GATE Environmental Microbiology: Growth and Control of Microorganisms – Previous Year Questions

6 GATE previous year questions on Growth and Control of Microorganisms (Environmental Microbiology, Environmental Science and Engineering) with answers and explanations, from every paper.

1. GATE 2021 ES Q34 (1 mark, Numerical answer) – A culture grows from 5×10⁴ to 1280×10⁴ cells/mL by binary fission with no deaths. Find number of generations as an integer.
2. GATE 2022 ES Q38 (2 marks, Multiple choice) – For exponential microbial growth with specific rate μ, find doubling time t d.
3. GATE 2024 ES Q44 (2 marks, Multiple select) – Which disinfection statements are correct?
4. GATE 2025 ES Q44 (2 marks, Multiple select) – Under substrate-unlimited conditions in Monod kinetics, which statements are correct?
5. GATE 2026 ES Q53 (2 marks, Numerical answer) – A batch culture starts with 2 cells. Its first hour is a lag phase without multiplication; subsequently the cells grow exponentially with a one-hour…
6. GATE 2026 ES Q54 (2 marks, Numerical answer) – At a fixed temperature, a thermal treatment gives a 2-log₁₀ reduction of non-thermotolerant pathogenic microorganisms in 20 minutes. Under the same…