Characterisation of a sulphite-tolerant Schizosaccharomyces pombe strain: potential as spoilage in oversulphited must and as starter cultures in wine

This study characterises a novel Schizosaccharomyces pombe (Sc. pombe) strain SP2 isolated from a winery where alcoholic fermentation has been prevented by sulphiting to obtain preserved grape must, in which spontaneous malo-alcoholic fermentation occurs despite high sulfur dioxide (SO2) concentrations. This work demonstrated that the same yeast strain can have a dichotomous relevance in the same agri-food chain: a spoilage agent in preserved grape must and ii) as a candidate starter culture for wine production. In the study, levels of tolerance to SO2 in the simulations of selective pressure exerted by this bacteriostatic agent are compatible with the phenomenon observed in the winery, demonstrating the spoilage potential of the strain in the preserved must industry. The selection of a highly resistant fission yeast strain highlights the importance of studying food niches to improve our understanding of evolutionary phenomena and phenotypic variability in model microorganisms. Fermentation trials in synthetic musts, white and red wines, contribute to assess the yeast behaviour under monoculture, co-inoculation, and sequential inoculation with Saccharomyces cerevisiae. Sc. pombe monocultures lagged in fermentation kinetics and produced more acetic acid, especially in red musts. Sequential and co-inoculation contributed to enhancing volatile profiles, especially esters and higher alcohols, contributing to superior aromatic complexity as illustrated by multivariate analysis. Sequential inoculation, in particular, enhances the production of key esters and alcohols, enabling efficient malic acid degradation with low acetic acid production. The results also underscore that the matrix type (synthetic must, red, or white wine) interacts strongly with the inoculation strategy in shaping the volatile composition.