The Use of Genetically Modified Yeasts in Winemaking

The Use of Genetically Modified Yeasts in Winemaking

People made fermented drinks throughout history through trial and error. Honey wine, or mead, was created in Asia during the Vedic period. It was also made by the Greeks, Saxons, Celts, and Vikings. Wine in Egypt, Rome, Babylon, and China was made from grapes[1].

In South Africa, people made Chicha from fruits or/and grains, whereas octli was produced in parts of North America from agave. Despite the ingredients, one thing held constant in winemaking: fermentation. Today, the use of genetically modified yeasts in winemaking is a vital part of the fermentation process.

Winemaking in the ancient world

Our ancestors stored fruits and grains in covered vessels for long periods to create wine. However, no one could explain the process behind it. Eventually, they discovered fermentation. Winemakers softened grapes with their feet before letting the mixture sit in buckets for long periods. Microorganisms from their feet were left in the mixture through this process[2].

However, people did not know that yeast was among the microorganisms. Yeast is a tiny one-celled fungus that creates alcohol during fermentation. High-quality microscopes allowed researchers to observe these microbes after several centuries of development.

Discovery of yeasts as microorganisms

For centuries, people wondered why fruit juice bubbled and became an intoxicating and aromatic beverage if stored for long enough. The process was a supernatural or spiritual entity in ancient times. In 1680, Antonie van Leeuwenhoek, a Dutch naturalist born on October 24, 1632, became the first person to observe yeast cells directly[3].

This transformed the wine industry. Many years later, French scientist Joseph-Louis Gay-Lussac made several observations about yeast in 1815. He experimented with a method that protected perishable food from rotting that was created by a confectioner and cook named Nicolas Appert.

Gay-Lussac wanted to use the process to keep grape juice wort unfermented for an infinite period. To avoid air exposure, the process involved boiling the wort in a vessel and firmly closing it. As long as the vessel was shut, the grape juice remained unfermented for long periods. However, the yeast fermented if added to the wort after it cooled.

Two centuries after the discovery, Louis Pesteur hypothesized that the yeast could generate different flavors in wine from similar grape varieties. He also discovered that it was the yeast that caused the fermentation process. Additionally, he learned that only bacteria can transform carbohydrates into alcohol from grape juice and the process takes place in the absence of oxygen.

He concluded his argument by stating that fermentation is a process of the respiration without air. Born on December 21, 1890, Hermann Muller would later become the first person to successfully isolate pure yeast strains and use them as starter cultures in winemaking in 1927[4].

Fast forward to winemaking in the present

Today, winemakers know how yeast affects how long wine takes to mature as well as the quality of the final product.  These days, most winemakers use cultivated yeast that are added prior to the fermentation, yet it’s worth mentioning, that some producers who make “natural” wines, do not add yeast, but rather let the yeast that is already present on the grapes do their magic.

Understanding the role of yeast in winemaking

Where and when did the use of yeasts in winemaking start? Firstly, wild yeast colonies thrive in outdoor crops. The skins of grapes in a vineyard host a range of yeast species, which swarm into the fermenter with the juice. Wild yeasts ferment the carbohydrates in crushed fruit into alcohol over time.

Hundreds of wild yeast species interact to produce low-quality wines with limited alcohol strength. With the growing need for high-quality fine wines, scientists are working towards using specific varieties of yeasts to control the flavors and qualities of the wine. To achieve that goal, they have developed genetically modified yeasts.

Genetically modified yeasts in winemaking

The use of genetically modified yeasts in winemaking improves the process in different ways. This includes increasing yeast ethanol tolerance, modifying a wine’s sensory elements, enhancing fermentation, and improving sugar usage and nitrogen assimilation.

The technology was actualized after the discovery of GMO methods in the mid-1990s. There are several strains of GMO yeasts that help in wine fermentation. One of them simultaneously undergoes malolactic and alcoholic fermentation while another strain lowers the acidity and reduces the overall fermentation period.

The third genetically engineered strain reduces H2S evolution in wine production. Winemakers want to employ yeast strains that do not generate hydrogen sulfides since they have a detrimental impact on flavor and aroma. Any commercial yeast strain can be crossed with this strain to gain this trait. In fact, several other yeast strains have already done so.

In the fermentation process, changes to the yeast strains do not alter crucial traits of the parent strain. However, they do somehow alter their metabolic activities. Although, some changes to the wine can have a sensory effect, such as increasing glycerol production in yeast and removing specific genes[8].

Increasing glycerol production in yeast reduces ethanol production by 1%, and deleting certain genes suppresses acetic acid production. Both alter the sensory aspect of a wine made from the genetically modified organism relative to the host strain.

The future of yeast in winemaking

Because of the growing need for a distinct and complex wine, scientists attempt to improve commercial yeasts. Microbiologists are trying to cultivate particular yeasts with population diversity similar to natural ferments.

Yeasts can be developed for specific uses as we learn more about the metabolic processes of grape ingredients and how they act during fermentation. Some sugars convert to glycerol rather than alcohol, which could be helpful in hot climates with high-alcohol wines. Alternatively, yeast can produce aroma molecules that disclose more of the varietal identity of grapes.

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On this Day

October 24, 1632:  Antonie van Leeuwenhoek, a Dutch naturalist, became the first individual to observe yeast cells directly. He used some lenses that he had developed to make the discovery. It was the origin of knowledge that would transform the wine industry.

December 21, 1890: Hermann Muller was born and would later become the first person to successfully isolate pure yeast strains and use them as starter cultures in winemaking.

References

[1] Alba-Lois, L., and C. Segal-Kischinevzky, “Beer & wine makers,” Nature (2010).

[2] Ibid

[3] https://www.britannica.com/biography/Antonie-van-Leeuwenhoek

[4] https://daily.sevenfifty.com/the-science-of-winemaking-yeasts/

[5] Ibid

[6] Husnik, John I., Heinrich Volschenk, Jurgen Bauer, Didier Colavizza, Zongli Luo, and Hennie JJ Van Vuuren, “Metabolic engineering of malolactic wine yeast,” Metabolic engineering 8, no. 4 (2006): 315-323.

[7] https://wineserver.ucdavis.edu/industry-info/enology/methods-and-techniques/winery-lab-techniques/genetically-modified-organisms

[8] Ibid