 



General reaction, 



f at + water +hydroly tic enzyme = fatty acid + glycerin. 

 Specific reaction, 

 stearin+3 mols. water+steanrazse = 3 mols. stearic acid+glycerin." 



H 2 O C 17 H 35 COOH CH 2 OH 

 I I 



C 17 H 36 CO-O-CH + H 2 O = Ci 7 H 35 COOH + CH 2 OH 

 I I 



Ci 7 H 35 CO.O-CH 2 H 2 C n H 35 COOH CH 2 OH 



Lipases decompose more especially the natural fats, 

 i.e., the glycerin esters of palmitic, stearic and oleic acids. 

 Lipases from different sources differ markedly in reactions. 



D. Vinegar fermentation. 



In order that this fermentation may take place, alcohol 

 must be present in the nutrient solution, either added arti- 

 ficially or as a product of fermentation. In the latter case, 

 reactions I, Ha and III, 116 and III, or He and III under A 

 above must precede those of the vinegar fermentation. 



Assuming that alcohol is present in the liquid in which 

 the vinegar bacteria are growing, the reactions take place in 

 two stages, as follows: (See p. 448, Marshall.) 



I. ethyl alcohol -f oxygen + oxidizing enzyme = acetaldehyde+ water 

 CH 3 CH 2 OH + O + alcoholase = CH 3 CHO + H 2 O. 



II. acetaldehy de+oxy gen + oxidizing enzyme = acetic acid 

 CHaCHO + O + acetaldehydase = CH 3 COOH 



If there is not plenty of air present the oxidation may not 

 become complete and small amounts of acetaldehyde may 

 form, i.e., the reaction stops at the first stage. 



If the initial percentage of alcohol is below 1 to 2% the 

 vinegar bacteria will soon attack the acetic acid, oxidizing 

 it completely to carbon dioxide and water, as follows : 



III. acetic acid +oxy gen + oxidizing enzyme = carbon dioxide+water 

 CHsCOOH + 4O + acetacidase = 2CO 2 +2H 2 O. 



