Question

During high-density mass cultivation in bioreactors, the two major metabolic by-products that accumulate and limit cell growth and productivity are

• A. Lactate and ammonia
• B. Ethanol and carbon dioxide
• C. Acetate and formate
• D. Urea and uric acid

Hint:

Remember: \[ \boxed{\text{Glucose } \rightarrow \text{ Lactate}} \] \[ \boxed{\text{Glutamine } \rightarrow \text{ Ammonia}} \] These two metabolites are the major growth-limiting waste products in animal cell culture.

Answer 1

The Correct Option is A

Concept: In animal cell culture bioreactors, cells continuously consume nutrients such as glucose and glutamine. During metabolism, waste products accumulate in the culture medium. Excessive accumulation of these metabolites becomes toxic and reduces cell growth, viability and production of desired biomolecules.
• Glucose metabolism produces lactate.
• Glutamine metabolism produces ammonia.
• Both metabolites inhibit cell growth when present at high concentrations.
• Removal or control of these wastes is essential for successful large-scale cell culture.

Step 1: Formation of lactate.
When glucose is metabolized through glycolysis, especially under high-density culture conditions, cells produce lactate. High lactate concentration lowers the pH of the culture medium. \[ \boxed{\text{Glucose} \longrightarrow \text{Lactate}} \]

Step 2: Formation of ammonia.
Glutamine undergoes deamination during metabolism, producing ammonia. Ammonia interferes with cell metabolism, decreases cell viability and lowers protein production. \[ \boxed{\text{Glutamine} \longrightarrow \text{Ammonia}} \]

Step 3: Choose the correct option.
Since lactate and ammonia are the principal toxic metabolic by-products responsible for limiting productivity in bioreactors, \[ \boxed{Option (A) is the correct answer. \]