Optimización del uso de levaduras no-saccharomyces en fermentaciones mixtasrequerimientos nutricionales e interacciones microbianas

Abstract

The use of non-Saccharomyces yeasts with S. cerevisiae to increase complexity in wines has become popular in the last years. There are several types of microbial interactions between yeast species that can cause fermentation problems. Therefore, the main objective of this thesis was to improve knowledge about the fermentative potential and nutritional requirements of different non-Saccharomyces yeasts, and to evaluate their impact on the development of mixed fermentations with S. cerevisiae. The results of the thesis show that nitrogen consumption and preferences depend on the yeast species used in fermentation, and the nitrogen composition of the must has a direct effect on the fermentation profile and growth yeast. Moreover, in mixed fermentations, S. cerevisiae was not always able to dominate fermentation, especially in sequential inoculations with non-Saccharomyces species with high fermentative capacity. To understand this lack of imposition, the possible interactions between S. cerevisiae and these species were studied: inhibition by cell contact, presence of inhibitory compounds, or limitation of nutrients. The results showed a nutrient competition between these non-Saccharomyces species and S. cerevisiae, which can cause problems in sequential fermentations. In particular, there was an improvement in fermentation with the addition of thiamine, zinc and amino acids to the must that had been partially fermented by the non-Saccharomyces species. Therefore, it is important to control nutrient availability and inoculum size to avoid fermentation problems in sequential inoculations. Finally, the possible use of T. delbrueckii and L. thermotolerans as a mixed inoculum without the presence of S. cerevisiae was evaluated. We observed that both species could complete alcoholic fermentation, in individual and mixed inoculation. The aromatic profile of the wines obtained depended on the inoculation strategy used, and was different from the profile obtained when S. cerevisiae was used.