Enzyme-catalyzed synthesis of alkyl- β-glucosides in a water–alcohol two-phase system

Abstract

The enzymic synthesis of alkyl- β-glucosides by water-immiscible alcohols was studied in stirred flasks as well as in a tubular enzymatic reactor. In the first case, direct alkylation of β- d-glucose from hexanol using immobilized β-glycosidase gave a higher conversion yield and final product concentration than that using the enzyme in its free state (yield 10 against 8% mol/mol, concentration 2 against 1.6 g/l). Direct glycosylation of β- d-glucose from hexanol resulted in a higher reaction performance (yield 10%) than that from octanol (yield 5%). However, the two different incubation temperatures tested (37°C and 50°C), showed no significant differences concerning final product concentrations. The more interesting results were obtained by transglycosylation of methyl-1- β-glucose from hexanol, with a conversion yield of 21% mol/mol (product amount 4 g/l). However, the transgalactosylation of lactose from hexanol, catalyzed by a fungal β-galactosidase, showed only a feeble reactivity. The feasibility of enzymic alkylation was also tested in a tubular enzymatic reactor; hexyl-1- β-glucoside was produced via direct glycosylation from hexanol catalyzed by free β-glycosidase with a final concentration 1.3–2.3 g/l and a yield varying between 11% and 20% mol/mol.