Penicillin fermentation — hallmark observations during the third (late) phase of Penicillium chrysogenum growth Which set of changes typically characterizes the third phase of a penicillin production run?

Introduction / Context:
Late-stage dynamics in penicillin fermentation influence timing of harvest and downstream processing. Recognizing biochemical and physiological markers ensures maximum recovery before quality declines due to autolysis.

Given Data / Assumptions:

• Organism: Penicillium chrysogenum in stirred-tank fermentation.
• Phase: third (late) phase where production is near peak or plateau.
• Observables: product titer trend, pH change, mycelial morphology.

Concept / Approach:

As fermentations age, active antibiotic accumulation may still occur or plateau, while cellular maintenance declines, leading to autolysis. Nitrogen turnover and deamination can release ammonia, slightly increasing pH. These factors together signal the approach of optimal harvest and the need to prevent product degradation.

Step-by-Step Solution:

Verification / Alternative check:

Classical penicillin fermentation curves (biomass, pH, antibiotic titer) show these late-phase signatures across many runs, guiding harvest time decisions.

Why Other Options Are Wrong:

Option e is inconsistent: rapid biomass increase is a first-phase trait, not third-phase, and antibiotic is certainly present by this stage.

Common Pitfalls:

Waiting too long after autolysis accelerates can reduce effective yield due to product instability or adsorption to debris; timely harvest matters.

Final Answer:

All of the above