Fluorescence study of galactose specific lectin like receptors involved in the flocculation and co-flocculation of wine yeast

OSCAR ANTONIO SOSA; FARIAS, MARTA ELENA; CASTELLANOS DE FIGUEROA, LUCIA

Wisconsin

Congreso; 13th INTERNATIONAL CONGRESS ON YEASTS (ICY 2012).; 2012

Kloeckera apiculata mc1, isolated from Argentinean grape berries, possess a remarkable capacity to adhere to yeast cells of the same species, which is called self-flocculation, and to cells of the different species, which is called co-flocculation. Flocculation is defined as the phenomenon wherein yeast cells adhere in clumps and sediment rapidly from the medium in which they are suspended. K. apiculata mc1 expresses a flocculent phenotype mediated by galactose-specific lectins and stabilized by Ca2+. Glucose showed to be an activator of the flocculent phenotype of K. apiculata mc1. The current work examines carbon sources effect on the expression of self-flocculation of this yeast and the co-flocculation with Saccharomyces cerevisiae mc2. The number of galactose-specific lectin sites on the surface of K. apiculata mc1 was determined by spectrofluorometric method using a neoglycoprotein fluorescent probe (BSA-galactose-FITC) and quantified with the Scatchard plot. The addition of assimilable carbon sources such as glucose, fructose or ethanol to YNB medium (without amino acids or ammonium sulphate) resulted in a number increase of galactose-specific zymolectin sites on K. apiculata mc1 surface. This effect was directly correlated with the increment of K. apiculata self-flocculation degree, and their respective co-flocculation with S. cerevisiae. The addition of non-assimilable carbon sources such as lactose and galactose, did not lead to increases in the both, flocculationand co-flocculation degree. Fluorescent probe study constitutes a direct confirmation of lectin presence on K. apiculatamc1 cell wall. This protein specifically interacts with galactose residues on the both neighboring cells of K. apiculata and S. cerevisiae. K. apiculata with Saccharomyces strains co-flocculation and its induction by glucose and fructose could be considered an important biotechnological tool for the early indigenous saccharomycetic flora decrease.