Immobilization Of β-glucosidase And Its Improvement In Cellulose Enzymatic Hydrolysis

In the cellulase preparation of Tichoderma reesei,β-glucosidase activity is too low to make synergism with endoglucanase and cellobiohydrolase, and lead to the accumulation of cellobiose in the hydrolysate, then reduce the amounts of fermentable sugars in the subsequent fermentation process. The thesis deals with separation of cellulase by ultrafiltration, immobilization ofβ-glucosidase, and its improvement in cellulose enzymatic hydrohysis. The main results are as follows:1. T. reesei cellulase was separated by ultrafiltration with different nominal molecular weight cutoff (NMWC) of hollow fiber cartridge. Protein, filter paper activity, CMCase activity,β-glucosidase activity and xylanase activity were mainly distributed above the section of NMWC 30kDa, less or no was detected under the section of NMWC 30kDa.2. The changing trend of the filter paper activity was consistent to that ofβ-glucosidase activity, but did not respect with CMCase activity. It meant that endoglucanase was enough, however, lack ofβ-glucosidase in T. reesei cellulase. Soβ-glucosidase was the key factor for the synergistic actions of T. reesei cellulase components.3.β-glucosidase was immobilized in chitosan beads by adsorption and crosslinking. The method of orthogonal test was used to investigate the optimal condition of immobilization. The optimal condition of immobilization was thatβ-glucosidase dosage of 4.86IU/g dry chitosan was absorbed with chitosan beads at pH5.0 for 12h, followed by crosslinking at 25℃for 2h in 1.0% glutaraldehyde solution. The result of immobilizedβ-glucosidase activity and ratio of recoverableβ-glucosidase activity were 41.76IU/g dry chitosan beads and 85.93%, respectively.4. The enzymology characteristics of immobilized and freeβ-glucosidase were investigated. The optimal pH of immobilized and freeβ-glucosidase was 4.5; the optimal temperature of immobilizedβ-glucosidase was 60℃, which was 5℃lower than that of freeβ-glucosidase; its stabilities of pH and storing were obviously higher than that of free...