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MANUAL OF MICROBIOLOGICAL METHODS 



atoms in the molecule and indicated as millimoles of C. The total C 

 millimoles of the products must equal the millimoles of the substrate 

 similarly calculated or must be within the range of the experimental 

 error of the analytical methods employed. Thus, the carbon-recovery 

 figure equals 100 per cent theoretically; the value of 97.4 per cent in the 

 balance presented below represents, however, very good carbon recovery. 

 To obtain the figures for the calculated amounts of CO2 expected on a 

 theoretical basis, a knowledge of the dissimilatory mechanism in opera- 

 tion must be available or certain assumptions concerning its operation 



Table 20. Carbon and Oxidation-reduction Balances 



Carbon recovery = 

 0/R = 



584.7 



= 97.4% 



obs COj 



600.0 ^'"^^"calc CO2 

 oxidation value _ 178.6 

 reduction value 178.6 



^ 89^ 

 93.2 



= 1.00 



= 0.958 



are made. In the balance presented above, the data suggest the opera- 

 tion of a mechanism of glucose dissimilation similar to the Embden- 

 Meyerhof-Parnas scheme of glycolysis (Baldwin, 1947). The hexose 

 glucose is split into two trioses which, by oxidation and reduction, are 

 converted to the end products lactic acid and glycerol. Thus, on this 

 basis, no CO2 is expected to be liberated during the formation of these 

 end products. However, a number of the triose molecules originating 

 from glucose are decarboxylated, at the pyruvic acid level, to a C2 com- 

 pound and CO2. By reduction, some of the C2 compound is converted 

 to ethanol while the rest of the C2 compound is oxidized to acetic acid. 

 Thus, for each mole of ethanol and of acetic acid formed, a mole of CO 2 is 

 also liberated. On this basis, the theoretical yield of CO2 is calculated. 

 When this figure is compared with the actual experimental yield of carbon 

 dioxide, a ratio of 1 is obtained if the reasoning and analyses are correct. 

 In the balance presented above, the ratio actually obtained is 0.958, which 

 is another indication of a very good balance. 



