Gelatin-templated biomimetic calcification for β-galactosidase immobilization

The alginate–gelatin–calcium phosphate hybrid carrier, which was the alginate capsule covered with gelatin film and calcified shell, was successfully prepared through a facile biomimetic mineralization process, and further utilized to immobilize β-galactosidase. Gelatin was firstly used to inspire and template the assembly of calcium phosphate for enzyme immobilization at ambient temperature and neutral pH. The surface morphology, swelling performance and mechanical stability of calcium alginate capsules and alginate–gelatin–calcium phosphate hybrid capsules were investigated. Experimental results indicated that the assembled calcium phosphate shell significantly enhanced the mechanical stability and lowered the swelling degree of the capsule, additionally improved the immobilization efficiency and dramatically inhibited the leakage of β-galactosidase. Thus, the relative activity of β-galactosidase immobilized in alginate–gelatin–calcium phosphate capsules was more than 60% after the 20th cycle and about 90% after 30 d storage. Meanwhile, β-galactosidase immobilized in hybrid capsules, in comparison to free enzyme and enzyme immobilized in calcium alginate capsules, exhibited the broadest temperature and pH ranges.