STUDIES ON MICROBIAL BETA-D-GLUCOSIDASE IMMOBILIZED IN ALGINATE GEL BEADS

About 50-60% beta-D-glucosidase (isolated from Pseudomonas pickettii and Aspergillus niger) was immobilized in calcium alginate gel beads by entrapment, retaining 15-26% of original activity. The pH values for maximum activitiy of the immobilized bacterial and fungal enzymes appeared to be 5.0 and 3.0 respectively, very similar to those of the free enzymes. The pH-activity curves were coincident, except at very low pH values where the fungal immobilized enzyme was more stable. Bacterial beta-glucosidase did not follow pure Michaelis kinetics, exhibiting substrate inhibition and showing similar K-m, values for immobilized and soluble enzymes. The K-m, of the immobilized fungal enzyme was larger than that of the free enzyme, suggesting that the alginate network limited the permeation rate of substrate and product. The V-max values of immobilized beta-glucosidases from A. niger and P. pickettii were 14.7 and 29.6 smaller than those of the native enzymes, respectively.