Unlocking the lipid potential of yeast derivatives

Abstract

Climate change brings about various challenges to the wine industry, including higher sugar content, lower acidity, and imbalances in yeast nutrients. Winemaking practices such as low fermentation temperature and excessive clarification of white grape must – that may lead to the partial loss of lipids – to produce fruitier wines in response to consumer demand may create conditions leading to sluggish or stuck fermentations. The latter conditions are typically overcome by the yeast Saccharomyces cerevisiae that can alter its membrane composition in fatty acids and ergosterol. Nevertheless, in the absence of oxygen, the yeast cannot produce the necessary lipids and therefore relies on those occurring in grape must. Without lipids, fermentation ceases prematurely due to early cell death. Subsequently, winemakers must account for the lack of lipids by supplementing the grape must with nutrients. In this work, a wide selection of non-Saccharomyces yeasts isolated from the broader wine environment was screened for their lipid content, after which six strains were selected based on the amount of lipids produced and diversity of lipid composition. Inactivated dry yeasts were produced from these strains and tested as lipid supplements in over-clarified Chenin Blanc juice. The addition of the inactivated yeasts enhanced fermentation performance compared to the reintroduction of fine lees and no addition. Furthermore, experiments with the addition of pure analytical standard lipids in the same concentrations yielded similar results, correlating the change in fermentation kinetics to lipid addition. Nevertheless, differences in fermentation performance were observed, largely due to the variation in lipid composition, as the supplementation of some inactivated yeast derivatives led to better fermentation performance than others. Differences in the production of a selection of aroma compounds linked with lipid metabolism were also observed between the addition of pure lipids and inactivated yeasts. Overall, the data showed that the wine yeast microbiota may serve as a sustainable source of lipids to improve fermentation under challenging environmental conditions and pave the way for further research on the availability and utilisation of lipids for wine yeasts.

References

Mbuyane LL, Bauer FF, Divol B. (2021) The metabolism of lipids in yeasts and applications in oenology. Food Res Int.