A new approach to the enzymatic production Of conjugated linoleic acid (CLA) ascorbyl ester with a remarkably high volumetric productivity (120-200 g L-1) has been developed, in which strong solvation by tOMA-TFA (methyltrioctylammonium trifluoroacetate) enables a high concentration of ascorbic acid to be applied, and in which t-butanol enhances conversion by changing the equilibrium constant of the activity coefficients. This work has experimentally demonstrated the practicability of achieving efficient reactions of polar compounds at high concentrations in ionic liquids without significant loss of enzyme activity.