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

Abstract

Sulfur-containing aroma compounds are key contributors to the flavor of a diverse range of foods and beverages. The tropical fruit characters of Vitis vinifera L. cv. Sauvignon blanc wines are attributed to the presence of the aromatic thiols 3-mercaptohexan-1-ol (3MH), 3-mercaptohexan-1-ol-acetate, and 4-mercapto-4-methylpentan-2-one (4MMP). These volatile thiols are found in small amounts in grape juice and are formed from nonvolatile cysteinylated precursors during fermentation. In this study, we overexpressed a Saccharomyces cerevisiae gene, STR3, which led to an increase in 3MH release during fermentation of a V. vinifera L. cv. Sauvignon blanc juice. Characterization of the enzymatic properties of Str3p confirmed it to be a pyridoxal-5-phosphate-dependent cystathionine ␤-lyase, and we demonstrated that this enzyme was able to cleave the cysteinylated precursors of 3MH and 4MMP to release the free thiols. These data provide direct evidence for a yeast enzyme able to release aromatic thiols in vitro that can be applied in the development of self-cloned yeast to enhance wine flavor.

Origins of Grape and Wine Aroma. Part 1. Chemical Components and Viticultural Impacts

“…For example, estimates from the literature vary from 0.1 to 12% conversion of cysteine-3MH to 3MH (and 3MHA) (Subileau et al 2008), representing only a small fraction of the polyfunctional thiols present in juice and leaving significant pools of both cysteine and glutathione precursors in finished wines . It has been established that yeast strains having carbon-sulfur β-lyase activity release these polyfunctional thiols during fermentation (Howell et al 2005, Ugliano 2009, Holt et al 2011. As the level of carbon-sulfur β-lyase activity varies due to yeast strain, yeast selection can be used, in part, to control the polyfunctional thiol content of wine , Roncoroni et al 2011.…”

Factors Influencing the Production of Sensory Active Substances in Brewer's and Wine Yeast

“…Nadměrná exprese genu STR3 kvasinky S. cerevisiae vede ke zvýšení produkce 3MH. Enzym Str3p je cystothionin-β-lyasa a má schopnost štěpit prekursory za vzniku 3MH (Holt et al, 2011). Je pravděpodobné, že uvolnění 3MH je zprostředkováno více než jedním genem.…”

“…Overexpression of STR3 gene from S. cerevisiae causes an increased production of 3MH. The enzyme Str3p is cystothionine-β-lyase and can cleave precursors to from 3MH (Holt et al, 2011). Release of 3MH is probably mediated by more than one gene.…”

Saccharomyces cerevisiae STR3 and yeast cystathionine β-lyase enzymes

“…It is worth noting that the pH optimum of Str3p is 8.75, and at the S. cerevisiae cytoplasmic pH of 7.0, only 25% of CBL activity remained, 7 whereas at the peroxisomal pH of 8.2, Str3p retains 80% of its maximum enzymatic activity. Str3p has a peroxisomal targeting signal type I (PTS1), and has been located in the peroxisome of S. cerevisiae cells grown with oleic acid as a carbon source.…”