Here we present a modular process for the flexible production of magnetic beads with variable magnetic properties and anion or cation exchanger functionalities. Magnetic beads are used in bio-separations and downstream processing to remove a valuable Substance from e.g., a fermentation broth (Magnetic Fishing). The magnetic beads we are presenting here consist of a composite material, containing nanoscale magnetite and ion exchanger particles which are embedded into a polymer matrix. With this composite concept, anion and cation exchanger properties are available in magnetic beads with different matrix polymers (PVB, PVA, PMMA, and PVAc). The content of magnetite was varied in a range between 0 and 40 wt % ion exchanger particles between 0 and 60 wt % and the matrix polymer between 20 and 60 wt %. The magnetic bead characteristics, which determine the application properties, are shown. Thermo gravimetrical analyses, FTIR spectra and measurements of the ion exchange capacity prove the different properties in respect to the magnetic beads composition. In in adsorption experiment, it was possible to achieve a maximum capacity of 270 mg/g for beta-galactosidase with PVB-beads. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 112: 2366-2373, 2009