Prebiotics and Probiotics – Fructo-oligosaccharides and Lactobacillus MCQs With Answer

Introduction: Prebiotics and probiotics are key topics in pharmaceutical sciences, bridging microbiology, formulation, and clinical nutrition. Fructo-oligosaccharides (FOS) are widely used prebiotics that resist gastric digestion, selectively stimulate beneficial bacteria, and promote short-chain fatty acid production. Lactobacillus species are common probiotic organisms with roles in gut barrier function, immunomodulation, and metabolic health. B. Pharm students must understand FOS chemistry, mechanisms of selective fermentation, Lactobacillus taxonomy, viability factors, formulation strategies, analytical assays, and safety/regulatory considerations. This set emphasizes mechanism-based learning, formulation challenges, and clinical implications. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What defines a prebiotic?

• A substance that kills pathogenic bacteria in the gut
• A non-digestible compound that selectively stimulates growth/activity of beneficial gut microbes
• A live microbial supplement that provides health benefits
• A synthetic antibiotic designed to modulate microbiota

Correct Answer: A non-digestible compound that selectively stimulates growth/activity of beneficial gut microbes

Q2. Fructo-oligosaccharides (FOS) are primarily composed of which monosaccharide units?

• Glucose
• Galactose
• Fructose
• Mannose

Correct Answer: Fructose

Q3. Which property makes FOS resistant to digestion in the upper gastrointestinal tract?

• Beta-glycosidic linkages hydrolyzed by human amylase
• Alpha(1→4) linkages easily cleaved by gastric acid
• Short-chain length that allows absorption in the stomach
• Beta-fructofuranosidic linkages not hydrolyzed by human enzymes

Correct Answer: Beta-fructofuranosidic linkages not hydrolyzed by human enzymes

Q4. The degree of polymerization (DP) typically associated with FOS is:

• DP > 50
• DP 2–10
• DP 11–30
• Monosaccharide only

Correct Answer: DP 2–10

Q5. A key beneficial metabolic product of FOS fermentation by gut bacteria is:

• Short-chain fatty acids (SCFAs) like acetate and butyrate
• Ammonia and hydrogen sulfide
• Long-chain fatty acids
• Pepsin

Correct Answer: Short-chain fatty acids (SCFAs) like acetate and butyrate

Q6. Which Lactobacillus trait enhances survival through the stomach?

• Bile salt hydrolase activity only
• Acid tolerance mechanisms and proton pumps
• Ability to form spores
• Production of endotoxin

Correct Answer: Acid tolerance mechanisms and proton pumps

Q7. Which culture medium is commonly used for isolation and enumeration of Lactobacillus?

• MacConkey agar
• MRS (de Man, Rogosa and Sharpe) agar
• Blood agar for Streptococcus selectivity
• Sabouraud dextrose agar

Correct Answer: MRS (de Man, Rogosa and Sharpe) agar

Q8. Synbiotic refers to:

• A product containing only prebiotics
• A product containing only probiotics
• A combination of probiotics and prebiotics that act synergistically
• An antibiotic used with probiotics

Correct Answer: A combination of probiotics and prebiotics that act synergistically

Q9. Which analytical method is commonly used to quantify FOS content in formulations?

• High-performance liquid chromatography (HPLC)
• Gram staining
• ELISA for proteins
• Atomic absorption spectroscopy

Correct Answer: High-performance liquid chromatography (HPLC)

Q10. Minimum effective dose for many commercial probiotic products is often expressed as:

• mg/kg body weight
• CFU per dose (colony-forming units)
• IU (international units)
• pH units

Correct Answer: CFU per dose (colony-forming units)

Q11. What is a major safety concern when selecting probiotic Lactobacillus strains for pharmaceutical use?

• High intrinsic acid production
• Transferable antibiotic resistance genes
• Excessive SCFA production
• Low growth rate in culture

Correct Answer: Transferable antibiotic resistance genes

Q12. Which technique provides species-level identification of Lactobacillus isolates rapidly?

• API biochemical strips only
• 16S rRNA gene sequencing or MALDI-TOF mass spectrometry
• Gram staining morphology
• Visual colony color assessment

Correct Answer: 16S rRNA gene sequencing or MALDI-TOF mass spectrometry

Q13. What mechanism links FOS intake to enhanced mineral absorption (e.g., calcium)?

• Direct chemical chelation of minerals by FOS
• SCFA-mediated lowering of colonic pH which increases mineral solubility and absorption
• Inhibition of intestinal transporters
• Destruction of enterocytes

Correct Answer: SCFA-mediated lowering of colonic pH which increases mineral solubility and absorption

Q14. Which storage condition best preserves viability of freeze-dried Lactobacillus probiotics?

• Room temperature with high humidity
• Ambient temperature in sunlight
• Refrigeration in low moisture, oxygen-impermeable packaging
• Continuous agitation at 37°C

Correct Answer: Refrigeration in low moisture, oxygen-impermeable packaging

Q15. Bile salt hydrolase (BSH) activity in Lactobacillus can result in:

• Increased bile toxicity and host damage
• Deconjugation of bile acids, affecting cholesterol metabolism
• Loss of acid tolerance
• Production of endotoxins

Correct Answer: Deconjugation of bile acids, affecting cholesterol metabolism

Q16. Which prebiotic test demonstrates selective fermentation by beneficial bacteria in vitro?

• Antibiogram
• Selective growth/fermentation assays showing increased lactobacilli and bifidobacteria with gas/SCFA measurement
• PCR amplification of human genes
• Protein electrophoresis

Correct Answer: Selective growth/fermentation assays showing increased lactobacilli and bifidobacteria with gas/SCFA measurement

Q17. Which Lactobacillus species is commonly used as a probiotic and is also part of fermented dairy starter cultures?

• Lactobacillus acidophilus
• Lactobacillus pneumophila
• Lactobacillus anthracis
• Lactobacillus cholerae

Correct Answer: Lactobacillus acidophilus

Q18. How do probiotics like Lactobacillus contribute to immune modulation?

• By directly producing human antibodies
• By interacting with intestinal epithelial cells and dendritic cells to modulate cytokine responses
• By replacing all commensal microbes permanently
• By increasing gastric acid secretion only

Correct Answer: By interacting with intestinal epithelial cells and dendritic cells to modulate cytokine responses

Q19. Which excipient is commonly used as a cryoprotectant during freeze-drying of probiotics?

• Sodium lauryl sulfate
• Sucrose or skim milk powder
• Concentrated hydrochloric acid
• Ethyl acetate

Correct Answer: Sucrose or skim milk powder

Q20. A pharmacopoeial requirement for probiotic labeling often includes:

• Exact metabolic pathways of the strain
• Declared viable count at end of shelf-life (CFU) and strain designation
• Guaranteed therapeutic cure claims
• Color additives used in capsules

Correct Answer: Declared viable count at end of shelf-life (CFU) and strain designation

Q21. Which metabolic pathway in Lactobacillus produces lactic acid from glucose?

• Tricarboxylic acid (TCA) cycle exclusively
• Homofermentative glycolysis (Embden–Meyerhof pathway) producing mainly lactic acid
• Beta-oxidation of fatty acids
• Urea cycle

Correct Answer: Homofermentative glycolysis (Embden–Meyerhof pathway) producing mainly lactic acid

Q22. In formulation development, a challenge unique to combining FOS with probiotics is:

• FOS reacts chemically to form toxins with probiotics
• Ensuring that FOS does not support contaminant growth during storage while promoting probiotic viability
• FOS prevents capsule filling
• Probiotics convert FOS to cholesterol

Correct Answer: Ensuring that FOS does not support contaminant growth during storage while promoting probiotic viability

Q23. Which in vivo outcome is commonly measured to demonstrate prebiotic efficacy in clinical trials?

• Changes in gut microbiota composition and increased fecal bifidobacteria
• Immediate reduction of blood pressure within minutes
• Rapid increase of hair growth
• Complete eradication of all gut bacteria

Correct Answer: Changes in gut microbiota composition and increased fecal bifidobacteria

Q24. Which method is used to enumerate viable Lactobacillus in a formulation?

• Total organic carbon measurement
• Plate count on selective agar expressed as CFU per gram or dose
• UV absorbance at 260 nm for DNA only
• Mass spectrometry of sugars

Correct Answer: Plate count on selective agar expressed as CFU per gram or dose

Q25. FOS from natural sources is commonly extracted from:

• Soy protein concentrate
• Inulin-rich plants like chicory and Jerusalem artichoke
• Animal liver
• Refined petroleum

Correct Answer: Inulin-rich plants like chicory and Jerusalem artichoke

Q26. Which regulatory claim is typically permitted for prebiotics and probiotics in many jurisdictions?

• Guaranteed cure for inflammatory bowel disease
• Structure/function claims like “supports a healthy gut microbiota” with scientific substantiation
• Claims that they replace prescription antibiotics
• Claims of zero side effects in all populations

Correct Answer: Structure/function claims like “supports a healthy gut microbiota” with scientific substantiation

Q27. Which measure indicates probiotic strain stability during shelf-life studies?

• Increase in contaminant fungi counts only
• Retention of declared viable CFU counts over storage time at specified conditions
• Change in capsule color
• Loss of prebiotic sweetness

Correct Answer: Retention of declared viable CFU counts over storage time at specified conditions

Q28. Mechanistically, how can Lactobacillus inhibit pathogen colonization?

• By producing bacteriocins, lactic acid and competing for adhesion sites
• By increasing intestinal pH to alkaline levels
• By secreting human insulin
• By lysing host epithelial cells

Correct Answer: By producing bacteriocins, lactic acid and competing for adhesion sites

Q29. Which molecular assay can quantify specific probiotic strains in complex samples?

• Culture-independent qPCR with strain-specific primers
• Standard Gram staining only
• Simple pH paper test
• Polarimetry

Correct Answer: Culture-independent qPCR with strain-specific primers

Q30. When designing a synbiotic product containing FOS and Lactobacillus, a key formulation consideration is:

• Maximizing water activity to keep bacteria active during storage
• Matching prebiotic DP and probiotic carbohydrate-utilization profile to ensure selective utilization by the probiotic
• Using strong acids to sterilize the product post-fill
• Eliminating all excipients to reduce cost regardless of stability

Correct Answer: Matching prebiotic DP and probiotic carbohydrate-utilization profile to ensure selective utilization by the probiotic

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

Mail- Sachin@pharmacyfreak.com