Activity and stability of bacterial cellulase immobilized on magnetic nanoparticles

Magnetic nanoparticles (Fe₃O₄) were synthesized by co-precipitating Fe²⁺ and Fe³⁺ ions in an ammonia solution and treating under hydrothermal conditions. Cellulase was immobilized onto Fe₃O₄ magnetic nanoparticles via glutaraldehyde activation. Using response surface methodology and Box-Behnken design, the variables such as magnetic nanoparticle concentration, glutaraldehyde concentration, enzyme concentration, and cross linking time were optimized. The Box-Behnken design analysis showed a reasonable adjustment of the quadratic model with the experimental data. Statistical contour plots were generated to evaluate the changes in the response surface and to understand the relationship between the nanoparticles and the enzyme activity. Scanning electron microscopy, X-ray diffraction analysis, and Fourier transform infrared spectroscopy were studied to characterize size, structure, morphology, and binding of enzyme onto the nanoparticles. The stability and activity of the bound cellulase was analyzed using various parameters including pH, temperature, reusability, and storage stability. The immobilized cellulase was compared with free cellulase and it shows enhanced stability and activity.