Enantioselective synthesis of (R)-citronellal from geraniol with an immobilised copper alcohol oxidase and ene reductase
Beatrice Tagliabue (TU Delft - BT/Biocatalysis)
C.M. Heckmann (TU Delft - BT/Biocatalysis)
Rocio Villa (TU Delft - BT/Biocatalysis)
Sacha Grisel (Aix Marseille Université)
Jean Guy Berrin (Aix Marseille Université)
Mickael Lafond (Aix Marseille Université)
David Ribeaucourt (Aix Marseille Université)
C.E. Paul (TU Delft - BT/Biocatalysis)
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Abstract
(R)-Citronellal is one of the key chiral intermediates in the synthesis of the isomer (−)-menthol, one of the most commercialised terpenoid flavours worldwide. Enzymatic approaches could represent a less energy-demanding alternative for its synthesis, such as a previously reported bienzymatic cascade starting from inexpensive, commercially available geraniol. A copper radical oxidase (CgrAlcOx) followed by a flavin-dependent ene reductase (OYE2) were used to obtain (R)-citronellal. Here, we used a metal-affinity immobilisation strategy on the His-tagged enzymes for the cascade and studied enzyme recovery and reusability as well as increased solvent tolerance. After screening a panel of resins for enzyme immobilisation and water-immiscible co-solvents, we successfully obtained 95% conversion to (R)-citronellal with 96.9% enantiomeric excess (ee) in a concurrent cascade after 7 h of reaction time, starting from 10 mM of geraniol.
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