Adsorptive removal of Ni(II) ions from aqueous solution and the synthesis of a Ni-doped ceramic: an efficient enzyme carrier exhibiting enhanced activity of immobilized lipase

We herein report a novel strategy for the removal of heavy metals and the subsequent preparation of a metal ceramic for immobilizing enzymes. To demonstrate this concept, Ni2+ ions were removed from an aqueous solution via entrapment by chitosan nanoparticles, and the resulting Ni(II)-containing precipitate was mixed with the ceramic matrix to give the Ni-doped ceramic (Ni-CP), which was subsequently applied in lipase immobilization. Under optimized conditions, Ni2+ removal reached 99.4%, and the Ni-CP showed significant chelation towards lipase following immobilization. In addition, a lipase activity yield of 164% was obtained under optimal conditions. Furthermore, the thermal and storage stabilities of Ni-CP-lipase exhibited a wider applied range, and the Ni-CP reusability was maintained at 97.5% following 20 cycles, suggesting high stability and excellent recyclability. Hence, the entrapped Ni2+ exhibited improved stability, thus reducing leakage into the environment. Furthermore, the chelation between Ni2+ and lipase improved enzyme activity and stability, and thus, may be suitable for application in large-scale production. It is therefore expected that this novel approach for enzyme immobilization has the potential to serve as an important technique in the field of biocatalysis.