The GATE Grind

GATE 2025 ES – Question 44

Environmental Microbiology · Growth and Control of Microorganisms · 2 marks · Multiple select

Under substrate-unlimited conditions in Monod kinetics, which statements are correct?

  1. Growth is zero-order with respect to substrate concentration.
  2. Growth is first-order with respect to substrate concentration.
  3. Specific growth rate is half its maximum.
  4. Specific growth rate is approximately its maximum.

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Show answer and explanation

Correct answer: (A) Growth is zero-order with respect to substrate concentration.; (D) Specific growth rate is approximately its maximum.

Explanation

Monod kinetics gives $\mu=\mu_{max}S/(K_s+S)$. If substrate is abundant,$S\gg K_s$,the ratio approaches 1: $\mu\approx\mu_{max}$ and becomes insensitive to S, or zero-order with respect to substrate. Half-maximum growth occurs at $S=K_s$,not unlimited substrate. Select **A, D**.

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