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M17 Agar
Used for cultivation and enumeration of lactic streptococci in milk and dairy products, also used for the differentiation of bacteriophages infecting lactic streptococci.
Catalog Number: AS-1280
M17 Agar is a culture medium that is designed for the selective culture and enumeration of lactic streptococci. It was created by Terzaghi and Sandine and offers these fastidious bacteria the ideal growing condition. To provide vital nutrients, the medium contains a well-balanced blend of peptones, yeast extract, and lactose. The di-sodium-β-glycerophosphate serves as a buffer to preserve pH stability, which is essential for the growth and recovery of lactic streptococci. Ascorbic acid and magnesium sulfate are two other ingredients that enhance bacterial growth and metabolic activity.
The dairy industry uses M17 Agar to isolate and enumeration lactic streptococci, especially Streptococcus thermophilus. It is an essential instrument for quality control and the generation of starting cultures due to its selective nature and ability for strong growth.
Storage
Keep the container at 15-30 °C and prepared medium at 2-8 °C.
| Composition | (gr/L) |
| Peptone from Casein | 2.5 |
| Peptone from Soymeal | 5 |
| Peptone from Meat | 2.5 |
| Yeast Extract | 2.5 |
| Meat Extract | 5 |
| Lactose | 5 |
| Ascorbic Acid | 0.5 |
| Sodium β-glycerophosphate | 19 |
| Magnesium Sulfate | 0.25 |
| Agar | 12.75 |
| Final pH at 25°C | 7.2 ± 0.2 |
| Dehydrated Appearance | Beige to medium tan, free flowing, homogeneous. |
| Prepared Appearance | Light to medium amber, very slightly to slightly opalescent, no significant precipitate. |
| Reaction of 5.5% Solution at 25°C | pH 7.2 ± 0.2 |
| incubate at 30 ± 2°C for Lactococcus lactis subsp. Cremoris and the remaining organisms at 35 ± 2°C for 40 – 48 hours. | |
| Organism (ATCC) | Recovery |
| Lactobacillus delbrueckii subsp. Bulgaricus (11842) | None to poor |
| Lactococcus lactis subsp. Cremoris (19257) | Good |
| Lactococcus lactis subsp. Cremoris (9625) | Good |
| Streptococcus thermophiles (19258) | Good |
