PRODUCTS OF THE LOWER EUXGI 



301 



HCOH- 



-CHOH HCOH- 



CHO 



CHOH 



CHOH 



CHO 



HCOH 

 HCOH 



(glucose) 



CHOH 



CHOH 



COOH 

 CH, 



CHOH 



I 

 CHOH 



/ 

 CHOH 



COOH 



(Glucuronic 

 (acid) 



COOH 



CH2 

 / 



C(OH) 

 COOH 



C(OH) 

 COOH 



(citric acid) 



Gudlet suggested that glucose split to give succinic 

 acid and acet aldehyde. The former was transformed 

 through fumaric acid to malic acid, whilst the acetalde- 

 hyde was oxidised to acetic acid which condensed with 

 the malic acid to give citric acid. Ciusa and Briill found 

 that increased yields of citric acid were obtained if 

 glycollic and malic acids were added to A. niger fer- 

 mentations, and suggested that citric acid was formed 

 by their condensation : — 



COOH 

 CH, 



^HOH.COOH > 



I 

 COOH 



COOH 



I 

 CH2 



C(OH).COOH 



CH2 



COOH 



This suggestion resembles that of Kluyver and of Virtanen 



for the formation of succinic acid (see p. 250) by bacteria. 



It is possible that citric acid may be formed by a 



series of reactions analogous to part of the tricarboxylic 



