M.R.S. BROTH without DEXTROSE 500 grams/bottle

MRS Broth w/o Dextrose provides the user with the ability to incorporate a desired carbohydrate for additional selectivity. It was developed by de Man, Rogosa and Sharpe to provide a medium that would support the good growth of lactobacilli, but in particular for those strains which showed poor growth in existing media such as L. brevis and L. fermenti, replacing a variable product (tomato juice). 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 source of vitamins, particularly the B-group. The growth of some Lactobacillus strains are inhibited at a higher pH of 6,0 and it is necessary to acidify the media to promote the growth. To acidify the media some drops of acetic acid can be added.