Yeast DNA recovery during the secondary fermentation step of Lombardy sparkling wines produced by Champenoise method

The possibility of recovering amplifiable DNA from sparkling wine produced by Champenoise method was investigated. Indeed, the sensory refining of this product occurs through the yeast autolysis with the release of cellular components, including nucleic acids. An efficient and reliable method to purify DNA is provided coupling two purification treatments: organic solvents and magnetic beads that have never been applied before on wine. The yield of DNA extraction ranged between 10 and 60 %. Starting from 150 mL spiked samples, up to 0.1–0.6 pg of yeast DNA was detected, potentially corresponding to about 4–24 cells of a diploid strain of S. cerevisiae. After development of new primers, the performance of the protocol was validated in real-time PCR by targeting the ITS region of Saccharomyces cerevisiae, one of the main species involved in the secondary fermentation. The monitoring of sparkling wines during the ageing on lees was carried out in four wineries in Franciacorta and Oltrepò Pavese areas up to 2 years from the tirage to wine samples ready for the market as well. Results show that DNA extraction and amplification are properly obtained all along the times, for the species identification; however, after 16 months of ageing, a pre-amplification step needed to be introduced to the procedure for finding a specific signal. Because of the strong DNA degradation, the typing of the inoculated strain or the grape cultivar was not achieved in commercialized wine samples.