Biotransformation of D-limonene to (+) trans-carveol by toluene-grown Rhodococcus opacus PWD4 cells

The toluene-degrading strain Rhodococcus opacus PWD4 was found to hydroxyla te D-limonene exclusively in the 6-position, yielding enantiomerically pure (+) trans-carveol and traces of (+) carvone. This biotransformation was st udied using cells cultivated in chemostat culture with toluene as a carbon and energy source. The maximal specific activity of (+) trans-carveol forma tion was 14.7 U (g of cells [dry weight])(-1), and the final yield was 94 t o 97%. Toluene was found to be a strong competitive inhibitor of the D-limo nene conversion. Glucose-grown cells did not form any trans-carveol from D- limonene. These results suggest that one of the enzymes involved in toluene degradation is responsible for this allylic monohydroxylation. Another tol uene degrader (Rhodococcus globerulus PWD8) had a lower specific activity b ut was found to oxidize most of the formed trans-carveol to (+) carvone, al lowing for the biocatalytic production of this flavor compound.