Fermentation: aerobic/anaerobic processes for antibiotics, vitamins and statins MCQs With Answer

Introduction

This quiz collection focuses on fermentation processes—both aerobic and anaerobic—relevant to industrial production of antibiotics, vitamins and statins, tailored for M.Pharm students studying MPC 204T Pharmaceutical Process Chemistry. Questions probe microbial physiology, bioreactor modes (batch, fed‑batch, continuous, solid‑state), critical process parameters (aeration, agitation, dissolved oxygen, pH, precursors), biosynthetic pathways (polyketide, nonribosomal peptide), and downstream implications. Designed to reinforce conceptual understanding and practical decision‑making in strain selection, medium design and process control, the set emphasizes differences in requirements for common producers such as Penicillium, Streptomyces, Aspergillus, Ashbya and Corynebacterium. Use these MCQs to test and deepen your applied knowledge for exam and industrial contexts.

Q1. Which fermentation condition is most critical for maximal penicillin (produced by Penicillium chrysogenum) titre in an industrial submerged process?

• Strict anaerobiosis with low agitation
• High dissolved oxygen and controlled glucose feed (avoid catabolite repression)
• High glucose concentration with static culture
• Low pH (<2) and high salt concentration

Correct Answer: High dissolved oxygen and controlled glucose feed (avoid catabolite repression)

Q2. Lovastatin, a statin produced by Aspergillus terreus, is derived biosynthetically mainly via which pathway?

• Shikimate pathway
• Nonribosomal peptide synthetase (NRPS) pathway
• Polyketide synthase (PKS) pathway
• Mevalonate-independent (DXP) pathway

Correct Answer: Polyketide synthase (PKS) pathway

Q3. Which microorganism is industrially used for microbial production of riboflavin (vitamin B2) in aerobic fermentation?

• Ashbya gossypii
• Clostridium acetobutylicum
• Propionibacterium freudenreichii
• Escherichia coli K12 under strict anaerobic conditions

Correct Answer: Ashbya gossypii

Q4. For production of antibiotics by filamentous actinomycetes (e.g., Streptomyces), which operational mode is often used to avoid morphological problems and to maintain productivity?

• Surface culture without agitation
• Fed‑batch submerged fermentation with controlled nutrient feed
• Continuous chemostat at extremely high dilution rates
• Semi‑aerobic static fermentation

Correct Answer: Fed‑batch submerged fermentation with controlled nutrient feed

Q5. Which parameter is the best online control variable to prevent oxygen limitation during aerobic antibiotic fermentations?

• Off‑gas CO2 composition only
• Dissolved oxygen concentration (DO) probe signal
• Final product assay every 24 hours
• Optical density measured offline twice daily

Correct Answer: Dissolved oxygen concentration (DO) probe signal

Q6. Production of vitamin B12 (cyanocobalamin) industrially often requires which of the following microbial features?

• Strictly aerobic Gram‑negative chemosynthetic bacteria only
• Microbes capable of complex cobalt incorporation and late cobalt insertion into corrin ring
• Organisms that produce polyketide backbone enzymes exclusively
• Strict anaerobic fungi that perform solid‑state fermentation

Correct Answer: Microbes capable of complex cobalt incorporation and late cobalt insertion into corrin ring

Q7. Which statement correctly contrasts aerobic and anaerobic antibiotic fermentations?

• Aerobic fermentations never require agitation; anaerobic always require high aeration
• Aerobic fermentations depend on oxygen transfer and agitation; anaerobic fermentations depend on maintaining exclusion of oxygen and redox balance
• Aerobic fermentations are always continuous; anaerobic are always batch
• Anaerobic fermentations produce statins while aerobic produce only vitamins

Correct Answer: Aerobic fermentations depend on oxygen transfer and agitation; anaerobic fermentations depend on maintaining exclusion of oxygen and redox balance

Q8. Which downstream challenge is particularly associated with statin production from filamentous fungi like Aspergillus terreus?

• High volatility of statin molecules requiring gas trapping
• Mycelial biomass entanglement and difficulty in solid‑liquid separation
• Statins being insoluble in organic solvents and only water soluble
• Complete thermal instability at room temperature making purification impossible

Correct Answer: Mycelial biomass entanglement and difficulty in solid‑liquid separation

Q9. Which feeding strategy is commonly used to avoid catabolite repression and acetate accumulation in high‑density antibiotic fermentations?

• Bolus addition of large glucose amounts at inoculation
• Constant high glucose concentration (>100 g/L)
• Controlled fed‑batch glucose feeding based on DO or pH spike
• Complete omission of carbon source after 6 hours

Correct Answer: Controlled fed‑batch glucose feeding based on DO or pH spike

Q10. Streptomycin production by Streptomyces griseus primarily requires which of the following culture conditions?

• Strictly anaerobic environment with no aeration
• High aeration, appropriate nitrogen limitation and complex precursors
• Primary reliance on high salt concentration (>10% NaCl)
• Continuous light exposure and phototrophic growth

Correct Answer: High aeration, appropriate nitrogen limitation and complex precursors

Q11. In industrial vitamin C bioprocesses using Ketogulonicigenium vulgare, what is the typical process arrangement?

• Pure culture anaerobic fermentation producing ascorbic acid directly
• Co‑culture two‑step fermentation where one organism converts sorbitol to 2‑keto‑L‑gulonic acid then chemically converted to vitamin C
• Single step submerged fermentation producing cyanocobalamin
• Solid‑state fermentation on cereal solids producing riboflavin

Correct Answer: Co‑culture two‑step fermentation where one organism converts sorbitol to 2‑keto‑L‑gulonic acid then chemically converted to vitamin C

Q12. Which antibiotic class is typically synthesized by nonribosomal peptide synthetases (NRPS) in microorganisms?

• Beta‑lactams like penicillins only
• Aminoglycosides exclusively
• Glycopeptides (e.g., vancomycin) and many peptide antibiotics
• Sterol‑like statins

Correct Answer: Glycopeptides (e.g., vancomycin) and many peptide antibiotics

Q13. Which bioreactor configuration is often preferred for maintaining high cell densities for recombinant antibiotic precursor production in bacteria like E. coli?

• Unagitated open pond reactor
• High‑oxygen transfer stirred tank reactor with fed‑batch operation
• Shallow tray solid‑state reactor without aeration
• Static surface fermentation flasks

Correct Answer: High‑oxygen transfer stirred tank reactor with fed‑batch operation

Q14. For anaerobic solvent-producing fermentations (relevant to process understanding), which organism and product pair is correct?

• Aspergillus terreus — butanol
• Clostridium acetobutylicum — acetone and butanol
• Streptomyces coelicolor — ethanol
• Ashbya gossypii — acetone

Correct Answer: Clostridium acetobutylicum — acetone and butanol

Q15. Which control strategy helps reduce foam formation in aerobic fermentation of antibiotics?

• Disabling antifoam addition permanently
• Using mechanical foam breakers and controlled antifoam dosing
• Maximizing bubble size by reducing surface tension to zero
• Operating at extremely low agitation to avoid gas transfer

Correct Answer: Using mechanical foam breakers and controlled antifoam dosing

Q16. Corynebacterium glutamicum is industrially important for which vitamin or metabolite production process?

• Lovastatin production via PKS
• Bio‑production of amino acids and as an engineered host for B‑vitamin precursors (e.g., riboflavin pathways)
• Production of glycopeptide antibiotics
• Strict anaerobic vitamin B12 production

Correct Answer: Bio‑production of amino acids and as an engineered host for B‑vitamin precursors (e.g., riboflavin pathways)

Q17. Which metabolic engineering strategy is commonly applied to increase statin precursor supply in fungal producers?

• Knocking out acetyl‑CoA supply pathways
• Overexpressing genes for precursor (acetyl‑CoA/malonyl‑CoA) supply and tailoring PKS regulatory genes
• Eliminating oxygen uptake systems to force anaerobic metabolism
• Reducing NADPH availability by inactivating pentose phosphate pathway

Correct Answer: Overexpressing genes for precursor (acetyl‑CoA/malonyl‑CoA) supply and tailoring PKS regulatory genes

Q18. Which factor primarily differentiates solid‑state fermentation (SSF) from submerged fermentation for certain antibiotic or enzyme productions?

• SSF uses free‑flowing liquid medium; submerged uses solid particles
• SSF mimics natural growth on solid substrates with low free water, often better for fungi; submerged uses high water content and is better for bacterial aerobic processes
• SSF always yields lower titers and is never used industrially
• Submerged fermentation cannot be aerated while SSF can

Correct Answer: SSF mimics natural growth on solid substrates with low free water, often better for fungi; submerged uses high water content and is better for bacterial aerobic processes

Q19. During scale‑up of an aerobic antibiotic fermentation, which dimensionless number is most useful to correlate oxygen transfer between scales?

• Reynolds number only
• kLa (volumetric oxygen transfer coefficient)
• Peclet number for heat transfer exclusively
• Biot number for mass transfer in solids

Correct Answer: kLa (volumetric oxygen transfer coefficient)

Q20. Which statement best describes use of precursor feeding to enhance secondary metabolite (e.g., antibiotic) yield?

• Feeding pathway precursors or elicitors at the appropriate growth phase can channel flux into secondary metabolism and increase yield
• Adding high concentrations of precursor at inoculation always maximizes yield regardless of growth phase
• Precursors are never used industrially due to regulatory prohibitions
• Feeding precursors converts a secondary metabolite into a primary metabolite

Correct Answer: Feeding pathway precursors or elicitors at the appropriate growth phase can channel flux into secondary metabolism and increase yield

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