The dynamics of the wine yeast strains presented in five spontaneous Malvasia wine fermentations have been studied. Five spontaneous fermentations were followed microbiologically and biochemically during 24 days. Several samples were taken during the fermentation process. The first sampling of must was performed from the container. Samples were taken from each fermenter, when about 20 pourcentage, 70 pourcentage, and 90 pourcentage of the sugar were fermented. The yeast isolates were characterized using molecular techniques and physiological testing. The total yeast population level in the must after sedimentation was 105 cfu/ml and included the following genera: Candida, Metschnikowia, Hanseniaspora, Rhodotorula, Issatchenkia and Debaryomyces. However, Saccharomyces sp. was not detected in fresh must samples plated on YEPD medium. Among 649 isolates from the subsequent phases of fermentation, 46 different strain of Saccharomyces cerevisiae were distinguished. A sequential substitution of S. cerevisiae strains occurred during the different phases of fermentation. At the slow fermentation rate, strain L4 was most abundant in almost all fermenters. At the beginning of the tumultuous fermentation phase, the most frequent strain became L1 followed by strain L4. Finally, during the fermentation process, pattern L4 was clearly replaced by strain L1 followed by pattern L12. Despite the same fermentation source (grape must), differences among five spontaneous fermentations were observed. The population dynamics of S. cerevisiae yeasts, especially the dynamics of the major S. cerevisiae strains (L1, L4, and L12) were quite similar in all five fermenters in opposite to the minor strains of S. cerevisiae.
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