MRS Broth Low pH 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 5,7Â±0,2, this medium favors the growth of these strains.
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