Screening of aroma metabolites within a set of 90 Saccharomyces strains

Currently, the main demand in the global wine market relies on products with unique flavour profiles, character, and typicity, and the metabolism of yeasts greatly influences the organoleptic properties of wines. Therefore, the natural diversity of Saccharomyces strains rises in interest over the last decade, but a large part of this phenotypic diversity remains unexplored. Moreover, the genetic basis underlying the variation in the production of flavour-active metabolites within the Saccharomyces genus remains poorly understood. The main purpose of this project is to provide a better understanding of how the synthesis of these flavour-active compounds is modulated at genetic level, aiming to identify genes with specific functions in the metabolism of yeasts. This information will be obtained through the generation of novel hybrids between different Saccharomyces species and the use of quantitative genetics. In this context, the first step was to assess the phenotypic diversity at the scale of Saccharomyces genus, regarding traits of industrial interest. With this aim, 90 yeast strains of all the eight species which compose the Saccharomyces clade were screened for their fermentative capacities and the production of aromas and other compounds of interest (such as glycerol or succinate). Fermentations in oenological conditions were carried out at different temperatures, monitoring the kinetic profiles and analysing the production of the main fermentation metabolites (by HPLC) as well as the production of more than 40 aroma compounds (by GC-MS). The sporulation ability of the strains, necessary for the hybridization, was also assessed. Important differences were found in the kinetic and volatile profiles of the strains, and the whole dataset provides a comprehensive picture of the phenotypic diversity within the genus Saccharomyces. This information confirms the interest in further development of genetic approaches to identify the molecular basis underlying the studied traits and opens the door for their improvement.

Authors: Rafael Álvarez-Rafael – UMR 1083 Sciences Pour l’Oenologie, INRAE, Montpellier SupAgro, Montpellier, France,Sylvie DEQUIN – UMR 1083 Sciences Pour l’Oenologie, INRAE, Montpellier SupAgro, Montpellier, France Edward J. LOUIS – Centre of Genetic Architecture of Complex Traits, University of Leicester, Leicester, UK Carole CAMARASA – UMR 1083 Sciences Pour l’Oenologie, INRAE, Montpellier SupAgro, Montpellier, France 

Email: rafael.alvarez-rafael@inrae.fr

Keywords: alcoholic fermentation; genus saccharomyces; phenotypic diversity; fermentative volatile compounds

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