Genetic analysis of geraniol metabolism during fermentation

Damien Steyer (1) , Claude Erny (2, 3) , Patricia Claudel (1) , Genevieve Riveill (1) , Francis Karst (1) , Jean-Luc Legras (4)

1 SVQV - Santé de la vigne et qualité du vin
2 Université de Haute-Alsace (UHA) - Université de Haute-Alsace (UHA) Mulhouse - Colmar
3 LVBE - Laboratoire Vigne Biotechnologie et Environnement
4 SPO - Sciences Pour l'Oenologie

Geraniol produced by grape is the main precursor of terpenols which play a key role in the floral aroma of white wines. We investigated the fate of geraniol during wine fermentation by Saccharomyces cerevisiae. The volatile compounds produced during fermentation of a medium enriched with geraniol were extracted by Stir-bar sorptive extraction and analysed by GC–MS. We were able to detect and quantify geranyl acetate but also citronellyl- and neryl-acetate. The presence of these compounds partly explains the disparition of geraniol. The amounts of terpenyl esters are strain dependant. We demonstrated both by gene overexpression and gene-deletion the involvement of ATF1 enzyme but not ATF2 in the acetylation of terpenols. The affinity of ATF1 enzyme for several terpenols and for isoamyl alcohol was compared. We also demonstrated that OYE2 is the enzyme involved in geraniol to citronellol reduction. Fermenting strain deleted from OYE2 gene produces far less citronellol than wild type strain. Moreover lab strain over-expressing OYE2 allows 87% geraniol to citronellol reduction in bioconversion experiment compared to about 50% conversion with control strain.

Mots clés: fermentation; citronellol; Saccharomyces cerevisiae; Fermentation; Geraniol; Geranyl acetate; OYE2; ATF1

Domaines: Ethique

Damien Steyer, Claude Erny, Patricia Claudel, Genevieve Riveill, Francis Karst, et al.. Genetic analysis of geraniol metabolism during fermentation. Food Microbiology, 2013, 33, pp.228-234. ⟨10.1016/j.fm.2012.09.021⟩. ⟨hal-01837674⟩