Productivity of cyclohexanone oxidation of the recombinant Corynebacterium glutamicum expressing chnB of Acinetobacter calcoaceticus

The biocatalytic efficiency of recombinant Corynebacterium glutamicum expressing the chnB gene encoding cyclohexanone monooxygenase (CHMO) of Acinetobacter calcoaceticus NCIMB 9871 was investigated. Optimization of an expression system and induction conditions enabled the recombinant biocatalyst to produce CHMO to a specific activity of ca. 0.5 U mg^-1 protein. Tight control of feeding of an energy source (i.e., glucose) and dissolved oxygen tension during fed-batch culture-based biotransformation allowed the cells to produce ε-caprolactone to a concentration of 16.0 g l^-1. The specific and volumetric productivity for cyclohexanone oxidation were 0.12 g g dry cells^-1 h^-1 (17.5 U g^-1 of dry cells) and 2.3 g l^-1 h^-1 (330 U l^-1), respectively. These values correspond to over 5.4- and 2.7-fold of recombinant Escherichia coli expressing the same gene under similar reaction conditions. It could be concluded that the recombinant C. glutamicum is a promising biocatalyst for Baeyer-Villiger oxidations.