Objective To synthesize octyl beta-d-glucopyranoside (OG) and decyl beta-d-glucopyranoside (DG) in three non-aqueous reaction systems, namely organic solvents, ionic liquids and co-solvent mixtures, via reverse hydrolysis reactions catalyzed by the N189F dalcochinase mutant. Results The highest yield of OG (67 mol%) was obtained in the reaction containing 0.5 M glucose, 3 unit ml(-1)enzyme in 20% (v/v) octanol and 70% (v/v) [BMIm][PF6] at 30 degrees C. On the other hand, the highest yield of DG (64 mol%) was obtained in the reaction containing 0.5 M glucose, 3 unit ml(-1)enzyme in 20% (v/v) decanol, 20% (v/v) acetone and 50% (v/v) [BMIm][PF6] at 30 degrees C. The identities of OG and DG products were confirmed by HRMS and NMR. Conclusion This is the first report of enzymatic synthesis of OG and DG via reverse hydrolysis reactions in ionic liquids and co-solvent mixtures. The N189F dalcochinase mutant and the non-aqueous reaction systems described here show great potential for future commercial production of long-chain alkyl glucosides.