Studies on the enantioselective oxidation of β-ionone with a whole E. coli system expressing cytochrome P450 monooxygenase BM3

Recombinant Escherichia coli cells, expressing an NADH-dependent cytochrome P450 monooxygenase BM-3 mutant, were used for the hydroxyalation of the sesquiterpenoid β-ionone to (R)-4-hydroxy-β-ionone. The decrease in enantioselectivity of cytochrome P450 monooxygenase BM-3 catalyzed hydroxylation of β-ionone can be ascribed to the overoxidation of the desired product. In this initial study we report, that by addressing reaction conditions the enantiomeric excess can be increased and the overoxidation can be reduced. Furthermore, we report herein the kinetic resolution of racemic 4-hydroxy-β-ionone using the same P450 monooxygenase for the production of (S)-4-hydroxy-β-ionone. Although the enantioselectivity of the enzyme is rather low for this reaction, this reaction could be of interest with improved P450 BM-3 variants. Both systems need further investigations and optimizations for preparative application.