Screening and characterization of indigenous Saccharomyces cerevisiae and non-Saccharomyces yeasts isolated from Sicilian vineyards

The use of Saccharomyces cerevisiae as starter cultures in winemaking is widespread in all over the world. However, a growing interest in exploring native non-Saccharomyces yeast species as co-starters has emerged, driven by their potential to enhance wine complexity and regional identity. The aim of the present study was to investigate indigenous yeasts from Sicily, to select novel strains with promising technological traits. A comprehensive screening of indigenous S. cerevisiae and non-Saccharomyces yeasts was conducted across seven locations in Sicily, including the unique volcanic zone of Mount Etna. A total of 95 yeast isolates were obtained and genetically characterized by RFLP-PCR and sequencing of 5.8S-ITS rDNA. Isolates were screened for oenological traits and the most promising, belonging to Starmerella bacillaris, Hanseniaspora uvarum, and Metschnikowia pulcherrima species, were used for single and sequential fermentations in synthetic must. Results revealed a remarkable diversity of physiological traits within and among the species, regarding stress tolerance, enzymatic activity and growth at different temperatures. Notably, isolates of H. uvarum and St. bacillaris exhibited great ethanol tolerance, and the latter also strong glycerol production. Furthermore, M. pulcherrima exhibited a wide range of aroma-related enzymatic activities, particularly beta-glucosidase. The remarkable diversity, the phenotypic traits of the indigenous yeasts, represents a promise for the improvement of innovative fermentation strategies and for the development of wine indigenous starters related with the region's terroir.