Survey on yeast biodiversity in Georgian vineyards: a pristine environment for the selection of wine strains

Wine market is undergoing a change due to the ever-growing request to improve the sensory features and nutritional properties of the final product. New styles of wines and innovative ways of managing fermentations directed the research towards the search for new strains to be employed as starters. The present work is aimed to investigate the yeast biodiversity in Georgia, an ancient vine growing area, where the use of starter cultures is not yet spread, and to select non-conventional yeast species for wine-making. Yeast isolation was carried out from grapes, musts and wines in six different Georgian regions. One hundred and seventy six isolates were identified as belonging to 14 different species: S. cerevisiae (36.4%), Hanseniaspora gulliermondi and Metshnikowia pulcherrima (about 20%), Cryptococcus flavescensis (8%), Cryptococcus carnescens and Torulaspora delbrueckii (about 3%), Candida intermedia, Pichia guilliermondi and Pichia kluyveri (about 2%), Candida gotoi, Issatchenkia terricola, Cystofilobasidium infirmominiatum, Kluyveromyces marxianus and Hanseniaspora osmophila (≤ 1%). S. cerevisiae isolates were further submitted to the whole-genome comparison to establish phylogenetic relationships and genome structure. Some non-saccharomyces yeasts were to investigated at technological level (alcohol and SO2 tolerance, acetic acid, glycerol and H2S production). One K. marxianus and one T. delbrueckii strains with interesting features inoculated in micro-vinification experiments proved to be promising for wine production