Preparation, characterization and application of Aspergillus sp. xylanase immobilized on Eudragit S-100.

Aspergillus sp. 5 (strain 5) and Aspergillus sp. 44 (strain 44) produced xylanase (34.3 and 32.7 IU ml-1, respectively) with very low levels of cellulases when grown on 1% wheat bran medium. Xylanase was non-covalently immobilized on Eudragit S-100 for saccharification. The system retained 70 and 80% of strain 5 and strain 44 xylanase activity, respectively. On immobilization, optimum temperature of activity broadened between 50 and 60 degrees C as compared to 50 degrees C in the case of the free enzymes. No significant shift in the pH optima was observed on immobilization. However, immobilization increased enzyme stability mainly by decreasing the temperature sensitivity to the inactivation reaction. The K(m) values increased from 5.6 to 8.3 mg ml-1 for strain 5 xylanase and 7.0 to 9.0 mg ml-1 for strain 44 xylanase. Enzymatic saccharification of xylan and wheat bran was improved on xylanase immobilization. Immobilized xylanase from both the strains produced three times more sugar as compared to free xylanase. In repeated batch saccharification studies immobilized xylanase was recycled three times without loss of enzyme activity.