Project Portugal 2030

Summary

As mentioned above, T. delbrueckii is one of the most promising non-Saccharomyces yeasts for innovative fermentation practices in wine and bread production. Nevertheless, significant challenges remain to be addressed so that the full benefits of T. delbrueckii are explored and its use becomes standard practice, benefiting Portuguese and global wine and baking industries. In wine production, T. delbrueckii faces challenges beyond the initial stages of grape must fermentation. Even when inoculated as a pure culture, T. delbrueckii usually fails to complete fermentation and disappears rather quickly when co-cultured with S. cerevisiae. It has been proposed that this phenotype is linked to its low resistance to the conditions present in the wine fermentation environment, such as high ethanol and sulfur dioxide (SO2) levels, and possible S. cerevisiae-derived toxicity. We hypothesize that this phenomenon may also stem from limited or inadequate nitrogen availability, or ethanol-induced inhibition of transport of nutrients such as of glucose, amino acid and ammonium. However, our understanding of the molecular mechanisms underlying these mechanisms remains limited, curtailing the development of successful strategies to overcome these limitations. We therefore propose an integrated approach to address the different questions, combining high-throughput methodologies with molecular level data. This will enable comprehensive understanding of T. delbrueckii physiological traits and pave the way for knowledge-driven design of more efficient practices. In sourdough bread making, a main challenge is achieving consistent products with well-balanced flavor profiles, which depend on maintaining consistent starteres and precise control of fermentation. Time management is also an issue, as sourdough bread-making is inherently time-consuming compared to the use of commercial yeast. It typically entails longer fermentation periods, including starter preparation, which may not always align with time- and consequently cost-saving needs in bread manufacturing. The development of readily available sourdough starters with improved resistance and flavor-imparting properties would enable preserving the benefits of natural fermentations, without the risk of spontaneous microbiota development in doughs. Incorporating T. delbrueckii into such starters, potentially in mixed cultures with S. cerevisiae—frequently a major component in sourdoughs -, or other frequently isolated yeasts and bacteria, could aggregate T. delbrueckii beneficial characteristics. However, there is a lack of studies describing potential interactions of T. delbrueckii with other yeasts, or even bacteria in bread doughs. Dynamic studies between T. delbrueckii and natural strains from sourdoughs would allow to assess the feasibility of using a co-fermentation of the dough and its advantages in improving bread quality. Specifically, we will: • Elucidate ecological interactions between different T. delbrueckii strains and natural grape must and dough microbial species (Task 1) • Characterize the nitrogen nutritional requirements of T. delbrueckii and assessment of their impact in the yeast growth during dough and grape must fermentation (Task 2) • Manipulate and characterize glucose transport in T. delbrueckii to improve growth and grape must fermentation (Task 3) • Elucidate the phenotypic and molecular responses of T. delbrueckii to stress conditions (Task 4)