Characterization of the yeast ecosystem in grape must and wine using real-time PCR

The complex microbial ecosystem of grape must and wine harbours a wide diversity of yeast species. Specific oligonucleotide primers for real-time quantitative PCR(QPCR) were designed to analyse several important non-Saccharomyces yeasts (Issatchenkia orientalis, Metschnikowia pulcherrima, Torulaspora delbrueckii, Candida zemplinina and Hanseniaspora spp.) and Saccharomyces spp. in fresh wine must, during fermentation and in the finished wine. The specificity of all primer couples for their target yeast species were validated and the QPCR methods developed were compared with a classic approach of colony identification by RFLP-ITS-PCR on cultured samples. Once the methods had been developed and validated, they were used to study these non-Saccharomyces yeasts in wine samples and to monitor their dynamics throughout the fermentation process. This study confirms the usefulness and the relevance of QPCR for studying non-Saccharomyces yeasts in the complex yeast ecosystem of grape must and wine.