Key Takeaway: Ammonium Sources Are Alternatives, Not Additives

• M9-type media use NH₄Cl, while M63-type media use (NH₄)₂SO₄ . These are designed as alternative nitrogen sources. It is not standard practice to include both NH₄Cl and (NH₄)₂SO₄ together in the main batch medium. If ammonium hydroxide is used for pH control in a fed-batch process, significant nitrogen is supplied through the base stream, reducing the need for high initial ammonium salt concentrations.

Practical Guidance for High-Cell-Density Fed-Batch Processes

• For high-cell-density fed-batch, the initial batch medium's nitrogen concentration does not need to be very high. The high densities are achieved through controlled feeding of carbon and nitrogen, not solely from the starting batch medium .
• Recommended starting ranges (for batch phase) are:
  • MgSO₄: ~1–2 mM
  • NH₄Cl: ~19–28 mM OR (NH₄)₂SO₄: ~15 mM
  • Vitamins: If using a complex source, use yeast extract at 5–12 g/L. For a defined medium, thiamine-HCl is common, but its optimal working concentration for high-density fermentation requires further DOE or consultation of specific recipes, as current evidence is insufficient to provide a reliable range .

References

High cell density media for Escherichia coli are generally ... (PMC)
Recipes and tools for culture of Escherichia coli (PMC)
High-Density Escherichia coli Fed-batch Fermentation ... (Eppendorf Application Note)
Formulation of a semi-defined medium for high cell density cultivation of E. coli in shake flasks (PeerJ Preprints)

Key Takeaway: Ammonium Sources Are Alternatives, Not Additives

• M9-type media use NH₄Cl, while M63-type media use (NH₄)₂SO₄ . These are designed as alternative nitrogen sources. It is not standard practice to include both NH₄Cl and (NH₄)₂SO₄ together in the main batch medium. If ammonium hydroxide is used for pH control in a fed-batch process, significant nitrogen is supplied through the base stream, reducing the need for high initial ammonium salt concentrations.

Practical Guidance for High-Cell-Density Fed-Batch Processes

• For high-cell-density fed-batch, the initial batch medium's nitrogen concentration does not need to be very high. The high densities are achieved through controlled feeding of carbon and nitrogen, not solely from the starting batch medium .
• Recommended starting ranges (for batch phase) are:
  • MgSO₄: ~1–2 mM
  • NH₄Cl: ~19–28 mM OR (NH₄)₂SO₄: ~15 mM
  • Vitamins: If using a complex source, use yeast extract at 5–12 g/L. For a defined medium, thiamine-HCl is common, but its optimal working concentration for high-density fermentation requires further DOE or consultation of specific recipes, as current evidence is insufficient to provide a reliable range .

References

High cell density media for Escherichia coli are generally ... (PMC)
Recipes and tools for culture of Escherichia coli (PMC)
High-Density Escherichia coli Fed-batch Fermentation ... (Eppendorf Application Note)
Formulation of a semi-defined medium for high cell density cultivation of E. coli in shake flasks (PeerJ Preprints)