Investigation of yeast population diversity and dynamics in spontaneous fermentation of Vidal blanc icewine by traditional culture-dependent and high-throughput sequencing methods

Yeast diversity and dynamics associated with the spontaneous fermentation of Vidal blanc icewine was investigated in icewine from the Huanren region of China. This knowledge is crucial to control fermentation and to screen for indigenous strains capable of producing icewines with regional characteristics. Laboratory-scale spontaneous fermentation was performed to monitor wine yeasts involved in the fermentation. Samples were collected from different stages of the fermentation and analyzed using culture-dependent (Wallerstein laboratory nutrient agar) and -independent methods (high-throughput sequencing, HTS). Two hundred eight yeast strains were isolated and identified by sequencing the internal transcribed spacer (ITS) region and the 26S rDNA D1/D2 domain genes; non-Saccharomyces yeasts were predominant in the initial stages, while Saccharomyces yeasts dominated in the final stages of the fermentation. Analysis of the HTS data of the ITS1 region gene revealed a more complex mycobiota. The wine yeast species found by HTS were more abundant than those found by cultivation; non-Saccharomyces yeasts were dominant initially, while Metschnikowia and Saccharomyces were predominant in the end. These results were not completely in agreement with the results obtained by using the cultivation-based method. Moreover, HTS revealed the presence of Mrakiella and Mrakia, which have never been reported in icewine before.