Chlortetracycline fermentation — aeration strategy for high yields During production of chlortetracycline by actinomycetes, which aeration strategy is associated with achieving consistently high antibiotic yields?

Introduction / Context:
Actinomycete antibiotic fermentations are strictly aerobic. Oxygen transfer rate (OTR) and power input (kLa) must be optimized to support secondary metabolite biosynthesis without damaging delicate filamentous morphology.

Given Data / Assumptions:

• Target product: chlortetracycline from Streptomyces aureofaciens or related strains.
• Filamentous growth is sensitive to excessive shear and foam.
• Aeration/agitator settings influence pellet size, broth rheology, and productivity.

Concept / Approach:

High-yield operation balances oxygen delivery with morphological control. Too little aeration limits respiration and biosynthesis; too much aeration or agitation increases shear, fragmenting mycelia and impairing productivity. Therefore, controlled aeration—coupled with antifoam management and appropriate agitation—is the proven strategy for peak titers.

Step-by-Step Solution:

Verification / Alternative check:

Process development literature consistently shows yield improvements when OTR is held within an optimal corridor, confirming the need for controlled aeration rather than all-or-nothing approaches.

Why Other Options Are Wrong:

No aeration (option a) is incompatible with actinomycete growth. Uncontrolled high aeration (option b) risks shear damage and strip-out of volatiles. “Does not affect yield” (option c) is false; O2 strongly affects titers. Vacuum degassing (option e) is not an aeration strategy.

Common Pitfalls:

Confusing antifoam addition with aeration control; both must be coordinated to avoid oxygen limitation or excessive shear.

Final Answer:

Controlled aeration (optimized oxygen transfer without shear damage)