Use of <i>Schizosaccharomyces pombe</i> to Consume Gluconic Acid in Grape Must in Unique and Sequential Inoculations With <i>Saccharomyces cerevisiae</i>

Background and Aims: Musts with a high concentration of gluconic acid can be obtained because of the colonization of grapes by spoilage fungi and bacteria or the treatment of musts with glucose oxidase. Our research aims to obtain yeast strains capable of degrading this gluconic acid. Methods and Results: Assays were conducted by inoculating selected strains of Schizosaccharomyces pombe in both must and wine. The most effective strategy to achieve the highest gluconic acid consumption was the inoculation of S. pombe strains into the must. Fermentations of Verdejo grape must, supplemented with sodium gluconate, were conducted using strains of S. pombe in both unique and sequential inoculations with a strain of Saccharomyces cerevisiae at 24 and 48 h. A metabolic and kinetic variability were observed in the consumption of glucose, fructose, malic acid, and gluconic acid among the strains under investigation that exhibited a high fermentation power and capacity to degrade up to 100% of malic acid. Conclusions: The S. pombe strains, Sp3 and Sp7, consumed the highest amount of gluconic acid, 90.5 ± 3.7% and 63.9 ± 3.6%, respectively. Sequential inoculations at 24 h significantly reduced gluconic acid consumptions. In contrast, sequential inoculations at 48 h demonstrated no differences with the unique Strains Sp1, Sp3, and Sp4.