The effect of water activity on the synthesis of n-alkyl-beta D-glucosides through condensation of glucose and n-alcohols has been studied using the commercially available almond beta-glucosidase and beta-glucosidase isolated from Fusarium oxysporum. The two enzymes exhibited a different water activity optimum. The specificity and alcohol reactivity of the two enzymes have also been investigated. Both enzymes prefer primary alcohols. beta-Glucosidase from F. oxysporum presents a higher affinity for primary alcohols with alkyl chain length of 4-6, whereas in the case of almond beta-glucosidase both initial velocity and yield decrease when the carbon chain length increases.