C6H1206 



Glucose 



GLUCONIC ACID FERMENTATION 



COOH -^ COOH -^ COOH -^ COOH 



• • • • 



CHOH CHOH CH2 CH2 

 CHOH CHOH C:0 HOC -COOH 



223 



CHOH 

 CHOH 



CHOH C:0 



• • 



CHOH CH2 



CH2OH COOH COOH 



CH2 



COOH 



Citric 

 acid 



Bernhauer/ however, feels that the gluconic and saccharic acids 

 found in the mold cultures (the presence of which is advanced as 

 supporting evidence by the proponents of the first school of thought) 

 originate from a side reaction. Various hypotheses have been ad- 

 vanced by the advocates of the second group of workers who main- 

 tain that sugar is first broken down and the intermediary substances 

 subsequently condensed to form citric acid. The mechanism pro- 

 posed by Bernhauer and Bockl - is typical of the various ones which 

 have been suggested in that all or most believe that a condensation 

 of a dicarboxylic acid and acetic acid occurs. (See reactions on the 

 following page.) 



As yet, even among the workers who claim that there is a con- 

 densation of intermediate carbon compounds, there seems to be a 

 divergence of opinions. For greater details, consult the publications 

 of Bernhauer and Iglauer,^ Ciusa and Briill,^^ Chrzaszcz and Janicki,^^ 

 and Wells and his associates.'^^ 



The latter group of workers has carried out careful carbon bal- 

 ance experiments which demonstrated that some of the theories which 

 have been advanced are quite untenable. They obtained yields of 

 citric acid which could not be explained by many of the fermentation 

 mechanisms which have been proposed, i.e., the actual yields proved 

 to be higher than the theoretical. Furthermore the citric acid-carbon 

 dioxide ratios found by them experimentally were higher than the 

 theoretical. 



Gluconic Acid Fermentation. That bacteria and molds are capable 

 of transforming glucose to gluconic acid by a simple oxidation has 

 been known for some time. As early as 1878, Boutroux noted that 

 a bacterium, "Mycoderma aceti" {Acetobacter aceti) , could produce 

 this acid. In 1922, IMolliard *° observed that "Sterigmatocystis nigra" 

 {Aspergillus niger) grown on sucrose mashes produced gluconic acid 



