Assessment of competition in wine fermentation among wild Saccharomyces cerevisiae strains isolated from Sangiovese grapes in Tuscany region

•Six different biotypes among 160 S. cerevisiae isolates were found.•The dominance character during mixed fermentation was tested.•A strain with high dominance and influencing composition of mixed-culture wines was selected.•In co-fermentation the existence of strain metabolic interaction was suggested.•Two strains are suggested as suitable starter candidates for industrial vinification.

In this study we analyzed Saccharomyces cerevisiae isolates obtained from spontaneous fermentations of grapes collected in one vineyard (same rows), during four harvest seasons (2006-2010). A total of 160 isolates were characterized by PCR amplification of inter-δ region. Six strains, representative of the different inter-δ profiles obtained, were tested in single and mixed fermentations at laboratory scale. In all the mixed fermentations, the strain possessing profile A (the only biotype found for two consecutive years) was tested in co-cultures with each of strains showing the other profiles. The strain “A” dominated in almost all the mixed fermentations. The experimental wines obtained from single and co-culture fermentations were analyzed for the content of main secondary compounds. The wines produced by mono-cultures were very different from the wines obtained by co-fermentations, except the wine by strain “A”, which grouped together with mixed-culture wines. Furthermore, the comparison between volatile components determined in mixed culture and blended wines, obtained by mixing monoculture wines, can suggest the existence of yeast metabolic interactions during mixed fermentations. The strain exhibiting the profile A resulted a good “competitor” not only among natural yeast population, but it was also capable to dominate mixed fermentations at lab scale.