Yeast and bacteria analysis of grape, wine and cellar equipments by PCR-DGGE

Abstract

<p style="text-align: justify;"><strong>Aims</strong>: Microorganisms play an important role in winemaking. Most of their metabolisms are beneficial to the wine quality but several species have spoilage effects. Microbiological knowledge are crucial for improving species and strains identification and avoiding contamination by spoilage agents. Our objective was to follow wine microbial consortia at each stage of the process from grapes to bottles, and also on cellar equipment surface: barrels for the yeast analysis and tanks for the bacteria analysis.</p><p style="text-align: justify;"><strong>Methods and results</strong>: For a global microbial monitoring, molecular tools are particularly efficient. We chose the PCR-DGGE for direct analyses without cultivation step. We used the rpoB gene as target for the bacteria, and the 26S rRNA gene for the yeast. Species inventories were made during the whole winemaking process, which had never been done before.</p><p style="text-align: justify;"><strong>Conclusion</strong>: From the grape surface to storage in bottles, the microbial diversity decreased. Only the most resistant species were able to survive to the ethanol, SO2, low oxygen and low pH constraints. Among them, Pediococcus parvulus for the bacteria and Brettanomyces bruxellensis for the yeast were the most resistant.</p><p style="text-align: justify;"><strong>Significance and impact of study</strong>: The use of a molecular method independent of the culture stage of the microorganisms like the PCRDGGE has allowed to have a more exhaustive vision of the diversity of the bacteria and yeasts species and to follow their evolution during the winemaking and in the cellar environment . These follow-ups could be extended to other estates in order to study the causes and the consequences of certain variations. The detection of these two prejudicial species was an argument for the PCR-DGGE approach in wine microbial studies.</p>