Isolation of yeast strains with ability to reduce volatile acidity of wines

The objective of the present study was to isolate and characterize wine yeasts able to reduce volatile acidity of wines. From a set of 135 yeast isolated during a refermentation wine procedure, four strains revealed ability to use glucose and acetic acid simultaneously. The strains were tested regarding their growth patterns in a differential medium containing glucose (0.2% w/v) and acetic acid (0.5% v/v), at pH 4.0 or 6.0. The selected strains displayed growth associated to color change of the pH indicator of the medium indicative of simultaneous glucose and acetic acid consumption. Three of them were identified as Saccharomyces cerevisiae and one as Lachancea thermotolerans by sequencing the D1/D2 domain of the large subunit (26S) ribosomal DNA. In two culture media containing acidic wines with high glucose/low ethanol or low glucose/high ethanol concentrations, the S. cerevisiae strains showed an initial simultaneous consumption pattern of glucose and acetic acid under both aerobic and limited aerobic conditions, independently of the relative amounts of glucose and ethanol. This results show a high physiological diversity among strains of this species, validating our approach to search for interesting strains among indigenous yeasts. Comparatively, the isolated L. thermotolerans 44C and Zygosaccharomyces bailii ISA1307 were able to exhaust acetic acid only when grown under aerobic conditions. The S. cerevisiae strains characterized in the present study appear promising for the decrease of volatile acidity in acidic wines under the low-oxygen conditions of a typical refermentation process.This study was supported by the programme POCI 2010 (project POCI/AGR/56102/2004