Twenty-eight flocculent wine strains were tested for adhesion and flocculation phenotypic variability. Moreover,
the expression patterns of the main genes involved in flocculation (FLO1, FLO5 and FLO8) were studied both in
synthetic medium and in presence of ethanol stress.
Molecular identification and typing were achieved by PCR-RFLP of the 5.8S ITS rRNA region and microsatellite
PCR fingerprinting, respectively. All isolates belong to Saccharomyces cerevisiae species. The analysis of
microsatellites highlighted the intraspecific genetic diversity of flocculent wine S. cerevisiae strains allowing
obtaining strain-specific profiles. Moreover, strains were characterized on the basis of adhesive properties. A
wide biodiversity was observed even if none of the tested strains were able to form biofilms (or ‘mats’), or to
adhere to polystyrene. Moreover, genetic diversity of FLO1 and FLO5 flocculating genes was determined by
PCR. Genetic diversity was detected for both genes, but a relationship with the flocculation degree was not
found. So, the expression patterns of FLO1, FLO5 and FLO8 genes was investigated in a synthetic medium and a
relationship between the expression of FLO5 gene and the flocculation capacity was established. To study the
expression of FLO1, FLO5 and FLO8 genes in floc formation and ethanol stress resistance qRT-PCR was carried
out and also in this case strains with flocculent capacity showed higher levels of FLO5 gene expression. This
study confirmed the diversity of flocculation phenotype and genotype in wine yeasts. Moreover, the importance
of FLO5 gene in development of high flocculent characteristic of wine yeasts was highlighted. The obtained
collection of S. cerevisiae flocculent wine strains could be useful to study the relationship between the genetic
variation and flocculation phenotype in wine yeasts.
© 2014 Elsevier B.V