Surface modification of magnetite nanoparticles using gluconic acid and their application in immobilized lipase

Superparamagnetic magnetite nanoparticles (SMN) were surface-modified with gluconic acid (GLA) to improve their hydrophilicity and bio-affinity. Gluconic acid was successfully coated on the surface of magnetite nanoparticles and characterized using Fourier transform infrared spectroscopy (FT-IR). With water-soluble carbodiimide (EDC) as the coupling reagent, lipase was successfully immobilized onto the hydroxyl-functionalized magnetic nanoparticles. The immobilized lipase had better resistance to temperature and pH inactivation in comparison to the free form and hence widened the reaction pH and temperature range. Thermostability and storage stability of the enzyme improved upon covalent immobilization. Immobilized lipase showed higher activity after recycling when compared to the free one and could be recovered by magnetic separation. (C) 2011 Elsevier B.V. All rights reserved.