Part 1: Microbes in Household Products & Food Processing (Q1–Q25)
Chapter 8 – Microbes in Human Welfare (Class 12 NCERT, NEET UG focus).
Subtopic Breakdown (Chapter 8)
- Microbes in Household Products & Food Processing – Fermented foods, beverages, probiotics.
- Microbes in Industrial Production – Antibiotics, organic acids, enzymes, beverages.
- Sewage Treatment (Primary, Secondary, Tertiary) – Microbial role.
- Biogas Production (Energy Generation) – Methanogens, biogas plants.
- Microbes as Biocontrol Agents – Biopesticides, natural enemies.
- Microbes as Biofertilizers – Symbiotic & free-living nitrogen-fixing bacteria, cyanobacteria, mycorrhiza.
- Antibiotics – Discovery & Use – Production, misuse, resistance.
- Mixed & Advanced Application-Based MCQs – Revision, NEET-style higher difficulty.
Part 1: Microbes in Household Products & Food Processing (Q1–Q25)
Q1. Curd is formed from milk with the help of:
a) Saccharomyces
b) Lactobacillus
c) Penicillium
d) Rhizobium
Answer: b
- b) Correct: Lactobacillus ferments lactose → lactic acid → coagulates milk into curd.
- a) Yeast ferments sugar, not milk.
- c) Penicillium = antibiotic producer.
- d) Rhizobium = nitrogen-fixer.
Q2. Which substance is produced in curd that helps in digestion?
a) Acetic acid
b) Lactic acid
c) Alcohol
d) Citric acid
Answer: b
- b) Correct: Lactic acid from Lactobacillus makes curd sour & aids digestion.
Q3. Idli, dosa, and dhokla dough fermentation is due to:
a) Yeast only
b) Lactic acid bacteria
c) Combination of bacteria and yeast
d) Moulds
Answer: c
- c) Correct: Fermentation of idli/dosa batter = bacteria (Lactobacillus) + yeast (Saccharomyces).
Q4. Which organism is used in bread making?
a) Rhizobium
b) Saccharomyces cerevisiae
c) Lactobacillus
d) Penicillium
Answer: b
- b) Correct: Saccharomyces cerevisiae = baker’s yeast → CO₂ bubbles make bread fluffy.
Q5. Alcoholic beverages are produced by fermentation of sugars using:
a) Lactic acid bacteria
b) Yeast
c) Actinomycetes
d) Algae
Answer: b
- b) Correct: Yeast ferments sugars → ethanol in beer, wine.
Q6. Toddy is a traditional drink of South India obtained by:
a) Fermentation of sap from palm trees
b) Wheat fermentation
c) Sugarcane juice fermentation
d) Milk fermentation
Answer: a
- a) Correct: Toddy = fermented palm sap by natural yeasts.
Q7. Swiss cheese is characterized by:
a) Blue color
b) Large holes due to CO₂
c) Green spots
d) Alcohol content
Answer: b
- b) Correct: Swiss cheese → Propionibacterium shermanii produces CO₂ holes.
Q8. Blue cheese gets its characteristic flavor due to:
a) Yeast
b) Penicillium roqueforti
c) Lactobacillus
d) Aspergillus
Answer: b
- b) Correct: Penicillium roqueforti → flavor & aroma in blue cheese.
Q9. Which of the following is a probiotic?
a) Lactobacillus acidophilus
b) Clostridium botulinum
c) Escherichia coli (pathogenic)
d) Vibrio cholerae
Answer: a
- a) Correct: Probiotics like Lactobacillus improve gut health.
Q10. The “scum” formed on surface of fermenting idli batter is due to:
a) Fungal growth
b) CO₂ bubbles from yeast
c) Protein denaturation
d) Lactic acid crystallization
Answer: b
- b) Correct: Yeast releases CO₂ bubbles, forming frothy scum.
Q11. Which microorganism is used in dough for bread and cakes?
a) Lactobacillus
b) Saccharomyces cerevisiae
c) Rhizopus
d) Azotobacter
Answer: b
- b) Correct: Baker’s yeast → carbon dioxide & ethanol for bread rise.
Q12. Which beverage is NOT obtained by microbial fermentation?
a) Wine
b) Beer
c) Whisky
d) Coffee
Answer: d
- d) Correct: Coffee = roasted beans, not fermented.
Q13. Saccharomyces cerevisiae used in brewing is called:
a) Brewer’s yeast
b) Baker’s yeast
c) Antibiotic yeast
d) Probiotic yeast
Answer: a
- a) Correct: Brewer’s yeast used in alcohol fermentation.
Q14. Which bacteria produce lactic acid in curd?
a) Streptococcus thermophilus
b) Lactobacillus bulgaricus
c) Both a and b
d) None
Answer: c
- c) Correct: Both Lactobacillus bulgaricus + Streptococcus thermophilus.
Q15. Alcohol concentration in wine is generally:
a) 5–9%
b) 20–30%
c) 40–50%
d) 70–80%
Answer: a
- a) Correct: Wine → mild alcohol (5–9%).
Q16. Alcohol concentration in whisky and rum is usually:
a) 5–10%
b) 20–30%
c) 40–50%
d) 80–90%
Answer: c
- c) Correct: Distilled drinks → 40–50% alcohol.
Q17. Which fermented milk product is rich in probiotics?
a) Butter milk
b) Yogurt
c) Kefir
d) All of the above
Answer: d
- d) Correct: All are probiotic-rich dairy products.
Q18. Tapai is a fermented food of:
a) Rice (Indonesia, Philippines)
b) Barley (Europe)
c) Wheat (India)
d) Milk (Russia)
Answer: a
- a) Correct: Tapai → fermented rice, Southeast Asia.
Q19. Microbes are involved in food spoilage and food processing. Which is beneficial?
a) Mould in bread
b) Salmonella in food
c) Lactobacillus in milk
d) Clostridium botulinum
Answer: c
- c) Correct: Lactobacillus (curd) beneficial, others spoil food.
Q20. Microbial fermentation in bread causes:
a) Alcohol formation only
b) CO₂ release making bread porous
c) Production of lactic acid only
d) Killing bacteria
Answer: b
- b) Correct: CO₂ bubbles from yeast → soft, porous bread.
Q21. Which fermented product uses Aspergillus oryzae?
a) Soy sauce
b) Wine
c) Beer
d) Bread
Answer: a
- a) Correct: Soy sauce → Aspergillus oryzae fermentation.
Q22. Which is an edible fungus used in food industry?
a) Rhizopus
b) Agaricus bisporus
c) Clostridium
d) Vibrio
Answer: b
- b) Correct: Button mushroom (Agaricus) = edible fungus.
Q23. Which microbe is associated with vinegar production?
a) Acetobacter aceti
b) Penicillium
c) Lactobacillus
d) Streptomyces
Answer: a
- a) Correct: Acetobacter aceti converts ethanol → acetic acid (vinegar).
Q24. Probiotic bacteria mainly act in:
a) Kidneys
b) Large intestine
c) Small intestine
d) Blood
Answer: b
- b) Correct: Probiotics colonize large intestine, improve gut flora.
Q25. Which beverage is produced without distillation?
a) Whisky
b) Wine
c) Rum
d) Vodka
Answer: b
- b) Correct: Wine & beer → not distilled. Spirits like rum/whisky are distilled.
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