Fact or Fiction: Busting Myths Around Starter Cultures, Probiotics, and Yeast Extract

The probiotics industry is booming globally as science and consumer demand drive an increase in diverse products designed for a wide range of applications.

Different products require not only specific probiotic strains, but also tailored production mechanisms. It can be confusing to keep everything straight, and a slew of conflicting information circulates around what probiotics even are, when and how they can be used, and how they are produced.

In this article, we debunk a few of the most common myths around probiotics, enabling you to separate truth from science fiction.

Myth #1: Probiotics and starter cultures strains are identical

Fact: There are important, subtle differences between starter cultures and probiotic microorganisms.

While very similar, probiotic strains and strains used for starter cultures have very different roles when it comes to the probiotic products we love.

There are several scientifically characterized probiotic microorganisms, including the commonly recognized Bifidobacterium and Lactobacillus species, as well as some species of Bacillus, Streptococcus, and even the yeast Saccharomyces. These organisms are used in a wide variety of applications (see myth #4 below for more information). Critically, the World Health Organization (WHO) defines probiotics as: “live microorganisms which when administered in adequate amounts confer a health benefit on the host.1

So, how do we deliver probiotic organisms to humans in adequate amounts?

When it comes to probiotic foods, the answer to this question relies on starter cultures. Bringing foods like cheeses, yogurts, kimchi and sauerkraut, sausages, or sourdough bread (among many others) to market requires industrial-scale processes that rely on specific microbial communities that help get the process started.

Those specific communities are called “starter cultures.” Starter cultures give the process of fermentation — the anaerobic breakdown of carbohydrates by bacteria and yeast — a kickstart. They are comprised of lactic acid bacteria (LAB; including Lactobacillus, Leuconostoc, Pediococcus, Lactococcus, and Streptococcus species), so named because of the lactic acid they produce as a byproduct of carbohydrate fermentation.

As you can see, some species that comprise starter cultures (Lactobacillus and Streptococcus, for example) are also recognized as probiotic species — but not all probiotic strains can be starter cultures, and starter cultures are not probiotics.

Eating a starter culture isn’t likely to make anyone healthier but eating the end result of a starter culture – a food product containing a mixture of live microorganisms at the appropriate dosage to have a beneficial effect on the host – now, that just might make a difference.

Myth #2 : Most industrial-scale probiotics are produced by/for yogurt companies.

Fact: Industrial probiotics can be found in a variety of forms: as food and beverages, dietary supplements, and in animal nutrition products.

Artisanal processes for producing fermented foods have been with us for millennia, but as science increasingly recognizes the beneficial effects of probiotic microorganisms – including in applications beyond food and beverage — industrial-scale production has exploded.

The major industrial probiotics sectors include food and beverage, dietary supplements, and animal nutrition. Altogether, the estimated market size for all three probiotic sectors combined globally is on the order of USD $50-60 billion2 and spans a range of companies in food, agriculture, and biotech.

Myth #3: The connection between probiotics and human health is still based on anecdotal evidence, not science.

Fact : Science hasn’t elucidated all of the details, but we know a lot about how probiotic microorganisms contribute to human health and well-being.

Until advances in culture-independent analyses, including the decreased cost of next-generation sequencing, became available to the research community, most evidence for the beneficial effects of probiotic microorganisms was anecdotal.

Now we recognize that our bodies are full of bacteria and microscopic eukaryotes, both inside and out — collectively, they and their gene products comprise the human microbiome.3 Most of them are harmless, and many of them are good for us.  As byproducts of their own metabolisms, they produce vitamins we can’t — such as K4 — and break down insoluble fiber (i.e., fiber our own bodies cannot digest) into short chain fatty acids, which are critical for intestinal and metabolic health.5,6

Research has also demonstrated that an intact gut microbiome is critical for immune system development and training.7,8  Our resident microbes also play a crucial role in fighting off pathogens9 and even preventing viral infections.10

As more and more research highlights the various beneficial effects our resident microbes confer, the variety of probiotics in development is also on the rise. Several probiotics have already proven effective for treating a wide range of conditions, including antibiotic-associated diarrhea11 and IBS.12

Additionally, given the intimate connection between the human digestive tract, immune system, and brain, several studies and clinical trials are also assessing the potential beneficial effects of probiotics for treating several autoimmune disorders,13 autism spectrum disorder,14 and depression.15 Many are also exploring other bacterial species that haven’t traditionally been classified as probiotic species.16

Myth #4: Probiotics are only useful for humans, and only in the gut.

Fact: Probiotics can be used for animals, or in other areas of the body, even for babies!

Probiotics have traditionally been consumed or administered to address gastrointestinal health, with some of the best research studying probiotics for IBS and antibiotic-associated diarrhea (see myth #3 above).

But probiotics, even if they are ingested, can have much more widespread effects on the human body. In fact, one of the biggest clinical trials ever performed to assess probiotic efficacy found that the probiotic species Lactobacillus plantarum ATCC-202195 could prevent sepsis in babies.17  It has also been recognized for several years that orally administered probiotics can have a protective effect against respiratory tract infections.18

But probiotics aren’t just for eating. Key players in academia and industry alike are developing probiotics for direct application to the skin to alleviate conditions such as eczema,19 or in the mouth to help fight oral disease.20 They aren’t just for humans, either: probiotics are used routinely in animal agriculture to aid in digestion and nutrient acquisition and strengthen animals’ immune systems to prevent disease.

Myth #5: Most probiotic species die during production.

Fact: This isn’t’ true — but viability is one of the biggest challenges in probiotics manufacturing.

Industrial scale probiotics production requires three main processes: batch fermentation (this is where the starter culture comes in), concentration, and stabilization.

Each step is critical to produce high concentrations of live, metabolically active microorganisms that will do what they’re supposed to do for the consumer.  This is especially critical for probiotics that are ingested in the form of pills or powders as supplements and must traverse the acidic conditions of the stomach before reaching the intestines where they can get to work.

Viability and vitality describe the ability of the probiotic to survive long-term storage and become metabolically active again when consumed. Because key producers in the growing probiotics market expect high-quality, consistent, and reliable microorganisms, viability and vitality matter – these qualities ensure that the probiotics deliver the benefits expected and demanded by consumers.

There are several approaches probiotics producers can take throughout the fermentation process to optimize viability and productivity. Strain-specific nutrients can be added to the media while limiting nutrient depletion and growth limitation caused by different media ingredients maximizes growth. Several factors, such as pH, gaseous phase, and harvest time can also be optimized to yield robust microorganisms.

Taking steps during fermentation to grow the most robust microorganisms possible ensures that the probiotic strains will be prepared to survive not only the concentration stage, which usually entails freeze- or spray-drying, but also storage and finally, passage through the human gastrointestinal tract.

Optimizing microorganism growth and productivity isn’t just good for the consumer, either — it contributes to significant cost savings associated with manufacture, which is one of the biggest challenges for companies seeking to optimize organism viability and vitality.

Myth #6: Yeast is just another type of probiotic.

Fact: Yeast can be a probiotic, but it can also protect probiotic bacteria during industrial fermentation processes.

Yeast strains, specifically Saccharomyces species, have been used for years as probiotics species and in the production of fermented foods and beverages.

Although yeast is expected to be the fastest growing ingredient segment in the probiotics industry according to Markets and Markets,2 they have far more value to the probiotics industry than just acting as another probiotic species.

Yeast extract, which is the contents of yeast cells minus the cell walls, has been shown to be a promising nutrient source for LAB, preserving both stability and viability, and therefore increasing quality and efficacy of the resulting probiotic.

By providing both macro- and micronutrients, yeast extract helps bacteria grow better during fermentation, enabling them to be as robust as possible and maximizing the number of bacteria that survive the freeze- or spray-drying process.  Yeast extract also shortens the time needed for the fermentation process by increasing bacterial productivity, which in the end means decreased costs and improved ROI.

By providing both macro- and micronutrients, yeast extract helps bacteria grow better during fermentation, enabling them to be as robust as possible and maximizing the number of bacteria that survive the freeze- or spray-drying process.

Our yeast-based nutrients can help you achieve higher stability and viability of your probiotic or starter culture.

Procelys combine technical expertise and global reach to help you achieve your goals. Learn how to optimize your probiotic production with this biological nitrogen source.



  1. http://www.fao.org/3/a-a0512e.pdf
  2. https://www.marketsandmarkets.com/Market-Reports/probiotic-market-advanced-technologies-and-global-market-69.html
  3. https://www.nature.com/articles/nature11234
  4. https://pubmed.ncbi.nlm.nih.gov/9167138/
  5. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4939913/
  6. https://www.frontiersin.org/articles/10.3389/fimmu.2019.00277/full
  7. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4095778/
  8. https://www.nature.com/articles/s41422-020-0332-7
  9. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5657496/
  10. https://www.frontiersin.org/articles/10.3389/fcimb.2019.00256/full
  11. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5745464/
  12. https://bmcgastroenterol.biomedcentral.com/articles/10.1186/s12876-018-0788-9
  13. https://clinicaltrials.gov/ct2/results?cond=Autoimmune+Diseases&term=microbiome&cntry=&state=&city=&dist=
  14. https://clinicaltrials.gov/ct2/results?cond=Autism&term=microbiome&cntry=&state=&city=&dist=
  15. https://clinicaltrials.gov/ct2/results?cond=Depression&term=microbiome&cntry=&state=&city=&dist=
  16. https://www.sciencedirect.com/science/article/pii/S1021949819300110
  17. https://www.nature.com/articles/nature23480.epdf?sharing_token=L5XAoaU3l90pg5dfo5Ps3tRgN0jAjWel9jnR3ZoTv0P4NW2v_a4IU38dncEGBFXJxXx7BTBRZVcu7NCfuIiekngJof2FEIGDMBCAWHwg_DL_w7PFrb0k3Gh8U3R9sgiE_WplF_h3bN3-DJ54Gvhj3GT_R2JpJFcV1jxm_bxlio7q3LkE-z03Pp_CEs5987HjlnfCse0Xygv_BFROfi3Pr3aR30r_aN0xcLlQg1sPFoV_PdO7kInqcxvBRs5ASS0yPC1V8YtEzdGV-7kKJZc6tdjkKhemdBC66eZBhy99whQz8PNZj-bE5oqTG2x0iwJr&tracking_referrer=www.theatlantic.com
  18. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4979858/
  19. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6517242/



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