Match the media component (Column I) with its role (Column II).
| Column I | Column II |
|---|---|
| P. Sucrose | 1. Anti-foam agent |
| Q. Zinc chloride | 2. Nitrogen source |
| R. Ammonium sulphate | 3. Carbon source |
| S. Silicone oil | 4. Trace element |
P-1, Q-2, R-3, S-4
P-2, Q-1, R-3, S-4
P-3, Q-2, R-4, S-1
P-3, Q-4, R-2, S-1
ANSWER
(D) P-3, Q-4, R-2, S-1: sucrose is the carbon source, zinc chloride the trace element, ammonium sulphate the nitrogen source and silicone oil the anti-foam agent.
Official answer: DSource: Official answer key, GATE 2022 BT (IIT Kharagpur)
P, sucrose: a disaccharide () that invertase splits into glucose and fructose. It supplies the cell's carbon and energy, so it is the carbon source: P-3.
Q, zinc chloride: supplies , a cofactor for many metalloenzymes (for example alcohol dehydrogenase and carbonic anhydrase). Cells need it only in micromolar amounts, so it is a trace element: Q-4.
R, ammonium sulphate: supplies . Cells build it into amino acids through glutamine synthetase and glutamate dehydrogenase, so it is the nitrogen source (it also supplies some sulphur): R-2.
S, silicone oil: polydimethylsiloxane has low surface tension and does not mix with water. It spreads over the films of foam bubbles and makes them burst, so it is added to aerated fermenters as an anti-foam agent: S-1.
The matching is P-3, Q-4, R-2, S-1, which is option (D).
Quick check by elimination: only (C) and (D) pair sucrose with 3 and silicone oil with 1. (C) makes the nitrogen source, but it contains no nitrogen, and it makes ammonium sulphate, a bulk salt, a trace element. So (C) is ruled out and (D) is the answer.
KEY IDEA
A fermentation medium has a job for each component. Read the chemical formula to find what each one can supply: a sugar gives carbon and energy, an ammonium salt gives nitrogen, a metal salt added in micromolar amounts gives a trace element (an enzyme cofactor), and a water-insoluble, low-surface-tension oil breaks foam.
WATCH OUT FOR
Picking (C) because zinc chloride and ammonium sulphate are both 'salts', and swapping their roles. contains no nitrogen, so it cannot be a nitrogen source. Ammonium sulphate is added in grams per litre as the main nitrogen supply, not in trace amounts.
From the GATE 2022 BT paper. Every question of this paper · Download the full paper · All 7 Upstream questions, with notes
