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Engineering volatile thiol release in Saccharomyces cerevisiae for improved wine aroma
Author(s) -
Swiegers Jan H.,
Capone Dimitra L.,
Pardon Kevin H.,
Elsey Gordon M.,
Sefton Mark A.,
Francis I. Leigh,
Pretorius Isak S.
Publication year - 2007
Publication title -
yeast
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.923
H-Index - 102
eISSN - 1097-0061
pISSN - 0749-503X
DOI - 10.1002/yea.1493
Subject(s) - aroma of wine , wine , malolactic fermentation , yeast in winemaking , winemaking , aroma , yeast , wine fault , fermentation , saccharomyces cerevisiae , biology , food science , biochemistry , aging of wine , ethanol fermentation , fermentation in winemaking , chemistry , bacteria , lactic acid , genetics
Volatile thiols, such as 4‐mercapto‐4‐methylpentan‐2‐one (4MMP), 3‐mercaptohexan‐1‐ol (3MH) and 3‐mercaptohexyl acetate (3MHA), are among the most potent aroma compounds found in wine and can have a significant effect on wine quality and consumer preferences. At optimal concentrations in wine, these compounds impart flavours of passionfruit, grapefruit, gooseberry, blackcurrant, lychee, guava and box hedge. The enzymatic release of aromatic thiols from grape‐derived, non‐volatile cysteinylated precursors (Cys‐4MMP and Cys‐3MH) and the further modification thereof (conversion of 3MH into 3MHA) during fermentation, enhance the varietal characters of wines such as Sauvignon Blanc. Wine yeast strains have limited and varying capacities to produce aroma‐enhancing thiols from their non‐volatile counterparts in grape juice. Even under optimal fermentation conditions, the most efficient thiol‐releasing Saccharomyces cerevisiae wine strain known realizes less than 5% of the thiol‐related flavour potential of grape juice. The objective of this study was to develop a wine yeast able to unleash the untapped thiol aromas in grape juice during winemaking. To achieve this goal, the Escherichia coli tna A gene, encoding a tryptophanase with strong cysteine‐β‐lyase activity, was cloned and overexpressed in a commercial wine yeast strain under the control of the regulatory sequences of the yeast phosphoglycerate kinase I gene ( PGK1 ). This modified strain expressing carbon–sulphur lyase activity released up to 25 times more 4MMP and 3MH in model ferments than the control host strain. Wines produced with the engineered strain displayed an intense passionfruit aroma. This yeast offers the potential to enhance the varietal aromas of wines to predetermined market specifications. Copyright © 2007 John Wiley & Sons, Ltd.