Preparation of immobilized Alcalase based on metal affinity for efficient production of bioactive peptides

The enzyme immobilization based on metal affinity has been applied in bioengineering and biochemical fields, but the effects of different metal ions on ligand and enzyme remain unexplored systematically. Here, different metal ions were initially chelated with triamino ligands on the Alcalase-immobilized hollow mesoporous silica spheres (HMSS) through metal–protein interaction forces. The results indicate the coordinated enzymes increased with the increase of metal ions, from which the transition metal ions (Zn2+, Cu2+ and Ni2+) were easier to chelate with triamino ligand than hard lewis acids (Fe3+, Ca2+). Compared to the free Alcalase which was deactivated at the condition of 85 °C incubation, the initial activity of immobilized Alcalase could be partially recovered with the highest activity recovery of 90% from Alcalase@HMSS-3N–Ni2+. Besides, all immobilized Alcalase maintained more than 40% of the initial activity after 5 cycles of successive reuse and Alcalase@HMSS-3N–Ni2+ particularly exhibited 75% of initial activity. Immobilized Alcalase could hydrolyze SPI （soy protein isolate）or WPI（whey protein isolate）to obtain the small peptides below 1500 Da, showing great hydrolysis efficiency for low-solubility proteins. Therefore, this study proposed the immobilized Alcalase on triamino-metal ions-functionalized materials to broaden the feasibility of immobilized enzymes on protein hydrolysis.