Kinetic resolution of chiral amines using packed-bed reactor

A kinetic resolution process for production of chiral amines is developed using entrapped whole cells of Vibrio fluvialis JS17 in 2% (w/v) Ca-alginate gel beads. External diffusion limitation does not appear to affect reaction rate, and the loss of enzyme activity of the entrapped whole cells would be mainly due to internal diffusion limitation. Stability of the entrapped whole cells is greatly dependent on pH, and the stability is best at pH 8 although the optimal pH for the enzyme activity is 9. The entrapped whole cells showed lower substrate inhibition by (S)-α-methylbenzylamine ((S)-α-MBA) and lower product inhibition by acetophenone than the free cells, whereas the reverse trends were observed for the inhibitions by pyruvate and L-alanine. The results can be explained by partitioning behavior of the compounds between bulk aqueous phase and gel beads. Kinetic resolutions of α-MBA, 1-aminotetralin, and 1-aminoindan were performed using a packed-bed reactor (PBR) packed with the entrapped whole cells and a hydrophobic membrane contactor to continuously remove inhibitory ketone. Considering different degree of substrate inhibitions by the racemic amines, feed method was varied carefully. The reaction profiles indicate that use of low concentration of the amine substrate and repetitive batch reaction rather than fed-batch reaction is preferable due to the substrate inhibition by slow-reacting (R)-amine as well as by (S)-amine.