Decomposition of Carbohydrates 109 



Decomposition of Carbohydrates 



The mechanism of decomposition of carbohydrates by microorgan- 

 isms depends entirely upon the nature of the carbohydrate, the 

 natine of the organisms, and the conditions of decomposition, espe- 

 cially the oxygen supply. Thus, if glucose is attacked by fungi, the 

 following reactions are involved: 



Citric 

 acid 



CeHioOo + 4^02 = 3C2H2O4 + '3H2O 



Oxalic 

 aciii 



C6H12O0 + 6O2 = OCO2 + 6H2O 



If the glucose is attacked by anaerobic bacteria and by yeasts, the 

 following reactions are invohed: 



C6H12O6 = 2C3H6O3 



Lactic 

 acid 



CfiHiaOe = 2C2H5OH + 2CO2 



Alcohol 



C6Hi20fi = C4H8O2 + 2CO2 + 2H2 



Butyric 

 acid 



If the glucose is attacked by anaerobically growing fungi, another 

 reaction may take place: 



CgHisOo + £H = C4H6O4 + C2H5OH + H2O 



Glucose Fumaric Alcohol 



acid 



Under aerobic conditions, the alcohol is further oxidized, through 

 the acetic acid stage, to fumaric acid: 



C2H5OH + 20 = CH3COOH + H2O 



2CH3COOH + = C4H0O4 + H2O 



Starch is first hydrolyzed by diastatic enzymes, to give rise to 

 dextrins, and finally to maltose and glucose: 



(CoHh,05)2„ + [n - ljH2() - /K:i2H220n 



Starch Maltose 



Ci2H220n + H2O = 2C6Hi20fi 



Maltose Glucose 



