Location of the double bond positions in microbial isomerization and hydrogenation products of α- and γ-linolenic acids

The biohydrogenation of α-linolenic acid (cis-9,cis-12,cis-15-octadecatrienoic acid) and γ-linolenic acid (cis-6, cis-9,cis-12-octadecatrienoic acid) by Eubacterium lentum Rega involves migration of the 12-double bond to the 11 position providing 9,11,15- and 6,9,11-octadecatrienoic acid, followed by reduction of the 9-double bond to 11,15- and 6,11-octadecadienoic acid, respectively. The positions of the double bonds in these acids have been determined by mass spectrometry of the methyl poly(trimethylsilyloxy)-octadecanoates, obtained by hydroxylation of the double bonds in the methyl esters and silylation of the resulting polyols. This method may be applied to trienic fatty acids containing a conjugated diene moiety.