52 BACTERIAL FERMENTATIONS 



reaction sequence would be a transfer of the phosphoryl 

 group of butyryl phosphate to ADP (reaction 30) followed 



Butyryl phosphate + ADP z^±: Butyrate + ATP (30) 



by a reaction of the resulting ATP with butyrate and 

 coenzyme A to give butyryl-SCoA as shown in reaction 29. 

 It may be noted that phosphotransacetylase cannot catalyze 

 a direct transfer of the butyryl group from butyryl phos- 

 phate to coenzyme A. 



The reduction of butyryl-SCoA to butyraldehyde by 

 DPNH (reaction 31) is catalyzed by the aldehyde dehydro- 

 genase of CI. kluyveri 30 and similar enzymes probably occur 



CH3CH2CH2COSC0A + DPNH + H+ z^z± 



CH3CH2CH2CHO + HSCoA + DPN+ (31) 



in other butyric acid bacteria. The CI. kluyveri enzyme 

 also reacts with acetyl-SCoA and propionyl-SCoA to give 

 acetaldehyde and propionaldehyde respectively. The alde- 

 hydes are finally reduced to the corresponding alcohols by 

 DPNH under the influence of alcohol dehydrogenase (reac- 

 tion 32) . In carbohydrate fermentations the DPNH is 

 probably supplied by the oxidation of triose phosphate. 



CH3CH2CH2CHO + DPNH + H+ ^=^= 



CH3CH2CH2CH2OH + DPN+ (32) 



Certain interrelations between acetone and butanol 

 formation are of some interest. In the fermentation of 

 carbohydrates by CI. acetobutylicum acetone, butanol, and 

 ethanol are formed simultaneously. 3 The reason for this is 

 not hard to find. The conversion of acetoacetyl-SCoA to 

 acetone results in the loss of two electron-accepting reactions, 



