BACE Bioprocessing and Fermentation 2 — Questions and Answers
Question 1: What is the function of a sparger in a bioreactor?
- To introduce small bubbles of air or oxygen into the culture medium (Correct answer)
- To measure the pH of the fermentation broth
- To add nutrients to the bioreactor during fed-batch operation
- To remove foam from the surface of the culture
Correct answer: To introduce small bubbles of air or oxygen into the culture medium
A sparger is a porous device at the bottom of the bioreactor that disperses compressed air or oxygen as fine bubbles to oxygenate the culture.
Question 2: What is 'downstream processing' in the context of biopharmaceutical manufacturing?
- The series of steps used to isolate and purify the biological product from the fermentation broth (Correct answer)
- The inoculation of cells into production bioreactors
- The sterilization of equipment before a production run
- The storage and distribution of raw materials
Correct answer: The series of steps used to isolate and purify the biological product from the fermentation broth
Downstream processing includes all purification steps after fermentation — such as centrifugation, filtration, and chromatography — to obtain a pure final product.
Question 3: Which culture mode continuously adds fresh nutrients while removing spent media at the same rate to maintain a constant volume?
- Continuous (chemostat) culture (Correct answer)
- Batch culture
- Fed-batch culture
- Perfusion culture
Correct answer: Continuous (chemostat) culture
In a chemostat, fresh medium is added at a constant rate equal to the outflow rate, maintaining steady-state cell density and nutrient concentration.
Question 4: What does pH control in a bioreactor typically involve?
- Automated addition of acid or base in response to pH probe readings to maintain the setpoint (Correct answer)
- Manually adjusting pH once per hour
- Using unbuffered media to allow natural pH equilibration
- Filtering the broth to remove acidic byproducts
Correct answer: Automated addition of acid or base in response to pH probe readings to maintain the setpoint
Bioreactors use feedback control loops where pH probes trigger addition of acid (e.g., HCl) or base (e.g., NaOH) to maintain the optimal pH setpoint.
Question 5: What is 'scale-up' in bioprocessing?
- Increasing the production volume from small laboratory bioreactors to large industrial-scale fermenters (Correct answer)
- Increasing the concentration of nutrients in the growth medium
- Increasing the number of cell passages before production
- Increasing the speed of centrifugation to improve yield
Correct answer: Increasing the production volume from small laboratory bioreactors to large industrial-scale fermenters
Scale-up involves transitioning processes from bench-scale (liters) to pilot scale and then to manufacturing scale (thousands of liters) while maintaining product quality.
Question 6: What is the role of antifoam agents in fermentation?
- To prevent excessive foam formation that can block air filters and reduce oxygen transfer (Correct answer)
- To increase the viscosity of the culture broth
- To serve as a carbon source for microbial growth
- To lower the temperature inside the bioreactor
Correct answer: To prevent excessive foam formation that can block air filters and reduce oxygen transfer
Antifoam agents (e.g., silicone-based compounds) reduce surface tension to collapse foam bubbles that can clog exhaust filters and reduce oxygen transfer.
BACE Bioprocessing and Fermentation 2
What is the function of a sparger in a bioreactor?