Bioprocessing of riboflavin MCQs With Answer

Introduction:

This quiz collection on Bioprocessing of Riboflavin is designed specifically for M.Pharm students preparing for advanced topics in Bioprocess Engineering and Technology. It covers core principles of microbial production, metabolic precursors, fermentation strategies, process control, downstream purification, analytical methods, and scale-up considerations. Questions emphasize mechanistic understanding, industrially relevant organisms and strains, metabolic engineering targets, and practical issues such as oxygen transfer, photostability, and formulation. Use these MCQs to test and deepen your conceptual knowledge as well as to identify areas for further study before exams or research work in vitamin bioprocess development.

Q1. Which microorganism is most commonly used industrially for fungal riboflavin production?

• Ashbya gossypii
• Escherichia coli
• Saccharomyces cerevisiae
• Bacillus subtilis

Correct Answer: Ashbya gossypii

Q2. What are the primary metabolic precursors for riboflavin biosynthesis in microorganisms?

• Acetyl-CoA and oxaloacetate
• GTP and ribulose-5-phosphate
• Pyruvate and phosphoenolpyruvate
• Glutamate and α-ketoglutarate

Correct Answer: GTP and ribulose-5-phosphate

Q3. Which enzyme catalyzes the initial committed step of the riboflavin biosynthetic pathway from GTP?

• Riboflavin synthase
• GTP cyclohydrolase II
• Ribulose kinase
• Ribose-phosphate isomerase

Correct Answer: GTP cyclohydrolase II

Q4. Which fermentation mode is most commonly employed to maximize riboflavin titres at industrial scale?

• Semi-continuous surface fermentation
• Batch submerged fermentation
• Fed-batch submerged fermentation
• Continuous perfusion fermentation

Correct Answer: Fed-batch submerged fermentation

Q5. Typical optimal pH range for industrial riboflavin fermentation with fungal producers like Ashbya is:

• pH 3.0–4.0
• pH 6.0–6.5
• pH 8.0–9.0
• pH 10.0–11.0

Correct Answer: pH 6.0–6.5

Q6. What is the commonly maintained incubation temperature for riboflavin production by Ashbya gossypii?

• 15 °C
• 28–30 °C
• 37–40 °C
• 50–55 °C

Correct Answer: 28–30 °C

Q7. Which downstream operation is widely used for final purification and isolation of crystalline riboflavin?

• Membrane ultrafiltration
• Ion-pair reverse-phase extraction
• Crystallization
• Lyophilization without prior concentration

Correct Answer: Crystallization

Q8. Which statement correctly describes riboflavin’s sensitivity relevant to processing and storage?

• Riboflavin is highly heat-stable and insensitive to light
• Riboflavin is photosensitive and degrades upon exposure to light
• Riboflavin is stable in strong alkali but unstable in acid
• Riboflavin is inert to oxidation and reduction during processing

Correct Answer: Riboflavin is photosensitive and degrades upon exposure to light

Q9. Which biologically active cofactors are direct derivatives of riboflavin?

• Biotin and lipoic acid
• NAD+ and NADP+
• Flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD)
• Pyridoxal phosphate and thiamine pyrophosphate

Correct Answer: Flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD)

Q10. What is a major physiological/process limitation during high‑yield riboflavin fermentations?

• Excessive nitrogen uptake causing foaming
• Severe oxygen demand and mass transfer limitations
• Complete inhibition by low carbon sources
• Excessive formation of volatile fatty acids

Correct Answer: Severe oxygen demand and mass transfer limitations

Q11. Which analytical technique is most commonly used for quantitative determination of riboflavin in process streams?

• Gas chromatography with FID
• HPLC with UV–visible detection
• Fluorescence microscopy
• Turbidimetric assay

Correct Answer: HPLC with UV–visible detection

Q12. Which carbon source is frequently used in conventional submerged riboflavin fermentations for microbial growth?

• Cellulose powder
• Glucose
• Lignin-derived oligomers
• Elemental sulfur

Correct Answer: Glucose

Q13. A common metabolic engineering strategy to increase riboflavin titers is:

• Knockout of the entire pentose phosphate pathway
• Overexpression of the rib operon and GTP cyclohydrolase genes
• Elimination of glycolysis to divert carbon to lipid synthesis
• Insertion of the lac operon for lactose utilization

Correct Answer: Overexpression of the rib operon and GTP cyclohydrolase genes

Q14. In bioprocess reporting, the typical unit used for volumetric riboflavin yield is:

• mg per cell
• g per liter (g/L)
• mmol per hour
• CFU per mL

Correct Answer: g per liter (g/L)

Q15. The parameter kLa in bioreactor design refers to:

• The rate constant for lactose assimilation
• The oxygen transfer coefficient (volumetric mass transfer coefficient)
• The thermal conductivity of the medium
• The adsorption constant for ion-exchange resins

Correct Answer: The oxygen transfer coefficient (volumetric mass transfer coefficient)

Q16. Which fermentation approach can offer higher volumetric productivity and reduced foaming for some fungal vitamin processes?

• Semi-anaerobic deep-tank fermentation
• Solid-state fermentation
• Chemostat continuous submerged culture at low dilution
• Packed-bed gas-phase fermentation

Correct Answer: Solid-state fermentation

Q17. Riboflavin exhibits a strong absorption or maximum in the visible/UV region at approximately which wavelength?

• 280 nm
• 365 nm
• 445 nm
• 600 nm

Correct Answer: 445 nm

Q18. Which reducing cofactor is most commonly required in biosynthetic reactions feeding into riboflavin assembly?

• FADH2 exclusively
• NADH only
• NADPH
• ATP (as reducing agent)

Correct Answer: NADPH

Q19. To increase flux toward riboflavin in a production strain, which metabolic modification is most appropriate?

• Downregulate pentose phosphate pathway to conserve ATP
• Enhance pentose phosphate pathway to increase ribulose-5-phosphate supply
• Delete GTP biosynthesis to reduce feedback inhibition
• Introduce anaerobic respiration genes to reduce oxygen demand

Correct Answer: Enhance pentose phosphate pathway to increase ribulose-5-phosphate supply

Q20. For storage and formulation of purified riboflavin to maintain stability, which condition is recommended?

• Store at elevated temperature and exposed to daylight
• Store in dark, cool conditions protected from light
• Keep in alkaline solution at high pH and room light
• Expose to UV to ensure sterility

Correct Answer: Store in dark, cool conditions protected from light

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