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

Abstract

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 <i>Starm. bacillaris</i> strains displaying metabolic properties, compared to the reference yeast <i>S. cerevisiae</i> The analysis of growth and fermentation parameters provided a comprehensive picture of <i>Starm. bacillaris</i> preferences with respect to nitrogen sources for sustained growth and fermentation. Important differences were observed in <i>S. cerevisiae</i> regarding rates, final population and CO₂ production. In particular, Lys and His supported substantial <i>Starm. bacillaris</i> growth and fermentation contrary to <i>S. cerevisiae,</i> while only 3 nitrogen sources, Arg, NH4⁺ and Ser, promoted <i>S. cerevisiae</i> growth more efficiently than that of <i>Starm. bacillaris</i> strains. Furthermore<i>, Starm. bacillaris</i> strains displayed a higher fermentative activity than <i>S. cerevisiae</i> 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 <i>Starm. bacillaris</i> regarding nitrogen sources 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.<b>IMPORTANCE</b> Mixed fermentations combining non-<i>Saccharomyces</i> and <i>S. cerevisiae</i> strains are increasingly implemented in the wine sector as they offer promising opportunities to diversify the flavour 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 <i>Starm. bacillaris</i>, 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 an appropriate nitrogen resource management during co- or sequential fermentation for fully exploiting the phenotypic potential of non-<i>Saccharomyces</i> yeasts.