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 was key to producing high-quality wine. 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 and is responsible for creating 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 considered 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. Joseph-Louis Gay-Lussac, a French scientist, made several observations about yeast in 1815. He was experimenting with a method for protecting perishable food from rotting created by Nicolas Appert, a confectioner, and cook.

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, if the yeast was added to the wort after it cooled, it fermented.

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].

Flash 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. One of the first decisions a winemaker makes is whether to use yeast. Only around 20% of the wine made worldwide is fermented by yeast cultures that are intentionally introduced to the batch. Most of it depends on the wild yeasts already present.

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 yeast

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 created to 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.

A third genetically engineered strain was created to reduce 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 acetic acid production is suppressed by deleting certain genes. 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 could be converted to glycerol rather than alcohol, which could be helpful in hot climates with high-alcohol wines. Alternatively, yeast can be engineered to produce aroma molecules that disclose more of the varietal identity of grapes.

See more Resources here

Want to know more about wine? Check out these books!

Yeasts in the Production of Wine 1st ed. 2019 Edition, Kindle Edition by Patrizia Romano.

Yeast Technology 1st Edition. by John F.T. Spencer (Editor), Dorothy M. Spencer (Editor).

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

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Winemaking, The Use of Genetically Modified Yeasts in Winemaking