Penicillin production — key events during the second (production) phase of P. chrysogenum In penicillin fermentation, which combination best describes the second phase of growth and production?

Introduction / Context:
Penicillin biosynthesis is linked to a production (idiophase) that follows initial biomass build-up. While growth slows compared with the first phase, mycelial mass can still increase as secondary metabolism intensifies, requiring careful control of nutrients and pH.

Given Data / Assumptions:

• Phase: second (production) phase of Penicillium chrysogenum.
• Outcomes: strong antibiotic biosynthesis and ongoing morphological development.
• Control variables: pH, carbon source (often lactose), ammonium assimilation, and aeration.

Concept / Approach:

After the primary growth phase establishes viable biomass, penicillin synthesis becomes robust. Although specific growth rate drops, net mycelial mass may still increase due to continued hyphal development and pellet maturation. pH often trends upward from earlier values as nitrogen metabolism shifts; however, the item’s paired option emphasizes production plus biomass growth as the key identifiers.

Step-by-Step Solution:

Verification / Alternative check:

Fermentation performance curves show ongoing mycelial accumulation with peak penicillin generation in mid-runs, consistent with production-phase behavior.

Why Other Options Are Wrong:

Option c alone is incomplete; pH trends vary with medium and control strategy. Option e is incorrect; persistent pH decrease is not characteristic throughout this phase. Choosing only one factor misses the dual hallmark of production plus biomass presence.

Common Pitfalls:

Assuming growth ceases entirely during secondary metabolism. In reality, biomass dynamics continue and affect oxygen transfer and broth rheology.

Final Answer:

Both (a) and (b)