THE LIPOIDS OF MICRO-ORGANISMS 383 



or stearic acids is hiiilf up, Avlien oxidation of the alde- 

 hyde group to a carboxyl group gives stearic acid, 

 CH3(CH2)i6COOH, for instance. The fatty acids so 

 produced esterify with glycerol, which is formed in the 

 early stages of the process, as in alcoholic fermentation 

 (see p. 277). 



Very similar is the suggestion of Smedley and 

 Lubrzynska that acetaldehyde and pynivic acid undergo 

 aldol condensation to give a-keto-y-hydroxy- valeric 

 acid : — 



CH3CHO + CH3CO.COOH — > CH3.CHOH.CH2.CO.COOH 



On decarboxylation, followed by internal oxidation- 

 reduction, butyric acid is formed : — 



CH3.CHOH.CK2-CO.COOH — > CH3.CH2.CH2.COOH + CO2 



a-Keto-y-hydroxyvaleric acid could also lose water to 

 give the unsaturated acid, which on decarboxylation 

 would give rise to crotonaldehyde : — 



CH3.CHOH.CB2.CO.COOH > CH3.CH=CH.C0.C00H 



CH3.CH=CH.C0.C00H > CH3.CH=CH.CH0 + COj 



Crotonaldehyde then condenses with another molecule of 

 pyruvic acid to give an aldol acid which in turn would 

 give rise to caproic acid and also to the homologue of 

 crotonaldehyde containing two extra carbon atoms : — 



CH,.CH=CH.CHO + CH3.CO.COOH — ^ 



CH3.CH = CH.CH.0H.CH2.C0.C00H 



CHo.CH=CH.CH0H.CH2.C0.C00H — ^ 



CH3.CH=CH.CH2.CH2.COOH + COj 



CH3.CH=CH.CH2.CH2.COOH + 2H > 



CH3.CH2.CH2.CH2.CH2.COOH 



CH3.CH = CH.CH=CH.C0.C00H > 



CHg.CH^CH.CH^CH.CHO + CO, 



Continuation of such steps would give rise to the fatty 

 acids starting with butyric acid and increasing in chain 

 length two carbon atoms at a time. a-Keto-y-hydroxy- 

 valeric acid and a-keto-y-hydroxy-valeraldehyde have 



