Bacillus Subtilis Probiotic: What It Is, Safety and the BS50 Trial

Updated Oct 28, 2026 · 11 sources

A Bacillus subtilis probiotic is a supplement built on B. subtilis, a spore-forming bacterium found in soil and in the human gut and used to make natto.^1,2 Strain matters: in a 2022 placebo-controlled trial in 76 healthy adults, 47.4% of those taking 2 billion CFU a day of the strain BS50™ for 6 weeks improved on a combined bloating, burping and flatulence score, against 22.2% on placebo.³

Key points

• B. subtilis can rest as a spore, a dormant form that endures heat, pH changes, salt and drying, a 2024 food science review explains.⁴
• Europe’s food safety agency lists Bacillus subtilis for a qualified presumption of safety, on two conditions each strain must meet: no toxigenic activity and no acquired resistance genes to clinically relevant antimicrobials.⁵
• FDA closed its review of the BS50™ safety notice in 2023 with no questions about the maker’s conclusion that the strain is generally recognized as safe as a food ingredient.⁶
• Physician’s Choice Bloat + Gas Probiotic has Bacillus subtilis OPTIBIOME BS50™ on its label, 2 billion CFUs per capsule (See the label); the trial used its own capsules, not this product.^3,7

What is Bacillus subtilis?

A spore-forming bacterium long filed as a soil microbe that also lives in people. A 2009 study isolated B. subtilis from intestinal biopsies and stool samples and concluded that it should be considered a gut resident, not only a soil organism.¹ People eat it on purpose too: natto, a traditional Japanese soy food, is made by fermenting soybeans with B. subtilis.²

BS50™ itself came from soil: FDA’s letter on its safety notice records that the maker isolated the strain from soil samples in Gallatin County, Montana.⁸

What is a spore-forming probiotic?

A probiotic made from bacteria that can rest inside a tough spore. The 2024 review describes a spore as a dormant, non-reproductive structure, and says Bacillus spores endure heat, pH changes, salt and drying that harm growing cells, then turn back into active cells once they meet nutrients and moisture in the gut.⁴

Our Digestive Enzymes product page puts it plainly: “spore-forming Bacillus strains are naturally acid-resistant.”⁹ The same review stresses that a probiotic’s stability, safety and effectiveness are set by the strain, not the species or genus.⁴ Why spore-formers suit a chewable is covered on our page do probiotic gummies work.

What was BS50™ studied for? A Bacillus subtilis probiotic in healthy adults

A combined score for bloating, burping and flatulence, in healthy adults. In a 2022 randomized, double-blind, placebo-controlled trial, 76 adults between 30 and 65, free of any significant digestive condition but with at least minimal bloating, burping or flatulence, took one capsule of BS50™ at 2 billion CFU, or a placebo, daily with their largest meal for 6 weeks.³

Is Bacillus subtilis safe?

Food regulators in Europe and the US have looked at it, with conditions checked strain by strain. Europe’s food safety agency (EFSA) lists Bacillus subtilis for a qualified presumption of safety, provided each strain shows no toxigenic activity and carries no acquired resistance genes against clinically relevant antimicrobials.⁵ EFSA uses the list as a generic pre-check that supports its safety assessments of microbes added to food and feed.⁵

In the US, FDA closed its review of the BS50™ notice on October 20, 2023, with no questions about the maker’s conclusion that the strain is generally recognized as safe (GRAS) as an ingredient in foods such as baked goods, cereals and beverages.⁶ The letter adds that it is not an affirmation of GRAS status, and notes earlier no-questions letters for five other B. subtilis strains.⁸ NCCIH says the risk of harmful effects from probiotics is greater in people with severe illnesses or compromised immune systems.¹⁰

Which Physician’s Choice products contain Bacillus subtilis?

Three, as their labels print it today. Bloat + Gas Probiotic and Digestive Enzymes list the strain Bacillus subtilis OPTIBIOME BS50™; Bloat + Gas Probiotic prints it at 2 billion CFUs per capsule, the strain and daily amount of the 2022 trial, which used its own capsules, not this product.^3,7,9 Probiotic Gummies list Bacillus subtilis by species only, so the BS50™ trial is not about them.¹¹

In our words: “Probiotics help to support occasional bloating, burping and gas, while digestive enzymes help to break down carbs and dairy.”‡ Each label, as printed: Bloat + Gas Probiotic (See the label), Digestive Enzymes (See the label) and Probiotic Gummies (See the label). How a probiotic and an enzyme capsule share one day is on our page on probiotics for bloating.

Who should check with a doctor first

If you are pregnant or breastfeeding, are seriously ill, or have a weakened immune system, consult your healthcare provider before taking a probiotic or any other dietary supplement.

If you have known allergies, review the product’s ingredient list and allergen information and consult your healthcare provider before purchasing or using it. Most of our products are formulated without the top 9 common allergens, but ingredients vary by product.

If bloating is persistent, severe, or feels different than usual, talk with your healthcare provider.

If you experience an adverse event, stop using the product and contact your healthcare provider immediately. Please also notify us at support@physicianschoice.com or 1-877-395-2707.

Questions people ask

The short version

A Bacillus subtilis probiotic carries a spore-forming bacterium that Europe lists for a presumption of safety and that FDA has reviewed as a food ingredient, strain by strain. In the 2022 BS50™ trial, the combined bloating, burping and flatulence score improved in more healthy adults on the strain than on placebo.

Sources

1. Hong HA, et al. Bacillus subtilis isolated from the human gastrointestinal tract. Res Microbiol, 2009.
2. Afzaal M, et al. Nutritional Health Perspective of Natto: A Critical Review. Biochem Res Int, 2022.
3. Garvey SM, et al. The probiotic Bacillus subtilis BS50 decreases gastrointestinal symptoms in healthy adults: a randomized, double-blind, placebo-controlled trial. Gut Microbes, 2022;14(1):2122668.
4. Payne J, Bellmer D, Jadeja R, Muriana P. The Potential of Bacillus Species as Probiotics in the Food Industry: A Review. Foods, 2024;13(15):2444.
5. European Food Safety Authority (EFSA), Panel on Biological Hazards. Updated list of QPS-recommended microorganisms for safety risk assessments carried out by EFSA (Panel Statement 24). Published September 17, 2026.
6. U.S. Food and Drug Administration (FDA). GRAS Notice Inventory: GRN No. 1131, Bacillus subtilis ATCC BS50 PTA-127287. Closed October 20, 2023.
7. Physician’s Choice. Bloat + Gas Probiotic product page and Supplement Facts label (version 3.1.0).
8. U.S. Food and Drug Administration (FDA). Agency response letter, GRAS Notice No. GRN 001131. 2023.
9. Physician’s Choice. Digestive Enzymes product page and Supplement Facts label (60 count, version 3.7.0).
10. National Center for Complementary and Integrative Health (NCCIH). Probiotics: Usefulness and Safety. Last updated August 2019.
11. Physician’s Choice. Probiotic Gummies product page and Supplement Facts label (version 3.0.0).

How this page was made

Sources fetched October 28, 2026. Label facts come from our Bloat + Gas Probiotic, Digestive Enzymes and Probiotic Gummies labels and product pages. Written by Physician’s Choice.

‡These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.