BUTYRIC ACID-BUTANOL FERMENTATIONS 29 



cerning the fermentation products did not become available 

 until the period between 1925 and 1932, when several fun- 

 damental studies such as those of Donker, 1 van der Lek, 2 

 and Peterson and Fred 3 were published. This information 

 provided a basis for reasonable deductions and specula- 

 tions concerning the chemical pathways involved in the 

 conversion of glucose and other substrates to fermentation 

 products. 



The state of knowledge of the chemistry of butyric acid- 

 butanol fermentations that existed in 1931 4 is summarized 

 schematically in Fig. 1. It was generally accepted without 



1. C 6 H 12 6 —> 2C 3 (?) — > 2C 2 (?) + 2Ci (?) 



2. 2CH 3 CHO (?) — > CH3CHOHCH2CHO (?) — > 



CH3CH2CH2COOH 



3. 2CH3COOH (?) — > CH3COCH2COOH — ^ 



CH3COCH3 + C0 2 



4. CH3CH2CH2COOH -^> CH3CH2CH2CH2OH 



5. HCOOH (?) —> H 2 + C0 2 



Fig. I. Chemistry of Butyric Acid-Butanol Fermentation, 1931. 



proof that the early stages of hexose decomposition fol- 

 lowed the general pattern of alcoholic fermentation. This 

 involved the fission of the hexose into two C 3 compounds 

 each of which was converted to a C 2 and a C ± compound. 

 Butyric acid and acetone were believed to be formed by a 

 condensation of C 2 units, followed in the case of acetone 

 by the removal of one carbon as carbon dioxide. Reilly 

 et al. 5 and Speakman 6 had provided evidence that acetate 

 and butyrate are intermediates in the formation of acetone 

 and butanol, respectively. The acids were shown to accu- 



