Résumé
We performed a dynamic and quantitative analysis of the synthesis of fermentative aromas by an aromatic wine yeast, ECA5, obtained by adaptive evolution. During fermentation at pilot scale on synthetic and natural musts, ECA5 produced volatile compounds (higher alcohols and their acetates, ethyl esters) at higher rates than the ancestral strain, with the exception of propanol. Marked differences in the chronology of synthesis of several compounds were observed between the two strains. Overproduction of phenyl ethanol occurred mainly during the growth phase for ECA5, consistent with its higher flux through the pentose phosphate pathway, which plays a key role in biosynthetic processes. The kinetics of production of isobutanol and isoamyl alcohol were differently affected by different media (synthetic or natural must) and, in particular, according to the nature of the sterols in the media (ergosterol or phytosterols). We also observed differences in the chronology of synthesis of ethyl acetate and isoamyl acetate or ethyl esters, suggesting that the regulation of the synthesis of these compoundsin the evolved strain differs from that in the ancestral strain. This study shows that a dynamic analysis of volatile compounds, using high acquisition frequency online gas chromatography, can provide novel insights into the synthesis and regulation of aromas and is thus a potentially powerful tool for strain characterization