The effective production and extraction of (S)-1-acetoxy-2-alkanol has been achieved using a bakers’ yeast cell-free extract in a membrane reactor. 1-Acetoxy-2-alkanones were reduced to (S)-1-acetoxy-2-alkanols with high optical purities (>98% ee) without hydrolysis of the a-acetoxy group. This reactor system required neither the isolation of the enzyme for the reduction of the substrate nor the addition of the enzymes participating the cofactor (NADPH) regeneration. Furthermore, the system needs not immobilize these enzymes to a carrier. The productive efficiency did not decrease during repetitive batch reductions.