초록
The efficacy of glycerol as an additive at enzyme immobilization on the catalytic performance (activity, stability, enantioselectivity and productivity) of immobilized ®-specific Parvibaculum lavamentivorans alcohol dehydrogenase in a continuous gas phase reactor was investigated. The enantioselective reduction of 4-methyl-2-pentanone with concomitant NADH regeneration by 2-propanol as co-substrate was used as a model reaction. Non-porous glass beads were used as immobilization carriers. The immobilized alcohol dehydrogenase performance was markedly enhanced by the addition of glycerol. Interestingly, the enantioselectivity was stabilized during the reaction progress. The optimal glycerol amount, thermodynamic activity of water in the feed gas phase, and reaction temperature were obtained at 10mg/g-glass carriers, 0.8 and 313K in terms of the productivity, respectively. As a function of the thermodynamic activity of substrate in the feed gas phase, it was also optimized at 0.103 for 2-propanol and 0.250 for 4-methyl-2-pentanone. Compared to the glycerol-free immobilized enzyme system, the productivity of the chiral compound was ca. 15-fold higher, on the other hand, based on the kinetic analysis the maximum reaction rate was found to be about 2-times higher, while the Michaelis constant for 2-propanol was about 2-fold lower and that for 4-methyl-2-pentanone decreased slightly. These findings indicate that the gas phase enzyme reaction exhibits an excellent catalytic performance in the presence of additive glycerol for chiral compound production, however needs to optimize the additive amount and reaction conditions for effective industrial operation.