OPTIMIZATION OF BETA-GLUCOSIDASE ENTRAPMENT IN ALGINATE AND POLYACRYLAMIDE GELS

Immobilisation of beta-glucosidase, isolated from Aspergillus niger, b y entrapment in both calcium alginate and polyacrylamide gels was stud ied. A retention of 66% of initial activity was observed in the algina te bends prepared with 3% (w/v) alginate, 0.2 M CaCl2 and 1 h of treat ment. The maximum beta-glucosidase activity in polyacrylamide gels (si milar to 55%) was achieved in gels prepared with 20% acrylamide and 1. 2% of crosslinking agent (bisacrylamide). beta-Glucosidase immobilised in alginate gel did not follow pure Michaelis kinetics, exhibiting su bstrate inhibition. The K-m of this enzyme was larger than that of the free beta-glucosidase, suggesting that the alginate network limited t he permeation rate of substrate and product. However beta-glucosidase entrapped in polyacrylamide gel showed a similar K-m value to that of native enzyme. The pH value for maximum activity of free and immobilis ed enzymes was 4.0. The pH-activity curves were coincident, except at very low pH values where the enzyme trapped in alginate was more stabl e. (C) 1998 Elsevier Science Ltd. All rights reserved.