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

SOSA OSCAR A.; FARÍAS MARTA E

Habana, Cuba

Congreso; Biotecnología Habana 2008: AgroBiotecnología: nuevos enfoques ante grandes retos; 2008

The lectin-like theory suggests that yeast flocculation is mediated by an aggregating lectinic factor. Kloeckera apiculata mc1, a non-Saccharomyces yeast isolated from grape berries, expresses a flocculent phenotype mediated by galactose-specific lectins and stabilized by Ca2+ . Glucose showed to be an activator of the flocculent phenotype of Kloeckera apiculata mc1. In this study we examined the suitability of neoglycoprotein fluorescent probe (BSA-galactose-FITC) to quantify the number of galactose specific lectins on the surface of K. apiculata mc1 and to evaluate the effect of glucose on the density of these specific receptors. Free and bound probe was determined by spectrofluorometric method and the amount of fixed probe was calculated as follow: fixed probe (µg) = (total probe – free probe)/ total probe. Data of fluorescence assay were analyzed by Scatchard method to estimate the number of lectin sites per cell. The «lectin-like» receptors on the surface of flocculent yeast specifically bound BSA-FITC-gal probe, showing saturation kinetic of binding. The number of lectinic sites was higher as increased the glucose concentrations. At 24 h of incubation was approximately 1.5-fold higher to cells grown with 20 g/L glucose than the yeasts grown with 2 g/L glucose. This study with fluorescent probe constitutes a direct confirmation of the existence protein (lectin) on the cell wall of K. apiculata mc1 that specifically interacts with the galactose residues on the neighboring cells. Self-flocculation induction by glucose seems to involve « de novo» lectin synthesis.