Preparation of salidroside with n-butyl -D-glucoside as the glycone donor via a two-step enzymatic synthesis catalyzed by immobilized -glucosidase from bitter almonds

beta-Glucosidase from bitter almonds was immobilized on epoxy group-functionalized beads for catalyzing salidroside synthesis in a two-step process with n-butyl--D-glucoside (BG) as the glucosyl donor. The formation of salidroside ((0.59 +/- 0.02) M) at a yield of 39.04%+/- 1.25% was accomplished in 8h by the transglucosylation of immobilized -glucosidase at pH8.0 and 50 degrees C when the ratio of BG to tyrosol was 1:2 (mol/mol). A study on the influence of different glycosyl acceptors demonstrated that the yield of the glucosylation reaction of phenylmethanol and cyclohexanol was higher than that of either phenol or cyclohexanol. This may account for the selectivity of the immobilized enzyme towards the alcoholic hydroxyl group of tyrosol in the salidroside synthesis reaction. A study on the synthesis of BG via the reverse hydrolysis of immobilized -glucosidase showed that a yield of 78.04%+/- 2.2% BG can be obtained with a product concentration of (0.23 +/- 0.015) M.