Liofilchem® MRS Agar

The Liofilchem MRS Agar is a selective and nutrient-rich medium designed for the isolation, cultivation, and enumeration of mesophilic lactic acid bacteria, including Lactobacillus spp., Pediococcus spp., and Leuconostoc spp.. It is formulated according to ISO 15214 standards and is widely used in microbiological testing of food, animal feed, and water samples.

Key Features:

1. Optimized for Lactic Acid Bacteria:
   • Supports the growth of Lactobacillus spp., as well as Pediococcus and Leuconostoc species.
   • Inhibits the growth of unwanted organisms, including Escherichia coli and Bacillus cereus.
2. Nutrient-Rich Composition:
   • Amino Acids and Vitamins: Provided by enzymatic digest of casein, meat extract, and yeast extract.
   • Growth Stimulants: Magnesium sulfate and manganese sulfate provide essential ions.
   • Selective Agents: Sodium acetate and ammonium citrate inhibit molds and streptococci.
   • Buffered pH: Dipotassium phosphate maintains the medium’s pH.
3. Supplement Compatibility:
   • Tween 80 Supplement provides essential oleic esters and fatty acids for lactic acid bacterial growth.
   • Optional Sorbic Acid Supplement (for yeast contamination) enhances selectivity.
4. ISO-Compliant:
   • Fully compliant with ISO 15214:1998 and APHA guidelines for lactic acid bacteria enumeration.

Typical Composition (per liter):

Preparation Instructions:

1. Suspend 68.3 g of MRS Agar powder in 1 liter of distilled or deionized water.
2. Mix well and heat to boiling with frequent shaking until fully dissolved.
3. Add 1 mL of Tween 80 Supplement.
4. Sterilize in an autoclave at 121°C for 15 minutes.
5. (Optional) Add 1.4 g of Sorbic Acid dissolved in sodium hydroxide solution if yeast contamination is suspected.

Protocol:

1. Sample Dilution:
   • Perform serial dilutions of the test sample using a suitable diluent like Buffered Peptone Water.
   • Aim for a colony count between 15–300 CFU per plate.
2. Inoculation:
   • Use 1 mL of sample suspension and inoculate via pour plating or overlay technique if needed.
3. Incubation:
   • Incubate plates at 30°C for 72 hours under microaerobic conditions.
4. Results Interpretation:
   • Count colonies on plates with 15–300 colonies and report as CFU/mL or CFU/g of the sample.
   • Confirm colonies by Gram staining or catalase testing if necessary.

Product Specifications:

Applications:

1. Food Microbiology:
   • Enumeration of lactic acid bacteria in dairy products, fermented foods, and beverages.
2. Animal Feed Testing:
   • Quantification of lactic acid bacteria in probiotics and feed supplements.
3. Water Testing:
   • Detection of lactic acid bacteria in environmental and industrial water samples.
4. Research:
   • Cultivation of Lactobacillus spp. and other lactic acid bacteria for microbiological studies.

Advantages:

1. Selective Growth:
   • Supports lactic acid bacteria while inhibiting competing organisms.
2. ISO-Compliant:
   • Suitable for use in standard regulatory and quality control assays.
3. Flexible Use:
   • Compatible with supplements for enhanced selectivity and growth.
4. Easy Preparation:
   • Simple autoclave sterilization ensures consistent results.

Quality Control:

Storage and Handling:

• Store the dehydrated medium in a dry environment at 10–30°C.
• Prepared plates should be stored at 2–8°C away from light.
• Avoid using the product after its expiry date or if contamination/deterioration is evident.

The Liofilchem MRS Agar is a reliable, ISO-compliant medium designed for precise enumeration and isolation of lactic acid bacteria in food, water, and environmental testing. Its nutrient-rich and selective formulation ensures accurate and reproducible results, making it an essential tool for microbiologists and quality control professionals.