YEAST FLOCCULATION - A NEW METHOD FOR CHARACTERIZING CELL-SURFACE INTERACTIONS

Flocculation is a property of yeast cells that has been traditionally used in industrial fermentations, especially in the brewing and wine i ndustries. It is a cell wall interaction and an increase in flocculati on is strongly correlated with an increase in cell surface hydrophobic ity. Methods to assay yeast cell surface hydrophobicity are only quali tative and while electrostatic interactions can play an important role , they are not always taken into account. In this work, a simple and a ccurate method based on contact angle measurements is described to det ermine yeast cell surface hydrophobicity. With this method, it is poss ible to quantify yeast cell surface hydrophobicity by determining the free energy of interaction between cells and water molecules. Several yeast strains with different flocculation characteristics have been us ed to validate the method.