C6H12O6 +2ADP + 2Pi! 2CH3CH2OH +2CO2 + 2ATP

glucose ethanol

As shown in the above equation, one molecule of glucose produces two molecules each of ethanol and CO2, under anaerobic conditions. In other words, 180 g of glucose (1 mol) should yield 92 g of ethanol (2 mol) and 88 g of CO2 (2 mol). The theoretical yield of ethanol production, therefore, comes to 51%. Under practical conditions, a very high percent (i. e., 47%) yield can be achieved. The metabolism though yields equimolar quantity of CO2 and ethanol, the actual amount of CO2 liberated is less than theoretical. This is because of partial reuti­lization of CO2 in anabolic carboxylation reactions [138]. According to an esti­mate, about 85% of the sugars are metabolized to ethanol and CO2, and the energy produced is used for various cell functions. The rest of the sugars are channeled for biosynthetic reactions. Figure 9.9 shows the pathway of conversion of pyruvate into ethanol and CO2.

Fig. 9.9 Pathway of conversion of pyruvate into ethanol

CH3- CHO

СНзСН2ОН

Ethanol