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)
