Stephenson Medium B, Modified

Stephenson Medium B, Modified is a specialized medium for the cultivation of nitrifying bacteria. It provides essential inorganic salts and buffering agents to support the growth of Nitrosomonas and related autotrophic nitrifiers. The presence of sodium nitrite as the energy source and carbonate salts as buffering and carbon sources ensures stable growth conditions.

This modified formulation contains calcium carbonate, which appears as a white insoluble precipitate, serving as an additional buffering system to maintain pH stability during bacterial growth.

Applications:

• Cultivation of nitrifying bacteria (Nitrosomonas, Nitrobacter, etc.)

• Microbial ecology and environmental microbiology research

• Studies of nitrogen cycle and nitrification processes

• Bioreactor and wastewater treatment research

Specifications:

• Form: Powder, 250 g/bottle

• Storage: Room temperature

• Shelf Life: 3 years

Formula (per liter):

• Sodium Nitrite – 1.0 g

• Dipotassium Phosphate – 0.75 g

• Monosodium Phosphate – 0.25 g

• Manganese Sulfate·4H₂O – 0.01 g

• Magnesium Sulfate·7H₂O – 0.03 g

• Sodium Carbonate – 1.0 g

• Calcium Carbonate – 1.0 g

Preparation Instructions:

1. Suspend 4.0 g of the medium in 1 liter of distilled or deionized water.

2. Warm slightly to dissolve.

3. Adjust pH with HCl so that after sterilization the pH will be 7.0–7.4 (25℃).

4. Dispense into suitable containers.

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

6. Allow to cool before use.

Note: The presence of calcium carbonate results in visible white insoluble precipitates in the medium.