Improved activity and stability of cellulase by immobilization on Fe₃O₄ nanoparticles functionalized with Reactive...

Cellulase is extensively used in the biorefinery of cellulosic materials to fermentable sugars in bioethanol production. Application of cellulase in the free form has disadvantages in enzyme wastage and low stability. The results of the present work showed these drawbacks can be solved by cellulase immobilization on functionalized Fe₃O₄ magnetic nanoparticles (MNPs) with reactive red 120 (RR120) as the affinity ligands. The Fe₃O₄ MNPs were activated by the chitosan layer and then functionalized with RR120 to attach with cellulase molecules. The evaluation on the attachment indicates a chemical adsorption which well described by Temkin isotherm with the adsorption potential (K_T) and an energy constant (B) of 19.83 mL mg^-1 and 128.1, respectively. The concentration of RR120 and glutaraldehyde addition as a liking agent were examined on the immobilization yield, cellulase loading capacity, and different hydrolytic activities of the prepared biocatalysts. The highest total cellulase activity at about 0.276 ± 0.038 μmol_Glucose mg_Enzyme^-1 h^-1 (37 °C and pH = 4.8) was obtained using 2000 mg L^-1 of RR120 and in the absence of glutaraldehyde. This immobilized cellulase was robust in storage (4 °C) for up to 180 days and saved 66 % of its original activity after 6 cycles.