Hollow spherical vaterite calcium carbonate prepared by spray-bubble template method for immobilization of papain

Calcium carbonate (CaCO3) possesses unique advantages as a carrier , however, some critical issues need to be addressed, such as low productivity, irregular structures, and weak adsorption ability. Herein, hollow spherical vaterite CaCO3 (HSVC) was synthesized in an improved spray apparatus with high mass transfer using carbon dioxide (CO2) as a template and was in turn applied for papain immobilization. Results revealed that HSVC can be prepared cleanly and efficiently with a regular spherical morphology having a surface area of 17.03 m2·g−1 and immobilization amount of 1068 mg·g−1 for papain. Interestingly, the pH stability, temperature stability and reusability of papain were dramatically improved after immobilization by HSVC. Molecular dynamics simulation (MDS) disclosed that the formation of CO32– and Ca2+ ion pairs was the key factor for the preparation of HSVC and the binding energy (BE) between amino acid molecules and vaterite (1 1 0) facilitated the ultra-high adsorption of papain. The decrease in BE of system after immobilization facilitated high catalytic capacity of the immobilized papain. The prepared HSVC exhibits promising prospects in enzymes immobilization based applications.