Local microbes persist in wine despite commercial yeast

American Society for Microbiology

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Key Points:

• Commercial yeast inoculation, adding a specific strain of yeast to start the fermentation process, is a common practice in winemaking.
• Researchers tested Nebbiolo grapes and discovered that regional microbial imprints remain detectable after inoculation.
• Microbes that come from the vineyard leave a lasting imprint on fermentation and wine aroma, even under controlled, inoculated conditions.

Washington, D.C.—A new study has demonstrated that regional microbial imprints can remain detectable under commercial winemaking conditions. The new research, appearing in Applied and Environmental Microbiology, an ASM journal, shows that inoculated fermentations do not “override” native microbial diversity and demonstrates that vineyard management and environmental conditions matter in the quality of wine. The study helps explain why wines from different regions taste distinct even when made with similar techniques and, supports regional flavors and branding.

“Regional identity in wine is biologically encoded and microbes from different vineyards behave differently and influence wine chemistry and aroma. Because microbial communities are shaped by geography, climate and viticultural practices, these factors indirectly influence fermentation outcomes and the regional typicity of wines,” said corresponding study author Kalliopi Rantsiou, Ph.D., Professor of Food Microbiology and Coordinator of the master’s degree in Viticulture and Enology at the University of Turin, Department of Agricultural, Forest and Food Sciences, in Italy. “Furthermore, commercial inoculation does not entirely erase microbial signatures associated with the origin of the grapes.”

The researchers conducted their study because recent research has shown that grape‑associated microbial communities are not randomly distributed but exhibit clear biogeographical structuring—meaning that different regions harbor distinct microbial assemblages. These microbial differences can influence fermentation dynamics, organic acid metabolism and volatile compound formation. This concept, often referred to as microbial terroir, has become a major frontier in wine science. However, despite this growing body of work, a gap remained: almost all microbial terroir studies have focused on spontaneous fermentations or pre‑fermentation grape microbiota. Very few have tested whether these regional microbial signatures persist when winemakers use commercial yeast inoculation, common practice in modern wineries. The researchers set out to determine whether microbial terroir persists under inoculated fermentation, and whether it still influences fermentation dynamics, chemical composition and wine aroma. The aim was to test whether microbial terroir is robust enough to subsist inoculation and remain a meaningful contributor to regional wine identity—a question of high relevance for both science and industry.

Nebbiolo grapes provided an ideal model for the study because they are grown across distinct regions with strong environmental contrasts and are known for having complex fermentative microbiota. The researchers collected Nebbiolo grapes from 38 vineyards across 3 regions in northern Italy. All grapes were fermented under identical small scale winery conditions using the same commercial yeast strain, temperature, equipment and nutrient additions. This strict standardization ensured that any differences observed in microbial behavior or wine chemistry were due to the grapes and their native microbes, not the winemaking process. Throughout fermentation, the researchers repeatedly sampled the must, freshly crushed juice of grapes and wine to assess microbes present, microbial communities’ changes over time, fermentation chemistry over time and aroma compounds development. The results allowed the scientists to check whether wines still carried a “regional microbial fingerprint.”

The researchers discovered that the vineyard’s microbial fingerprint persists throughout fermentation, even when a commercial yeast is added. Regional microbial differences were clear from the start and these differences did not disappear after inoculation. Microbial differences were linked to chemical and aroma differences. The researchers concluded that the microbes that come from the vineyard leave a lasting imprint on fermentation and wine aroma, even under controlled, inoculated conditions.

“The outcomes support the concept that microbial terroir is robust. Even when winemakers use commercial yeast inoculation—a widespread practice—the vineyard’s native microbial community still shapes fermentation trajectories and contributes to wine identity,” Rantsiou said.

 

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Journal

Applied and Environmental Microbiology