Influence of Single Nitrogen Compounds on Growth and Fermentation Performance of Starmerella bacillaris and Saccharomyces cerevisiae during Alcoholic Fermentation

Nitrogen is among the essential nutriments that govern interactions between yeast species in the wine environment. A thorough knowledge of how these yeasts assimilate the nitrogen compounds of grape juice is an important prerequisite for a successful co- or sequential fermentation. In the present study, we investigated the efficiency of 18 nitrogen sources for sustaining the growth and fermentation of two Starmerella bacillaris strains displaying metabolic properties, compared to the reference yeast Saccharomyces cerevisiae. The analysis of growth and fermentation parameters provided a comprehensive picture of S. bacillaris preferences with respect to nitrogen sources for sustained growth and fermentation. Important differences were observed with S. cerevisiae regarding rates, final population, and CO2 production. In particular, Lys and His supported substantial S. bacillaris growth and fermentation contrary to S. cerevisiae, while only 3 nitrogen sources, Arg, NH4+, and Ser, promoted S. cerevisiae growth more efficiently than that of S. bacillaris strains. Furthermore, S. bacillaris strains displayed a higher fermentative activity than S. cerevisiae during the first phase of culture with Gly or Thr, when the former species consumed solely fructose. Finally, no correlation has been shown between the ability of nitrogen sources to support growth and their fermentation efficiency. The specificities of S. bacillaris regarding nitrogen source preferences are related to its genetic background, but further investigations are needed to elucidate the molecular mechanisms involved. These data are essential elements to be taken into account in order to make the best use of the potential of the two species. IMPORTANCE Mixed fermentations combining non-Saccharomyces and S. cerevisiae strains are increasingly implemented in the wine sector, as they offer promising opportunities to diversify the flavor profile of end products. However, competition for nutrients between species can cause fermentation problems, which is a severe hindrance to the development of these approaches. With the knowledge provided in this study on the nitrogen preferences of S. bacillaris, winemakers will be able to set up a nitrogen nutrition scheme adapted to the requirement of each species during mixed fermentation through must supplementation with relevant nitrogen compounds. This will prevent nitrogen depletion or competition between yeasts for nitrogen sources and, consequently, potential issues during fermentation. The data of this study highlight the importance of appropriate nitrogen resource management during co- or sequential fermentation for fully exploiting the phenotypic potential of non-Saccharomyces yeasts.

Automated summary

This study explored the nitrogen preferences of two Starmerella bacillaris strains compared to Saccharomyces cerevisiae, highlighting differences in growth and fermentation efficiency. S. bacillaris strains displayed distinct preferences for nitrogen sources, influenced by genetic background, which can be optimized to prevent competition and nutrient depletion during fermentation. Understanding nitrogen resource management is crucial for fully exploiting the potential of mixed fermentations with non-Saccharomyces yeasts.