Production of glucose isomerase MCQs With Answer

Production of glucose isomerase MCQs With Answer

Introduction: This question bank focuses on the production, properties, and industrial application of glucose isomerase (xylose isomerase), an enzyme critical for manufacturing high-fructose corn syrup and other biotechnological processes. Tailored for M.Pharm students studying Advanced Pharmaceutical Biotechnology, the set covers microbial sources, gene cloning, fermentation strategies, catalytic requirements, assay and purification methods, immobilization and reactor design, and modern protein-engineering approaches to improve stability and metal dependence. These 20 MCQs with answers emphasize conceptual understanding and technical details relevant to enzyme production, downstream processing, and industrial implementation, helping students prepare for exams and practical work involving enzyme biotechnology.

Q1. What is the primary catalytic function of glucose isomerase used in industry?

• Catalyzes the reversible isomerization of D-glucose to D-fructose used for HFCS production
• Hydrolyzes polysaccharides to monosaccharides
• Oxidizes glucose to gluconic acid
• Reduces fructose to sorbitol

Correct Answer: Catalyzes the reversible isomerization of D-glucose to D-fructose used for HFCS production

Q2. Which gene name is most commonly associated with bacterial glucose (xylose) isomerase?

• amyA
• xylA
• gluZ
• isoB

Correct Answer: xylA

Q3. Which thermophilic organism is a well-known source of a thermostable glucose isomerase used in industrial processes?

• Escherichia coli
• Thermotoga maritima
• Streptococcus pneumoniae
• Saccharomyces cerevisiae

Correct Answer: Thermotoga maritima

Q4. Which metal ion pair is most commonly required as cofactors for optimal glucose isomerase activity?

• Zn2+ and Cu2+
• Mg2+ and Co2+
• Ca2+ and Fe2+
• Na+ and K+

Correct Answer: Mg2+ and Co2+

Q5. What is the typical optimal pH range for many commercial glucose isomerases used in fructose production?

• pH 3.0–4.5 (acidic)
• pH 5.0–6.0 (slightly acidic)
• pH 7.0–8.5 (neutral to slightly alkaline)
• pH 9.5–11.0 (strongly alkaline)

Correct Answer: pH 7.0–8.5 (neutral to slightly alkaline)

Q6. Which immobilization strategy is widely used industrially to enhance the reusability and stability of glucose isomerase?

• Simple adsorption onto untreated plastic
• Covalent binding to activated solid supports (e.g., Eupergit)
• Keeping the enzyme entirely in free-solution batch reactors
• Lyophilization without a carrier

Correct Answer: Covalent binding to activated solid supports (e.g., Eupergit)

Q7. Which fermentation mode is typically preferred for high-yield industrial production of microbial glucose isomerase?

• Solid-state fermentation in shallow trays only
• Submerged aerobic fermentation in stirred-tank reactors
• Static surface fermentation without aeration
• Anaerobic fermentation in sealed vessels

Correct Answer: Submerged aerobic fermentation in stirred-tank reactors

Q8. Which sugar commonly acts as an inducer of xylose isomerase expression in many microbial producers?

• D-glucose
• D-fructose
• D-xylose
• Sucrose

Correct Answer: D-xylose

Q9. Which analytical method gives the most specific and quantitative measurement of glucose isomerase activity by directly measuring fructose formation?

• Dinitrosalicylic acid (DNS) assay for reducing sugars
• Seliwanoff’s test for ketoses (qualitative colorimetric)
• High-performance liquid chromatography (HPLC) quantification of fructose
• Biuret protein assay

Correct Answer: High-performance liquid chromatography (HPLC) quantification of fructose

Q10. Which host organism is most commonly used for recombinant overexpression of glucose isomerase genes for research and industrial strain development?

• Saccharomyces cerevisiae
• Escherichia coli
• Clostridium thermocellum
• Pseudomonas putida

Correct Answer: Escherichia coli

Q11. Many native glucose (xylose) isomerases show higher catalytic affinity (lower Km) for which substrate?

• D-fructose
• D-glucose
• D-xylose
• L-arabinose

Correct Answer: D-xylose

Q12. Which modern strategy is most effective to reduce Co2+ dependence and improve thermostability of glucose isomerase?

• Reducing fermentation aeration rates
• Protein engineering through site-directed mutagenesis and directed evolution
• Adding excess Zn2+ to the medium
• Shortening fermentation time only

Correct Answer: Protein engineering through site-directed mutagenesis and directed evolution

Q13. For microbial producers where glucose isomerase is intracellular, what is the essential first downstream processing step?

• Direct immobilization of whole cells without disruption
• Cell disruption (e.g., sonication, French press) to release intracellular enzyme
• Gel-filtration chromatography as the very first step
• Freeze-drying whole fermentation broth

Correct Answer: Cell disruption (e.g., sonication, French press) to release intracellular enzyme

Q14. Which reactor configuration is most commonly used for continuous industrial conversion of glucose to fructose using immobilized glucose isomerase?

• Batch stirred-tank reactor with free enzyme
• Packed-bed (fixed-bed) column reactor filled with immobilized enzyme
• Membrane bioreactor with free enzyme permeation
• Fluidized-bed reactor without immobilization

Correct Answer: Packed-bed (fixed-bed) column reactor filled with immobilized enzyme

Q15. Because cobalt is toxic and regulated, which practical approach is used to mitigate cobalt dependence in industrial glucose isomerase?

• Complete removal of metal cofactors (enzyme remains fully active)
• Protein engineering to alter active-site metal specificity toward Mn2+ or Mg2+
• Using higher concentrations of Co2+ to overcome toxicity concerns
• Replacing enzyme with chemical catalysts only

Correct Answer: Protein engineering to alter active-site metal specificity toward Mn2+ or Mg2+

Q16. Typical isomerization under industrial conditions without post‑enrichment yields which approximate percent fructose product known as HFCS-42?

• About 10% fructose
• About 42% fructose
• About 75% fructose
• About 95% fructose

Correct Answer: About 42% fructose

Q17. What is the usual operating temperature range for thermostable glucose isomerases used in continuous industrial processes?

• 10–25 °C
• 30–45 °C
• 60–80 °C
• 90–110 °C

Correct Answer: 60–80 °C

Q18. Immobilization of glucose isomerase primarily provides which operational advantages?

• Increased reaction pH dependence and single-use only
• Enhanced thermal stability, mechanical stability and enzyme reusability
• Complete elimination of metal cofactor requirements
• Instantaneous substrate specificity change to new sugars

Correct Answer: Enhanced thermal stability, mechanical stability and enzyme reusability

Q19. Which chromatographic technique is commonly employed in laboratory purification of glucose isomerase during downstream processing?

• Reverse-phase HPLC as the primary step
• Ion-exchange chromatography (e.g., DEAE-cellulose)
• Hydrophobic interaction without prior fractionation
• Paper chromatography only

Correct Answer: Ion-exchange chromatography (e.g., DEAE-cellulose)

Q20. Which amino-acid substitution strategy is often used in site-directed mutagenesis to increase the thermostability of glucose isomerase?

• Substituting proline into flexible loops to reduce conformational entropy
• Replacing cysteines to eliminate disulfide bonds always
• Introducing multiple glycine residues in core helices
• Converting all charged residues to hydrophobic residues on the surface

Correct Answer: Substituting proline into flexible loops to reduce conformational entropy

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