Metabolism of Dekkera/Brettanomyces Isolated from Wine

The objectives of this proposal were to conduct a descriptive analysis of a group of
strains of the yeast Dekkera/Brettanomyces in wine in order to define the diversity of
metabolites produced and to characterize these strains physiologically for comparison to
the genetic and molecular analysis being conducted by collaborator Dr. Thomas Henick-
Kling. The aim of this work is to be able to define the molecular basis of specific traits of
Dekkera/Brettanomyces so that a rapid DNA-based analysis of strains could be conducted
and used to predict phenotypic behaviors such as aroma metabolite production. Thirtyfive
strains of Brettanomyces were selected that had been characterized for growth on a
variety of substrates and environmental conditions. The strains were used to inoculate a
Cabernet Sauvignon wine, left in the wine for 46 days, and the wines evaluated by a
sensory panel. A descriptive analysis was initially done, and the wines were then
evaluated for the appearance of the specific characters selected by the panel. A statistical
analysis was performed to define the factors most impacting the aromas of the wines. In
addition, synthetic wines and juices were inoculated with a subset of these strains with a
variety of amino acid and phenolic compound additions to define the aromatic characters
associated with specific precursor compounds.

Our previous research has helped winemakers and enologists understand the diversity of
the Dekkera/Brettanomyces that can be found in wines and how difficult it is to make
generalizations about these organisms. This research begins to define how important
substrate availability is to the production of typical aromas produced by
Dekkera/Brettanomyces. This study will determine the role of specific nutritional
supplements that may have been added to stimulate Saccharomyces or lactic acid bacteria
in the formation of aroma characters by Dekkera/Brettanomyces. This work also starts to
differentiate the contribution of the different strains of Dekkera/Brettanomyces from the
importance of the substrate they are growing on when it comes to the aromas being
produced. This project has also shown that there does not appear to be a suite of traits of
Dekkera/Brettanomyces that segregate by geographic origin.