Major contribution of the E hrlich pathway for 2‐phenylethanol/rose flavor production in A shbya gossypii

Abstract Aroma alcohols of fermented food and beverages are derived from fungal amino acids catabolism via the Ehrlich pathway. This linear pathway consists of three enzymatic reactions to form fusel alcohols. Regulation of some of the enzymes occurs on the transcriptional level via Aro80. The riboflavin overproducer Ashbya gossypii produces strong fruity flavours in contrast to its much less aromatic relative Eremothecium cymbalariae . Genome comparisons indicated that A. gossypii harbors genes for aromatic amino acid catabolism ( ARO 8a , ARO 8b , ARO 10 , and ARO 80 ) while E. cymbalariae only encodes ARO 8a and thus lacks major components of aromatic amino acid catabolism. Volatile compound ( VOC ) analysis showed that both Eremothecium species produce large amounts of isoamyl alcohol while A. gossypii also produces high levels of 2‐phenylethanol. Deletion of the A. gossypii ARO ‐genes did not confer any growth deficiencies. However, A. gossypii ARO ‐mutants (except Agaro8a ) were strongly impaired in aroma production, particularly in the production of the rose flavour 2‐phenylethanol. Conversely, overexpression of ARO 80 via the Ag TEF 1 promoter resulted in 50% increase in VOC production. Together these data indicate that A. gossypii is a very potent flavour producer and that amongst the non‐ Saccharomyces biodiversity strains can be identified that could provide positive sensory properties to fermented beverages.