Influence of yeasts on wine acidity: new insights into <i>Saccharomyces cerevisiae</i>

Climate change is strongly affecting the winemaking sector, notably by decreasing wine acidity due to lower malic acid levels in the grapes. Wine-related microorganisms can greatly affect the organic acid contained in wines as they are able to metabolise or synthesise different acids. Major advances in biochemistry, ecophysiology and molecular biology have led to numerous yeast strains being selected for that have specific oenological properties, including acidity modulation. The yeast Saccharomyces cerevisiae is the most extensively studied species, harbouring both malic acid-consuming and producing strains which are of interest in various vinification itineraries. Yeast-derived acidification of wines can indeed be achieved via malic acid production by S. cerevisiae, as well as via lactic acid production by Lachancea thermotolerans. Co-fermentations of these two species become promising tools to manage wine acidity while ensuring fermentation completion and wine quality. Deacidification of wines via malic acid consumption is relevant in cooler winemaking regions, and/or for shortening malolactic fermentation and thereby increasing wine stability. This review delivers an in-depth overview of the effect of various oenologically relevant yeasts on wine acidity, with a focus on the latest findings on novel (de)acidifying S. cerevisiae strains.