The asymmetric reduction of benzyl to (S)-benzoin with Penicillium claviforme IAM 7294 was applied to a liquid-liquid interface bioreactor (L-L IBR) using a unique polymeric material, ballooned microsphere (MS). The L-L IBR showed superior performance, as compared with suspension, organic-aqueous two-liquid-phase, and solid-liquid interface bioreactor (S-L IBR) systems, affording 14.4 g/l-organic phase of (S)-benzoin (99.0% ee).