Kinetic evaluation of biotransformation of benzaldehyde to L-phenylacetylcarbinol by immobilized pyruvate decarboxylase from Candida utilis

Biotransformation of benzaldehyde to L-phenylacetylcarbinol (L-PAC) as a key intermediate for L-ephedrine has been evaluated using immobilized pyruvate decarboxylase (PDC) from Candida utilis. PDC immobilized in spherical polyacrylamide beads was found to have a longer half-life compared with free enzyme. In a batch process, the immobilized PDC generally produced lower L-PAC than free enzyme at the same concentrations of substrates due to increased by-products acetaldehyde and acetoin and reduced benzaldehyde uptake. With immobilized PDC, L-PAC formation occurred at higher benzaldehyde concentrations (up to 300 mM) with the highest L-PAC concentration being 181 mM (27.1 g/L). For a continuous process, when 50 mM benzaldehyde and 100 mM sodium pyruvate were fed into a packed-bed reactor at 4 degrees C and pH 6.5, a productivity of 3.7 mM/h (0.56 g/L . h) L-PAC was obtained at an average concentration of 30 mM (4.5 g/L). The half-life of immobilized PDC reactor was 32 days. (c) 1996 John Wiley & Sons, Inc.