MRS broth is nutrients rich liquid medium for the cultivation of Lactobacilli. It was developed by de Man, Rogosa, and Sharpe. It can be purchased from several suppliers in a ready-to-use form (a mixture of all ingredients). Here we describe a recipe for preparing 250 ml MRS broth from a ready-to-use mix.
Reagents and solutions
MRS Broth (Dehydrated) (ThermoFisher Scientific, #CM0359B)
Equipment and disposables
500 ml screw-capped bottle/conical flask
Microwave oven/Hot plate
Filter unit (Sarstedt #83.3941.001) or Autoclave
Preparation of 250 ml MRS Broth
Step 1: Weigh out 13 g of MRS broth in a 500 ml bottle. Add 250 ml water and a magnetic stirrer bead. Mix and dissolve the powder completely. It will form a yellowish transparent solution.
Step 2: Heat the solution in the microwave for 1 to 2 min. The warm solution will become translucent. Cool the solution to room temperature. The solution will turn into a yellowish transparent liquid.
Step 3: Sterilize the solution either by autoclaving or using a 0.2µ filter unit.
Sterilization by autoclaving: Sterilize the solution at 121°C for 15 minutes. Cool the solution to Room temperature and check the pH. If the pH is not between 6.2 – 6.6, adjust the pH using acetic acid or sodium hydroxide.
Sterilization using filter unit: Pass the solution through the filter unit containing a filter paper with a pore size of 0.2 µ.
Store the MRS broth at 4°C.