Saccharomyces cerevisiae and S. kudriavzevii Synthetic Wine Fermentation Performance Dissected by Predictive Modeling

David Henriques, Javier Alonso-del-Real, Amparo Querol, Eva Balsa-Canto

Wineries face unprecedented challenges due to new market demands and climate change effects on wine quality. New yeast starters including non-conventionalSaccharomycesspecies, such asS. kudriavzevii, may contribute to deal with some of these challenges. The design of new fermentations using non-conventional yeasts requires an improved understanding of the physiology and metabolism of these cells. Dynamic modeling brings the potential of exploring the most relevant mechanisms and designing optimal processes more systematically. In this work we explore mechanisms by means of a model selection, reduction and cross-validation pipeline which enables to dissect the most relevant fermentation features for the species under consideration,Saccharomyces cerevisiaeT73 andSaccharomyces kudriavzeviiCR85. The pipeline involved the comparison of a collection of models which incorporate several alternative mechanisms with emphasis on the inhibitory effects due to temperature and ethanol. We focused on defining a minimal model with the minimum number of parameters, to maximize the identifiability and the quality of cross-validation. The selected model was then used to highlight differences in behavior between species. The analysis of model parameters would indicate that the specific growth rate and the transport of hexoses at initial times are higher forS. cervisiaeT73 whileS. kudriavzeviiCR85 diverts more flux for glycerol production and cellular maintenance. As a result, the fermentations withS. kudriavzeviiCR85 are typically slower; produce less ethanol but higher glycerol. Finally, we also explored optimal initial inoculation and process temperature to find the best compromise between final product characteristics and fermentation duration. Results reveal that the production of glycerol is distinctive inS. kudriavzeviiCR85, it was not possible to achieve the same production of glycerol withS. cervisiaeT73 in any of the conditions tested. This result brings the idea that the optimal design of mixed cultures may have an enormous potential for the improvement of final wine quality.