Preparation of magnetic nanoparticles and their use for immobilization of C-terminally lysine-tagged Bacillus sp. TS-23 α-amylase.

The aim of this investigation was to synthesize the adipic acid-modified magnetic nanoparticles for the efficient immobilization of C-terminally lysine-tagged α-amylase (BACΔNC-Lys7) from thermophilic Bacillus sp. strain TS-23. The carboxylated magnetic nanoparticles were prepared by the simple co-precipitation of Fe³âº/Fe²âº 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 BACΔNC-Lys7. Free enzyme was active in the temperature range of 45-70 °C and had an optimum of 60 °C, whereas the thermal stability of BACΔNC-Lys7 was improved as a result of immobilization. The immobilized BACΔNC-Lys7 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.