Nanoimmobilization of β-glucosidase onto hydroxyapatite

beta-Glucosidase is an enzyme of great industrial interest that is used in biorefineries and in the pharmaceutical, food, and beverage sectors, among others. These industrial processes would benefit from the use of immobilized enzyme systems that allow several reuses of the enzyme. A promising inorganic and nontoxic material for such application is hydroxyapatite (HA), which can be synthesized at nanometric scale, hence providing good accessibility of the substrate to the catalyst. Here, we carried out a systematic study to evaluate the feasibility of immobilizing beta-glucosidase on HA nanoparticles. The immobilization process was highly effective over wide ranges of pH and ionic strength, resulting in immobilization yields and recovered activities up to 90%. Investigation of the type of interaction between beta-glucosidase and HA (using FT-IR, zeta potential measurements, and desorption tests with different salts) indicated the formation of coordination bonds between Ca2+ sites of HA and COO- of amino acids. Even after 10 cycles of reuse, the immobilized beta-glucosidase retained about 70% of its initial activity, demonstrating the operational stability of the immobilized enzyme. The results showed that beta-glucosidase could be efficiently immobilized on HA nanoparticles by means of a very simple adsorption protocol, offering a promising strategy for performing repeated enzymatic hydrolysis reactions. (C) 2018 Elsevier B.V. All rights reserved.