Dictyostelium discoideum is a social amoeba. It shows promising characteristics as an expression system for the production of recombinant glycoproteins owing to its ability to perform a whole spectrum of post-translational modifications. However, its application is seriously affected by slow growth rates as well as low maximal cell densities. Since the technique of immobilization often is applied in order to achieve high cell concentrations, D. discoideum was cultivated in the presence of different porous supports with the aim of studying its growth in an immobilized state. On a small scale a shake flask cultivation system with external loop was applied for this purpose. On a larger scale a bioreactor was coupled with an external loop of a column containing a fixed bed of the porous support. During growth on standard axenic (soluble) media, cell densities in the pores of the supports were attained, which were more than one magnitude higher than those normally obtained during suspension culture. Electron micrograph images indicate how D. discoideum colonizes porous support particles. (C) 2003 Elsevier Science Ltd. All rights reserved.