Hydroxyapatite-CoFe<sub>2</sub>O<sub>4</sub> Magnetic Nanoparticle Composites for Industrial Enzyme Immobilization, Use, and Recovery
Thamara Carvalho Coutinho, João Otávio Donizette Malafatti, Elaine Cristina Paris, Paulo Waldir Tardioli, Cristiane S. Farinas
Abstract
Hydroxyapatite (HA) is an inorganic material with high ability to interact with proteins and has been recently explored as a support for enzyme immobilization. However, there are still some drawbacks concerning the recovery of these biocatalysts, which could be overcome using magnetic supports. Cobalt ferrite (CoFe2O4) is a purely magnetic material, which offers excellent chemical stability, ease of synthesis, and mechanical hardness, being a promising candidate to form composites with HA and produce magnetic HA nanoparticles. Therefore, investigation of synthesis procedures and applications of HA/CoFe2O4 composites to facilitate enzyme recovery by means of a magnetic field could find interest in a broad spectrum of biotechnological processes. Here, the co-precipitation method was used to synthesize HA/CoFe2O4 composites with different HA/CoFe2O4 mass ratios, for application as supports for enzyme immobilization. The enzymes β-glucosidase, phytase, and xylanase were selected for proof of concept due to their wide range of industrial applications. The composite with the highest cobalt ferrite content (2:1 mass ratio) was highly effective for immobilization of the three different enzymes, with immobilization yields (IYs) of 70–100% and recovered activities of 78–100%. The biocatalysts could be easily recovered from the reaction media by both centrifugation and application of an external magnetic field, demonstrating their potential for use in industrial processes. The materials exhibited good reusability, especially in the case of the β-glucosidase biocatalyst, which could be reused 10 times, maintaining around 70% of its initial activity.