Recovery of endo-polygalacturonase activity in wine yeast and its effect on wine aroma

The PGU1 gene, which encodes an endo-polygalacturonase, is present in most strains of Saccharomyces cerevisiae. In some strains that lack activity, the PGU1 gene was replaced by a partial transposon. In an attempt to restore enzyme activity, the PGU1 gene was successfully reintroduced into its native position in five of these strains. Polygalacturonase activity was recovered in strains UCLMS-1, -3 and -4, while Collection Cépage Cabernet and L2226 did not show any transcription of the gene after integration. Small-scale fermentations, under conditions mimicking those of winemaking, were carried out with the recombinant strains to determine the effect of an endo-polygalacturonase-producing wine strain on the wine aroma. Some statistically significant tendencies were observed for the production of certain compounds whose concentrations were higher in the wine made from the recombinant strains than that from their respective wild types. These differences might therefore induce a slight change in the aroma profile of the wines. Moreover, recovery of endo-polygalacturonase activity in certain wine strains did, however, provide an insight into the regulation of PGU1 in these strains.