Novel Strategies for Enhancing Torulaspora delbrueckii Performance in Wine Fermentation

Torulaspora delbrueckii (Td) improves wine organoleptic quality but struggles with fermentation efficiency and sensitivity to SO₂, ethanol, and CO₂ compared to Saccharomyces cerevisiae (Sc). To boost its industrial application, we explored several improvement strategies.

Firstly, genetic improvement involved isolating spore clones free of growth-retarding alleles from wine Td strains. Mutants resistant to SO₂, ethanol, and high CO₂ pressure were then obtained. These showed enhanced base wine fermentation, some approaching Sc's capability, with good genetic stability.

Secondly, we investigated yeast mixture for eventual hybridization between Td and Sc. The resulting mixed clones (Sc-mixed Td) exhibited intermediate phenotypes for critical biotechnological properties, including resistance to SO₂, ethanol, and high CO₂ pressure. Several mixed clones improved base wine fermentation and sparkling wine organoleptic quality, coinciding with increased acetate and ethyl esters. Their genetic stability supports commercial use.

Finally, we explored increasing Td inocula ploidy. Unlike Sc, Td transitions to diploid or polyploid states under stressful conditions. This increased ploidy enhances Td's viability and metabolic activity. Consequently, Td inocula with increased ploidy exhibited enhanced fermentation efficiency. These combined strategies offer promising avenues for optimizing Td's performance in industrial wine production.