Preparation of MRS Broth

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)
Deionized water

Equipment and disposables
Measuring cylinder
500 ml screw-capped bottle/conical flask
Weighing balance
Microwave oven/Hot plate
Magnetic stirrer
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.

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