Abstract Description

Yeasts are widely employed in industrial bioprocesses, such as winemaking, through fermentation, where they convert substrates into valuable products such as ethanol, organic acids, and flavour compounds during alcoholic fermentation. Beyond sugars, these yeasts require a wide range of nutrients, including nitrogenous compounds, lipids, minerals and vitamins. The latter are essential micronutrients, specifically water-soluble B-vitamins which play an important role in yeast physiology, as they function as co-factors or precursors of co-factors in various metabolic pathways. Additionally, these B vitamins contribute to membrane integrity and cellular signalling highlighting their importance as essential micronutrients. Although yeast species such as Saccharomyces cerevisiae can synthesise their own vitamins, various physiological and environmental factors may lead them to prioritise extracellular vitamin uptake. Despite their significance, little research has focused on the specific effects of B vitamins on different yeast species, especially non-Saccharomyces yeasts. These yeasts have gained increasing attention in winemaking due to their antimicrobial activity and their unique sensory and metabolic contributions. However, their vitamin requirements remain largely unexplored because most research has focused on S. cerevisiae. In mixed-species fermentations, yeasts compete for available nutrients, and vitamin availability can influence both microbial community dynamics and metabolite production. Therefore, this study investigated the B-vitamin requirements of various yeast species and strains and evaluated how varying vitamin concentrations affect their fermentative performance and metabolic profiles. The B vitamin requirements of S. cerevisiae, Torulaspora delbruecki, Lachancea thermotolerans and Metschnikowia pulcherrima were assessed through fermentations in synthetic must with altered B vitamin concentrations. Results showed that vitamin requirements varied across species with differential growth responses observed in the absence, presence, and excess of individual B vitamins. Moreover, metabolic footprints were altered under these varying vitamin conditions. Notably, the absence and excess concentrations of vitamins had significant impacts, reducing growth and fermentative capacity. These findings highlight the importance of B vitamins in regulating cellular function and metabolite production. The observation that yeast species and strains exhibit distinct vitamin requirements at varying vitamin concentrations contributes to the understanding of yeast nutrient requirement, physiology, and community dynamics in mixed-species fermentations. Additionally, these insights could aid in optimising nutrient supplementation strategies to enhance yeast performance, fermentation efficiency, and product quality.