Flocculation of yeast suspensions by a cationic flocculant

Suspensions of yeasts which are negatively charged have been flocculated using a cationic polyelectrolyte. The initial rate of flocculation and growth of the floc particles were dependent on the flocculant dosage and flocculation time. During flocculation, the cationic polyelectrolyte chains can adsorb via electrostatic interactions onto the yeast particle surface. The flocculant can also form bridges between yeast particles. Flocculation characteristics were measured by zeta potential, dynamic mobility, conductivity and pH measurements with two different flocculant dosages as a function of time. The zeta potential of the particles was negative during the flocculation process and its magnitude decreased with higher flocculant dosage. Micrograph images of the flocculation process indicate an increasing floc size with time.

The biological cells are often difficult to filter because of the insoluble particulate matter deposits on the micro-porous membrane surface forming a highly viscous cake layer. The larger particles formed by flocculation will provide more porous cake during filtration and reduce plugging of the membrane pores by cell debris. This paper studies the yeast cell flocculation by a cationic polyelectrolyte.Figure optionsDownload as PowerPoint slideHighlights
► Flocculation of yeast suspension was studied.
► Cationic polyelectrolyte was used as potential flocculant.
► Floc size became denser and bigger as the flocculation proceeds.