Understanding Yeast and Its Industrial Importance
Yeast is a living organism: a single-celled microorganism belonging to the fungus family. Under the right conditions, a yeast cell is capable of fermenting. During this process, its enzymes convert a substrate into carbon dioxide (CO₂), alcohol, and organic acids.
The yeast species Saccharomyces cerevisiae is the best known. However, there are many domesticated yeast strains, each with its own specific characteristics and applications. They are used, in particular, to make bread, beer, wine, yeast extracts to enhance the flavor of foods, dietary supplements, and biofuels. Since yeast is a source of nutrients, it is also used in the fields of human and animal health and wellness.
Yeast can also be used to produce molecules of interest, such as enzymes, vitamins, flavorings, and even pharmaceutical molecules like insulin for people with diabetes.
Yeast strains selected by the fermentation industry offer numerous advantages:
- they grow rapidly;
- they feed on renewable sugars;
- they naturally produce valuable molecules;
- they are safe for many food applications;
- they contain nutrients, including proteins, B vitamins, and minerals.
Because yeast reproduces rapidly and can be cultivated under carefully controlled conditions, industries can reliably produce consistent, high-quality products on a very large scale.
The Most Common Industrial Yeast Strains
Saccharomyces cerevisiae, Saccharomyces pastorianus, Kluyveromyces lactis, Candida utilis, Yarrowia lipolytica, Debaryomyces hansenii, Brettanomyces… More than 1,500 species of yeast have been identified to date1.
Although we often simply refer to “yeast,” scientists identify yeasts by their genus (e.g., Saccharomyces) followed by the species (e.g., cerevisiae), and then the strain. Many strains are now commonly used in industrial production. These strains differ from one another in terms of genetic characteristics and metabolic properties.
For each application, manufacturers carefully select strains that perform exceptionally well under specific conditions. One strain may tolerate high concentrations of alcohol. Another may produce fruity aromas. A third may grow effectively even in the presence of high sugar concentrations, such as osmotolerant strains. Osmotolerant baker’s yeasts are thus used by baking professionals to make brioche or croissants.
These small genetic differences explain why the industry selects
Saccharomyces cerevisiae, the best known
Commonly referred to as “baker’s yeast” and “brewer’s yeast,” Saccharomyces cerevisiae is the most widely used industrial yeast species worldwide. Easy to handle, hardy, and fast-growing, it is used both to produce everyday foods and in research and biotechnology.
- In baking, it is the key ingredient that causes bread dough to rise. The strains of Saccharomyces cerevisiae used by bakers are adapted to the specific requirements of different recipes and production processes, such as sweet doughs and frozen doughs. In bread dough, enzymes in the yeast cells break down the sugars in the flour and produce, in particular, CO₂, a gas that causes the dough to rise. Fermentation also generates molecules that contribute to the desired flavors in bread.
- Saccharomyces cerevisiae is also one of the most commonly used species in beer brewing. It is used in the production of top-fermented ales. During fermentation, the microorganism consumes the sugars present in the wort, which is generally composed of water, malted grains (barley, wheat), and hops. It produces ethanol (alcohol) and CO₂, which give the beer its bubbles and head. Hundreds of secondary metabolites that influence the beer’s flavor are also produced during this process.
- In wine production, Saccharomyces cerevisiae is the most commonly used yeast, alongside various indigenous yeasts naturally present on grapes. The primary role of yeast is to convert the sugars in grape must into alcohol. Other byproducts are produced as a result of this fermentation, such as glycerol, sulfur dioxide, methanol, and acids… When inactivated, yeast can also be used as a source of nutrients to ensure successful wine fermentation, as well as to preserve the wine’s aromas throughout the aging process.
- In bioethanol production, strains of Saccharomyces cerevisiae are used to generate ethanol through fermentation from both food and non-food raw materials.
Other Notable Yeast Strains
Other yeast strains are commonly used in various industrial applications. For example:
- Saccharomyces boulardii is a probiotic yeast used in dietary supplements and certain health products. Capable of remaining active as it passes through the digestive system, it contributes to the balance of the gut microbiota and helps support proper intestinal function. Unlike many probiotic bacteria, this yeast is naturally resistant to antibiotics, which explains its particular value during certain antibiotic treatments.
- Saccharomyces pastorianus is used in the production of lager-style beers. It has the unique ability to ferment at low temperatures, producing more subtle flavor profiles than Saccharomyces cerevisiae.
- Kluyveromyces lactis, on the other hand, breaks down lactose and converts it into lactic acid. It is used to produce chymosin on a commercial scale—the rennet used in the production of certain cheeses.
- Candida utilis, another species, is inactivated by heating and then used as a flavoring agent in food products, as a dietary supplement, and in animal feed.
Innovating to Improve Yeast Performance
The yeast strains currently available on the market—in the form of fresh active yeast or instant yeast, for example—have been rigorously selected for their performance in the application for which they are intended. Genetically modified strains are also being developed to be more resistant to high alcohol concentrations, to generate more aromas in beer, or to produce bioethanol from certain types of plant waste.
Challenges and the Future of Yeast in the Industry
Industrial yeast currently faces several technical and environmental challenges: controlling fermentation temperatures, sourcing the sugars used, and improving strains for better beer brewing and bread dough rising…
Yeast manufacturers are constantly seeking to improve their products, particularly to address global sustainability challenges. For example, it is now possible to produce certain compounds of interest through precision fermentation: sweeteners, colorants, egg alternatives, compounds for cosmetics… These substances are identical to those traditionally sourced from nature but are produced sustainably.
Conclusion
From baking to biotechnology, yeast has established itself as a central player in modern industrial processes. Thanks to the diversity of its strains, it contributes both to our daily diet and to the development of innovative and sustainable products.
