Microbial biotransformation and pharmaceutical applications MCQs With Answer

Introduction: Microbial biotransformation is the use of microorganisms or their enzymes to chemically modify drug molecules, producing metabolites, stereoselective products, or impurity profiles valuable in drug development. For B. Pharm students, understanding biocatalysis, microbial strains, enzyme systems, cofactors, and biotransformation pathways is essential for applications such as metabolite synthesis, chiral resolution, prodrug activation, and green chemistry approaches. Practical skills include selecting whole-cell versus isolated-enzyme systems, optimizing bioreactor conditions, and analyzing products by HPLC or GC–MS. This topic connects pharmacology, medicinal chemistry, and pharmaceutics, preparing students for research and industry roles. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What is microbial biotransformation?

• The chemical modification of drugs by mammalian liver cells
• The use of microorganisms or their enzymes to modify chemical compounds
• The physical separation of enantiomers using chromatography
• The synthesis of drugs by total chemical synthesis without enzymes

Correct Answer: The use of microorganisms or their enzymes to modify chemical compounds

Q2. Which is a common advantage of microbial biotransformation in pharmaceutical synthesis?

• High temperatures required
• Low stereoselectivity
• Ability to perform regio- and stereoselective reactions
• Inability to regenerate cofactors

Correct Answer: Ability to perform regio- and stereoselective reactions

Q3. Whole-cell biotransformation differs from isolated-enzyme systems primarily because:

• Whole cells cannot regenerate cofactors
• Isolated enzymes are always more stable than whole cells
• Whole cells provide endogenous cofactor regeneration and multiple enzymes
• Isolated enzymes perform multi-step metabolism better than cells

Correct Answer: Whole cells provide endogenous cofactor regeneration and multiple enzymes

Q4. Which microbial enzyme class commonly catalyzes oxidation reactions in biotransformation?

• Hydrolases
• Oxidoreductases (e.g., monooxygenases)
• Lyases
• Transferases

Correct Answer: Oxidoreductases (e.g., monooxygenases)

Q5. Cytochrome P450-like enzymes in microbes are important because they:

• Hydrolyze esters into acids and alcohols
• Introduce oxygen into substrates via monooxygenation
• Polymerize small molecules into biopolymers
• Always require no cofactors for activity

Correct Answer: Introduce oxygen into substrates via monooxygenation

Q6. A major pharmaceutical application of microbial biotransformation is:

• Generating stable solid-state forms only
• Synthesizing drug metabolites for safety and ADME studies
• Avoiding any chiral center manipulation
• Replacing all chemical steps with chemical catalysts

Correct Answer: Synthesizing drug metabolites for safety and ADME studies

Q7. Which microorganism is commonly used for stereoselective reductions in industry?

• Streptomyces species
• Escherichia coli expressing specific dehydrogenases
• Influenza virus
• Human hepatocytes

Correct Answer: Escherichia coli expressing specific dehydrogenases

Q8. In biotransformation, cofactor regeneration is essential because:

• Cofactors are not used by enzymes
• Cofactors inhibit enzyme activity
• Many enzymatic reactions require NAD(P)H or ATP which must be recycled
• Cofactors make products unstable

Correct Answer: Many enzymatic reactions require NAD(P)H or ATP which must be recycled

Q9. Glycosylation of drugs by microbes is useful because it:

• Always decreases drug solubility
• Produces polar glycosides that can modify activity and ADME
• Destroys pharmacological activity in all cases
• Is impossible with microbial systems

Correct Answer: Produces polar glycosides that can modify activity and ADME

Q10. Which analytical technique is most commonly used to identify biotransformation products?

• Light microscopy
• HPLC coupled with mass spectrometry (LC–MS)
• Basic pH paper test
• Paper chromatography only

Correct Answer: HPLC coupled with mass spectrometry (LC–MS)

Q11. Stereoselective biotransformations are particularly valuable in pharmaceuticals because they:

• Always produce racemic mixtures
• Allow formation of a specific enantiomer with desired therapeutic effect
• Eliminate need for purity testing
• Are slower than chemical methods in all cases

Correct Answer: Allow formation of a specific enantiomer with desired therapeutic effect

Q12. Nitrile hydratase produced by Rhodococcus is industrially used to:

• Hydrolyze esters into alcohols
• Convert nitriles to amides (nitrile hydration)
• Oxidize alcohols to aldehydes exclusively
• Reduce nitro groups to amines

Correct Answer: Convert nitriles to amides (nitrile hydration)

Q13. Immobilized cells or enzymes are used in biotransformations mainly to:

• Prevent product formation
• Improve operational stability and enable reuse
• Make the system single-use only
• Eliminate the need for substrate

Correct Answer: Improve operational stability and enable reuse

Q14. Which factor is least influential in optimizing microbial biotransformation?

• pH of the reaction medium
• Temperature
• Substrate concentration
• Color of the reaction vessel

Correct Answer: Color of the reaction vessel

Q15. Biotransformation to produce a human drug metabolite for toxicity testing typically uses:

• Random chemical reagents only
• Microbial strains or recombinant enzymes that mimic human metabolism
• Plant extracts exclusively
• Purely theoretical computational models without experiments

Correct Answer: Microbial strains or recombinant enzymes that mimic human metabolism

Q16. Which of the following reactions is commonly achieved by microbial enzymes?

• Hydroxylation of non-activated carbon atoms
• Nuclear fission
• Direct electroplating of metals
• Spontaneous combustion

Correct Answer: Hydroxylation of non-activated carbon atoms

Q17. Which microbial genus is well-known for producing diverse secondary metabolites and enzymes used in biotransformation?

• Staphylococcus
• Streptomyces
• Influenza
• Homo sapiens

Correct Answer: Streptomyces

Q18. Biotransformation can help in lead optimization by:

• Generating metabolite profiles to avoid toxic motifs and improve potency
• Eliminating the need for biological testing
• Making all compounds more lipophilic
• Preventing any structural modification

Correct Answer: Generating metabolite profiles to avoid toxic motifs and improve potency

Q19. A primary challenge when scaling microbial biotransformations to industrial scale is:

• Microbial systems scale linearly without issues
• Maintaining oxygen transfer, mixing, and consistent cofactor regeneration
• Lack of regulatory considerations
• Too few substrate molecules at large scale

Correct Answer: Maintaining oxygen transfer, mixing, and consistent cofactor regeneration

Q20. Amidases in microbes are useful in pharmaceuticals for:

• Reducing alkenes to alkanes
• Hydrolyzing amide bonds to form carboxylic acids and amines
• Performing photochemical reactions only
• Driving polymer cross-linking exclusively

Correct Answer: Hydrolyzing amide bonds to form carboxylic acids and amines

Q21. Use of recombinant E. coli expressing a specific enzyme is beneficial because it:

• Prevents expression of the enzyme of interest
• Allows high-level, controllable production of biocatalysts
• Always causes product contamination
• Is never allowed in industry

Correct Answer: Allows high-level, controllable production of biocatalysts

Q22. Which regulation-related concern is important for microbial biotransformation products intended for human testing?

• Color of the microorganism
• Absence of microbial impurities and endotoxins
• Use of any solvent regardless of toxicity
• Ignoring documentation and validation

Correct Answer: Absence of microbial impurities and endotoxins

Q23. Dealkylation of a drug molecule by microbes typically yields:

• A larger alkyl chain attached
• A demethylated or dealkylated metabolite with increased polarity
• Only gaseous products
• Complete polymerization of the drug

Correct Answer: A demethylated or dealkylated metabolite with increased polarity

Q24. Which is a green chemistry advantage of microbial biotransformation?

• High energy consumption compared to chemical synthesis
• Use of toxic heavy metal catalysts exclusively
• Milder reaction conditions and fewer hazardous reagents
• Production of more hazardous waste

Correct Answer: Milder reaction conditions and fewer hazardous reagents

Q25. In selecting a microbial strain for a desired transformation, which approach is commonly used?

• Random selection without screening
• High-throughput screening of strain libraries for activity
• Choosing the strain with the funniest name
• Only using fungal strains regardless of substrate

Correct Answer: High-throughput screening of strain libraries for activity

Q26. Phase I biotransformation reactions generally involve:

• Conjugation with glucuronic acid exclusively
• Functionalization reactions such as oxidation, reduction, and hydrolysis
• Evaporation of solvents
• Only photochemical cleavage

Correct Answer: Functionalization reactions such as oxidation, reduction, and hydrolysis

Q27. Which microbial enzyme is useful for enantioselective hydrolysis of esters?

• Cellulase
• Esterase or lipase
• DNA polymerase
• Reverse transcriptase

Correct Answer: Esterase or lipase

Q28. Metabolite profiling using microbial biotransformation helps drug development by:

• Obscuring potential toxic metabolites
• Providing standards and understanding metabolic pathways for safety assessment
• Ensuring drugs never reach the market
• Reducing analytical requirements

Correct Answer: Providing standards and understanding metabolic pathways for safety assessment

Q29. Which condition often improves selectivity in a microbial biotransformation?

• Using extremely high substrate concentrations causing toxicity
• Optimizing pH, temperature, and co-substrates
• Ignoring oxygen supply in aerobic reactions
• Adding random metal salts without testing

Correct Answer: Optimizing pH, temperature, and co-substrates

Q30. A common strategy to expand microbial biotransformation capabilities is:

• Deleting all metabolic genes from the microorganism
• Using metabolic engineering and recombinant expression of desired enzymes
• Avoiding any genetic modifications always
• Only using environmental samples without characterization

Correct Answer: Using metabolic engineering and recombinant expression of desired enzymes

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