Industrial production of vitamin B12 MCQs With Answer

Industrial production of vitamin B12 MCQs With Answer

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Industrial production of vitamin B12 (cobalamin) MCQs With Answer

The industrial production of vitamin B12 is a complex biotechnological process combining microbial biosynthesis, fermentation optimization and rigorous downstream processing. Key topics include choice of high‑yield strains (e.g., Pseudomonas denitrificans, Propionibacterium freudenreichii), cobalt and lower‑ligand (DMB) requirements, aerobic versus anaerobic biosynthetic pathways, metabolic engineering of cob genes, and scale‑up strategies such as fed‑batch culture and oxygen control. Downstream steps involve cell disruption, extraction, adsorption, ion‑exchange purification and conversion to stable cyanocobalamin, followed by HPLC and microbiological assays for quality control. This overview prepares B.Pharm students for practical and regulatory aspects of cobalamin manufacture. ‘Now let’s test your knowledge with 30 MCQs on this topic.’

Q1. Which microbial species is most commonly used for aerobic industrial production of vitamin B12?

  • Pseudomonas denitrificans
  • Propionibacterium freudenreichii
  • Escherichia coli
  • Bacillus subtilis

Correct Answer: Pseudomonas denitrificans

Q2. Which organism is favored for anaerobic production of cobalamin in dairy‑based processes?

  • Pseudomonas denitrificans
  • Propionibacterium freudenreichii
  • Streptomyces griseus
  • Clostridium acetobutylicum

Correct Answer: Propionibacterium freudenreichii

Q3. Which metal ion is an essential cofactor required for cobalamin biosynthesis?

  • Iron
  • Copper
  • Cobalt
  • Zinc

Correct Answer: Cobalt

Q4. Production strains are often supplemented with 5,6‑dimethylbenzimidazole (DMB) or its precursors because DMB:

  • Acts as a carbon source for growth
  • Serves as the lower axial ligand (base) in cobalamin
  • Enhances oxygen transfer in fermentation
  • Prevents contamination by phages

Correct Answer: Serves as the lower axial ligand (base) in cobalamin

Q5. The gene bluB is important in vitamin B12 biosynthesis because it:

  • Encodes a transport protein for cobalt
  • Is involved in DMB (lower ligand) biosynthesis
  • Catalyzes cyanidation to form cyanocobalamin
  • Controls aerobic respiration genes

Correct Answer: Is involved in DMB (lower ligand) biosynthesis

Q6. Which fermentation mode is commonly used to maximize vitamin B12 titers while controlling substrate inhibition?

  • Continuous culture without feed control
  • Fed‑batch fermentation
  • Plate cultivation on solid media
  • Shake‑flask static incubation

Correct Answer: Fed‑batch fermentation

Q7. Why is oxygen tension tightly controlled in B12 fermentation processes?

  • Oxygen prevents cobalt uptake by cells
  • Different biosynthetic pathways are favored under aerobic or anaerobic conditions
  • Oxygen increases foaming but does not affect yield
  • Oxygen degrades the vitamin in the medium

Correct Answer: Different biosynthetic pathways are favored under aerobic or anaerobic conditions

Q8. In industrial downstream processing of cobalamin, cyanidation is performed to:

  • Sterilize the extract
  • Convert cobalamin variants to stable cyanocobalamin
  • Remove proteins by precipitation
  • Adjust pH for crystallization

Correct Answer: Convert cobalamin variants to stable cyanocobalamin

Q9. Which analytical technique is most specific for quantifying cobalamin and its analogs in production samples?

  • UV‑Vis spectrophotometry at fixed wavelength
  • HPLC coupled with UV or MS detection
  • Simple titration with iodine
  • Gravimetric analysis

Correct Answer: HPLC coupled with UV or MS detection

Q10. Microbiological assay for vitamin B12 typically uses which test organism?

  • Lactobacillus delbrueckii
  • Escherichia coli
  • Salmonella typhimurium
  • Lactobacillus leichmannii (or similar cobalamin‑dependent bacteria)

Correct Answer: Lactobacillus leichmannii (or similar cobalamin‑dependent bacteria)

Q11. Which of the following is a common first step in downstream processing of B12 from biomass?

  • Direct crystallization from broth
  • Cell disruption or extraction to release intracellular cobalamins
  • Freeze‑drying the whole culture
  • Ion‑exchange chromatography as the initial step

Correct Answer: Cell disruption or extraction to release intracellular cobalamins

Q12. Activated charcoal is often used in purification because it:

  • Specifically binds cobalt
  • Adsorbs pigments and hydrophobic impurities
  • Inactivates microbial contaminants
  • Converts hydroxocobalamin to cyanocobalamin

Correct Answer: Adsorbs pigments and hydrophobic impurities

Q13. Which cobalamin form is most commonly marketed and used as the stable pharmaceutical raw material?

  • Adenosylcobalamin
  • Methylcobalamin
  • Cyanocobalamin
  • Hydroxocobalamin

Correct Answer: Cyanocobalamin

Q14. Genetic engineering to overexpress cob genes in production strains primarily aims to:

  • Reduce cobalt requirements
  • Increase flux through the cobalamin biosynthetic pathway to raise yield
  • Enhance spore formation for easier harvest
  • Eliminate the need for downstream purification

Correct Answer: Increase flux through the cobalamin biosynthetic pathway to raise yield

Q15. Which medium component is most likely to be limiting for B12 biosynthesis if not adequately supplied?

  • Sodium chloride
  • Cobalt salts
  • Magnesium sulfate
  • Calcium carbonate

Correct Answer: Cobalt salts

Q16. Light exposure during processing of cobalamin can cause:

  • Increased microbial growth
  • Photodegradation and loss of vitamin potency
  • Improved crystallization
  • Enhanced binding to ion‑exchange resins

Correct Answer: Photodegradation and loss of vitamin potency

Q17. Which downstream technique separates cobalamin based on charge differences?

  • Gel filtration chromatography
  • Ion‑exchange chromatography
  • Liquid–liquid extraction with hexane
  • Ultrafiltration using absolute molecular weight cutoff

Correct Answer: Ion‑exchange chromatography

Q18. During scale‑up of a B12 fermentation, maintaining similar oxygen transfer is important. Which parameter is most used to characterize oxygen transfer capability?

  • Redox potential (Eh)
  • kLa (volumetric oxygen transfer coefficient)
  • Osmotic pressure
  • pH drift

Correct Answer: kLa (volumetric oxygen transfer coefficient)

Q19. Which strategy can increase intracellular cobalamin accumulation in production strains?

  • Reducing cobalt concentration to trace levels
  • Enhancing precursor supply and cofactor availability via metabolic engineering
  • Omitting vitamins from the medium
  • Lowering incubation temperature to near 0°C

Correct Answer: Enhancing precursor supply and cofactor availability via metabolic engineering

Q20. Why is cyanocobalamin often preferred industrially over methylcobalamin or adenosylcobalamin?

  • Cyanocobalamin is the biologically active coenzyme in humans
  • It is chemically more stable and easier to purify and store
  • It does not require cobalt for synthesis
  • It avoids any regulatory approval

Correct Answer: It is chemically more stable and easier to purify and store

Q21. Which parameter is routinely monitored during fermentation to prevent acidification that can inhibit B12 synthesis?

  • Optical density only at the end
  • pH and buffer capacity
  • Light intensity in the fermenter
  • Solid content by visual inspection

Correct Answer: pH and buffer capacity

Q22. What is the purpose of converting various cobalamin forms to a single form during downstream processing?

  • To reduce cobalt content in the final product
  • To standardize stability and analytical measurement (e.g., convert to cyanocobalamin)
  • To make the product more colorful
  • To eliminate microbial contaminants

Correct Answer: To standardize stability and analytical measurement (e.g., convert to cyanocobalamin)

Q23. Which impurity class must be stringently controlled in pharmaceutical‑grade B12 preparations?

  • Residual sugars only
  • Residual solvents, heavy metals, and microbial contaminants
  • Natural pigments that enhance color
  • Excess cobalt that improves potency

Correct Answer: Residual solvents, heavy metals, and microbial contaminants

Q24. Which unit operation helps concentrate B12 from dilute fermentation extracts before chromatography?

  • High dilution with water
  • Evaporation or adsorption concentration (e.g., resin capture and elution)
  • Direct tablet compression
  • Gel casting

Correct Answer: Evaporation or adsorption concentration (e.g., resin capture and elution)

Q25. What is the role of buffer systems in B12 fermentation media?

  • Buffers supply cobalt directly
  • They maintain pH within a range that supports enzyme activity for biosynthesis
  • Buffers prevent foam formation entirely
  • They sterilize the medium during fermentation

Correct Answer: They maintain pH within a range that supports enzyme activity for biosynthesis

Q26. Which factor can lead to formation of inactive corrinoid analogs rather than active cobalamin during biosynthesis?

  • Optimal cobalt and DMB supply
  • Imbalanced precursor pools or incorporation of incorrect lower ligands
  • Careful control of redox conditions
  • Use of quality fermentation vessels

Correct Answer: Imbalanced precursor pools or incorporation of incorrect lower ligands

Q27. Regulatory quality control of pharmaceutical vitamin B12 requires which of the following tests?

  • Only appearance and color
  • Identity, potency, purity, residual solvents, heavy metals and microbial limits
  • No testing is required for vitamins
  • Only cobalt content measurement

Correct Answer: Identity, potency, purity, residual solvents, heavy metals and microbial limits

Q28. Which approach is commonly used to enhance oxygen transfer in large B12 fermenters for aerobic producers?

  • Decrease agitation and rely on diffusion
  • Increase agitation, sparging rate, and use oxygen‑enriched air if needed
  • Use still bottles and static cultures
  • Eliminate all antifoam agents

Correct Answer: Increase agitation, sparging rate, and use oxygen‑enriched air if needed

Q29. In downstream crystallization of cyanocobalamin, which parameter is crucial to obtain high‑purity crystals?

  • Rapid heating during crystallization
  • Controlled cooling, solvent composition and seeding
  • Leaving the solution unfiltered
  • Adding random salts without control

Correct Answer: Controlled cooling, solvent composition and seeding

Q30. Which modification to production strains can reduce formation of unwanted corrinoid analogs and improve product quality?

  • Knockout of specific competing pathway genes and overexpression of correct cob gene set
  • Removal of cobalt from the medium
  • Growing at extremely low temperatures
  • Allowing uncontrolled contamination to enhance diversity

Correct Answer: Knockout of specific competing pathway genes and overexpression of correct cob gene set

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