Non-Saccharomyces Yeasts Cut Pesticide Residues by Up to 53 Percent in Wine Fermentation Study

A recent study from the University of Montpellier has provided new insights into how wine yeasts interact with copper and pesticides during fermentation, with important implications for both wine quality and environmental safety. The research, published in the journal OENO One, examined 13 strains of wine yeasts, including the widely used Saccharomyces cerevisiae and several non-Saccharomyces species such as Metschnikowia, Starmerella, and Torulaspora. The team set out to understand how these yeasts respond to copper and a mix of 23 commonly used vineyard pesticides, and how effectively they can remove these substances from grape must during the early stages of fermentation.

The study was motivated by ongoing concerns about the presence of xenobiotic substances—foreign chemical compounds like pesticides and heavy metals—in grape juice and wine. In conventional viticulture, synthetic pesticides are widely used to protect vines from disease and pests. Organic vineyards, while avoiding most synthetic chemicals, often rely on copper-based treatments to control fungal infections. Both approaches can leave residues in the harvested grapes, which then make their way into the must and potentially into finished wines. These residues are not only a health concern but can also interfere with the fermentation process itself.

To investigate these issues, researchers conducted controlled fermentations using synthetic grape must spiked with either copper or a pesticide mix at concentrations reflecting those found in real-world vineyard conditions. They monitored yeast growth, fermentation activity (measured by CO2 release), cell viability, and the levels of copper and pesticides remaining in the must over time.

The results showed that copper, even at concentrations typical for organic vineyards (up to 7.5 mg/L), had little effect on most yeast strains’ growth or fermentation performance. Only a few strains—one Saccharomyces cerevisiae and two non-Saccharomyces—showed reduced viability or slower fermentation when exposed to copper. For most yeasts, copper was efficiently removed from the must within 48 hours of fermentation. This removal was stable even after ethanol was added to simulate the end of fermentation, suggesting that once sequestered by yeast cells, copper is not easily released back into the wine.

In contrast, exposure to pesticides had a much more pronounced effect on yeast activity. All strains tested showed some degree of slowed fermentation when pesticides were present, with non-Saccharomyces yeasts being particularly sensitive. The maximum rate of CO2 production dropped significantly for many strains, indicating that pesticides can directly inhibit yeast metabolism or reduce cell viability. However, despite this inhibition, most yeasts maintained high viability (over 90%) after 70 hours of fermentation.

When it came to detoxification—the ability of yeasts to remove these substances from the must—the results were mixed. Most strains could efficiently remove copper regardless of their species or overall growth rate; this ability appeared to be highly strain-dependent rather than species-specific. The mechanism is thought to involve binding copper ions inside cells or on cell walls through proteins like metallothioneins or other cellular components.

Pesticide detoxification was less efficient and more variable between strains and pesticide types. While all yeasts reduced total pesticide levels in the must to some extent (with residual concentrations ranging from 47% to 76% of initial levels after 70 hours), non-Saccharomyces yeasts generally outperformed Saccharomyces cerevisiae in this regard. Some pesticides were readily removed by all strains (such as cyazofamid and zoxamide), while others (like folpel) resisted detoxification entirely. The efficiency did not correlate with yeast population size or overall fermentation activity but seemed linked to specific properties of each strain.

The study also found that pesticide exposure altered yeast metabolism in subtle ways. Sensitive strains increased their production of glycerol—a compound involved in osmoregulation—and acetate, which is important for lipid biosynthesis and membrane integrity. These changes may reflect an adaptive response to stress caused by membrane-disrupting xenobiotics.

The findings have practical implications for winemakers and organic growers seeking to minimize chemical residues in their products. By carefully selecting yeast strains with strong detoxification abilities—especially among non-Saccharomyces species—it may be possible to reduce both copper and pesticide levels in grape must before bottling. This could improve wine quality while also addressing consumer concerns about chemical contaminants.

Researchers caution that more work is needed to fully understand the genetic and physiological mechanisms behind these detoxification processes. Further studies will also need to examine whether similar results are seen in natural grape juice (which contains polyphenols and other solids) rather than synthetic media, as well as how different combinations or concentrations of pesticides affect yeast performance.

The study highlights both the resilience and diversity of wine yeasts in coping with environmental contaminants introduced through modern agriculture. It also points toward biological solutions—using selected microorganisms—to address challenges that have traditionally been managed through chemical or physical means alone. As interest grows in sustainable winemaking practices, these findings may help guide future strategies for cleaner wines and healthier vineyard ecosystems.