The microbial dynamics of the fermentation of Vino Santo, a typical sweet wine Trentinian production

Vino Santo, a sweet wine produced from Nosiola grapes in a small, well defined geographical area in the Italian Alps, is one of the most evident examples of strict connection between geography and product. Despite the homogeneity of the initial material and of the strictly regulated traditional procedures, the final products from different wineries show distinct organoleptic properties, raising the question of the contribution of microbial populations present before and during the fermentation. Using metagenomics, we characterize definition of microbial the dynamics of microbial communities in the fermentations in three wineries’ productions, resulting from the fermentation of the same grape type a regionally typical vine type (Nosiola) and based on almost the same timing and procedure, prepared the ground for the description of the contribution of microbial populations to the “terroir”. We found that the shared microbiota of Vino Santo fermentations consists of environmental fungi and bacteria (Candida zemplinina, Aureobasidium pullulans, Penicillium bialowiezense, Sphingomonas, Propionibacter and Corynebacterium) and other fermentative microorganisms (Saccharomyces cerevisiae, Candida ethanolica). Despite the apparent territorial homogeneity, relevant differences were observed in the microbiota of the three fermentations: i) the fungal content of musts significantly varied among the wineries; ii) Pichia membranifaciens lasted in only one of the wineries; iii) one fermentation was characterized by the balanced presence of Saccharomyces cerevisiae and Hanseniaspora osmophila during the latest phases.