Oenological capabilities of yeasts isolated from high-sugar matrices (manna and honey) as potential starters and co-starters for winemaking

Non-Saccharomyces yeasts have recently garnered significant interest in oenology. When co-inoculated with Saccharomyces cerevisiae, they contribute to the improvement of wine quality from a sensory point of view. In the present study, a group of yeasts previously isolated from manna and honey by-products were subjected to a genotypic identification. The D1/D2 variable domains of the 26-sRNA gene and the ITS region of the 5.8S gene were sequenced. Additionally, a differentiation of strains was carried out by RAPD-PCR. All strains underwent in vitro screening. Subsequently, a micro-vinification experiment was conducted, focusing on strains with favourable technological characteristics: Lachancea thermotolerans, Starmerella lactis-condensi, and Candida oleophila. These strains were sequentially inoculated alongside a control strain of Saccharomyces cerevisiae. Technological screening revealed that some strains exhibited limited H2S production, ethanol tolerance (up to 8% v/v), resistance to potassium metabisulphite (200 mg/L), osmotic stress tolerance (up to 320 g/L of glucose), and copper resistance (on average 5 mM). The findings from this study can guide the selection of new starters and co-starters for regional wine production