Industrial microbiology: medium composition for oxytetracycline (terramycin) fermentation Select the typical medium formulation components used for producing oxytetracycline at scale.

Introduction / Context:
Oxytetracycline (terramycin) production by Streptomyces species requires a balanced fermentation medium supplying carbon, nitrogen, minerals, and pH buffering. Recognizing standard components is central to bioprocess design questions.

Given Data / Assumptions:

• CSL (corn steep liquor) provides vitamins, amino acids, and growth factors.
• Starch is a primary carbon source for secondary metabolite production.
• (NH4)2SO4 provides inorganic nitrogen; NaCl provides osmotic balance; CaCO3 buffers pH and supplies Ca²⁺.

Concept / Approach:
Secondary metabolite production often favors complex nitrogen sources (CSL) plus slowly metabolized carbohydrates (starch). Buffering with CaCO3 maintains near-neutral pH, which is important for Streptomyces morphology and productivity. Sodium chloride improves osmotic conditions and sometimes influences morphology and yields.

Step-by-Step Solution:

Verification / Alternative check:
Classical Streptomyces process descriptions use CSL + starch with mineral salts and CaCO3; omission of starch or NaCl is atypical for the canonical teaching formulation.

Why Other Options Are Wrong:

• Options lacking starch provide no principal carbon source for robust production.
• Replacing NaCl with ammonium chloride alters mineral balance from the canonical list.
• Molasses-only media are used for other fermentations and are not standard for oxytetracycline.

Common Pitfalls:
Confusing seed medium vs. production medium; both may differ, but the teaching example includes starch and CaCO3 buffering.

Final Answer:
CSL, starch, (NH4)2SO4, sodium chloride, and CaCO3