Research & Insights
Live Yeast vs Inactivated Brewer's Yeast: What Feed and Pet Food Buyers Should Know
Published
Live yeast and inactivated brewer's yeast can come from the same species, Saccharomyces cerevisiae, but buyers purchase them for different jobs. Live yeast is a probiotic whose value depends on cells staying alive, and in the EU it is regulated as a feed additive. Inactivated brewer's yeast is a feed material, bought as a protein and nutrient ingredient in which no yeast cells survive.
How are live and inactivated yeast classified?
The clearest line is in EU law, which the UK kept after Brexit. Commission Regulation (EU) No 68/2013, the Catalogue of feed materials, groups fermentation products in Division 12 under a heading that reads "inactivated", "resulting in absence of live micro-organisms". Its footnote says the microorganisms used in the fermentation "have been inactivated with the result that no such microorganisms are viable in the feed materials."
Brewer's yeast sits in that division as entry 12.1.5, "Yeasts [brewers' yeast]". Live yeast is a different legal object. Annex I of Regulation (EC) No 1831/2003 lists "gut flora stabilisers: micro-organisms or other chemically defined substances" among the zootechnical additives, and additives need an authorization before they can be sold.
| Point | Inactivated brewer's yeast | Live yeast |
|---|---|---|
| EU and UK status | Feed material, Reg. 68/2013 entry 12.1.5 | Zootechnical feed additive, Reg. 1831/2003 |
| What you are paying for | Protein, amino acids, B vitamins, palatability | A count of viable cells |
| How it is dosed | Percent of the diet | Colony forming units (CFU) per kg or per head per day |
| Heat in processing | Cells are already inactive | Activity can drop with heat |
| Label declarations (EU) | Moisture and crude protein; propionic acid if above 0.5% | Set by the additive's authorization |
Sources: Regulation (EU) No 68/2013, Annex Part C, Division 12; Regulation (EC) No 1831/2003, Annex I.
Why is brewer's yeast inactivated?
Fresh brewer's yeast leaves the brewery as a wet slurry. Feedipedia notes that drying inactivates the yeast. That is the point of the process for a feed ingredient: a dry, stable powder with a known protein content, which can travel in a container and sit in a warehouse for months.
Inactivation also makes the buyer's job simpler. A live yeast product has to arrive with enough viable cells to do its job, and the review by Pang and colleagues in the Journal of Fungi notes that high-temperature disinfection of feed "seriously reduces the activity" of active dry yeast. Inactivated brewer's yeast does not depend on cell survival for its protein value, so pelleting or extrusion does not change what you bought it for.
What does each one do in the animal?
Live yeast is used for its activity in the gut. In ruminants, Pang et al. describe how live yeast may take up oxygen in the rumen, which favors the anaerobic microbes that digest fiber, and may help steady rumen pH. Doses are counted in cells. One calf study in the review gave Saccharomyces boulardii at 1 x 10^10 CFU per day. Feedipedia notes that responses to live yeast vary with dose, timing and strain.
Inactivated brewer's yeast is used as a nutrient source. Feedipedia reports an average of 48.9% crude protein on a dry matter basis for dehydrated brewer's yeast, with a range of 39.3 to 56.8% across 108 samples. Pet food makers also value it for flavor, which we cover in our palatability guide. It goes into diets at percent levels, which is why buyers compare it with other protein ingredients rather than with probiotics.
Some products sit in between. Yeast culture contains yeast together with the medium it grew on, and yeast cell wall is a fraction rather than the whole cell. Our guides to yeast culture vs brewer's dried yeast and yeast cell wall vs brewer's dried yeast explain those differences.
Which one should you buy?
Start from the job. If you need a protein and flavor ingredient for pet food, aquafeed or livestock diets, you are buying inactivated brewer's yeast and comparing it on protein, moisture, ash and price per point of protein. If you want a probiotic effect, you are buying a specific authorized strain at a stated CFU count, usually from an additive company, and the brewer's yeast in your recipe does not replace it.
Many formulators use both. The live yeast goes in at the small dose set by its authorization, for its effect on the gut, and the brewer's yeast goes in at percent levels for nutrition. They are not interchangeable, and they are not competing for the same line in the formula.
What should you ask a brewer's yeast supplier?
- Is the product inactivated, and does the specification say so?
- Which feed material entry or ingredient name will appear on your label in your market?
- What are the guaranteed values for crude protein, moisture, ash, fat and fibre?
- What is the shelf life, and what packing sizes are available?
- Which registrations and certificates can the supplier share with your QA team?
For TBESBY, the answers are short. Our brewer's yeast is inactivated and drum-dried, with crude protein of 40 to 46%, moisture below 10%, ash below 6%, fat of 0.5% max and crude fibre of 1.5% max. Shelf life is 12 months, and we pack in 25 kg bags or jumbo bags of 600 to 1,200 kg. We are U.S. FDA registered and ISO 22000:2018 certified, and the product is non-GMO.
Where does TBESBY fit?
TBESBY supplies inactivated dried brewer's yeast as a feed material. We do not sell live yeast probiotics. Our yeast is made from fresh brewer's yeast from leading international breweries in Vietnam and dried at our own facilities in Vietnam, for pet food and animal nutrition importers in the UK, EU, Australia and the US.
See the full specification on our product page, read how it is used on our brewer's yeast for pet food and livestock and poultry pages, or contact us for documents.
Frequently asked questions
Is brewer's yeast in pet food alive?
No. Dried brewer's yeast used in pet food and feed is inactivated during drying. Under EU feed law, fermentation products in Division 12 of the feed material catalogue must contain no viable microorganisms.
Is inactivated yeast a probiotic?
No. A probiotic depends on live cells. Inactivated brewer's yeast is a feed material bought for protein, amino acids, B vitamins and flavor.
Is live yeast a feed additive in the EU?
Yes. Microorganisms used as gut flora stabilisers fall under the zootechnical additives in Annex I of Regulation (EC) No 1831/2003 and need an authorization.
Does heat destroy the value of brewer's yeast?
Heat does not remove its protein value, because the cells are already inactive. Heat can reduce some vitamins, so measure the nutrients you care about in the finished product.
Sources
- Commission Regulation (EU) No 68/2013 on the Catalogue of feed materials, Annex Part C, Division 12.
- Regulation (EC) No 1831/2003 on additives for use in animal nutrition, Annex I.
- Pang Y et al. (2022). Yeast Probiotic and Yeast Products in Enhancing Livestock Feeds Utilization and Performance: An Overview. Journal of Fungi 8(11): 1191.
- Heuzé V et al. (2018). Brewers yeast. Feedipedia, a programme by INRAE, CIRAD, AFZ and FAO.