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M17 Broth
Used for isolating lactic streptococci from yogurt, cheese starters and other dairy products.
Catalog Number: AS-1281
A nutrient-rich medium developed especially for the cultivation and counting of lactic streptococci is M17 broth. M17 broth provides better growth conditions than M16 medium, based on the initial research of Terzaghi and Sandine. Lactic streptococci are fastidious organisms that need a complicated nutritional environment for optimal growth. Di-sodium-β-glycerophosphate must be added to keep the buffering condition for pH, avoid bacterial damage, and ensure strong cell recovery. The critical nutrients for the growth and metabolism of lactic streptococci are provided by the medium’s composition, which includes peptones, yeast extract, beef extract, lactose, ascorbic acid, and magnesium sulfate. In the dairy sector, M17 broth is frequently used to cultivate starter cultures and isolate lactic streptococci from a variety of samples.
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 Sulphate | 0.25 |
| Final pH at 25°C | 7.2 ± 0.2 |
| Dehydrated Appearance | Beige to medium tan, free-flowing, homogeneous. |
| Prepared Appearance | Light medium to medium amber, clear to very slightly opalescent, no significant precipitate. |
| Reaction of 4.25% 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 |
