초록
<P><B>Background</B></P><P>Apocarotenoids, like the C13-norisoprenoids, are natural compounds that contribute to the flavor and/or aroma of flowers and foods. They are produced in aromatic plants—like raspberries and roses—by the enzymatic cleavage of carotenes. Due to their pleasant aroma and flavour, apocarotenoids have high commercial value for the cosmetic and food industry, but currently their production is mainly assured by chemical synthesis. In the present study, a <I>Saccharomyces cerevisiae</I> strain that synthesizes the apocarotenoid β-ionone was constructed by combining integrative vectors and high copy number episomal vectors, in an engineered strain that accumulates FPP.</P><P><B>Results</B></P><P>Integration of an extra copy of the geranylgeranyl diphosphate synthase gene (<I>BTS1</I>), together with the carotenogenic genes <I>crtYB</I> and <I>crtI</I> from the ascomycete <I>Xanthophyllomyces dendrorhous</I>, resulted in carotenoid producing cells. The additional integration of the carotenoid cleavage dioxygenase gene from the plant <I>Petunia hybrida</I> (<I>PhCCD1</I>) let to the production of low amounts of β-ionone (0.073 ± 0.01 mg/g DCW) and changed the color of the strain from orange to yellow. The expression of the <I>crtYB</I> gene from a high copy number plasmid in this former strain increased β-ionone concentration fivefold (0.34 ± 0.06 mg/g DCW). Additionally, the episomal expression of <I>crtYB</I> together with the <I>PhCCD1</I> gene in the same vector resulted in a final 8.5-fold increase of β-ionone concentration (0.63 ± 0.02 mg/g DCW). Batch fermentations with this strain resulted in a final specific concentration of 1 mg/g DCW at 50 h, which represents a 15-fold increase.</P><P><B>Conclusions</B></P><P>An efficient β-ionone producing yeast platform was constructed by combining integrative and episomal constructs. By combined expression of the genes <I>BTS1</I>, the carotenogenic <I>crtYB</I>, <I>crtI</I> genes and the plant <I>PhCCD1</I> gene—the highest β-ionone concentration reported to date by a cell factory was achieved. This microbial cell factory represents a starting point for flavor production by a sustainable and efficient process that could replace current methods.</P><P><B>Electronic supplementary material</B></P><P>The online version of this article (doi:10.1186/s12934-015-0273-x) contains supplementary material, which is available to authorized users.</P>