Biotransformation of benzeldehyde to l-phenylacetylcarbinol, an intermediate in l-ephedrine production, by immobilized Candida utilis

Abstract

Biotransformation of benzaldehyde to l-phenylacetylcarbinol (l-PAC) as a key intermediate for l-ephedrine synthesis has been evaluated using immobilized Candida utilis. During biotransformation, the benzaldehyde level and respiratory quotient significantly affected both l-PAC and by-product benzyl alcohol formation. By controlling the benzaldehyde level at 2 g/l, maintaining a respiratory quotient of 5–7 and pulse feeding glucose, a final concentration of 15.2 g/l l-PAC was achieved in a fed-batch process. This compares with previous published results of 10–12 g/l in batch culture and 10 g/l l-PAC in a semicontinuous process with immobilized Saccharomyces cerevisiae. In a single stage continuous process with immobilized C. utilis, the steady state l-PAC concentration was significantly reduced because of the sustained toxic effects of benzaldehyde.