Biosynthesis of γ-Nonalactone in Yeast

γ-Nonalactone is known as aroma active compound in fermented products such as beer. In a series of labeling experiments with deuterated linoleic acid and [18O1]-13- and 9- hydroxyoctadecadienoic acid, respectively, two biosynthetic routes to γ-nonalactone in yeast were elucidated: (i) 13-lipoxygenation / reduction and (β-oxidation followed by one α-oxidation step results in (S)-γ-nonalactone (~ 60 % e.e.); (ii) 9-lipoxygenation / reduction and Baeyer-Villiger oxidation yields azelaic acid and 2E,4E-nonadien-1-ol which is further transformed into (R)-γ-nonalactone (~ 46 % e.e.).