The enzymatic hydrolysis of Cardamine violifolia residues with cellulase immobilized on porous biochar via physical and chemical adsorption

In this study, porous biochar prepared by the pyrolysis of Cardamine violifolia residues impregnated with metal salts (ZnCl 2 , MgCl 2 or FeCl 3 ) was used as support to immobilize cellulase for the enzymatic saccharification of Cardamine violifolia residues. The results showed that a higher specific surface area along with abundant mesopores favored the immobilization of cellulase. As such, biochar prepared from the pyrolysis of 40 wt% FeCl₃-modified biomass at 800 ℃ (BC-800–0.4Fe) achieved the maximum cellulase loading capacity of 483.03 mg/g under optimized immobilization conditions. The adsorption isotherm and adsorption kinetic experiments showed that cellulase adsorption on BC-800–0.4Fe was driven by both physical and chemical adsorption, which was also confirmed by the structural change of cellulase and BC-800–0.4Fe after immobilization through characterization using FTIR and XPS. Compared to free cellulase, the immobilized cellulase demonstrated significantly enhanced pH, thermal, and storage stability. Furthermore, at an immobilized cellulase dosage of 20 FPU/g and temperature of 60°C, the enzymatic hydrolysis of pretreated Cardamine violifolia residues using BC-800–0.4Fe immobilized cellulase for 72 h produced a glucose yield of 90.54 %, and the glucose yield still remained at 46.40 % after 10-cycle reuse of the immobilized cellulase.