GATE BT topic:bioreactor-engineering PYQs & Answers — Page 3

Questions 21–30 of 35. Imported answers require independent review unless marked reviewed.

A batch reactor is inoculated with 1 g/L biomass. Under these conditions, cells exhibit a lag phase of 30 min. If the specific growth rate in the log phase is 0.00417 min⁻¹, the time taken for the biomass to increase to 8 g/L is ____________ min (round off to 2 decimal places).

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Growth of an organism on glucose in a chemostat is characterized by Monod model with specific growth rate = 0.45 h⁻¹ and Kₛ = 0.5 g/L. Biomass from the substrate is generated as Yₓₛ = 0.4 g/g. The chemostat volume is 0.9 L and media is fed at 1 L/h and contains 20 g/L of glucose. At steady state, the concentration of biomass in the chemostat is ______________ g/L.

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Which one of the following can NOT be a limiting substrate if Monod’s growth kinetics is applicable?

Your answerChoose one option.

Extracellular carbon source

Extracellular nitrogen source

Dissolved oxygen

Intracellular carbon source

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Which one of the following is catabolized during endogenous metabolism in a batch bacterial culture?

Your answerChoose one option.

internal reserves

extracellular substrates

extracellular products

toxic substrates

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Which of the following factors can influence the lag phase of a microbial culture in a batch fermenter?

P. Inoculum size Q. Inoculum age R. Medium composition

Your answerChoose one option.

P and Q only

Q and R only

P and R only

P, Q and R

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Which of the following statements is ALWAYS CORRECT about an ideal chemostat? P. Substrate concentration inside the chemostat is equal to that in the exit stream Q. Optimal dilution rate is lower than critical dilution rate R. Biomass concentration increases with increase in dilution rate S. Cell recirculation facilitates operation beyond critical dilution rate

Your answerChoose one option.

P and Q only

P, R and S only

P and S only

P, Q and S only

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Phenolic wastewater discharged from an industry was treated with Pseudomonas sp. in an aerobic bioreactor. The influent and effluent concentrations of phenol were 10,000 and 10 ppm, respectively. The inlet feed rate of wastewater was 80 L h⁻¹. The kinetic properties of the organism are as follows: Maximum specific growth rate (μₘ) = 1 h⁻¹ Saturation constant (Kₛ) = 100 mg L⁻¹ Cell death rate (k_d) = 0.01 h⁻¹ Assuming that the bioreactor operates under ‘chemostat’ mode, the working volume required for this process is ______ L (rounded off to the nearest integer).

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The dimensions and operating condition of a lab-scale fermentor are as follows: Volume = 1 L Diameter = 20 cm Agitator speed = 600 rpm Ratio of impeller diameter to fermentor diameter = 0.3 This fermentor needs to be scaled up to 8,000 L for a large scale industrial application. If the scale-up is based on constant impeller tip speed, the speed of the agitator in the larger reactor is ______ rpm. Assume that the scale-up factor is the cube root of the ratio of fermentor volumes.

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Which one of the following bioreactor configurations is the basis for a trickling biological filter?

Your answerChoose one option.

Stirred tank

Packed bed

Air lift

Fluidized bed

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In a chemostat, the feed flow rate and culture volume are 100 ml/h and 1.0 L, respectively. With glucose as substrate, the values of

and

are 0.2 h⁻¹ and 1 g/L, respectively. For a glucose concentration of 10 g/L in the feed, the effluent substrate concentration (in g/L) is

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GATE BT topic:bioreactor-engineering PYQs

Question 45

Question 49

Question 15

Question 17

Question 40

Question 43

Question 52

Question 55

Question 13

Question 47