  The combination of single cells to form doublets is regarded as the
rate-limiting step of flocculation and requires the presence of surface
proteins in active form. The process of activation of the flocculation proteins
of yeast cells is described in the frame of the autocrine interaction regime
(Cantrell, D. A. and Smith, K. A., 1984, Science 224, 1312-1316). The influence
of several effectors (the cell efficiency to use sugars, the calcium content in
the external medium and the probability that free cells collide each other
under thermal motion conditions) on the initial rate of flocculation and on the
fraction of remaining free cells in the steady state is briefly discussed in
the paper. The present model offers an useful tool for further quantitative
investigations in this topic. Also, it indicates qualitatively a way in which
the regulation of flocculation might be controlled at the level of the
expression of cell-surface activation abilities.
  Keywords: flocculation; yeast; autocrine binding; lectin hypothesis
