PREPARATION AND ACTIVITY OF BUBBLING-IMMOBILIZED CELLOBIASE WITHIN CHITOSAN-ALGINATE COMPOSITE

Abstract

Cellobiase can hydrolyze cellobiose into glucose; it plays a key role in the process of cellulose hydrolysis by reducing the product inhibition. To reuse the enzyme and improve the economic value of cellulosic ethanol, cellobiase was immobilized using sodium alginate and chitosan as carriers by the bubbling method. The immobilization conditions were optimized as follows: enzyme loading of 100 U cellobiase/g carrier, 30 min immobilization, 3.5 wt% sodium alginate, 0.25 wt% chitosan, and 2 wt% calcium chloride. Compared to free enzyme, the immobilized cellobiase had a decreased apparent K _m and the maximum activity at a lower pH, indicating its higher acidic and thermal stability. The immobilized cellobiase was further tested in the hydrolysis of cellobiose and various cellulosic substrates (microcrystalline cellulose, filter paper, and ammonia-pretreated corn cobs). Together with cellulases, the immobilized cellobiase converted the cellulosic substrates into glucose with the rate and extent similar to the free enzyme.

Keywords:

• bubbling
• cellobiase
• chitosan
• immobilization
• sodium alginate

ACKNOWLEDGMENTS

The authors acknowledge the financial support received from Natural Science Foundation of China (No. 20576095), National Key Technology R&D program (2007BAD42B02), the International Science and Technology cooperation program (2006DA62400), and the Program for Changjiang Scholars and Innovative Research Team in University of China (IRT0641).