System configuration in automated fermentation MCQs With Answer

Introduction: System configuration in automated fermentation is a critical topic for M.Pharm students focusing on bioprocess engineering. This blog presents a targeted set of MCQs designed to deepen understanding of control architectures, instrumentation, and automation strategies used in modern fermentation plants. Questions emphasize selection and placement of sensors and actuators, control loop design (including PID and cascade strategies), data acquisition, alarm philosophy, validation (IQ/OQ/PQ), and regulatory considerations. The aim is to bridge theoretical control principles with practical configuration decisions that impact product quality, process robustness, and compliance in pharmaceutical-scale fermentations.

Q1. What is the primary advantage of using a cascade control configuration in automated fermentation?

• It eliminates the need for setpoints entirely
• It allows a fast inner loop to correct disturbances before the slower outer loop responds
• It reduces the number of sensors required by the system
• It converts all control loops to feedforward control

Correct Answer: It allows a fast inner loop to correct disturbances before the slower outer loop responds

Q2. Which sensor placement is most appropriate for accurate dissolved oxygen (DO) control in a stirred-tank fermenter?

• On the exhaust gas line
• Directly in the broth near the gas-liquid interface
• At the bottom drain port
• Outside the tank in the sampling loop

Correct Answer: Directly in the broth near the gas-liquid interface

Q3. Which actuator is typically used for controlling aeration rate as a primary DO control action?

• Valve on the exhaust line
• Mass flow controller on the air/oxygen inlet
• Agitator motor inverter
• Heating mantle power controller

Correct Answer: Mass flow controller on the air/oxygen inlet

Q4. What is the main purpose of implementing soft and hard alarm levels in fermentation automation?

• To disable all control loops during startup
• To differentiate between advisory conditions and conditions requiring immediate operator action or shutdown
• To create redundancy in sensor measurement
• To calibrate the sensors automatically

Correct Answer: To differentiate between advisory conditions and conditions requiring immediate operator action or shutdown

Q5. Which control strategy is most appropriate for maintaining pH during a high-rate acid/base dosing response requirement?

• Open-loop timed dosing
• PID control with derivative term emphasized
• On-off control with long hysteresis
• Manual periodic titration

Correct Answer: PID control with derivative term emphasized

Q6. For feed addition in a fed-batch fermentation to maintain substrate concentration, which control approach is commonly used?

• Constant volumetric feed regardless of biomass
• Setpoint tracking using feedback from off-line substrate assays only
• Rate control using cascade loop from a substrate or DO-based inferred signal
• Open-loop exponential feed without sensors

Correct Answer: Rate control using cascade loop from a substrate or DO-based inferred signal

Q7. In automated fermentation, what is the benefit of distributed control (DCS/PLC) versus a centralized standalone controller for large plants?

• DCS/PLC always costs less than centralized systems
• Distributed control provides improved modularity, fault isolation, and scalability across multiple vessels and utilities
• Centralized controllers offer better redundancy than DCS
• Distributed control removes the need for any operator interface

Correct Answer: Distributed control provides improved modularity, fault isolation, and scalability across multiple vessels and utilities

Q8. Which validation stage verifies that installed automation hardware and software meet design specifications prior to process runs?

• Performance Qualification (PQ)
• Operational Qualification (OQ)
• Installation Qualification (IQ)
• Continued Process Verification (CPV)

Correct Answer: Installation Qualification (IQ)

Q9. What is the key reason to implement sensor redundancy for critical measurements (e.g., temperature, pH) in pharmaceutical fermentations?

• To increase process variability intentionally
• To allow selective bypass of calibration procedures
• To ensure reliability and failover capability so control remains valid if one sensor drifts or fails
• To reduce the need for proper calibration standards

Correct Answer: To ensure reliability and failover capability so control remains valid if one sensor drifts or fails

Q10. Which data handling requirement is essential for automated fermentation control systems to comply with 21 CFR Part 11?

• Encrypted network layers for all process variables
• Electronic audit trails, secure user access controls, and validated data integrity
• Real-time publication of data to public servers
• Removal of all raw data after batch review

Correct Answer: Electronic audit trails, secure user access controls, and validated data integrity

Q11. What is the advantage of using a mass flow controller (MFC) instead of a simple control valve for gas flow control in fermentation?

• MFCs are cheaper and require no calibration
• MFCs provide accurate, repeatable flow control irrespective of downstream pressure fluctuations
• Control valves are always more accurate than MFCs
• MFCs remove the need for oxygen sensors

Correct Answer: MFCs provide accurate, repeatable flow control irrespective of downstream pressure fluctuations

Q12. Which control algorithm is best suited when actuator saturation and constraints are significant in feed or aeration control?

• Simple proportional control without anti-windup
• PID with anti-windup or Model Predictive Control (MPC) for constraint handling
• Pure integral control only
• Open-loop scheduling

Correct Answer: PID with anti-windup or Model Predictive Control (MPC) for constraint handling

Q13. During automated fermentation, anti-foam addition is typically controlled based on which signal?

• Direct foam volume measurement using a foam sensor or conductivity probe at headspace
• Temperature rise in the vessel
• Agitator RPM only
• pH excursions above 9

Correct Answer: Direct foam volume measurement using a foam sensor or conductivity probe at headspace

Q14. What is the primary role of an HMI (Human-Machine Interface) in an automated fermentation system?

• To physically stir the fermenter
• To provide operators with visualization, setpoint changes, alarm acknowledgment and batch recipe management
• To replace PLC logic entirely
• To sterilize sensors automatically

Correct Answer: To provide operators with visualization, setpoint changes, alarm acknowledgment and batch recipe management

Q15. For automated in-situ sterilization (SIP) control of a fermenter, which element is critical to include in the configuration?

• Manual-only control of steam valves
• Interlocks, temperature profiling, time control, and verification sensors to ensure lethal exposure
• Disabling all alarms for the duration of SIP
• Use of open-loop manual dosing of sterilant into the broth

Correct Answer: Interlocks, temperature profiling, time control, and verification sensors to ensure lethal exposure

Q16. What is the best practice for calibration scheduling of critical online sensors used in closed-loop control?

• Calibrate once during commissioning and never thereafter
• Implement a risk-based periodic calibration schedule with trending and pre-run checks
• Only calibrate when the process fails
• Rely solely on vendor-specified intervals without in-house verification

Correct Answer: Implement a risk-based periodic calibration schedule with trending and pre-run checks

Q17. In a fermentation automated control hierarchy, what is the typical function of the supervisory layer (SCADA)?

• Directly switching solenoids at the field level
• Aggregating data, supervisory alarming, recipe management, long-term trending and operator dashboards
• Replacing process models in MPC
• Performing low-level PID loop calculations exclusively

Correct Answer: Aggregating data, supervisory alarming, recipe management, long-term trending and operator dashboards

Q18. When designing control for nutrient feed in perfusion fermentation, which requirement is most critical compared to batch systems?

• No need to monitor cell density
• Precise, continuous control of nutrient and bleed rates tied to cell density or metabolic markers to maintain steady-state
• Single endpoint feed schedule suffices
• Frequent manual interventions are preferred

Correct Answer: Precise, continuous control of nutrient and bleed rates tied to cell density or metabolic markers to maintain steady-state

Q19. What is a common validation activity to demonstrate that automated alarm thresholds are appropriate and effective?

• Ignoring alarms during PQ runs
• Alarm rationalization: testing alarm annunciation, response procedures, and verifying setpoints against risk analysis and historical data
• Setting all alarms to the widest possible range
• Relying solely on vendor default alarm values without documentation

Correct Answer: Alarm rationalization: testing alarm annunciation, response procedures, and verifying setpoints against risk analysis and historical data

Q20. Which documentation is essential to include in the system configuration deliverables for automated fermenter qualification?

• Only vendor brochures for each instrument
• Functional design specification (FDS), instrument index, control narratives, I/O list, and test protocols (IQ/OQ/PQ)
• Handwritten notes from commissioning only
• Marketing materials for SCADA software

Correct Answer: Functional design specification (FDS), instrument index, control narratives, I/O list, and test protocols (IQ/OQ/PQ)

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