Written by: Kari Raman, PharmD, RPh
Published March 2, 2023

Saccharomyces is a genus of probiotic yeast that consist of several different species, the most well-known of this genus are Saccharomyces cerevisiae and Saccharomyces boulardii (S. boulardii). Scientists and pharmacists don’t generally think of this yeast as being one that is typically found in the human gut, but many probiotic supplements contain S. boulardii because it is thought to have some possible health advantages in the human digestive tract.

Image source: Wikipedia

S. cerevistiae is incredibly important for fermenting beer and wine, and making sourdough bread. I first practiced pharmacy in San Francisco, so I have to say some sourdough bread and a nice glass of a cab sounds pretty good right now. 🙂

Studies have demonstrated that S. boulardii can survive transit through the acidic environment of the stomach and remain alive and functioning in the small and large intestine for several days after ingestion. However, it does not appear to establish a long-term presence in the gut, and its effects on gut microbiota composition and function are still under investigation.

Saccharomyces – one of the first recognized probiotics

The origin story of Saccharomyces boulardii is pretty interesting. In 1923, a French scientist named Henri Boulard was on a mission to Southeast Asia to study the local fermentation techniques used in food production. While in Indochina, he came across a traditional medicinal drink made from the skins of lychee and mangosteen fruits that was known to treat diarrhea.

Intrigued by this remedy, Boulard began investigating the microorganisms responsible for its therapeutic properties. He eventually isolated a strain of yeast that he named Saccharomyces boulardii, which he found was effective in treating a variety of digestive disorders.

Boulard’s discovery of S. boulardii was groundbreaking at the time. It’s actually one of the first times people began to understand that probiotics are a thing, and that they can be good for our guts and health. Boulard’s work not only led to the discovery of a beneficial microorganism but also highlighted the importance of traditional remedies in scientific research.

What are Saccharomyces probiotics used for?

Saccharomyces probiotics, specifically Saccharomyces boulardii, are primarily used to support digestive health. This type of probiotic has been studied extensively for its ability to prevent and treat various gastrointestinal conditions. (Skip down to read about S. cerevisiae, which is even more well known since it’s used in brewing beer and wine).

Some possible advantages of the different Saccharomyces species involve:

  • Saccharomyces boulardii has been shown to improve gut and digestive health by decreasing inflammation and diarrhea caused by several types of bacteria. If you are talking probiotics, this is the most common/popular species of the Saccharomyces genus of yeasts. In my opinion, this is one of the probiotics with the best research showing a positive impact on diarrhea.
  • Various research implies that Saccharomyces boulardii may assist in stimulating the immune system which may reduce the incidence of infection.
  • Certain research suggests that S. boulardii may be beneficial in reducing symptoms of Irritable Bowel Syndrome (IBS)
  • S. boulardii has been found in some studies to help reduce the symptoms of atopic eczema in children and adults.
  • Saccharomyces cerevisiae can help to reduce overgrowth of candida albicans in the gut.

Other uses of Saccharomyces

In addition to its use as a probiotic, Saccharomyces has several non-probiotic uses in various fields. Some examples include:

  • Brewing and Distilling: Saccharomyces cerevisiae, also known as brewer’s yeast, is commonly used in the production of beer, wine, and other fermented beverages. It is responsible for converting sugar into alcohol and carbon dioxide during the fermentation process. Probably the best known species of this yeast!
  • Baking: Saccharomyces cerevisiae is also used in baking to make bread and other baked goods rise. It works by producing carbon dioxide gas as it ferments sugars in the dough. Oh, and sourdough bread has a connection to this yeast as well – S. exiguus is commonly used to make sourdough bread, well sour. Makes me want to head back to San Francisco for a bread bowl and some crab chowder!
  • Nutritional Supplements: Saccharomyces cerevisiae is a rich source of B vitamins, minerals, and other nutrients. It is often used as a nutritional supplement in the form of yeast-based products, such as nutritional yeast.
  • Pet Food: Saccharomyces cerevisiae is sometimes used as a nutritional ingredient in pet food due to its high content of B vitamins, amino acids, and other nutrients. It is believed to support overall health and wellbeing in dogs and cats, particularly in relation to skin and coat health. Supposedly cats and dogs like the taste of this ingredient, although most humans probably won’t (it’s bitter!).
  • Research: Saccharomyces cerevisiae is a model organism used in biological research due to its simple cellular structure and well-understood genetics. It has been used to study a wide range of biological processes, including aging, cancer, and neurodegenerative diseases.

Commonly found types of Saccharomyces

There are several types of Saccharomyces, but some of the most commonly found include:

  • Saccharomyces cerevisiae: This is the most well-known and widely studied type of Saccharomyces. It is commonly used in baking, brewing, and winemaking, and is also used as a nutritional supplement due to its high content of B vitamins and other nutrients.
  • Saccharomyces boulardii: This is a probiotic strain of Saccharomyces that is often used to support digestive health. It has been studied for its ability to prevent and treat diarrhea and other gastrointestinal conditions; I wrote about that above.
  • Saccharomyces pastorianus: This type of Saccharomyces is commonly used in the brewing of lagers, and is sometimes known as “bottom-fermenting yeast” due to its tendency to settle at the bottom of the fermentation vessel.
  • Saccharomyces uvarum: This type of Saccharomyces is commonly found in wine and cider, and is sometimes known as “bayanus yeast.”
  • Saccharomyces exiguus: This type of Saccharomyces is commonly found in sourdough bread and other fermented foods. I’ve got to stop writing about sourdough bread, it’s making me miss San Francisco!

Quick bit about Brewers Yeast – S. Cerevisiae

Sacchromyces cerevisiae (also known as Brewer’s Yeast) is probably one of the oldest used yeasts in human history. Historians believe that it has been used for thousands of years to brew beer, wine and other things that make you drunk. The yeast is believed to have first been domesticated for use in beer production by ancient civilizations in the Middle East and Mediterranean regions, where it was likely isolated from the wild and cultivated for its unique fermentation properties.

The reason why this is such a special yeast is that it reliably produces alcohol through fermentation – and it can do this at pretty high alcohol levels, more than most yeasts can tolerate. Saccharomyces cerevisiae is able to tolerate high levels of alcohol because it has several unique adaptations that allow it to thrive in such conditions. During fermentation, the yeast breaks down the sugar molecules into smaller compounds, including ethanol (alcohol) and carbon dioxide. Too much alcohol kills yeast, and this yeast can stay alive with a high concentration of alcohol. There are some other yeasts that can tolerate even higher alcohol levels, but only S. cerevisiae is known as brewer’s yeast! And I’m not an expert in brewing, but this is an interesting study looking into how it impacts beer and wine flavors.

Today, Saccharomyces cerevisiae is still one of the most commonly used yeasts in beer, wine and other alcoholic drink production, prized for its ability to ferment sugars and produce alcohol and carbon dioxide.

Where is Saccharomyces found?

The different types of Saccharomyces can be found naturally in a lot of different environments, including:

  • Soil: Saccharomyces can be found in soil, particularly in areas where plant material is decomposing.
  • Plants: Saccharomyces can be found on the surface of many plants, including fruits and vegetables like grapes, mangos,
  • Water: Saccharomyces can be found in freshwater and marine environments, particularly in areas with high levels of organic matter.
  • Fermented Foods: Saccharomyces is often found in fermented foods such as bread, beer, wine, and cheese. Is this natural? I’d say so, pass me a glass of merlot people.

Overall, Saccharomyces is a microorganism that can be found in many different environments, from tropical areas to your friends home brewing kit.

Saccharomyces FAQ

How is Sacchromyces boulardii made?

For Saccharomyces boulardii, the most commonly used strain for probiotic supplements, the yeast is typically cultured in a mixture of simple sugars and other nutrients, such as peptones and amino acids. The yeast is grown under controlled conditions of temperature, pH, and oxygen levels to ensure optimal growth and survival. It is also important for it to be cultured in a completely sterile environment so that no other yeasts, molds or bacteria can contaminate it. Once the yeast has reached a sufficient density, it is typically harvested, washed, and dried or freeze-dried to produce a stable powder or capsule form that can be used as a probiotic supplement.

How are other Sacchromyces species made?

To produce S. cerevisiae (brewer’s yeast) for brewing, a small amount of the yeast is first added to a nutrient-rich medium to form a culture of cells. This culture is then transferred to a larger vessel containing a fermentable sugar source, such as barley or malt. The yeast consumes the sugars in the medium, producing ethanol and carbon dioxide as byproducts. The conditions of the fermentation process, including temperature, pH, and nutrient levels, can be adjusted to optimize the growth and performance of the S. cerevisiae culture. Brewers often use specific strains of S. cerevisiae and adjust the fermentation conditions to produce beer with desired flavors and aromas.

Saccharomyces cerevisiae is also commonly used in the production of sourdough bread. For breadmakers and home bakers, a small amount of S. cerevisiae is added to a mixture of flour and water to create a starter culture. The starter culture is allowed to ferment over several days, during which time the S. cerevisiae consumes the carbohydrates in the flour.

How is Saccharomyces boulardii good for your gut?

Saccharomyces boulardii is believed to help the gut in a few ways. First of all, it is thought to make it harder for bad stuff Clostridium difficile, Salmonella, and Escherichia coli to thrive. Since these can cause problems in the human digestive tract, and by competing with these harmful bacteria for nutrients and adhesion sites, S. boulardii can reduce their impact on health and make the gut feel better. Secondly, some studies (note that I think that was a study in mice) show that S. boulardii can stimulate the production of protective mucins, which are substances that form a protective layer over the intestinal lining. Finally, S. boulardii can modulate the immune response, promoting a healthy balance of immune cells in the gut and reducing inflammation, which can also contribute to diarrhea prevention. One quality producer is Florastor, who I review in my comparison of Florastor vs Culturelle..

Is Saccharomyces cerevisiae used as a probiotic?

When people talk about S. cerevisiae, they generally mean brewer’s yeast, which is not usually used as a probiotic (unlike S. boulardii, which is typically used as a probiotic). While S. cerevisiae is a beneficial yeast that has many uses, including in baking and brewing, it does not have the same probiotic properties as S. boulardii. S. cerevisiae is not as well-suited to survive the acidic environment of the stomach and colonize the intestines, which are important properties for a probiotic to have. But it does have some nutritional benefits, including being a rich source of B vitamins.

Pharmacist Kari Raman

I’m Kari Raman PharmD, RPh, and I am a licensed, practicing pharmacist. I hold a Doctorate in Pharmacy from The University of the Pacific, and I’ve served patients in retail, compounding and hospital pharmacies.

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I hope Pharmacist Probiotics helps you find out if there is a type of probiotic that works for you!