Magna Floc LT25 is a high molecular weight anionic polymer that has been described as increasing reaction rates inside flocs of yeast cells. However, no clear indication has been given on how this anionic polymer interacts with flocculent cells. Flocculation experiments made with a strain ofSaccharomyces cerevisiae corroborate that it bridges calcium ions bound to flocculent yeast cell walls, thus enlarging the available flux area for the transport of solutes inside the flocs.