Immobilization of Cellulase on Non-Porous Ultrafine Silica Particles

The immobilization of cellulase onto non-porous ultrafine silica particles was studied. Cellulase was extracted from a Trichoderma reesei culture after partial purification with ammonium sulfate (pH = 5.0), which was then immobilized onto non-porous ultrafine silica particles, with or without the use of glutaraldehyde as a crosslinking agent. Cellulase was immobilized by adsorption onto ultrafine silica particles efficiently, as well as by covalent cross-linking with glutaraldehysde. Increasing the concentration of the free form of enzyme increased the amount of immobilized cellulase. The maximum enzyme immobilization happened at the free enzyme concentration of 0.48 mg/ml. In general, the optimum pH for immobilization was found to be 5.0, which is close to the pI of the enzyme. The relative activity of the immobilized enzyme was also increased as the amount of immobilized enzyme was increased. However, immobilization of the enzyme on the ultrafine silica particles, with or without the use of glutaraldehyde, showed almost the same enzyme activities. The immobilized cellulase showed a higher thermal stability, with respect to temperature, compared to the free cellulase.