Microbes in household and industrial products is a recall-heavy topic that NEET tests through precise organism–product pairing. The high-frequency trap here is confusing which microbe makes which product — particularly mixing up bacterial and fungal fermentations, or swapping the genus behind two similar dairy products.
Household products: Lactic Acid Bacteria (LAB), primarily Lactobacillus, convert milk to curd by producing lactic acid. LAB also increase vitamin B₁₂ content and check disease-causing organisms in the gut. Dough for idli and dosa rises due to CO₂ produced by yeast (Saccharomyces cerevisiae). The same yeast ferments sugars to ethanol in toddy (from palm sap). Cheese ripening uses specific microbes — Propionibacterium sharmanii produces the large holes in Swiss cheese, while Penicillium roqueforti and P. camemberti give Roquefort and Camembert their characteristic flavours (NCERT Class 12 Biology Chapter 8, page 151).
Industrial products: Fermented beverages — beer (without distillation) and whisky/rum/brandy (with distillation) — use Saccharomyces cerevisiae on different substrates. Industrial ethanol also uses yeast. Antibiotics: Penicillium notatum produces penicillin. Organic acids: Aspergillus niger → citric acid; Acetobacter aceti → acetic acid. Enzymes: lipases (used in detergents), pectinases and proteases (clarify fruit juices), streptokinase (clot buster, from Streptococcus). Statin (blood-cholesterol-lowering agent) is produced by Monascus purpureus. Cyclosporin A (immunosuppressant) is from Trichoderma polysporum.
Watch-out: NEET distractors exploit the genus-level similarity between Penicillium notatum (antibiotic) and Penicillium roqueforti (cheese). Read the species name.
Select an option to see the explanation. Wrong answers show why your choice was tempting — and name the exact trap it exploits.
Which microorganism is responsible for the large holes in Swiss cheese?
Answer: B. Propionibacterium sharmanii produces CO₂ during ripening, forming the characteristic large holes (eyes) in Swiss cheese (NCERT Class 12 Biology Chapter 8, page 151).
Why A is wrong: A is wrong because Penicillium roqueforti ripens Roquefort cheese (blue-veined), not Swiss cheese — a common genus-level swap trap.
Why C is wrong: C is wrong because Lactobacillus species are involved in curd/yoghurt production, not cheese ripening holes.
Why D is wrong: D is wrong because Aspergillus niger is used industrially for citric acid production, not in cheese manufacturing.
Statin, used as a blood-cholesterol-lowering agent, is produced by:
Answer: C. Monascus purpureus (a yeast) produces statins that competitively inhibit HMG-CoA reductase, lowering cholesterol synthesis (NCERT Class 12 Biology Chapter 8, page 153).
Why A is wrong: A is wrong because Trichoderma polysporum produces Cyclosporin A (an immunosuppressant), not statins — these two bioactive products are frequently swapped in NEET options.
Why B is wrong: B is wrong because Streptococcus produces streptokinase (a clot-dissolving enzyme), not a cholesterol-lowering agent.
Why D is wrong: D is wrong because Penicillium notatum produces the antibiotic penicillin, not statins.
Cyclosporin A, used as an immunosuppressive agent in organ transplants, is obtained from:
Answer: A. Trichoderma polysporum produces Cyclosporin A, which inhibits T-cell activation and is used to prevent transplant rejection (NCERT Class 12 Biology Chapter 8, page 153).
Why B is wrong: B is wrong because Penicillium notatum produces penicillin (antibiotic), not Cyclosporin A.
Why C is wrong: C is wrong because Monascus purpureus produces statins (cholesterol-lowering), not immunosuppressants.
Why D is wrong: D is wrong because Saccharomyces cerevisiae (brewer's yeast) is used in fermentation for ethanol/bread/beverages, not pharmaceutical immunosuppressants.
A student observes that adding a small amount of curd to warm milk converts it entirely to curd overnight. Which of the following correctly explains the vitamin change in the product?
Answer: D. Lactic Acid Bacteria (LAB) in curd increase the vitamin B₁₂ content of the product during fermentation (NCERT Class 12 Biology Chapter 8, page 153).
Why A is wrong: A is wrong because LAB do not synthesise vitamin C; this vitamin is associated with citrus fruits, not bacterial fermentation.
Why B is wrong: B is wrong because LAB primarily ferment lactose to lactic acid; they do not preferentially degrade vitamin A or fat in a way that reduces vitamin A content.
Why C is wrong: C is wrong because vitamin D synthesis requires UV irradiation of ergosterol/cholesterol — curd setting occurs in covered containers without UV exposure.
In a brewery, the same yeast species is used for beer and whisky production. What is the key processing difference that distinguishes whisky from beer?
Answer: B. Both beer and whisky use Saccharomyces cerevisiae on cereal substrates. The distinction is that whisky undergoes distillation after fermentation to increase alcohol concentration, while beer is consumed without distillation (NCERT Class 12 Biology Chapter 8, page 152).
Why A is wrong: A is wrong because the same species (Saccharomyces cerevisiae) is used for both — the processing (distillation), not the organism, differs.
Why C is wrong: C is wrong because both beer and whisky fermentation are anaerobic processes (ethanol production requires absence of oxygen).
Why D is wrong: D is wrong because both beer and whisky typically use cereal grain (malted barley) as substrate; fruit-based fermentation yields wine, not whisky.
A pharmaceutical company needs an enzyme that dissolves blood clots for use in patients with myocardial infarction. Which organism should they culture?
Answer: C. Streptococcus produces streptokinase, a fibrinolytic enzyme that converts plasminogen to plasmin and dissolves blood clots. It is used as a 'clot buster' in myocardial infarction (NCERT Class 12 Biology Chapter 8, page 153).
Why A is wrong: A is wrong because Aspergillus niger produces citric acid (an organic acid used in food industry), not a clot-dissolving enzyme.
Why B is wrong: B is wrong because Monascus purpureus produces statins that lower cholesterol — a preventive agent, not a clot-dissolving emergency drug.
Why D is wrong: D is wrong because Propionibacterium sharmanii is used in Swiss cheese production; it has no pharmaceutical clot-busting application.
Pectinases and proteases are used in the fruit juice industry. What is the specific role of these enzymes in juice production?
Answer: D. Pectinases break down pectin (which causes cloudiness and gel formation) and proteases break down proteins, together clarifying bottled fruit juices by removing components that cause turbidity (NCERT Class 12 Biology Chapter 8, page 153).
Why A is wrong: A is wrong because pectinases and proteases degrade structural polymers (pectin, proteins), not synthesise sugars — sugar content depends on the fruit itself.
Why B is wrong: B is wrong because pectinases/proteases are degradative enzymes that remove turbidity-causing molecules; they do not synthesise or add flavour compounds.
Why C is wrong: C is wrong because these enzymes are processing aids for physical clarity, not antimicrobial preservatives — preservation uses pasteurisation or chemical preservatives.
A student lists four microbe–product pairs. Which list is entirely correct?
(i) Aspergillus niger — citric acid
(ii) Acetobacter aceti — acetic acid
(iii) Saccharomyces cerevisiae — ethanol
(iv) Lactobacillus — streptokinase
Answer: A. Pairs (i), (ii), and (iii) are correct: A. niger → citric acid, A. aceti → acetic acid, S. cerevisiae → ethanol. Pair (iv) is wrong because streptokinase is produced by Streptococcus, not Lactobacillus. Identifying the single incorrect pair and eliminating options that include it requires checking all four pairs (NCERT Class 12 Biology Chapter 8, page 153).
Why B is wrong: B is wrong because pair (iv) is incorrect — streptokinase is from Streptococcus, not Lactobacillus. Lactobacillus produces lactic acid in curd formation.
Why C is wrong: C is wrong because it includes the incorrect pair (iv) while excluding the correct pair (i) — Aspergillus niger does produce citric acid.
Why D is wrong: D is wrong because it omits pair (ii), which is correct — Acetobacter aceti produces acetic acid.
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Given
A NEET question asks: "Match the following microbes with their industrial products" and provides:• Column I: (a) Penicillium notatum, (b) Monascus purpureus, (c) Trichoderma polysporum, (d) Aspergillus niger• Column II: (i) Cyclosporin A, (ii) Statin, (iii) Citric acid, (iv) Penicillin
Required
Correct matching of all four pairs.
Concept
Each industrial microbe produces a specific bioactive compound. NEET exploits genus-level similarity (Penicillium appears in both antibiotic and cheese contexts) and product-function confusion (statin vs. streptokinase vs. Cyclosporin A).
Key associations (no formula — pure recall)
• Penicillium notatum → Penicillin (antibiotic)• Monascus purpureus → Statin (cholesterol-lowering)• Trichoderma polysporum → Cyclosporin A (immunosuppressant)• Aspergillus niger → Citric acid (organic acid)
Matching
(a)–(iv), (b)–(ii), (c)–(i), (d)–(iii)
Verification
Cross-check: no product is assigned twice. Each organism has exactly one product. The two most commonly swapped pairs (statin ↔ Cyclosporin A) are verified by the mnemonic: Monascus → Medicine for cholesterol (statin); Trichoderma → Transplant drug (Cyclosporin A).
Final answer
(a)–(iv), (b)–(ii), (c)–(i), (d)–(iii).
Common trap
Swapping Monascus purpureus (statin) with Trichoderma polysporum (Cyclosporin A). Both are bioactive molecules from fungi used in medicine — the distractor exploits functional-category similarity.
Similar NEET-style question
"Which of the following is correctly matched? (A) Trichoderma polysporum — Statin (B) Monascus purpureus — Cyclosporin A (C) Aspergillus niger — Citric acid (D) Penicillium roqueforti — Penicillin." Answer: C. Options A and B are the classic swap; D confuses the cheese Penicillium species with the antibiotic species.
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Curd: Lactobacillus. Bread: Saccharomyces cerevisiae. Cheese: Penicillium roqueforti (Roquefort), P. camemberti. Industrial: ethanol (yeast), antibiotics (penicillin from Penicillium notatum — Fleming 1928), citric acid (Aspergillus niger).
-- NCERT Class 12 Biology, Chapter 8, p. 151More in Biology and Human Welfare: 4 exam traps and mistakes · 1 question pattern from its other lessons.
6 questions from NEET 2022, 2024, 2025, 2026. Answers verified against NTA official keys.
Which of the following is used as a clot buster ?
Streptokinase produced by bacterium Streptococcus is used for
Which of the following is an example of non-distilled alcoholic beverage produced by yeast?
All 37 past-paper questions from Biology and Human Welfare →
Page numbers are the ones printed in the current NCERT textbook (2023 rationalised edition), unless marked pre-2023. The books are free at ncert.nic.in.
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