Growth of the yeast Kluyveromyces bulgaricus in a glucose peptone liquid medium supplemented or not with calcium led to flocculent and weakly flocculent cells, respectively. Phosphopeptidomannans (PPM), which are cell wall peripheral components, are involved in recognition phenomena as lectin ligands. PPM were extracted from whole yeasts, their chemical composition as well as their molecular mass were determined. The PPM chemical composition was different between flocculent and weakly flocculent cells. Treatment of the PPM with imidazol buffer and/or mercaptoethanol, showed differences of stability. The PPM of weakly flocculating cells were much less stable than that of the high flocculent ones. Infrared spectra of the polymers reinforced that the change of stability may result from an alteration of the glucidic moiety with respect to the peptidic moiety. (C) 2004 Elsevier Ltd. All rights reserved.