Carveol Rhodococcus

Figure 16.2-39. Enantiospecific oxidation of racemic carveol to (-)-carvone and (—)-c/s carveol using whole cells of Rhodococcus erythropolis.

By using whole cells of Rhodococcus erythropolis DCL14, a racemic mixture of (-)-carveol was converted to (-)-carvone and (-)-cis-carveol (Fig. 16.2-39). The system was optimized using the two-liquid concept, in which a second organic phase serves as substrate and product reservoir. (-)-Carvone is an important flavor compound. 

The enzyme responsible for this bioconversion, catalyzed by wild-type cells of Rhodococcus erythropolis DCL14, is carveol dehydrogenase11911. A high enantiose-lectivity and no further conversion of (-)-carvone was obtained. Carveol dehydrogenase has a broad substrate specificity and prefers substituted cyclohexanols as substrates11911. The regeneration of the cofactor NAD+ was accomplished by the use of living cells. 

In another study, Rhodococcus globerulus PWD8 was found to oxidize D-limonene regio- and enantioselectively via (-t-)-trans-carveol to (+)-carvone [192l... 

Rhodococcus DCLi4 degrades limonene via limonene oxide and p-menth-7-ene-l,2-diol. This is a novel microbial degradation pathway for limonene. Further research is necessary to establish if this microorganism also contains a monooxygenase converting limonene into carveol. 

Duetz W.A., Fjallman A.H.M., Ren S., Jourdat C., Witholt B. Biotransformation of d-limonene to (-F)-frans-carveol by toluene-grown Rhodococcus opacus PWD4 Cells. Applied and Environmental Microbiology, 67 2829-2832 (2001). 

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