Q.Which one of the following pairs is not correctly matched ? (A) Clostridium butylicum – Butyric acid (B) Trichoderma polysporum – Cyclosporin A (C) Monascus purpureus – Citric Acid (D) Streptococcus – Streptokinase

The question asks you to spot the mismatched pair. Let's check each one against what NCERT says.

• Clostridium butylicum is indeed used to produce butyric acid. That pair is correct.
• Trichoderma polysporum is the fungus that yields Cyclosporin A, a powerful immunosuppressant used in organ transplants. That pair is correct.
• Monascus purpureus is a yeast used to produce statins (blood-cholesterol-lowering agents), not citric acid. Citric acid is produced by Aspergillus niger. So this pair is wrong. …

Let’s walk through each option carefully, because this question tests your grasp of which microbe is famous for which industrial product — a classic NCERT-based topic from the chapter on Microbes in Human Welfare.

Option (A): Clostridium butylicum – Butyric acid. This is correct. Clostridium butylicum is a bacterium used in the industrial production of butyric acid. Butyric acid is a short-chain fatty acid with applications in food flavouring, perfumes, and as a chemical intermediate. NCERT explicitly mentions this pairing.

Option (B): Trichoderma polysporum – Cyclosporin A. This is also correct. Trichoderma polysporum is a fungus that produces Cyclosporin A, a powerful immunosuppressant drug used in organ transplant patients to prevent rejection. This is a well-known example from the NCERT section on biological control and pharmaceutical products.

Option (C): Monascus purpureus – Citric Acid. This is the incorrect match. Monascus purpureus is a fungus (a type of red yeast) that produces statins — specifically, a compound called monacolin K, which lowers blood cholesterol. Citric acid, on the other hand, is produced by Aspergillus niger (a different fungus). NCERT clearly states that Monascus purpureus is used for producing blood-cholesterol-lowering agents, not citric acid.