Preparation and characterization of cellulase-bound magnetite nanoparticles

The covalent binding of cellulase enzyme complex to magnetic (Fe3O4) nanoparticles via carbodiimide activation was investigated. The size, structure, and morphology of the magnetic nanoparticles were determined using transmission electron microscopy (TEM). The micrographs revealed a mean diameter of 13.3 nm and showed that the magnetic particles remained discrete with no significant change in size after binding of the enzyme complex. Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) indicated binding to the magnetic nanoparticles and suggested a possible binding mechanism. Maximum binding (∼90%) occurred at low enzyme loadings (1–2 mg) and the enzyme-to-support saturation point occurred at a weight ratio of 0.02. Thermal measurements for the nanoparticles indicated increased stability over a broader range of temperatures, with a peak relative enzyme activity at 50 °C. The ionic forces between the enzyme and support surface caused a shift in the optimum pH from 4.0 to 5.0.