The influence of yeast glycosylated proteins on tannins aggregation in model solution

The incidence of glycosylated yeast proteins on tannins aggregation in model solution was investigated using the spectrophotometric method (absorbance 700 nm). Glycosylated proteins released by two commercial Saccharomyces cerevisiae strains (RC212 and BM 45) during alcoholic fermentation in synthetic media, glycosylated proteins extracted by Peat’s method and industrial glycosylated proteins purified and separated by chromatography on Sepharose Concanavalin A were used to visualize effects on tannins aggregation. Results showed that tannins aggregation was limited by the glycosylated proteins according to their origin and their mode of preparation, glycosylated protein BM45 released during alcoholic fermentation in synthetic media being the most efficient. The use of mannan from yeast indicated that the polysaccharidic fraction of glycosylated proteins was efficient on tannins aggregation but at a lower level than glycosylated proteins. In the stabilisation of tannins, glycosylated proteins with a mannose / glucose ratio close to one were more efficient than the others. The present work suggests i) that the proteic fraction of glycosylated protein is likely a link between tannins and the polysaccharidic fraction of glycosylated protein, ii) that the conformation of a glycosylated protein is more or less likely to stabilise tannins, according to the mannose/glucose ratio.