How to Specify a Probiotic: Strain, CFU and Viability

When you buy citric acid, a CAS number and a purity figure tell you exactly what you are getting. A probiotic has no CAS number, because CAS numbers identify chemical substances and a live bacterial culture is not one. Specifying a probiotic properly means naming the organism down to the strain, and stating how many of them are alive.

1. Identity: genus, species and strain

"Lactobacillus" names a genus. "Lactobacillus plantarum" names a species. Neither is enough, because strains of the same species can behave very differently. Ask for the strain designation, normally a deposit number at a recognised culture collection such as DSM, ATCC or CGMCC. In the EU, probiotics used in feed are authorised strain by strain, so the exact strain decides whether the product is legal to sell for that use.

2. Viable count: CFU per gram

Potency is stated in colony-forming units per gram (CFU/g), the number of live bacteria that can multiply. Check two things on the specification:

• whether the count is guaranteed at manufacture or at the end of shelf life. Counts fall during storage, so an end-of-shelf-life guarantee is the stronger promise;
• which plate-count method was used, which should be named on the Certificate of Analysis.

3. Survival: spore-formers and non-spore-formers

Bacillus species, such as Bacillus subtilis and Bacillus licheniformis, form spores. Spores survive heat, pressure and long storage, which is why they are widely used in pelleted animal feed. Lactobacillus and Bifidobacterium do not form spores, are more sensitive to heat, moisture and oxygen, and usually need cool, dry storage and protective packaging.

4. Carrier and storage

Probiotic powders are standardised on a carrier such as maltodextrin, and the carrier affects flowability and water activity. Confirm the storage temperature on the specification, because some cultures need refrigeration while spore-formers are stable at room temperature.

5. Customs classification

Live cultures are classified as cultures of micro-organisms under HS heading 3002. They are often wrongly declared under 2102.90, which covers dead single-cell micro-organisms.

Browse our feed and supplement probiotics, and request the strain specification with your quotation.