Production of Flavours and Fragrances via Bioreduction of (4R)-(-)-Carvone and (1R)-(-)-Myrtenal by Non-Conventional Yeast Whole-Cells

As part of a program aiming at the selection of yeast strains which might be of
interest as sources of natural flavours and fragrances, the bioreduction of (4R)-(−)-carvone
and (1R)-(−)-myrtenal by whole-cells of non-conventional yeasts (NCYs) belonging to the
genera Candida, Cryptococcus, Debaryomyces, Hanseniaspora, Kazachstania, Kluyveromyces,
Lindnera, Nakaseomyces, Vanderwaltozyma and Wickerhamomyces was studied. Volatiles
produced were sampled by means of headspace solid-phase microextraction (SPME) and the
compounds were analysed and identified by gas chromatography–mass spectroscopy
(GC-MS). Yields (expressed as % of biotransformation) varied in dependence of the strain.
The reduction of both (4R)-(−)-carvone and (1R)-(−)-myrtenal were catalyzed by some
ene-reductases (ERs) and/or carbonyl reductases (CRs), which determined the formation of
(1R,4R)-dihydrocarvone and (1R)-myrtenol respectively, as main flavouring products. The
potential of NCYs as novel whole-cell biocatalysts for selective biotransformation of electron-poor
alkenes for producing flavours and fragrances of industrial interest is discussed.