Q.1 Which unit operation is primarily used to remove whole cells from a fermentation broth?
Ultrafiltration
Centrifugation
Diafiltration
Chromatography
Explanation - Centrifugation exploits density differences to separate intact cells from the liquid phase efficiently.
Correct answer is: Centrifugation
Q.2 In downstream processing, the purpose of a depth filter is to:
Separate proteins based on charge
Remove fine particulates and cell debris
Concentrate the product
Increase product purity by size exclusion
Explanation - Depth filters have a three‑dimensional matrix that captures particles larger than its pore size while allowing the liquid to pass.
Correct answer is: Remove fine particulates and cell debris
Q.3 Which chromatography technique separates molecules based on their hydrophobic interactions?
Ion‑exchange chromatography
Affinity chromatography
Hydrophobic interaction chromatography
Size‑exclusion chromatography
Explanation - HIC uses a high‑salt buffer to promote binding of hydrophobic regions; decreasing salt elutes the product.
Correct answer is: Hydrophobic interaction chromatography
Q.4 What is the main advantage of using aqueous two‑phase extraction (ATPE) in protein recovery?
It requires high organic solvent volumes
It provides gentle conditions preserving protein activity
It is only suitable for small molecules
It always yields >99% purity
Explanation - ATPE uses water‑based phases, minimizing denaturation and maintaining biological activity.
Correct answer is: It provides gentle conditions preserving protein activity
Q.5 In a fed‑batch fermentation, which downstream step is most affected by increasing the broth viscosity?
Ultrafiltration
Centrifugation
Precipitation
Lyophilization
Explanation - Higher viscosity hampers solid‑liquid separation efficiency in centrifuges.
Correct answer is: Centrifugation
Q.6 Which of the following is a common precipitant used for protein recovery from clarified broth?
Ammonium sulfate
Ethanol
Acetone
Sodium chloride
Explanation - Ammonium sulfate precipitation exploits the 'salting out' effect to precipitate proteins selectively.
Correct answer is: Ammonium sulfate
Q.7 The term 'tangential flow filtration' (TFF) refers to:
Perpendicular flow through a membrane
Flow parallel to the membrane surface
Flow through a chromatography column
Flow in a batch mixer
Explanation - In TFF, the feed flows tangentially, reducing fouling and allowing continuous operation.
Correct answer is: Flow parallel to the membrane surface
Q.8 What is the main purpose of a virus inactivation step in biopharmaceutical downstream processing?
To increase product yield
To reduce host‑cell protein content
To ensure product safety by eliminating viral contaminants
To adjust pH of the solution
Explanation - Regulatory guidelines require validated virus clearance to protect patients.
Correct answer is: To ensure product safety by eliminating viral contaminants
Q.9 Which drying method is most suitable for thermolabile biologics?
Spray drying
Freeze‑drying (lyophilization)
Drum drying
Oven drying
Explanation - Lyophilization removes water under low temperature and pressure, preserving activity of heat‑sensitive molecules.
Correct answer is: Freeze‑drying (lyophilization)
Q.10 In size‑exclusion chromatography, larger molecules elute:
Before smaller molecules
After smaller molecules
At the same time as smaller molecules
Do not elute at all
Explanation - Larger molecules cannot enter the pores of the stationary phase, so they travel faster and elute first.
Correct answer is: Before smaller molecules
Q.11 What is the primary function of a polishing step in downstream processing?
To concentrate the product
To remove the bulk of impurities
To achieve final high purity and remove trace contaminants
To sterilize the product
Explanation - Polishing uses high‑resolution techniques (e.g., affinity or ion‑exchange chromatography) to meet final purity specifications.
Correct answer is: To achieve final high purity and remove trace contaminants
Q.12 Which of the following is a major challenge when scaling up chromatography from lab to production scale?
Increasing buffer consumption
Decreasing column pressure
Improving membrane pore size
Reducing the need for temperature control
Explanation - Scale‑up often requires proportionally larger volumes of expensive buffers, impacting cost and waste management.
Correct answer is: Increasing buffer consumption
Q.13 In the context of downstream processing, the term 'breakthrough' refers to:
The point at which a solute starts to appear in the filtrate during chromatography
The moment when a centrifuge reaches its maximum speed
The moment a product becomes unstable
The initiation of a fermentation batch
Explanation - Breakthrough curves help determine binding capacity and optimal loading of columns.
Correct answer is: The point at which a solute starts to appear in the filtrate during chromatography
Q.14 Which membrane material is commonly used for high‑temperature ultrafiltration in downstream processing?
Polypropylene
Polysulfone
Cellulose acetate
Nylon
Explanation - Polysulfone membranes have high thermal stability, chemical resistance, and mechanical strength.
Correct answer is: Polysulfone
Q.15 What is the role of a 'buffer exchange' step after affinity chromatography?
To increase product concentration
To remove the ligand from the product
To replace the elution buffer with a formulation‑compatible buffer
To sterilize the product
Explanation - Buffer exchange (often via diafiltration) prepares the product for downstream steps or final formulation.
Correct answer is: To replace the elution buffer with a formulation‑compatible buffer
Q.16 Which of the following is NOT a typical impurity in a recombinant protein downstream process?
Host‑cell DNA
Endotoxin
Product‑related aggregates
Sodium chloride
Explanation - NaCl is often a component of buffers and not considered an impurity; the others are critical quality attributes.
Correct answer is: Sodium chloride
Q.17 In a high‑pressure liquid chromatography (HPLC) system, the term 'gradient' refers to:
A change in temperature during the run
A gradual change in mobile phase composition
A variation in column length
An increase in flow rate over time
Explanation - Gradients improve separation by altering solvent strength, allowing elution of compounds with different affinities.
Correct answer is: A gradual change in mobile phase composition
Q.18 Which analytical technique is most commonly used to assess protein purity after chromatography?
Mass spectrometry
SDS‑PAGE
NMR spectroscopy
X‑ray crystallography
Explanation - SDS‑PAGE separates proteins based on molecular weight, providing a visual estimate of purity.
Correct answer is: SDS‑PAGE
Q.19 The process of removing residual solvent from a dried product is called:
Lyophilization
Desolvation
Dialysis
Adsorption
Explanation - Desolvation eliminates trapped solvents, often required after spray drying or freeze‑drying.
Correct answer is: Desolvation
Q.20 Which parameter is most critical for preventing shear‑induced damage during cell disruption by high‑pressure homogenization?
Feed temperature
Number of passes
Applied pressure
Valve geometry
Explanation - Higher pressures increase shear forces; controlling pressure minimizes protein denaturation.
Correct answer is: Applied pressure
Q.21 In downstream processing, the term 'yield' refers to:
The purity of the final product
The percentage of target molecule recovered relative to the starting amount
The speed of the chromatography run
The cost of consumables
Explanation - Yield quantifies the efficiency of the overall recovery process.
Correct answer is: The percentage of target molecule recovered relative to the starting amount
Q.22 Which of the following is a primary advantage of using affinity chromatography for monoclonal antibodies?
Very low buffer consumption
High selectivity based on antigen‑antibody interaction
Ability to separate based on size
Low operating pressure
Explanation - Protein A/G columns exploit specific binding, delivering high purity in a single step.
Correct answer is: High selectivity based on antigen‑antibody interaction
Q.23 During ultrafiltration, the term 'cut‑off' refers to:
The maximum operating pressure
The pore size that determines the molecular weight limit of retained species
The temperature limit of the membrane
The flow rate limit
Explanation - Cut‑off is expressed in kDa and dictates which molecules are concentrated vs. passed through.
Correct answer is: The pore size that determines the molecular weight limit of retained species
Q.24 Which downstream step is most effective at reducing endotoxin levels?
Anion‑exchange chromatography
Affinity chromatography
Nanofiltration
Size‑exclusion chromatography
Explanation - Endotoxin is negatively charged; anion exchangers can bind and remove it efficiently.
Correct answer is: Anion‑exchange chromatography
Q.25 When using a 0.22 µm filter for sterilization, which statement is true?
It removes all viruses
It removes bacterial spores
It removes bacteria but not viruses
It removes both bacteria and viruses
Explanation - Typical bacterial dimensions exceed 0.22 µm; most viruses are smaller and can pass through.
Correct answer is: It removes bacteria but not viruses
Q.26 In a bioprocess, the term 'critical quality attribute' (CQA) refers to:
A parameter that does not affect product safety
A property of the product that must be controlled to ensure safety and efficacy
The cost of raw materials
The speed of the downstream steps
Explanation - CQAs include purity, potency, identity, and are monitored throughout development.
Correct answer is: A property of the product that must be controlled to ensure safety and efficacy
Q.27 Which technique is commonly used to concentrate a protein solution after chromatography?
Diafiltration
Reverse osmosis
Ion‑exchange chromatography
Electrophoresis
Explanation - Diafiltration (a form of ultrafiltration) removes solvent while retaining the protein, increasing concentration.
Correct answer is: Diafiltration
Q.28 A major advantage of using continuous chromatography over batch chromatography is:
Higher resin cost
Reduced buffer usage and increased productivity
Simpler equipment design
Lower product purity
Explanation - Continuous operation allows overlapping steps, saving time and reagents.
Correct answer is: Reduced buffer usage and increased productivity
Q.29 Which factor most influences the binding capacity of an ion‑exchange resin?
Resin particle size
pH of the loading buffer
Flow rate during loading
Temperature of the column
Explanation - pH determines the ionization state of the protein and thus its interaction with the charged groups on the resin.
Correct answer is: pH of the loading buffer
Q.30 The process of 'clarification' in downstream processing mainly aims to:
Increase product activity
Remove insoluble cell debris and large particles
Change the pH of the broth
Sterilize the product
Explanation - Clarification (e.g., centrifugation or depth filtration) creates a clear supernatant suitable for finer purification steps.
Correct answer is: Remove insoluble cell debris and large particles
Q.31 Which of the following drying methods typically yields the smallest particle size for a protein powder?
Spray drying
Freeze‑drying
Vacuum drying
Air‑oven drying
Explanation - Spray drying atomizes the liquid into fine droplets, forming small particles upon rapid solvent removal.
Correct answer is: Spray drying
Q.32 In downstream processing, a 'virus filtration' step uses membranes with a nominal pore size of:
0.1 µm
0.45 µm
0.02 µm
1 µm
Explanation - Virus filters have pore sizes around 20 nm to retain most viral particles while allowing proteins to pass.
Correct answer is: 0.02 µm
Q.33 What is the main purpose of adding a protease inhibitor during cell lysis?
To increase the rate of cell disruption
To prevent degradation of the target protein
To enhance protein solubility
To lower the temperature of the lysate
Explanation - Proteases released from cells can cleave the product; inhibitors protect it during extraction.
Correct answer is: To prevent degradation of the target protein
Q.34 The term 'titer' in the context of bioprocessing most closely refers to:
The concentration of product per volume
The viscosity of the broth
The pH of the buffer
The temperature of the reactor
Explanation - Titer is expressed as mg/L, IU/mL, etc., indicating how much product is present.
Correct answer is: The concentration of product per volume
Q.35 During a chromatography run, the 'void volume' (V₀) is defined as:
The volume at which the first non‑bound component elutes
The total volume of the column
The volume of the mobile phase that does not interact with the stationary phase
The volume required to flush the column
Explanation - V₀ corresponds to the inter‑particle volume; markers that do not bind elute at this volume.
Correct answer is: The volume of the mobile phase that does not interact with the stationary phase
Q.36 Which of the following is a typical characteristic of a high‑density centrifuge used for cell harvesting?
Low g‑force (≤1,000 g)
Closed‑system design to maintain sterility
Operates only at room temperature
Requires no cooling
Explanation - High‑density (e.g., disc‑stack) centrifuges are often sealed to avoid contamination during large‑scale processing.
Correct answer is: Closed‑system design to maintain sterility
Q.37 In downstream processing, the term 'process analytical technology' (PAT) refers to:
Software for data storage
Real‑time monitoring and control tools for critical process parameters
A type of chromatography resin
A brand of filtration membranes
Explanation - PAT enables consistent product quality by providing immediate feedback and adjustments.
Correct answer is: Real‑time monitoring and control tools for critical process parameters
Q.38 Which of the following is the most common method to determine residual host‑cell DNA in a biologic product?
ELISA
qPCR (quantitative PCR)
Mass spectrometry
SDS‑PAGE
Explanation - qPCR offers high sensitivity and specificity for detecting trace amounts of DNA.
Correct answer is: qPCR (quantitative PCR)
Q.39 A 'load‑wash‑elute' sequence is typical of which chromatography mode?
Affinity chromatography
Ion‑exchange chromatography
Hydrophobic interaction chromatography
All of the above
Explanation - All three modes commonly employ loading of sample, washing away impurities, then eluting bound product.
Correct answer is: All of the above
Q.40 Which factor most directly influences the pressure drop across a filtration membrane?
Membrane pore size distribution
Temperature of the feed
pH of the solution
Viscosity of the feed
Explanation - Higher viscosity leads to greater resistance and higher pressure drop for a given flow rate.
Correct answer is: Viscosity of the feed
Q.41 What is the purpose of a 'salt gradient' in ion‑exchange chromatography?
To change the pH of the mobile phase
To gradually increase ionic strength and elute bound proteins based on charge strength
To increase column temperature
To reduce column back‑pressure
Explanation - Increasing salt concentration competes with protein‑resin interactions, causing elution.
Correct answer is: To gradually increase ionic strength and elute bound proteins based on charge strength
Q.42 During the lyophilization cycle, the primary drying step removes:
Bound water from the product matrix
Ice crystals by sublimation
Residual solvents
All moisture at once
Explanation - Primary drying is the sublimation of ice under reduced pressure; secondary drying removes unfrozen water.
Correct answer is: Ice crystals by sublimation
Q.43 Which of the following is a common method to inactivate viruses in a protein solution?
High‑pH treatment
Low‑temperature storage
UV irradiation
Addition of EDTA
Explanation - Alkaline conditions (e.g., pH 10–12) can irreversibly damage many viruses while preserving many proteins.
Correct answer is: High‑pH treatment
Q.44 The term 'Molecular weight cut‑off' (MWCO) of a membrane is expressed in:
Daltons (Da)
Nanometers (nm)
Micrometers (µm)
Milliliters (mL)
Explanation - MWCO indicates the approximate molecular weight above which solutes are retained.
Correct answer is: Daltons (Da)
Q.45 In downstream processing, the term 'scale‑down model' refers to:
A miniature version of the full‑scale process used for experimentation
A process that operates at lower temperature
A method to reduce product size
A software simulation of the plant
Explanation - Scale‑down models replicate key parameters at bench scale to study performance before scale‑up.
Correct answer is: A miniature version of the full‑scale process used for experimentation
Q.46 Which type of chromatography is most suitable for removing aggregates from a monoclonal antibody preparation?
Ion‑exchange chromatography
Hydrophobic interaction chromatography
Size‑exclusion chromatography
Affinity chromatography
Explanation - SEC separates based on size, allowing separation of monomers from larger aggregates.
Correct answer is: Size‑exclusion chromatography
Q.47 Which of the following is a major disadvantage of using precipitation for protein recovery?
High solvent consumption
Low product purity
Long processing time
All of the above
Explanation - Precipitation often requires large amounts of salts/solvents, yields moderate purity, and may need multiple steps.
Correct answer is: All of the above
Q.48 When performing a buffer exchange by diafiltration, the number of diavolumes needed to achieve >95% exchange is roughly:
1‑2 diavolumes
3‑4 diavolumes
5‑6 diavolumes
7‑8 diavolumes
Explanation - Each diavolume replaces about 63% of the original buffer; 3‑4 diavolumes reach >95% exchange.
Correct answer is: 3‑4 diavolumes
Q.49 In a continuous centrifuge, the term 'residence time' refers to:
The time required for the centrifuge to reach operating speed
The time the feed spends inside the centrifuge bowl
The time needed for cleaning the centrifuge
The downtime between batches
Explanation - Residence time determines the extent of particle separation; longer residence yields better clarification.
Correct answer is: The time the feed spends inside the centrifuge bowl
Q.50 Which analytical method is best suited for detecting trace amounts of endotoxin in a biologic product?
Limulus Amebocyte Lysate (LAL) assay
ELISA
Western blot
HPLC
Explanation - LAL exploits the clotting reaction of horseshoe crab blood to quantify endotoxin with high sensitivity.
Correct answer is: Limulus Amebocyte Lysate (LAL) assay
Q.51 The term 'solvent‑detergent treatment' in downstream processing is used to:
Remove host‑cell DNA
Inactivate enveloped viruses
Stabilize proteins
Reduce viscosity
Explanation - Organic solvents combined with detergents disrupt viral envelopes, providing a viral inactivation step.
Correct answer is: Inactivate enveloped viruses
Q.52 Which of the following is NOT a typical parameter monitored by PAT during chromatography?
pH of the mobile phase
UV absorbance at 280 nm
Column temperature
Ambient room lighting
Explanation - PAT focuses on critical process variables; ambient lighting does not affect chromatography performance.
Correct answer is: Ambient room lighting
Q.53 In downstream processing, the term 'clarified harvest' usually refers to:
The broth after removal of cells and debris
The final drug product
The culture medium before inoculation
The product after lyophilization
Explanation - Clarified harvest is the supernatant obtained post‑centrifugation or filtration, ready for further purification.
Correct answer is: The broth after removal of cells and debris
Q.54 A key advantage of using membrane chromatography over packed‑bed chromatography is:
Higher resolution
Lower pressure drop and faster processing
Greater resin capacity
Ability to operate at extreme pH
Explanation - Membranes have convective flow, allowing rapid processing and reduced fouling compared to packed columns.
Correct answer is: Lower pressure drop and faster processing
Q.55 During a protein purification campaign, the term 'process loss' refers to:
Loss of product due to incomplete recovery at each step
Loss of buffer during cleaning
Loss of time due to equipment downtime
Loss of personnel during training
Explanation - Cumulative losses across steps affect overall yield and cost of goods.
Correct answer is: Loss of product due to incomplete recovery at each step
Q.56 Which of the following is the most appropriate method to sterilize a heat‑sensitive protein solution?
Autoclaving at 121 °C
0.22 µm filtration
Pasteurization at 70 °C
Gamma irradiation
Explanation - Filtration removes microbes without exposing the protein to high temperatures.
Correct answer is: 0.22 µm filtration
Q.57 In downstream processing, the term 'load factor' refers to:
The ratio of feed volume to column volume
The amount of target protein loaded relative to the column’s binding capacity
The speed of the pump
The temperature of the mobile phase
Explanation - A load factor >1 risks breakthrough and loss of product.
Correct answer is: The amount of target protein loaded relative to the column’s binding capacity
Q.58 Which of the following is a common buffer component used to stabilize proteins during chromatography?
Sodium dodecyl sulfate (SDS)
Polyethylene glycol (PEG)
Tris‑HCl
Acetone
Explanation - Tris provides pH buffering and is compatible with many proteins and chromatography resins.
Correct answer is: Tris‑HCl
Q.59 A high product recovery but lower purity after the primary capture step can be improved by:
Increasing the flow rate
Adding a polishing chromatography step
Reducing the buffer volume
Lowering the temperature
Explanation - Polishing removes remaining impurities, enhancing overall purity while preserving recovered product.
Correct answer is: Adding a polishing chromatography step
Q.60 Which of the following is the most likely cause of fouling in a depth filter?
High pH of the feed
Presence of fine particulate matter and cell debris
Low temperature operation
Excessive buffer salts
Explanation - Fine particles clog the porous matrix, reducing flow and increasing pressure.
Correct answer is: Presence of fine particulate matter and cell debris
Q.61 During a scale‑up from 10 L to 1000 L, which parameter typically needs to be re‑optimized first?
Column length
Resin type
Flow rate per unit cross‑sectional area (linear velocity)
pH of the buffer
Explanation - Maintaining similar linear velocity ensures comparable mass transfer and residence time at larger scale.
Correct answer is: Flow rate per unit cross‑sectional area (linear velocity)
Q.62 Which downstream unit operation is most effective for removing host‑cell proteins (HCPs) with a net negative charge at pH 7?
Cation‑exchange chromatography
Anion‑exchange chromatography
Hydrophobic interaction chromatography
Affinity chromatography
Explanation - Negatively charged HCPs bind to positively charged groups on an anion exchanger at neutral pH.
Correct answer is: Anion‑exchange chromatography
Q.63 In a bioprocess, the term 'batch time' refers to:
The time taken for downstream purification only
The total time from inoculation to final product release
The time required for equipment cleaning
The time a sample spends in the analytical lab
Explanation - Batch time encompasses upstream growth, harvest, purification, and formulation.
Correct answer is: The total time from inoculation to final product release
Q.64 Which of the following is an advantage of using a mixed‑mode chromatography resin?
It combines ionic and hydrophobic interactions for enhanced selectivity
It only works at low pH
It requires no buffer preparation
It eliminates the need for downstream filtration
Explanation - Mixed‑mode resins provide multiple interaction mechanisms, improving impurity removal.
Correct answer is: It combines ionic and hydrophobic interactions for enhanced selectivity
Q.65 The primary purpose of a 'filtration skid' in a GMP facility is to:
Increase the speed of centrifugation
Provide a modular, validated filtration system for sterile filtration
Reduce the need for trained personnel
Perform analytical testing
Explanation - Filtration skids are pre‑qualified, ready‑to‑use units for aseptic processing.
Correct answer is: Provide a modular, validated filtration system for sterile filtration
Q.66 Which of the following is NOT a typical step in the purification of a recombinant enzyme?
Affinity capture
Ion‑exchange polishing
Fermentation broth sterilization
Size‑exclusion polishing
Explanation - Sterilization is performed before fermentation, not during downstream purification of the product.
Correct answer is: Fermentation broth sterilization
Q.67 What is the typical pore size range for a 0.22 µm membrane filter used for sterile filtration?
0.1–0.2 µm
0.22–0.45 µm
0.5–1.0 µm
1.0–2.0 µm
Explanation - Filters rated 0.22 µm have actual pore sizes slightly smaller to guarantee bacterial retention.
Correct answer is: 0.1–0.2 µm
Q.68 In downstream processing, the term 'lean‑mass balance' is used to describe:
The mass of product only, ignoring water
The balance of salts in the buffer
The total mass of all solids in the process
The mass of waste streams
Explanation - Lean‑mass focuses on the mass of active ingredient, simplifying yield calculations.
Correct answer is: The mass of product only, ignoring water
Q.69 Which of the following best describes the principle of 'counter‑current chromatography'?
Mobile phase flows in the same direction as the sample
Mobile phase flows opposite to the direction of solute migration, improving separation efficiency
Resin particles move opposite to the flow direction
Column is rotated during operation
Explanation - Counter‑current flow enhances mass transfer, achieving sharper peaks and higher resolution.
Correct answer is: Mobile phase flows opposite to the direction of solute migration, improving separation efficiency
Q.70 The use of 'high‑shear homogenization' for cell disruption is most appropriate for:
Gram‑negative bacteria with thin cell walls
Yeast cells with robust cell walls
Mammalian cells
Plant cells
Explanation - High‑shear forces efficiently break softer bacterial membranes, while tougher cells need alternative methods.
Correct answer is: Gram‑negative bacteria with thin cell walls
Q.71 Which regulatory document outlines the requirements for viral clearance validation in biopharmaceutical manufacturing?
ICH Q5A
ICH Q5B
FDA 21 CFR Part 11
EU GMP Annex 1
Explanation - ICH Q5B provides guidance on viral safety testing and validation for biologics.
Correct answer is: ICH Q5B
Q.72 In downstream processing, the term 'critical process parameter' (CPP) is defined as:
A parameter that has no impact on product quality
A parameter that directly influences a critical quality attribute (CQA)
A parameter used only for documentation
A parameter that only affects equipment wear
Explanation - CPPs must be monitored and controlled to ensure consistent product quality.
Correct answer is: A parameter that directly influences a critical quality attribute (CQA)
Q.73 During the final formulation of a protein drug, the addition of a cryoprotectant primarily serves to:
Increase the protein's activity
Prevent aggregation during freeze‑thaw cycles
Adjust the solution pH
Improve color stability
Explanation - Cryoprotectants (e.g., sucrose, trehalose) protect protein structure during freezing and thawing.
Correct answer is: Prevent aggregation during freeze‑thaw cycles
Q.74 Which downstream operation typically follows virus filtration in the purification train?
Affinity chromatography
Ultrafiltration/diafiltration
Ion‑exchange polishing
Precipitation
Explanation - After virus removal, ion‑exchange steps are used to polish the product and meet purity specifications.
Correct answer is: Ion‑exchange polishing
Q.75 What is the primary benefit of using a 'single‑use' (disposable) bioprocessing system?
Higher pressure tolerance
Elimination of cleaning and validation for the disposable components
Higher product yield
Reduced risk of product degradation
Explanation - Single‑use systems reduce cross‑contamination risk and lower turnaround time between batches.
Correct answer is: Elimination of cleaning and validation for the disposable components
Q.76 The term 'tangential flow' in microfiltration is used to describe:
Flow perpendicular to the membrane surface
Flow parallel to the membrane surface
Flow that reverses direction periodically
Flow that passes through a gel matrix
Explanation - Tangential flow reduces fouling by sweeping away retained particles along the membrane surface.
Correct answer is: Flow parallel to the membrane surface
Q.77 Which of the following is a common indicator used to assess the integrity of a sterile filter after use?
Pressure drop measurement
pH shift of the filtrate
Color change of the membrane
Conductivity of the filtrate
Explanation - A sudden increase in pressure indicates clogging or breach of filter integrity.
Correct answer is: Pressure drop measurement
Q.78 In the context of downstream processing, 'mass balance' calculations are essential for:
Estimating equipment cost
Ensuring material accounting and identifying losses at each step
Determining the optimal pH
Choosing the right buffer
Explanation - Mass balance tracks the amount of material entering and exiting each unit operation.
Correct answer is: Ensuring material accounting and identifying losses at each step
Q.79 Which of the following is NOT a typical characteristic of a high‑resolution chromatography step?
Narrow peak widths
High selectivity
Very high flow rates
Low impurity carry‑over
Explanation - High‑resolution steps often operate at lower flow rates to maximize interaction time and selectivity.
Correct answer is: Very high flow rates
Q.80 When scaling up a membrane filtration step, which parameter must be kept constant to maintain performance?
Membrane area to feed volume ratio
Membrane thickness
Filter housing material
Batch size
Explanation - Keeping the area-to-volume ratio constant maintains similar flux and residence time during scale‑up.
Correct answer is: Membrane area to feed volume ratio
Q.81 The main purpose of a 'pre‑filter' in a sterile filtration train is to:
Increase the final product concentration
Remove large particles that could block the final sterile filter
Adjust the pH of the solution
Add a preservative
Explanation - Pre‑filters protect the downstream 0.22 µm filter, extending its life and ensuring sterility.
Correct answer is: Remove large particles that could block the final sterile filter
Q.82 In a downstream process, the term 'throughput' generally refers to:
The amount of product that can be processed per unit time
The purity level of the final product
The number of columns used
The temperature of the process
Explanation - Throughput is a key metric for evaluating equipment capacity and process efficiency.
Correct answer is: The amount of product that can be processed per unit time
Q.83 Which type of chromatography would be most effective for separating a protein based on its isoelectric point (pI)?
Hydrophobic interaction chromatography
Ion‑exchange chromatography
Affinity chromatography
Size‑exclusion chromatography
Explanation - At a pH near the protein's pI, its net charge changes, allowing separation on an ion‑exchange resin.
Correct answer is: Ion‑exchange chromatography
Q.84 When performing an endotoxin removal step using anion‑exchange chromatography, the flow direction is typically:
From the resin surface to the column base (upflow)
From the column base to the resin surface (downflow)
Circular flow inside the column
No flow; the column is static
Explanation - Upflow reduces the risk of channeling and improves contact between endotoxin and resin.
Correct answer is: From the resin surface to the column base (upflow)
Q.85 The main reason for performing a 'pH adjustment' after ultrafiltration is to:
Increase membrane fouling
Prepare the solution for the next chromatographic step that requires a specific pH
Reduce product concentration
Remove dissolved gases
Explanation - Correct pH ensures optimal binding conditions for downstream chromatography.
Correct answer is: Prepare the solution for the next chromatographic step that requires a specific pH
Q.86 Which of the following statements about 'single‑use bioreactors' is true?
They cannot be used for mammalian cell cultures
They eliminate the need for cleaning validation of the vessel
They always have a larger volume than stainless steel reactors
They increase the risk of cross‑contamination
Explanation - Disposable bioreactor bags are pre‑sterilized and discarded after use, removing cleaning steps.
Correct answer is: They eliminate the need for cleaning validation of the vessel
Q.87 In downstream processing, the term 'capture step' refers to:
The final formulation of the drug product
The first purification step that recovers the majority of target protein from the feed
The sterilization of the product
The analytical testing of the final batch
Explanation - Capture aims to obtain high recovery while removing bulk impurities.
Correct answer is: The first purification step that recovers the majority of target protein from the feed
Q.88 Which of the following is the most appropriate method to assess the particle size distribution of a protein aggregate after purification?
Dynamic light scattering (DLS)
High‑performance liquid chromatography (HPLC)
UV‑Vis spectroscopy
pH meter
Explanation - DLS measures hydrodynamic radius, providing size distribution of particles in solution.
Correct answer is: Dynamic light scattering (DLS)
Q.89 During a chromatography run, an unexpected early breakthrough of the target protein most likely indicates:
Overloading the column beyond its binding capacity
Insufficient column pressure
Too low flow rate
Excessive column temperature
Explanation - When the resin's capacity is exceeded, unbound protein appears in the flow-through earlier than expected.
Correct answer is: Overloading the column beyond its binding capacity
Q.90 The primary purpose of a 'clean‑in‑place' (CIP) system in downstream equipment is to:
Increase product yield
Remove residual product and contaminants without disassembly
Sterilize the product solution
Measure pH continuously
Explanation - CIP allows rapid cleaning of vessels, filters, and columns, maintaining hygiene and reducing downtime.
Correct answer is: Remove residual product and contaminants without disassembly
Q.91 In downstream processing, the term 'process robustness' describes:
The ability of a process to produce consistent product quality despite minor variations
The speed at which a process can be completed
The cost efficiency of a process
The number of steps involved in a process
Explanation - Robust processes tolerate fluctuations in parameters without compromising CQAs.
Correct answer is: The ability of a process to produce consistent product quality despite minor variations
Q.92 Which of the following is a common cause of product loss during diafiltration?
Membrane fouling leading to reduced flux
Excessive temperature causing protein denaturation
High pH causing resin degradation
Low pressure causing air bubbles
Explanation - Fouling reduces permeate flow, prolonging process time and potentially causing product retention losses.
Correct answer is: Membrane fouling leading to reduced flux
Q.93 When assessing the environmental impact of downstream processing, which metric is most commonly evaluated?
Carbon footprint (CO₂ equivalents)
Number of personnel required
Length of the purification train
Color of the final product
Explanation - Life‑cycle analysis often quantifies greenhouse gas emissions to gauge sustainability.
Correct answer is: Carbon footprint (CO₂ equivalents)
Q.94 Which downstream operation is typically the most cost‑intensive for a monoclonal antibody production process?
Primary capture via Protein A chromatography
Centrifugation
Ultrafiltration
pH adjustment
Explanation - Protein A resin is expensive, and the capture step consumes large quantities of resin and buffer.
Correct answer is: Primary capture via Protein A chromatography
Q.95 A 'mass transfer coefficient' (k₁) in chromatography is most directly related to:
The speed of the pump
The diffusion rate of solutes between mobile and stationary phases
The pH of the buffer
The column length
Explanation - k₁ quantifies how quickly solutes can move between phases, influencing resolution.
Correct answer is: The diffusion rate of solutes between mobile and stationary phases
Q.96 In a downstream process for a recombinant vaccine, the step most critical for ensuring sterility is:
Affinity chromatography
0.22 µm sterile filtration
Ion‑exchange polishing
Diafiltration
Explanation - Final sterile filtration removes any residual microorganisms before final fill.
Correct answer is: 0.22 µm sterile filtration
Q.97 The term 'process yield' is calculated as:
(Amount of product recovered ÷ Amount of starting material) × 100
(Amount of buffer used ÷ Amount of product) × 100
(Time of processing ÷ Amount of product) × 100
(Number of steps ÷ Amount of product) × 100
Explanation - Yield expresses the efficiency of material recovery throughout the process.
Correct answer is: (Amount of product recovered ÷ Amount of starting material) × 100
Q.98 Which of the following is the most suitable technique to remove residual host‑cell DNA to below 10 pg per dose?
Anion‑exchange chromatography
Affinity chromatography
Hydrophobic interaction chromatography
Nanofiltration
Explanation - DNA is highly negatively charged; anion exchange efficiently binds and removes it to low levels.
Correct answer is: Anion‑exchange chromatography
Q.99 In a downstream process, the purpose of a 'holding tank' is to:
Increase the temperature of the product
Provide a temporary buffer for product before the next unit operation
Remove all impurities from the product
Measure product potency
Explanation - Holding tanks allow decoupling of unit operations and provide time for buffer adjustments.
Correct answer is: Provide a temporary buffer for product before the next unit operation
Q.100 When using a high‑density disc‑stack centrifuge, the term 'G‑force' refers to:
Gravitational force generated by the centrifuge, expressed as multiples of Earth’s gravity
The magnetic field applied during separation
The temperature inside the centrifuge
The pressure drop across the disc stack
Explanation - G‑force determines the sedimentation rate of particles during centrifugation.
Correct answer is: Gravitational force generated by the centrifuge, expressed as multiples of Earth’s gravity
Q.101 Which of the following best describes the principle of 'affinity chromatography'?
Separation based on charge differences
Separation based on size exclusion
Specific binding between a ligand on the resin and the target molecule
Separation based on hydrophobicity
Explanation - Affinity chromatography exploits a unique interaction (e.g., antibody‑antigen) for highly selective capture.
Correct answer is: Specific binding between a ligand on the resin and the target molecule
Q.102 During spray drying of a protein solution, the most critical factor to prevent denaturation is:
Inlet temperature
Outlet temperature
Airflow rate
Particle size
Explanation - High inlet temperatures can cause rapid heating and protein denaturation; controlling it preserves activity.
Correct answer is: Inlet temperature
Q.103 Which analytical technique is commonly used to verify the molecular weight of a purified protein?
SDS‑PAGE
ELISA
Gas chromatography
FTIR spectroscopy
Explanation - SDS‑PAGE separates proteins by molecular weight, allowing size verification.
Correct answer is: SDS‑PAGE
Q.104 A 'process validation' in downstream processing primarily demonstrates:
That the process can consistently produce product meeting pre‑defined quality attributes
That the equipment is the cheapest available
That the process is the fastest possible
That the product has a pleasant odor
Explanation - Regulatory validation ensures reproducibility and compliance with quality standards.
Correct answer is: That the process can consistently produce product meeting pre‑defined quality attributes
Q.105 Which of the following is the most appropriate method to remove trace amounts of organic solvents after a precipitation step?
Diafiltration
Ion‑exchange chromatography
Heat treatment
pH adjustment
Explanation - Diafiltration exchanges the solvent with aqueous buffer, efficiently removing low‑level organics.
Correct answer is: Diafiltration
Q.106 When performing a 'high‑pH viral inactivation' step, the typical pH range used is:
3.0–4.0
5.0–6.0
7.0–8.0
10.0–12.0
Explanation - Alkaline conditions (pH 10–12) denature many viruses while maintaining protein stability for short periods.
Correct answer is: 10.0–12.0
Q.107 In downstream processing, the term 'clean‑room classification' (e.g., ISO 5) primarily refers to:
The temperature of the room
The number of personnel allowed inside
The allowable particulate and microbial contamination levels
The size of the room
Explanation - ISO classifications define permissible air cleanliness for aseptic processing.
Correct answer is: The allowable particulate and microbial contamination levels
Q.108 Which of the following best describes the function of a 'load‑step' in chromatography?
Elution of the target protein
Removal of loosely bound impurities
Application of the feed onto the column
Regeneration of the resin
Explanation - The load step introduces the sample to the resin for binding.
Correct answer is: Application of the feed onto the column
Q.109 For a protein with a high isoelectric point (pI > 9), which type of ion‑exchange chromatography would be most suitable for capture at pH 7?
Cation‑exchange chromatography
Anion‑exchange chromatography
Hydrophobic interaction chromatography
Size‑exclusion chromatography
Explanation - At pH 7, the protein carries a net positive charge and binds to a negatively charged cation‑exchange resin.
Correct answer is: Cation‑exchange chromatography
Q.110 The term 'buffer capacity' refers to:
The total volume of buffer required for a process
The ability of a buffer to resist changes in pH upon addition of acid or base
The concentration of salts in the buffer
The temperature stability of the buffer
Explanation - A high buffer capacity maintains pH stability during purification steps.
Correct answer is: The ability of a buffer to resist changes in pH upon addition of acid or base
Q.111 Which of the following is the most common reason for implementing a 'pH shift' after a capture chromatography step?
To increase product solubility
To facilitate binding of impurities in a subsequent polishing step
To sterilize the product
To reduce viscosity
Explanation - Adjusting pH can change charge properties, improving removal of specific contaminants in later steps.
Correct answer is: To facilitate binding of impurities in a subsequent polishing step
Q.112 In downstream processing, which technology provides the highest level of viral removal for non‑enveloped viruses?
Low‑pH viral inactivation
Nanofiltration (20 nm pore size)
Affinity chromatography
Precipitation
Explanation - Nanofiltration physically blocks particles larger than the pore size, effectively removing many viruses.
Correct answer is: Nanofiltration (20 nm pore size)
Q.113 During a batch chromatography run, the term 'gradient slope' refers to:
The temperature change per minute
The rate at which salt concentration is increased in the mobile phase
The speed of the pump
The size of the column
Explanation - Gradient slope determines how quickly the elution strength changes, affecting peak resolution.
Correct answer is: The rate at which salt concentration is increased in the mobile phase
Q.114 Which of the following is a typical indicator that a protein has formed aggregates during downstream processing?
Increase in UV absorbance at 280 nm
Shift in retention time on size‑exclusion chromatography
Decrease in conductivity
Change in pH
Explanation - Aggregates have larger apparent size and elute earlier on SEC columns.
Correct answer is: Shift in retention time on size‑exclusion chromatography
Q.115 The primary purpose of a 'buffer exchange' step after ultrafiltration is to:
Increase the product concentration
Remove salts and small molecules that may interfere with subsequent steps
Adjust the pH to acidic values
Add preservatives
Explanation - Diafiltration swaps the existing buffer for a new one suitable for downstream operations.
Correct answer is: Remove salts and small molecules that may interfere with subsequent steps
Q.116 Which of the following best describes a 'continuous chromatography' system?
A single column operated in batch mode
Multiple columns linked in series or parallel to enable uninterrupted product flow
A chromatography step performed only once per batch
A system that does not require buffers
Explanation - Continuous chromatography increases productivity and reduces buffer consumption.
Correct answer is: Multiple columns linked in series or parallel to enable uninterrupted product flow
Q.117 When designing a downstream process for a thermally sensitive enzyme, which drying method should be avoided?
Lyophilization (freeze‑drying)
Spray drying
Vacuum drying at low temperature
Desiccation under inert gas
Explanation - Spray drying involves high inlet temperatures that can denature heat‑sensitive enzymes.
Correct answer is: Spray drying
Q.118 Which unit operation is most suitable for separating a protein from a high‑salt fermentation broth without changing the salt concentration?
Size‑exclusion chromatography
Hydrophobic interaction chromatography
Diafiltration (ultrafiltration)
Ion‑exchange chromatography
Explanation - Diafiltration can concentrate the protein while maintaining salt levels, facilitating downstream steps.
Correct answer is: Diafiltration (ultrafiltration)
Q.119 In downstream processing, the term 'resin regeneration' typically involves:
Increasing the temperature of the column
Removing bound material and restoring the resin to its original functional state
Changing the column diameter
Adding more resin to the column
Explanation - Regeneration cleans and re‑equilibrates the resin for subsequent cycles.
Correct answer is: Removing bound material and restoring the resin to its original functional state
Q.120 Which of the following is a major advantage of using 'high‑throughput screening' (HTS) during method development for downstream processing?
It reduces the need for analytical testing
It allows rapid evaluation of many conditions to identify optimal parameters
It eliminates the need for scale‑up studies
It guarantees 100% purity in the final product
Explanation - HTS accelerates optimization by testing multiple variables simultaneously.
Correct answer is: It allows rapid evaluation of many conditions to identify optimal parameters
Q.121 When a protein product is formulated as a lyophilized powder, the primary benefit is:
Increased solubility in water
Enhanced long‑term stability at ambient temperatures
Higher viscosity
Reduced manufacturing cost
Explanation - Lyophilization removes water, reducing degradation pathways and extending shelf‑life.
Correct answer is: Enhanced long‑term stability at ambient temperatures
Q.122 During a chromatography run, an unexpected high back‑pressure is most likely caused by:
Column over‑temperature
Resin compaction or blockage due to fouling
Low flow rate
Excessive pH
Explanation - Fouling reduces pore space, increasing hydraulic resistance and pressure.
Correct answer is: Resin compaction or blockage due to fouling