Volume 7, Issue 6 (June 2010)
Immobilization of Cellulase and Hemicellulases on Porous Glass Beads
Experiments on immobilization of cellulase complex (cellulase, Novozymes) and enzyme complex (cellulases and hemicellulases, Novozymes) were performed on porous Siran™ beads using covalent and non-covalent bonding methods. Free enzyme complex was used for hydrolyzing various pretreated biomass such as corn stover, distillers dried grain with solubles, switch grass and blue stem grass. Maximum activity of enzyme complex was found with corn stover and was used as a substrate for measuring cellulase and hemicellulases activities. Protein loading for immobilized cellulase complex and enzyme complex on Siran™ carriers was found in the range of 10.776–18.000 % and 19.932–23.082 %, respectively. Activity loading for immobilized cellulase complex with avicel was in the range of 16.610–22.026 %. For enzyme complex, activity loading was found in the range of 43.558–61.222 %, 8.274–19.124 %, and 7.180–14.114 % with avicel, xylan, and corn stover as substrates, respectively. Recycling experiments for immobilized cellulase complex and enzyme complex were carried out using various substrates, and the residual enzyme activity was measured after the third cycle. Carbodiimide bonded cellulase complex retained more residual enzyme activity with avicel (49.460 %), which indicates a good cross linker for cellulase immobilization. The enzyme complex bonded to carbodiimide, and glutaraldehyde retained residual activity of 44.160 % with xylan and 73.230 % with corn stover, respectively. Recycling studies showed greater retention in residual enzyme activity with covalent bonded enzymes than non-covalent bonded enzymes. Glutaraldehyde and carbodiimide were found to be effective cross linkers for immobilizing both cellulase and hemicellulases in covalent bonding method.