Bioprocessing of alcohol MCQs With Answer

Bioprocessing of alcohol MCQs With Answer is a focused study resource designed for M.Pharm students taking Bioprocess Engineering and Technology. This quiz set emphasizes core principles of ethanol production — from microbial physiology, metabolic pathways, substrates and inhibitors, to reactor operation, downstream separation, and strain improvement strategies. Questions are framed to deepen conceptual understanding and to link laboratory practice with industrial-scale considerations such as yields, productivity, and process design choices. Use these MCQs to test knowledge, prepare for exams, and identify areas requiring review. Each question includes plausible distractors and the correct answer to support targeted revision and reinforce critical thinking about alcohol bioprocessing.

Q1. Which microorganism is the most widely used industrially for ethanol production from fermentable sugars?

• Saccharomyces cerevisiae
• Zymomonas mobilis
• Escherichia coli
• Clostridium acetobutylicum

Correct Answer: Saccharomyces cerevisiae

Q2. Which metabolic pathway is primarily responsible for converting glucose to pyruvate in yeast ethanol fermentation?

• Tricarboxylic acid (TCA) cycle
• Entner-Doudoroff pathway
• Embden–Meyerhof–Parnas (glycolysis)
• Pentose phosphate pathway

Correct Answer: Embden–Meyerhof–Parnas (glycolysis)

Q3. What is the typical optimal temperature range for Saccharomyces cerevisiae during industrial ethanol fermentation?

• 10–15 °C
• 20–25 °C
• 28–32 °C
• 40–45 °C

Correct Answer: 28–32 °C

Q4. What is the theoretical maximum ethanol yield from glucose on a mass basis (g ethanol per g glucose)?

• 0.36 g ethanol/g glucose
• 0.51 g ethanol/g glucose
• 0.67 g ethanol/g glucose
• 0.80 g ethanol/g glucose

Correct Answer: 0.51 g ethanol/g glucose

Q5. Under which oxygen condition is Saccharomyces cerevisiae fermentation directed predominantly toward ethanol production?

• Strictly aerobic conditions
• Microaerobic (low oxygen) conditions
• Anaerobic (absence of oxygen) conditions
• Hyperbaric oxygenation

Correct Answer: Anaerobic (absence of oxygen) conditions

Q6. Which common feedstock is primarily composed of fermentable simple sugars and typically does NOT require enzymatic saccharification before fermentation?

• Starch (e.g., corn starch)
• Lignocellulosic hydrolysate
• Molasses
• Cellulose pulp

Correct Answer: Molasses

Q7. Why do yeast cells produce glycerol during ethanol fermentation?

• To increase ATP yield per glucose
• To reoxidize NADH and maintain intracellular redox balance
• To act as the main carbon storage compound
• To facilitate oxygen uptake

Correct Answer: To reoxidize NADH and maintain intracellular redox balance

Q8. Which compounds formed during pretreatment of lignocellulosic biomass are major inhibitors of yeast fermentation?

• Methanol and ethanol
• Formic acid and lactic acid
• Furfural and hydroxymethylfurfural (HMF)
• Sucrose and fructose

Correct Answer: Furfural and hydroxymethylfurfural (HMF)

Q9. What is a primary advantage of immobilizing yeast cells in industrial ethanol production?

• Complete elimination of by-product formation
• Cell reuse and higher volumetric productivity
• Increased genetic stability of the strain
• Automatic detoxification of inhibitors

Correct Answer: Cell reuse and higher volumetric productivity

Q10. At atmospheric pressure, ethanol and water form an azeotrope at approximately what ethanol concentration, limiting simple distillation purity?

• 80.0% (v/v) ethanol
• 90.0% (v/v) ethanol
• 95.6% (v/v) ethanol
• 99.9% (v/v) ethanol

Correct Answer: 95.6% (v/v) ethanol

Q11. Which fermentation mode is most commonly used to minimize substrate inhibition while achieving high cell density and product titers?

• Batch fermentation
• Fed-batch fermentation
• Continuous chemostat at single dilution rate
• Solid-state fermentation

Correct Answer: Fed-batch fermentation

Q12. Which cofactor is oxidized during the conversion of acetaldehyde to ethanol by alcohol dehydrogenase?

• FAD
• NAD+
• NADP+
• ATP

Correct Answer: NAD+

Q13. Which ethanologenic bacterium is notable for using the Entner–Doudoroff pathway and exhibiting high specific ethanol productivity?

• Saccharomyces cerevisiae
• Zymomonas mobilis
• Klebsiella pneumoniae
• Clostridium thermocellum

Correct Answer: Zymomonas mobilis

Q14. What is the commonly maintained pH range for yeast ethanol fermentations to balance enzyme activity and contamination control?

• pH 2.0–3.0
• pH 4.0–5.0
• pH 6.5–7.5
• pH 8.0–9.0

Correct Answer: pH 4.0–5.0

Q15. What is the primary cellular mechanism by which ethanol exerts toxicity on yeast cells at high concentrations?

• Inhibition of DNA replication
• Disruption of cell membrane integrity and increased membrane fluidity
• Irreversible denaturation of ribosomes
• Specific inhibition of glycolytic enzymes only

Correct Answer: Disruption of cell membrane integrity and increased membrane fluidity

Q16. Typical industrial batch ethanol fermentation processes are commonly completed within which time frame for sugar-based feedstocks?

• 2–6 hours
• 12–24 hours
• 48–72 hours
• 7–14 days

Correct Answer: 48–72 hours

Q17. Which strain improvement approach involves cultivating microbes under selective stress over many generations to obtain improved ethanol tolerance?

• Adaptive laboratory evolution (ALE)
• Site-directed mutagenesis of a single gene
• Transformation with random plasmid libraries
• Immediate CRISPR knockout of multiple targets

Correct Answer: Adaptive laboratory evolution (ALE)

Q18. Volumetric productivity, an important industrial performance metric for fermenters, is typically expressed in which units?

• Cells/mL
• g/L·h
• mol/s
• mL/min

Correct Answer: g/L·h

Q19. Which dehydration technology is commonly used to obtain anhydrous ethanol (for fuel) after distillation because it breaks the ethanol–water azeotrope effectively?

• Simple atmospheric distillation only
• Membrane dialysis
• Molecular sieves (zeolite adsorption)
• Vacuum crystallization

Correct Answer: Molecular sieves (zeolite adsorption)

Q20. What is the balanced stoichiometric equation for anaerobic fermentation of one mole of glucose to ethanol and carbon dioxide?

• C6H12O6 → 3 C2H5OH + 3 CO2
• C6H12O6 → 2 C2H5OH + 2 CO2
• C6H12O6 → C2H5OH + CO2
• C6H12O6 → 6 CO2 + 6 H2O

Correct Answer: C6H12O6 → 2 C2H5OH + 2 CO2

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