GLUCO-OLIGOSACCHARIDE SYNTHESIS BY FREE AND IMMOBILIZED BETA-GLUCOSIDASE

Gluco-oligosaccharides were synthesized through the enzymatic condensa tion of D-glucose at high concentration using a commercial almond beta -glucosidase. The synthesis reactions were carried out with both free and immobilized enzyme, with or without sorbitol, an efficient depress or of water activity (a(w)) in the presence of different glucose conce ntrations. The yield and the composition of the gluco-oligosaccharides produced changed with the reaction mixture and the form of the enzyme used (free or immobilized). The use of 5 M glucose solution permitted only disaccharides to be obtained, whereas with a glucose concentrati on of 7.5 M glucose, di-, tri-, and tetrasaccharides were produced. A 7.5 M glucose solution used with 4.4 M sorbitol gave three times more disaccharides than the same solution without sorbitol. Moreover, the i mmobilized enzyme was much more active in synthesis. The synthesis yie ld (oligomers mg/mL . mg of enzyme) after immobilization was 573% comp ared to that of the free enzyme, when a 7.5 M glucose solution was tes ted. The effects of substrate concentration, sorbitol addition and enz yme immobilization were investigated.