Engineering volatile thiol release in Saccharomyces cerevisiae for improved wine aroma

Area of Science:

• Enology and Viticulture
• Molecular Biology
• Biotechnology

Background:

• Volatile thiols (e.g., 4-mercapto-4-methylpentan-2-one, 3-mercaptohexan-1-ol) are key aroma compounds in wine, influencing quality and consumer preference.
• Their release from grape precursors during fermentation enhances varietal characteristics, particularly in wines like Sauvignon Blanc.
• Current wine yeast strains exhibit limited capacity to produce these desirable thiols, leaving significant aroma potential untapped.

Purpose of the Study:

• To develop an improved wine yeast strain capable of maximizing the release of volatile thiols from grape juice.
• To enhance the aromatic profile of wines by unlocking the full potential of thiol precursors.

Main Methods:

• Cloned and overexpressed the Escherichia coli tnaA gene, encoding tryptophanase with cysteine-beta-lyase activity, in a commercial wine yeast.
• Utilized the regulatory sequences of the yeast phosphoglycerate kinase I gene (PGK1) for gene expression control.
• Assessed the production of 4-mercapto-4-methylpentan-2-one (4MMP) and 3-mercaptohexan-1-ol (3MH) in model wine fermentations.

Main Results:

• The engineered yeast strain demonstrated a significant increase in volatile thiol production, releasing up to 25 times more 4MMP and 3MH compared to the control.
• Wines produced using the modified yeast exhibited a pronounced passionfruit aroma.
• The enhanced yeast effectively released thiols from their non-volatile precursors.

Conclusions:

• The genetically modified wine yeast successfully enhances the release of potent aroma compounds, significantly improving wine's aromatic complexity.
• This engineered yeast offers a powerful tool for the wine industry to achieve specific varietal aroma profiles and meet market demands.
• The study highlights the potential of targeted gene expression in yeast for optimizing wine sensory characteristics.