One letter apart
Tryptose and tryptone are confused so often that orders get placed for the wrong one. Both are peptones and both are enzymatic hydrolysates, but the raw material and the purpose differ.
- Tryptone: casein alone, hydrolysed with pancreatic (tryptic) enzymes. Complete amino acid profile, high tryptophan, the main nitrogen source of LB, TSB and Tryptone Water.
- Tryptose: a mixture of casein and meat protein hydrolysed with enzymes, designed for nutritionally fastidious organisms such as Brucella, Listeria, streptococci and Pasteurella. Any medium with "Tryptose" in its name uses it.
Comparison
| Tryptone | Tryptose | |
|---|---|---|
| Raw material | Casein | Casein plus meat protein |
| Hydrolysis | Pancreatic enzymes | Mixed enzymes |
| Peptide character | Short and medium peptides, high tryptophan | Wider peptide length distribution, meat-derived growth factors |
| AN/TN | about 30 to 40 % | about 25 to 35 % |
| Animal origin | Milk | Milk and meat |
| Representative formulations | LB Broth, Tryptic Soy Broth, Tryptone Water | Tryptose Broth, Tryptose Phosphate Broth, Tryptose Blood Agar Base, Lauryl Tryptose Broth |
| Typical use | E. coli, molecular biology, sterility testing | Brucella, Listeria, streptococci, blood agar bases, coliform MPN |
When tryptose is required
Whenever a standard method specifies it. For example:
- Lauryl Tryptose Broth (LST): the MPN coliform test for food and water (FDA BAM, ISO and CNS methods), built on 20 g/L tryptose.
- Tryptose Phosphate Broth (TPB): a cell culture supplement and streptococcal medium.
- Tryptose Blood Agar Base: the base for blood plates used to isolate fastidious pathogens.
Substituting tryptone in these formulations may still give growth, but the method is no longer the standard one and the test report is compromised.
When they are interchangeable
In general bacteriology and non-standard fermentations the two can be swapped or blended; the differences are growth rate and cost. Tryptone is cheaper and more readily available. Tryptose contains meat and cannot be used in Halal or animal-origin-free formulations.
Frequently asked questions
Is there a plant-based tryptose? Genuine tryptose contains meat protein, so there is no purely plant version. Halal or vegetarian alternatives are usually re-optimised with soy peptone plus yeast extract, but cannot then be labelled as the standard method.
Is tryptone the same as casein peptone? Tryptone is the pancreatic digest of casein; enzymatic casein peptone may use other enzymes. They are close but not identical in specification. See the article on casamino acids, tryptone and casein peptone.
Does STBIO MEDIA supply both? Yes. Tryptone and Tryptose are both available, as are dehydrated Lauryl Tryptose Broth, Tryptose Phosphate Broth and related media.