Synthesis of magnetic nanoparticles functionalized with histidine and nickel to immobilize His-tagged enzymes using β-galactosidase as a model.

The aim of this study was to synthesize iron magnetic nanoparticles functionalized with histidine and nickel (Fe3 O4 -His-Ni) to be used as support materials for oriented immobilization of His-tagged recombinant enzymes of high molecular weight, using β-galactosidase as a model. The texture, morphology, magnetism, thermal stability, pH and temperature reaction conditions, and the kinetic parameters of the biocatalyst obtained were assessed. In addition, the operational stability of the biocatalyst in the lactose hydrolysis of cheese whey and skim milk by batch processes was also assessed. The load of 600 Uenzyme /gsupport showed the highest recovered activity value (~50%). After the immobilization process, the recombinant β-galactosidase (HisGal) showed increased substrate affinity and greater thermal stability (~50×) compared to the free enzyme. The immobilized β-galactosidase was employed in batch processes for lactose hydrolysis of skim milk and cheese whey, resulting in hydrolysis rates higher than 50% after 15 cycles of reuse. The support used was obtained in the present study without modifying chemical agents. The support easily recovered from the reaction medium due to its magnetic characteristics. The iron nanoparticles functionalized with histidine and nickel were efficient in the oriented immobilization of the recombinant β-galactosidase, showing its potential application in other high-molecular-weight enzymes.