The present study investigates continuous gas phase stereoselective reduction catalyzed by commercial thermophilic alcohol dehydrogenase. The alcohol dehydrogenase and cofactor beta-nicotinamide adenine dinucleotide phosphate were simultaneously immobilized on non-porous spherical glass beads. The reduction of 4-methyl-2pentanone to (S)-4-methyl-2-pentanol with concomitant cofactor regeneration by 2-propanol was employed as a model reaction. According to the differing buffer pH dependence of the enzyme activity on both substrates, the maximal reactivity was obtained at a pH of 7.5 used for immobilized enzyme preparation. Owing to the higher stereoselective production, the water activity in the feed gas phase and reaction temperature were optimized at 0.9 and 333 K, respectively.