Bioprocessing of lactic acid MCQs With Answer

Introduction: Bioprocessing of lactic acid MCQs With Answer is designed for M.Pharm students to deepen understanding of lactic acid production from microbial fermentation through focused, exam-oriented multiple-choice questions. This collection emphasizes core concepts such as microbial strains, metabolic pathways, fermentation strategies (batch, fed-batch, continuous), process parameters (pH, temperature, substrate feeding), downstream recovery (precipitation, electrodialysis, membrane separation), and issues of stereochemistry and product purity. Questions integrate both theoretical and practical aspects of bioprocess engineering, including scale-up challenges, immobilization, and metabolic/strain improvements. Use these MCQs to consolidate knowledge, prepare for viva or exams, and identify areas needing further study.

Q1. Which microorganism group is most commonly used industrially for microbial production of lactic acid?

• Lactobacillus spp.
• Bacillus subtilis
• Rhizopus oryzae
• Saccharomyces cerevisiae

Correct Answer: Lactobacillus spp.

Q2. What best describes a homolactic fermentation pathway?

• Conversion of glucose primarily to lactic acid via Embden–Meyerhof–Parnas pathway producing mainly lactate and ATP
• Conversion of glucose to lactic acid, ethanol and CO2 via pentose phosphate pathway
• Oxidative conversion of lactate to pyruvate under aerobic conditions
• Simultaneous production of lactic acid and citric acid

Correct Answer: Conversion of glucose primarily to lactic acid via Embden–Meyerhof–Parnas pathway producing mainly lactate and ATP

Q3. Which carbon source is most widely used for large-scale lactic acid fermentation in industry?

• Glucose derived from starch hydrolysates
• Lactose from whey without hydrolysis
• Pure sucrose from sugarcane juice
• Crude glycerol from biodiesel production

Correct Answer: Glucose derived from starch hydrolysates

Q4. Which organism is commonly used to produce optically pure L‑(+)-lactic acid in industrial fungal fermentation?

• Lactobacillus delbrueckii
• Lactobacillus casei
• Rhizopus oryzae
• Leuconostoc mesenteroides

Correct Answer: Rhizopus oryzae

Q5. What is the principal inhibitory factor limiting lactic acid fermentation productivity?

• Accumulation of lactic acid causing pH drop and product inhibition
• Excess dissolved oxygen in the broth
• High nitrogen concentration in medium
• Excessive foam formation only

Correct Answer: Accumulation of lactic acid causing pH drop and product inhibition

Q6. Which neutralizing agent is most commonly used during industrial lactic acid fermentation to control pH?

• Calcium hydroxide (Ca(OH)2)
• Sodium hydroxide (NaOH)
• Ammonium hydroxide (NH4OH)
• Potassium hydroxide (KOH)

Correct Answer: Calcium hydroxide (Ca(OH)2)

Q7. A widely used downstream strategy for lactic acid recovery at industrial scale is:

• Direct distillation of lactic acid from fermentation broth
• Adsorption on activated carbon followed by desorption
• Precipitation as calcium lactate followed by acidification
• Pertraction with organic solvents without prior neutralization

Correct Answer: Precipitation as calcium lactate followed by acidification

Q8. What is a major advantage of electrodialysis as a recovery method for lactic acid?

• It eliminates the need for chemical neutralizers and reduces salt waste
• It always gives higher stereochemical purity of lactic acid
• It uses organic solvents that enhance recovery yield
• It is the lowest capital cost option for all plant scales

Correct Answer: It eliminates the need for chemical neutralizers and reduces salt waste

Q9. Typical optimal temperature range for mesophilic lactic acid bacteria fermentation is:

• 20–25 °C
• 30–37 °C
• 45–55 °C
• 60–75 °C

Correct Answer: 30–37 °C

Q10. What is the main advantage of fed‑batch fermentation for lactic acid production?

• Maintains low residual substrate to avoid substrate inhibition and increases productivity
• Maximizes final volume without affecting substrate concentration
• Ensures continuous removal of cells and product
• Eliminates the need for pH control

Correct Answer: Maintains low residual substrate to avoid substrate inhibition and increases productivity

Q11. Immobilized cell systems for lactic acid production mainly provide:

• Lower cell density and single-use operation
• Higher cell density, operational stability and cell reuse
• Complete elimination of product inhibition
• Faster sterilization requirements only

Correct Answer: Higher cell density, operational stability and cell reuse

Q12. In bioprocess terminology, yield of lactic acid is usually expressed as:

• Grams lactic acid produced per liter broth
• Grams lactic acid per hour
• Grams lactic acid per gram substrate consumed
• Percentage biomass increase per batch

Correct Answer: Grams lactic acid per gram substrate consumed

Q13. Volumetric productivity of a fermentation process is commonly reported in which units?

• g per batch
• g/L/h
• mol/L
• % w/v

Correct Answer: g/L/h

Q14. Which analytical technique is most appropriate for determining enantiomeric purity of lactic acid?

• Chiral high-performance liquid chromatography (chiral HPLC)
• Standard reversed-phase HPLC without chiral column
• UV–Vis spectrophotometry at 210 nm
• Gravimetric titration only

Correct Answer: Chiral high-performance liquid chromatography (chiral HPLC)

Q15. Which of the following lactic acid bacteria used in dairy starters is homofermentative?

• Lactobacillus brevis
• Leuconostoc mesenteroides
• Streptococcus thermophilus
• Weissella confusa

Correct Answer: Streptococcus thermophilus

Q16. Heterofermentative lactic acid bacteria produce which set of major end-products from hexose fermentation?

• Lactic acid only
• Lactic acid and ethanol/acetic acid plus CO2
• Only ethanol and CO2 without lactic acid
• Citric acid and succinic acid

Correct Answer: Lactic acid and ethanol/acetic acid plus CO2

Q17. Which enzyme catalyzes the conversion of pyruvate to lactate in lactic acid fermentation?

• Pyruvate decarboxylase
• Lactate dehydrogenase (LDH)
• Pyruvate kinase
• Citrate synthase

Correct Answer: Lactate dehydrogenase (LDH)

Q18. Genetic engineering to overexpress lactate dehydrogenase and to knock out competing pathways is a strategy to:

• Decrease lactic acid stereospecificity
• Reduce substrate utilization efficiency
• Increase lactic acid yield and tolerance
• Convert lactic acid to ethanol

Correct Answer: Increase lactic acid yield and tolerance

Q19. During scale-up of lactic acid fermentation, which engineering parameter is critical to maintain to ensure similar oxygen transfer and mixing?

• Tip speed only
• Volumetric oxygen transfer coefficient (kLa)
• Final broth color
• Initial inoculum volume fraction only

Correct Answer: Volumetric oxygen transfer coefficient (kLa)

Q20. For production of high-molecular-weight polylactic acid (PLA) by ring-opening polymerization, the immediate monomeric precursor is:

• Direct lactic acid without further conversion
• Lactide (cyclic dimer of lactic acid)
• Polyglycolic acid
• Lactic acid ethyl ester only

Correct Answer: Lactide (cyclic dimer of lactic acid)

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