Improved thermal stability of laccase immobilized on carboxyl functionalized chitosan magnetic nanoparticles

Laccase is an enzyme with remarkably broad substrate specificity and high catalytic activity, so this enzyme has a good potential for industrial applications. However, the industrial applications are limited due to the low stability and poor reusability of free laccase. In an attempt to improve the thermal stability of laccase, a novel immobilized laccase on carboxyl functionalized chitosan/Fe2O3 magnetic nanoparticle with high activity was synthesized and characterized by transmission electron microscopy, Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The optimal conditions for laccase immobilized onto carboxychitosan/Fe2O3 magnetic nanoparticle were 20 mM of 1-(3-(dimethylamino) propyl) 3-ethylcarbodiimide hydrochloride (EDC), 400 mM of N-hydroxysuccinimide (NHS), 100 μl enzyme solution (approximately 0.5 U/mL) and 24 h immobilization time. Based on our results, the optimum temperature for free and immobilized laccase was found at 50ºC and 55ºC, respectively. So, the immobilized laccase showed enhanced resistance to thermal denaturation compared with free laccase. Results of this study demonstrated that the immobilized enzyme could be used in many applications due to the better immobilization efficiency and thermal stability of immobilized laccase.

Keywords:

Chitosan , Magnetic nanoparticle , Laccase , Thermal stability