Dehydrated culture media
MRS Broth
For the cultivation and enumeration of Lactobacillus spp.
- Cat. No.
- LC-1215
- Category
- Dehydrated culture media
- Format
- 500 g
- Storage
- 2 to 25 °C
- Minimum guaranteed shelf life
- 15 months
MRS Broth is a medium for the cultivation and enumeration of Lactobacillus spp. It has the same formulation as MRS Agar (LC-1043) without the agar as a solidifying agent. It is used when a fluid medium is preferred.
Key features
Applications
Selective enrichment and selective enumeration of lactobacilli.
Industry
Alcoholic beverages, dairy products, food.
Preparation
52.25 g in one liter of distilled water; boil for one minute, sterilize in autoclave at 121 °C for 12 minutes.
Principles and uses
It was developed by De Man, Rogosa and Sharpe to provide a medium which allows a good growth of lactobacilli, particularly L. brevis and L. fermenti strains, which have had a poor growth in existing media. This has been achieved by replacing the tomato juice from the Tomato Juice Agar with other nutrients, creating a suitable medium for the growth of lactic acid bacteria, including Lactobacillus, Pediococcus and Leuconostoc.
Ammonium citrate at a low pH inhibits most microorganisms, but allows the growth of lactobacilli. Dipotassium phosphate and sodium acetate are buffer agents to maintain a low pH. Tween 80 is an emulsifier. Manganese and magnesium sulfates are sources of ions and sulfate. Bacteriological peptone and beef extract provide nitrogen, vitamins, minerals and amino acids essential for growth. Yeast extract is a source of vitamins, particularly the B-group. Dextrose is the fermentable carbon and energy source.
The growth of some Lactobacillus strains is inhibited at pH higher than 6.0, so it is necessary to acidify the medium to promote the growth. To acidify the medium some drops of acetic acid can be added.
Technical specifications
| Solubility | Without residues |
|---|---|
| Appearance | Fine powder |
| Color of the dehydrated medium | Beige |
| Color of the prepared medium | Clear amber |
| Final pH (25 °C) | 6.2 ± 0.2 |
| Amount per litre | 52.25 g |
Formula
| Ingredient | g/L |
|---|---|
| Bacteriological peptone | 10 |
| Dextrose | 20 |
| Dipotassium phosphate | 2 |
| Magnesium sulfate | 0.2 |
| Manganese sulfate | 0.05 |
| Beef extract | 8 |
| Sodium acetate | 5 |
| Tween 80 | 1 |
| Yeast extract | 4 |
| Ammonium citrate | 2 |
Typical formula in g/L, adjusted and/or supplemented as required to meet performance criteria.
Preparation and use
Preparation
Suspend 52.25 grams of the medium in one liter of distilled water. Mix well and dissolve by heating with frequent agitation. Boil for one minute until complete dissolution. Dispense into appropriate containers and sterilize in autoclave at 121 °C for 12 minutes.
Instructions for use
- Take the inoculum with a sterile loop.
- Submerge the loop into the medium and shake gently.
- Incubate at 35 °C for 3 days or at 30 °C for 5 days, in both cases in a CO₂-enriched atmosphere.
Quality control
Microbiological test
Incubation conditions: (35 °C / 3 days) or (30 °C / 5 days) in a CO₂-enriched atmosphere.
| Microorganism | Specification |
|---|---|
| Escherichia coliATCC 25922 | Good-moderate growth |
| Pseudomonas aeruginosaATCC 27853 | Inhibited growth |
| Lacticaseibacillus caseiATCC 393 | Good growth |
| Lactobacillus acidophilusATCC 4356 | Good growth |
| Lactobacillus fermentumATCC 9338 | Good-moderate growth |
Bibliography
- Sharpe M. Elisabeth, Fryer T.F. and Smith D.G. (1966) "Identification of the Lactic Acid Bacteria in Identification Methods for Microbiologists Part A" (Gibbs B.M. and Skinner F.A. eds.) London and New York, Academic Press.
- Briggs M. (1953) J. Dairy Res., 20: 36-40
- Reuter G. (1985) Intern. J. Food Microbiol 2: 55-68.
What you receive
The product
Shipped under controlled temperature when the product requires it.
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