To be or not to be required: Yeast vitaminic requirements in winemaking.

Although vitamins are prime actors in yeast metabolism, the nature and the extent of their requirement in Saccharomyces cerevisiae in winemaking remains little understood. To fill this gap, the evolution of 8 water-soluble vitamins and their diverse vitamers during its alcoholic fermentation in a synthetic must medium was monitored, providing the first evidence of the consumption of vitamers by five commercial S. cerevisiae strains, and highlighting the existence of preferential vitameric sources for its nutrition. The vitamins required by the yeast, B1, B5, and B8, were then identified, and the nature of their requirement characterized, strongly asserting the required trait of B1 for fermentation, B8 for growth, and B5 for both processes. The extent of the requirement for B5, that with the most impact of the three vitamins, was then quantified in three S. cerevisiae strains, resulting in the conclusion that 750 µg.L-1 should prove sufficient to cover the yeast's requirements. This investigation offers the first insight into S. cerevisiae vitaminic requirements for winemaking.

To each their own: Delving into the vitaminic preferences of non-Saccharomyces wine yeasts.

Considering the growing interest in non-Saccharomyces wine yeasts, and notably in the context of mixed fermentations with S. cerevisiae, understanding their nutritional behaviors is essential to ensure better management of these fermentations. The vitaminic consumption of three non-Saccharomyces yeasts (Starmerella bacillaris, Metschnikowia pulcherrima and Torulaspora delbrueckii) was investigated during their growth in wine-like conditions, providing initial evidence that they consume different vitamers. The vitamin consumption profiles during their growth highlighted releases of certain vitamers by the yeasts before re-assimilation, strongly suggesting the existence of synthesis pathways. Not only did the essential character of vitamin B1, in particular, appear to be a trait common to these yeasts, since all its vitamers are consumed, this investigation also provided evidence of the existence of species-dependent preferences for their vitaminic sources. These different behaviors were quite striking in certain vitamers, as was observed in nicotinamide: while it was consumed by T. delbrueckii, it was left untouched by S. bacillaris and produced by M. pulcherrima during growth. Furthermore, this offers grounds for further investigation into these yeasts' requirements, and provides the first tool for managing vitamin resources during mixed fermentations with S. cerevisiae, and for preventing nutritive deficiencies from occurring.