Overflow metabolism and yield in Escherichia coli: Under which operating scenario would the biomass yield (g cells per g glucose) be the lowest for E. coli?

Introduction / Context:
Biomass yield in E. coli depends strongly on glucose availability and the onset of overflow metabolism (acetate formation). High glucose pulses drive rapid glycolytic flux beyond respiratory capacity, lowering ATP per substrate and reducing biomass yield.

Given Data / Assumptions:

• Aerobic conditions for all cases.
• Yield is defined on glucose (g cells per g glucose consumed).
• Overflow metabolism (acetate) is triggered at high glucose uptake rates.

Concept / Approach:
When glucose is initially high in a batch, E. coli often secretes acetate (overflow), which reduces carbon efficiency and yield. In contrast, low-glucose strategies (fed-batch or well-controlled continuous) limit substrate uptake to respiratory capacity, minimizing by-products and improving yield.

Step-by-Step Solution:
High initial glucose → high uptake → overflow → acetate formation.Carbon lost as acetate lowers biomass yield on substrate.Maintaining low glucose (fed-batch, continuous) controls uptake and improves yield.Therefore, the lowest yield occurs in the high-glucose batch case.

Verification / Alternative check:
Typical yield trends: batch (high glucose) < batch (low glucose) < continuous/fed-batch (controlled low glucose), consistent with measured acetate profiles and oxygen uptake limits.

Why Other Options Are Wrong:
Low-glucose batch: lower risk of overflow, higher yield.

Fed-batch with low glucose: designed to maximize yield by avoiding overflow.

Continuous at low glucose: also maintains high yield by matching uptake to respiration.

Common Pitfalls:

• Confusing growth rate with yield; high initial growth can coincide with low yield.
• Ignoring oxygen transfer limits that exacerbate overflow metabolism.

Final Answer:
An aerated batch culture with an initially high glucose concentration