Direct Identification of the Indigenous Yeasts in CommercialWine Fermentations

A method is presented to directly characterize the yeast diversity in wine fermentations using denaturing gradient gel electrophoresis (DGGE) of polymerase chain reaction (PCR) amplified ribosomal RNA genes. PCR-DGGE analysis of a commercial sweet wine fermentation clearly profiled the shifts in microbial diversity that occurred throughout the fermentation. Botrytis populations identified in press pan samples were absent from the settling tank and ensuing fermentation samples. Indigenous yeasts including Candida, Metschnikowia, and Pichia species were distinguished in the early stages of the fermentation prior to emergence of a Saccharomyces population. Surprisingly, the PCR-DGGE signature of Candida species persisted well into the fermentation long after the development of a dominant Saccharomyces population. By direct identification of yeast populations, PCR-DGGE can provide a rapid and comprehensive view of the microbial diversity present in wine fermentations without the necessity for enrichment plating.