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GATE 2026 BT – Question 44

Fundamentals of Biological Engineering · Bioreaction Engineering: Batch, fed-batch and continuous processes, microbial and enzyme reactors, optimization and scale up · 2 marks · Multiple select

A microbial culture is being grown in a bioreactor with continuous aeration. The dissolved oxygen probe provided with the system shows a reading of zero. In this context, which of the following inferences is/are correct?

  1. The culture has died due to absence of oxygen
  2. The culture has run out of carbon source
  3. The culture growth becomes oxygen limited
  4. The culture growth is independent of dissolved oxygen

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Correct answer: (C) The culture growth becomes oxygen limited

Explanation

With continuous aeration, a dissolved oxygen of zero means that the cells use oxygen as fast as it is supplied, so oxygen is the limiting factor for growth. It does not show that the culture has died (the cells are consuming oxygen) or that the carbon source is used up (when it runs out the dissolved oxygen rises).