Modified MRS Agar Medium – de Man, Rogosa & Sharpe Medium for Lactic Acid Bacteria Counting

Modified MRS Agar Medium – 250g / Bottle

The Modified MRS Medium (de Man, Rogosa & Sharpe) is a nutrient-rich agar medium specifically formulated for counting and cultivating lactic acid bacteria. This medium can be enhanced by adding Mupirocin Lithium Salt Solution and 5% L-Cysteine Hydrochloride Solution (MRS-CyHCl) to improve selective growth for probiotic and lactic acid bacterial studies.

Product Information:

• Name: Modified MRS Agar Medium / de Man, Rogosa & Sharpe Medium

• Form: Dehydrated agar medium (powder)

• Pack Size: 250g per bottle

• Storage: Room temperature

• Shelf Life: 3 years

Composition (per liter):

• Peptone – 10.0 g

• Beef Extract – 5.0 g

• Yeast Extract – 4.0 g

• Dextrose – 20.0 g

• Tween 80 – 1.0 g

• Sodium Acetate·3H₂O – 5.0 g

• K₂HPO₄·7H₂O – 2.0 g

• Ammonium Citrate Tribasic – 2.0 g

• MgSO₄·7H₂O – 0.2 g

• MnSO₄·4H₂O – 0.05 g

• Agar – 15.0 g

• pH: 6.2 ± 0.1 (25℃)

Preparation Instructions:

1. Dissolve 64.3 g of the medium in 1L distilled or deionized water.

2. Heat gently to boiling until fully dissolved.

3. Dispense into suitable containers.

4. Sterilize by autoclaving at 121℃ for 15 minutes.

5. Shake well after sterilization to prevent agar settling at the bottom.

Optional Selective Modification:

• For Mupirocin Lithium Salt and L-Cysteine Hydrochloride Modified MRS Medium, cool the sterilized medium to 55℃, then add 1 vial of Mupirocin Lithium Salt Solution and 1 vial of 5% L-Cysteine Hydrochloride Solution (MRS-CyHCl) per 100 mL of medium. Mix thoroughly and use immediately.

⚠️ Note: The medium may clump due to Tween 80, but this does not affect performance.