Nitrogen catabolic repression controls the release of volatile thiols bySaccharomyces cerevisiaeduring wine fermentation

Abstract

Volatile thiols such as 4-methyl-4-sulfanylpentan-2-one (4MSP) and 3-sulfanylhexan-1-ol (3SH) are aromatic molecules having an important organoleptic impact on white wines. These components are produced from inodorous nonvolatile cysteinylated precursors by Saccharomyces cerevisiae metabolic activity during alcoholic fermentation. Here we provide a new insight into the genetic determinism of the production of volatile thiols by yeast. Using a gene deletion approach, we investigated the role of three yeast beta-lyases and demonstrate that Irc7p, a putative cystathionine beta-lyase, is one of the main proteins catalyzing the 4MSP and 3SH release under enological conditions. Moreover, we demonstrate that Ure2p/Gln3p proteins mainly control the bioconversion of volatile thiols by the transcriptional regulation of the IRC7 gene through the general mechanism of nitrogen catabolic repression. Finally, our findings suggest that the enantiomer balance of 3SH may be modulated by activating specifically stereoselective enzymes such as Irc7p.

Genomic Insights into the Saccharomyces sensu stricto Complex

“…The IRC7 gene encodes a b-lyase that is responsible for the release of volatile thiols that are especially important during winemaking (Thibon et al 2008;Roncoroni et al 2011). While the genomes of all strains of S. cerevisiae, including S288c, appear to contain IRC7, a highly diverse homolog of this gene (88% DNA identity to S288c IRC7) was identified in the human clinical isolate YJM540.…”

Engineering Saccharomyces cerevisiae To Release 3-Mercaptohexan-1-ol during Fermentation through Overexpression of an S. cerevisiae Gene, STR3 , for Improvement of Wine Aroma

“…Since then, the potential for enhanced thiol release in grape juice has been demonstrated by the constitutive expression of the Escherichia coli tnaA gene, a tryptophanase with strong CS ␤-lyase activity (29). Thus far, there is no direct evidence of such yeast-derived enzymatic activity releasing aromatic thiols under oenological conditions although some candidate genes have been suggested based on a gene deletion approach (15,31). The release of aromatic thiols by other microorganisms has been linked to the activity of cystathionine ␤-and ␥-lyases, for example, Lactobacillus casei and Lactobacillus lactis in cheese production (16,20), Staphylococcus haemolyticus in the release of human body odor (37), and Streptococcus anginosus in mouth malodor (42).…”

Botrytized wines – current perspectives

“…13,14 These precursors are present in the healthy grape as well, but their quantities dramatically increase due to noble rot. The botrytization process increased the P-3SH level in grapes ~100-fold in 1 week, compared to healthy grapes.…”