36 BACTERIAL FERMENTATIONS 



dilute buffer. This simple procedure gave a soluble prepa- 

 ration that contained an amazingly complete fermentation 

 system. Clostridium kluyveri extracts were found to cata- 

 lyze the oxidation of alcohol via acetaldehyde to acetyl 

 phosphate (equation 8) , the oxidation of butyrate to acetyl 

 phosphate and acetate (equation 9) , and the synthesis of 

 butyrate from acetyl phosphate and acetate using hydrogen 

 as the reducing agent (equation 10) . 



CH3CH2OH + H3PO4 + 2 — > 



CH3COOPO3H2 + 2H 2 (8) 



CH3CH2CH2COOH + H3PO4 + 2 — > 



CH3COOPO3H2 + CH3COOH + H 2 (9) 



CH3COOPO3H2 + CH3COOH + 2H 2 — > 



CH3CH2CH2COOH + H3PO4 + H 2 (10) 



The formation of acetyl phosphate by the oxidation of 

 acetaldehyde, which was comparable to its formation from 

 pyruvate by CI. butylicum extracts, indicated that acetyl 

 phosphate might play a key role in butyric acid fermenta- 

 tions. This idea was supported by the observation that 

 under the conditions of these experiments acetyl phosphate 

 was required for butyrate synthesis; it could not be replaced 

 by acetate. A comparison of reactions 9 and 10 also indi- 

 cated that the oxidation and synthesis of butyrate probably 

 involve the same sequence of reversible reactions. 



Early Studies on the Path of Butyrate Synthesis in 

 Clostridium kluyveri. After the discovery of the enzy- 

 matic synthesis of butyrate from acetyl phosphate and ace- 

 tate, the mechanism of this synthesis became the central 

 problem of the butyric acid fermentation and indeed of 

 fatty acid metabolism in general. The formation of butyr- 

 ate from C 2 precursors was obviously a complex reaction 



