An interface bioreactor was used for the enantioselective degradation of (RS)-ibuprofen (IBU). An isolated yeast, Trichosporon cutaneum KPY 30802, preferentially degraded (R)-IBU to accumulate (S)-isomer. The addition of hydroquinone (10 mM) into a hydrophilic carrier was effective for the elevation of enantiomeric excess and the repression of excess degradation of (S)-IBU (E value, 9.3).