Reassessment of phenotypic traits for Saccharomyces bayanus var. uvarum wine yeast strains

Among Saccharomyces yeast, S. cerevisiae and S. bayanus var. uvarum are related species, sharing the same ecosystem in sympatry. The physiological and technological properties of a large collection of genetically-identified S. bayanus var. uvarum wine strains were investigated in a biometric study and their fermentation behavior was compared at 24 °C and 13 °C. The variability of the phenotypic traits was considered at both intraspecific and interspecific levels. Low ethanol tolerance at 24 °C and production of high levels of 2-phenylethanol and its acetate were clearly revealed as discriminative technological traits, distinguishing the S. bayanus var. uvarum strains from S. cerevisiae. Although some S. bayanus var. uvarum strains produced very small amounts of acetic acid, this was not a species-specific trait, as the distribution of values was similar in both species. Fermentation kinetics at 24 °C showed that S. bayanus var. uvarum maintained a high fermentation rate after Vmax, with low nitrogen requirements, but stuck fermentations were observed at later stages. In contrast, a shorter lag phase compared with S. cerevisiae, higher cell viability, and the ability to complete alcoholic fermentation at 13 °C confirmed the low-temperature adaptation trait of S. bayanus var. uvarum. This study produced a phenotypic characterization data set for a collection of S. bayanus var. uvarum strains, thus paving the way for industrial developments using this species as a new genetic resource.