Isolation and characterization of yeast strains from Badacsony, Hungary

In modern winery, starter strains are used for wine making to avoid the risk of slow or incomplete fermentation. However, application of commercial starter yeasts sometimes leads to a uniform character of the wines. On the other hand, indigenous ("terroir") strains are adapted better to local conditions highlighting the specific taste of wine. In this study, we isolated local yeast strains from Badacsony wine region of Hungary and investigated with microbiological and molecular biological tests in order to develop indigenous starter selection method. As many as 480 yeast strains were isolated and grouped using carbohydrate and nitrogen sources. Finally, 80 selected isolates were characterized for important oenological features, including tolerance of glucose, ethanol and acetic acid. Fermentation ability, killer toxin, hydrogen sulfide and acid production of 80 selected isolates were also tested. Isolates were studied by applying two molecular methods based on rRNA gene sequencing and analysis of Ty retrotransposon's delta elements in case of Saccharomyces strains. Our results have shown that the isolated strains belong to 15 yeast species of 8 genera, and the diversity of yeast population was significantly high in the investigated vineyard. We have found that selection for technological properties was a potential way to find suitable strains from the local microbiome, because a high proportion of isolated wild yeast strains show beneficial oenological properties for wine making. Further, we studied 35 available starter yeasts to avoid re-isolation and we identified only 3 starter yeasts from grape and must samples, which can be considered as very low incidence.