MRS BROTH low pH
CAT Nº: 1431
Recommended medium for the growth of lactobacilli in general
FORMULA IN g/l
Dextrose
20.00
Dipotassium Phosphate
2.00
Enzymatic Digest of Casein
10.00
Triammonium Citrate
2.00
Beef Extract
10.00
Tween 80
1.08
Sodium Acetate
5.00
Magnesium Sulfate
Heptahydrate
0.20
Yeast Extract
4.00
Manganese Sulfate
tetrahydrate
0.05
Final pH 5.7 ± 0.1 at 25ºC
PREPARATION
Suspend 54 grams of the medium in one 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 15
minutes. The prepared medium should be stored at 2-8°C. The color is amber, slightly opalescent.
The dehydrated medium should be homogeneous, free-flowing and beige in color. If there are any physical changes,
discard the medium.
USES
MRS BROTH is a selective medium that supports the good growth of lactobacilli in general.
The medium is apt 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 of the B-group. Dextrose
is the fermentable carbohydrate.
The growth of some lactobacillus strains is inhibited at a pH higher than 6.0 and it is necessary to acidify the medium to
favour the growth. With a pH of 5.7 ± 0.2, this medium favors the growth of these strains.
MICROBIOLOGICAL TEST
The following results were obtained in the performance of the medium from type cultures after incubation at a
temperature of 37ºC during 3 days, or at 30ºC during 5 days, under a CO2 enriched atmosphere in an anaerobic jar, and
observed after 24 hours.
Microorganisms
Growth
Lactobacillus acidophilus ATCC 4356
Good
Lactobacillus casei ATCC 393
Good
Lactobacillus fermentum ATCC 9338
Moderate-Good
Escherichia coli ATCC 25922
Moderate-Good
1
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Pseudomonas aeruginosa ATCC 27853
Inhibited
BIBLIOGRAPHY
ROGOSA, M., a. SHARPE, M.E.: An approach to the classification of the lactobacilli. – J. Appl. Bact., 22; 329-340 (1959].
STORAGE
8ºC
Once opened keep powdered medium closed to avoid hydration.
2ºC
2
LABORATORIOS CONDA, S.A.
www.condalab.com