The aim of this investigation was to synthesize the adipic acid-modified magnetic nanoparticles for the efficient immobilization of C-terminally lysine-tagged alpha-amylase (BAC Delta NC-Lys(7)) from thermophilic Bacillus sp. strain TS-23. The carboxylated magnetic nanoparticles were prepared by the simple co-precipitation of Fe3+/Fe2+ in aqueous medium and then subsequently modified with adipic acid. Transmission electron microscopy micrographs showed that the carboxylated magnetic nanoparticles remained discrete and had no significant change in size after the binding of BAC Delta NC-Lys(7). Free enzyme was active in the temperature range of 45-70 A degrees C and had an optimum of 60 A degrees C, whereas the thermal stability of BAC Delta NC-Lys(7) was improved as a result of immobilization. The immobilized BAC Delta NC-Lys(7) could be recycled 20 times without a significant loss of the amylase activity and had a better stability during storage with respect to free enzyme. Taken together, the magnetic nanoparticles coated with this functional moiety can be a versatile platform for the effective manipulation of various kinds of engineered proteins.