Microbial transformation of alkaloids MCQs With Answer

Microbial transformation of alkaloids MCQs With Answer

Introduction: Microbial transformation of alkaloids is a key area in bioprocess engineering that exploits microorganisms or their enzymes to modify complex nitrogen-containing natural products. For M.Pharm students this topic links biocatalysis, metabolic engineering, and pharmaceutical chemistry: it covers regio- and stereoselective modifications (hydroxylation, demethylation, N‑oxidation, glycosylation), cofactor requirements, whole-cell versus isolated-enzyme systems, and analytical methods for product characterization. Understanding microbial pathways and process parameters enables production of novel derivatives, human-like metabolites, and synthetic intermediates under mild, sustainable conditions. These MCQs focus on mechanistic, practical and scale-up aspects relevant to drug development and bioprocess design.

Q1. Which advantage most accurately explains why microbial transformation is preferred over many traditional chemical methods for modifying complex alkaloids?

• Ability to function at extremely high temperatures for faster reactions
• Greater regio- and stereoselectivity with milder reaction conditions
• Complete removal of all functional groups without selectivity
• Production of large amounts of inorganic by-products to drive equilibrium

Correct Answer: Greater regio- and stereoselectivity with milder reaction conditions

Q2. Which class of microbial enzymes is most commonly responsible for regiochemical hydroxylation of alkaloids?

• Transaminases
• Cytochrome P450 monooxygenases
• Hydrolases
• Lyases

Correct Answer: Cytochrome P450 monooxygenases

Q3. Which microbial species is widely used as a fungal model to simulate mammalian phase I metabolism of alkaloids?

• Candida albicans
• Cunninghamella elegans
• Aspergillus niger
• Saccharomyces cerevisiae

Correct Answer: Cunninghamella elegans

Q4. N‑dealkylation of tertiary alkaloids in microbial biotransformation typically proceeds via which mechanism?

• Hydrolytic cleavage by esterases forming carboxylic acids
• Cytochrome P450-catalyzed N‑dealkylation producing secondary amines
• Transamination producing ketones and ammonia
• Radical-mediated polymerization

Correct Answer: Cytochrome P450-catalyzed N‑dealkylation producing secondary amines

Q5. Which cofactor is most commonly required for microbial monooxygenase-mediated hydroxylations of alkaloids?

• ATP
• NADPH
• S-adenosylmethionine (SAM)
• Coenzyme A

Correct Answer: NADPH

Q6. What is the primary advantage of using whole microbial cells instead of isolated enzymes for alkaloid biotransformation?

• Whole cells eliminate the need for temperature control
• Whole cells provide in situ cofactor regeneration and multiple complementary enzymes
• Whole cells ensure reactions occur without any side-products
• Whole cells always increase the solubility of hydrophobic alkaloids

Correct Answer: Whole cells provide in situ cofactor regeneration and multiple complementary enzymes

Q7. Which bacterial genus is renowned for producing tailoring enzymes capable of complex alkaloid modifications in industrial biotransformations?

• Escherichia
• Streptomyces
• Lactobacillus
• Bacillus

Correct Answer: Streptomyces

Q8. Immobilization of microbial cells or enzymes during alkaloid biotransformation is primarily used to achieve what benefit?

• Increase genetic mutation rates to evolve new activities
• Enhance operational stability and enable reusability in repeated batches
• Convert enzymes into non-specific chemical catalysts
• Prevent any interaction between substrate and media

Correct Answer: Enhance operational stability and enable reusability in repeated batches

Q9. In scale-up of alkaloid biotransformation processes, which challenge is most often encountered?

• Excessively fast reaction rates that cannot be controlled
• Substrate or product toxicity limiting cell viability and productivity
• Unavailability of oxygen in small-scale reactors only
• Complete immunity of cells to process conditions

Correct Answer: Substrate or product toxicity limiting cell viability and productivity

Q10. Which analytical technique provides the highest sensitivity and molecular mass information for identifying microbial alkaloid metabolites?

• Thin-layer chromatography (TLC)
• Infrared spectroscopy (IR)
• Liquid chromatography–mass spectrometry (LC‑MS)
• Ultraviolet-visible spectroscopy (UV‑Vis)

Correct Answer: Liquid chromatography–mass spectrometry (LC‑MS)

Q11. Microbial glycosylation of alkaloids most commonly alters which pharmacokinetic property?

• Decreases molecular weight dramatically
• Increases water solubility and alters absorption/distribution
• Removes all nitrogen atoms from the molecule
• Converts alkaloids into inorganic salts

Correct Answer: Increases water solubility and alters absorption/distribution

Q12. Stereoselective reduction of a prochiral ketone in an alkaloid scaffold is usually catalyzed by which enzyme class?

• Lipases
• NADPH-dependent ketoreductases (KREDs)
• Ribozymes
• DNases

Correct Answer: NADPH-dependent ketoreductases (KREDs)

Q13. Why are resting (non-growing) microbial cells often chosen for focused biotransformation of alkaloids?

• They maximize biomass production during the reaction
• They reduce side metabolism associated with growth and channel resources to the target transformation
• They reproduce faster and thus increase enzyme concentration
• They eliminate the need for cofactors entirely

Correct Answer: They reduce side metabolism associated with growth and channel resources to the target transformation

Q14. Which type of microbial biotransformation introduces an oxygen atom into a carbon atom without cleaving the C–C skeleton?

• Deamination
• Hydroxylation
• Decarboxylation
• Fragmentation

Correct Answer: Hydroxylation

Q15. Which enzyme is commonly used in cofactor regeneration systems to supply NADPH for alkaloid biotransformations?

• Glucose dehydrogenase (GDH)
• Hexokinase
• DNA polymerase
• Invertase

Correct Answer: Glucose dehydrogenase (GDH)

Q16. What best describes a chemoenzymatic approach in alkaloid modification?

• Using only chemical methods followed by biological disposal
• Combining chemical synthesis steps with enzymatic transformations to access products not reachable by either alone
• Replacing all enzymes with metal catalysts
• Performing reactions under no control of pH or temperature

Correct Answer: Combining chemical synthesis steps with enzymatic transformations to access products not reachable by either alone

Q17. Producing human drug metabolites using microbial transformation is primarily valuable because:

• Microbes always give identical metabolites to animals except humans
• Microbial metabolites can act as authentic standards for human metabolite identification and toxicity studies
• Microbes eliminate the need for regulatory studies
• Microbial metabolites are always more active than parent drugs

Correct Answer: Microbial metabolites can act as authentic standards for human metabolite identification and toxicity studies

Q18. Which factor most directly influences the regioselectivity of a microbial enzyme acting on an alkaloid substrate?

• Ambient room color during fermentation
• Enzyme active site geometry and substrate orientation
• Total nitrogen content of the growth medium only
• Presence of inert gases like argon only

Correct Answer: Enzyme active site geometry and substrate orientation

Q19. Flavin-dependent monooxygenases involved in alkaloid oxidation typically require which pair of cofactors for activity?

• PLP and ATP
• FAD (or FMN) and NADPH
• CoA and NADH
• Biotin and GTP

Correct Answer: FAD (or FMN) and NADPH

Q20. For definitive structural and stereochemical elucidation of a novel microbial alkaloid metabolite, which analytical method is most informative?

• Ultraviolet-visible spectroscopy (UV‑Vis)
• Nuclear magnetic resonance spectroscopy (NMR)
• Simple paper chromatography
• Basic colorimetric assays

Correct Answer: Nuclear magnetic resonance spectroscopy (NMR)

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