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Bioreaction Engineering(44)Upstream and Downstream Processing(32)

Bioreaction Engineering

44 Questions

GATE→2026→Fundamentals of Biological Engineering→Bioreaction Engineering

Q1

NAT[1 Mark]

You are characterizing a new enzyme isolated and purified in the laboratory. If the maximum velocity of the enzyme is $1800~\mu\text{moles L}^{-1}~\text{min}^{-1}$ and the total concentration of the enzyme in the reaction mixture is $1.5~\mu\text{M}$ then the turnover number of the enzyme is $\text{s}^{-1}$. (answer in integer)

Explanation

GATE→2026→Fundamentals of Biological Engineering→Bioreaction Engineering

Q2

NAT[1 Mark]

You have purified an enzyme using a series of chromatographic methods. It was observed that a $10~\mu\text{g mL}^{-1}$ of this purified enzyme converted 10 mM substrate per hour at $25^{\circ}\text{C}$ and pH 7. Its specific activity is $\text{IU }\mu\text{g}^{-1}$. (rounded off to three decimal places)

Explanation

GATE→2026→Fundamentals of Biological Engineering→Bioreaction Engineering

Q3

MCQ[2 Marks]

By elemental analysis of a biomass sample, it was found that the cells in the given sample are composed of (by weight) C = 50%, H = 8%, O = 20%, N = 10% and ash content = 12%. Which of the following is the correct empirical formula of the ash-free cells, normalized with respect to Nitrogen?

(A)

$C_{5.8}H_{11.2}O_{1.7}N$

(B)

$C_{5.0}H_{10.2}O_{1.1}N$

(C)

$C_{6.8}H_{12.2}O_{2.1}N$

(D)

$C_{4.8}H_{9.2}O_{3.1}N$

Explanation

GATE→2026→Fundamentals of Biological Engineering→Bioreaction Engineering

Q4

MSQ[2 Marks]

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?

(A)

The culture has died due to absence of oxygen

(B)

The culture has run out of carbon source

(C)

The culture growth becomes oxygen limited

(D)

The culture growth is independent of dissolved oxygen

Explanation

GATE→2026→Fundamentals of Biological Engineering→Bioreaction Engineering

Q5

MSQ[2 Marks]

In an aerobic fermentation with air sparging, which of the following options can be used to increase the volumetric mass transfer coefficient for oxygen transfer?

(A)

Using pure oxygen in place of air

(B)

Increasing the volumetric flow rate of air

(C)

Reducing the bubble diameter

(D)

Decreasing the agitation rate

Explanation

GATE→2026→Fundamentals of Biological Engineering→Bioreaction Engineering

Q6

MSQ[2 Marks]

For an ideal plug flow reactor, which of the following statements is/are true?

(A)

It can be approximated by a large number of ideal continuous stirred tank reactors connected in series

(B)

It has significant back mixing

(C)

It has significant axial mixing

(D)

It has a uniform velocity profile across any cross section

Explanation

GATE→2026→Fundamentals of Biological Engineering→Bioreaction Engineering

Q7

NAT[2 Marks]

A microbial culture (following Monod model for growth) has a maximum specific growth rate of $0.1\text{ h}^{-1}$, Monod constant of $1\text{ mg L}^{-1}$ and endogenous decay rate of $0.1\text{ day}^{-1}$. At limiting substrate concentration of $23\text{ g L}^{-1}$, the net specific growth rate will be $\text{day}^{-1}$. (rounded off to one decimal place)

Explanation

GATE→2026→Fundamentals of Biological Engineering→Bioreaction Engineering

Q8

NAT[2 Marks]

A CSTR with a volume of $100\text{ m}^{3}$ is operated in cell recycle mode. At a volumetric flow rate of $10\text{ m}^{3}\text{day}^{-1}$ and effluent biomass of $20\text{ mg L}^{-1}$, the steady state biomass concentration is $200\text{ mg L}^{-1}$. The mean cell retention time in the reactor is days. (answer in integer)

Explanation

GATE→2026→Fundamentals of Biological Engineering→Bioreaction Engineering

Q9

NAT[2 Marks]

A substrate is consumed in a zero order reaction such that its concentration falls from $42\text{ g L}^{-1}$ to $14\text{ g L}^{-1}$ in 4 hours. The total time taken for complete utilization of substrate will be hours. (answer in integer)

Explanation

GATE→2026→Fundamentals of Biological Engineering→Bioreaction Engineering

Q10

NAT[2 Marks]

A microbe that follows Monod growth kinetics on a limiting substrate (maximum specific growth rate of $0.5\text{ h}^{-1}$ and Monod constant of $0.1\text{ mg L}^{-1}$ is cultivated in a continuous reactor for microbial growth (chemostat) with sterile feed. Given that the chemostat volume is 5 L and inlet concentration of limiting substrate is $10\text{ g L}^{-1}$, the minimum inlet feed flow rate for chemostat washout is $\text{h}^{-1}$. (rounded off to one decimal place)

Explanation

GATE→2026→Fundamentals of Biological Engineering→Bioreaction Engineering

Q11

NAT[2 Marks]

It is desired to cultivate 150 mg (dry weight) microbial cells with an empirical formula of $C_{5}H_{7}O_{2}N$. If the phosphorus requirement for the cells is 20% of the nitrogen requirement (on a weight/weight basis), the minimum amount of phosphorous required to be added to the cultivation medium is mg. (rounded off to one decimal place)

Explanation

GATE→2025→Fundamentals of Biological Engineering→Bioreaction Engineering

Q12

MSQ[1 Mark]

Which of the following compounds have the same degree of reduction per carbon-mole?

(A)

Glucose

(B)

Lactic acid

(C)

Acetic acid

(D)

Formic acid

Explanation

GATE→2025→Fundamentals of Biological Engineering→Bioreaction Engineering

Q13

NAT[1 Mark]

If the doubling time of a bacterial population is 3 hours, then its average specific growth rate during this period is $\text{h}^{-1}$. (Round off to two decimal places)

Explanation

GATE→2025→Fundamentals of Biological Engineering→Bioreaction Engineering

Q14

MCQ[2 Marks]

For a specific bioreactor configuration, the power requirement for a Rushton-turbine impeller agitating an unaerated Newtonian fluid in the turbulent regime will be

(A)

proportional to the stirring speed of the impeller

(B)

proportional to the square of the stirring speed of the impeller

(C)

proportional to the cube of the stirring speed of the impeller

(D)

inversely proportional of the stirring speed of the impeller

Explanation

GATE→2025→Fundamentals of Biological Engineering→Bioreaction Engineering

Q15

MSQ[2 Marks]

An enzyme immobilised in a porous spherical pellet, catalyses a strongly mass-transfer limited first-order reaction. The effectiveness factor for the immobilised enzyme reaction increases with the

(A)

decrease in the size of the pellet

(B)

increase in the pore diffusivity within the pellet

(C)

increase in the enzyme concentration within the pellet

(D)

decrease in the enzyme concentration within the pellet

Explanation

GATE→2025→Fundamentals of Biological Engineering→Bioreaction Engineering

Q16

NAT[2 Marks]

In a fermentation process, each mole of glucose is converted to biomass $(CH_{1.8}O_{0.5}N_{0.2})$, with a biomass yield coefficient of $0.4\text{ C-mol/C-mol}$, according to the unbalanced equation given below. $$C_{6}H_{12}O_{6}+NH_{3}+O_{2}\rightarrow CH_{1.8}O_{0.5}N_{0.2}+CO_{2}+H_{2}O$$ The moles of oxygen consumption per mole of glucose consumed during fermentation is (Round off to two decimal places)

Explanation

GATE→2025→Fundamentals of Biological Engineering→Bioreaction Engineering

Q17

NAT[2 Marks]

A 2 L chemostat is being operated at a flow rate of $0.8~\text{L/h}$ and sterile feed of $10~\text{g/L}$ substrate. The bacterial growth follows Monod kinetics at a maximum specific growth rate of $0.6~\text{h}^{-1}$ with a Monod constant of $0.5~\text{g/L}$ and a biomass yield coefficient of $0.4~\text{g/g}$. The exit biomass concentration is $\text{g/L}$ (Round off to one decimal place)

Explanation

GATE→2024→Fundamentals of Biological Engineering→Bioreaction Engineering

Q18

MCQ[1 Mark]

Which one of the following statements is correct about Reynolds Number ($N_{Re}$) in a stirred tank bioreactor?

(A)

$N_{Re}$ is independent of the viscosity of the medium

(B)

In laminar flow, mixing time increases with an increase in $N_{Re}$

(C)

$N_{Re}$ is inversely proportional to the impeller speed

(D)

In turbulent flow, mixing time is independent of $N_{Re}$ mixing

Explanation

GATE→2024→Fundamentals of Biological Engineering→Bioreaction Engineering

Q19

NAT[1 Mark]

The degree of reduction (reductance) for oxalic acid $(C_{2}H_{2}O_{4})$ is

Explanation

GATE→2024→Fundamentals of Biological Engineering→Bioreaction Engineering

Q20

NAT[1 Mark]

If the rate at which E. coli divides is $0.5\text{ h}^{-1}$, then its doubling time is h.

Explanation

GATE→2024→Fundamentals of Biological Engineering→Bioreaction Engineering

Q21

MSQ[2 Marks]

Which of the following factors can affect the growth of a microbial culture in a batch cultivation process?

(A)

pH of the medium

(B)

Osmolarity of the medium

(C)

Dissolved oxygen concentration

(D)

Vessel color (or similar)

Explanation

GATE→2024→Fundamentals of Biological Engineering→Bioreaction Engineering

Q22

MSQ[2 Marks]

Under complete cell washout condition of a chemostat with sterile feed, which of the following statements is/are correct?

(A)

Biomass concentration in the reactor is maximum

(B)

Substrate concentration in the exit stream is less than that in the inlet stream

(C)

Substrate concentration in the exit stream is equal to that in the inlet stream

(D)

Substrate concentration in the exit stream is zero

Explanation

GATE→2024→Fundamentals of Biological Engineering→Bioreaction Engineering

Q23

NAT[2 Marks]

Aspergillus niger is grown in a 10,000 L stirred batch bioreactor under aerated conditions to produce citric acid. At steady state oxygen transfer conditions, the specific oxygen uptake rate of the organism and the volumetric mass transfer coefficient are $1\times 10^{-4}$ g oxygen consumed s$^{-1}$ (per g biomass) and $60\text{ min}^{-1}$, respectively. If the oxygen solubility is $8\times 10^{-3}\text{ kg m}^{-3}$ under the operating conditions, based only on oxygen dynamics, the maximum possible cell concentration is $\text{kg m}^{-3}$ (Answer in integer).

Explanation

GATE→2024→Fundamentals of Biological Engineering→Bioreaction Engineering

Q24

NAT[2 Marks]

Ethanol is produced in a 10,000 L stirred bioreactor using an impeller of diameter 1 m. The density and viscosity of fermentation broth are $1000\text{ kg m}^{-3}$ and 1 cp, respectively. Using the data, the power required for the stirrer to operate at 300 rpm is kW (Answer in integer).

Explanation

GATE→2024→Fundamentals of Biological Engineering→Bioreaction Engineering

Q25

NAT[2 Marks]

E. coli is inoculated in a shake flask containing nutrient rich medium. The initial number of viable cells in the medium is $10^2$. After few hours, the number of viable cells is $10^6$. Assuming cell divides by binary fission, the number of generations that have taken place is (rounded off to the nearest integer).

Explanation

GATE→2024→Fundamentals of Biological Engineering→Bioreaction Engineering

Q26

NAT[2 Marks]

A fermentor is filled with medium at a rate of $1\text{ L min}^{-1}$. A leak develops at the bottom of the fermentor when the medium in the fermentor reaches 200 L. The rate of medium leakage is $2t\text{ L min}^{-1}$, where 't' is the time at which the leak begins. The volume of medium in the fermentor after 10 min of leakage is L (Answer in integer).

Explanation

GATE→2024→Fundamentals of Biological Engineering→Bioreaction Engineering

Q27

NAT[2 Marks]

A fed batch process is running at quasi-steady state with respect to substrate and biomass concentration. At 2 h, the culture volume is 500 L with a constant sterile inlet feed at $50\text{ L h}^{-1}$ of glucose. The culture kinetic parameters $\mu_{m}$ and $K_{S}$ are $0.2\text{ h}^{-1}$ and $0.1\text{ g L}^{-1}$, respectively. The substrate concentration in the reactor will be $\text{g L}^{-1}$ (rounded off to one decimal place).

Explanation

GATE→2024→Fundamentals of Biological Engineering→Bioreaction Engineering

Q28

NAT[2 Marks]

Consider scale-up of fungal fermentation from a 20 L model-type to 20,000 L prototype stirred tank reactor. The model-type and prototype have the same aspect ratio during scale-up. The impeller speed in the model-type is 500 rpm and the scale-up criterion is constant shear. The impeller speed in the prototype reactor will be rpm (Answer in integer).

Explanation

GATE→2023→Fundamentals of Biological Engineering→Bioreaction Engineering

Q29

NAT[2 Marks]

The following reaction represents biomass synthesis from hexadecane $$C_{16}H_{34}+12.5O_{2}+2.13NH_{3}\rightarrow10.6CH_{1.66}O_{0.27}N_{0.27}+5.37CO_{2}+11.4H_{2}O$$ where $CH_{1.66}O_{0.27}N_{0.27}$ represents the biomass. The value of respiratory quotient (rounded off to two decimal places) is

Explanation

GATE→2023→Fundamentals of Biological Engineering→Bioreaction Engineering

Q30

NAT[2 Marks]

Temperature of a reaction with an activation energy value of $15~\text{kcal.mol}^{-1}$ is increased from 300 K to 310 K. If the value of the ideal gas constant (R) is $1.9872~\text{cal.mol}^{-1}\text{K}^{-1}$, the ratio of the reaction rate constants $(k_{310}/k_{300})$ (rounded off to two decimal places) is

Explanation

GATE→2023→Fundamentals of Biological Engineering→Bioreaction Engineering

Q31

NAT[2 Marks]

E. coli is cultivated in a chemostat operated at a dilution rate of $0.2\text{ h}^{-1}$. The values of biomass yield due to oxygen consumption and the steady state biomass concentration are $0.2\text{ g.g}^{-1}$ and $10\text{ g.L}^{-1}$, respectively. The oxygen transfer rate (in $\text{g.L}^{-1}.\text{h}^{-1}$) is

Explanation

GATE→2023→Fundamentals of Biological Engineering→Bioreaction Engineering

Q32

NAT[2 Marks]

Chemostat with cell recycle schematic... If $\frac{X_{0}}{X_{1}}=1.5,\frac{F_{r}}{F_{0}}=0.7$ and $X_{1}$ is $7.3\text{ g.L}^{-1}$, the value of X (in $\text{g.L}^{-1}$, rounded off to one decimal place) is

Explanation

GATE→2022→Fundamentals of Biological Engineering→Bioreaction Engineering

Q33

MCQ[1 Mark]

The overall stoichiometry for an aerobic cell growth is $$3C_{6}H_{12}O_{6}+2.5NH_{3}+O_{2}\rightarrow1.5C_{a}H_{b}O_{c}N_{d}+3CO_{2}+5H_{2}O$$ What is the elemental composition formula of the biomass?

(A)

$C_{9}H_{18.2}O_{5}N_{1.667}$

(B)

$C_{9}H_{22.33}O_{6}N_{1.667}$

(C)

$C_{10}H_{18.2}O_{5}N_{1.667}$

(D)

$C_{10}H_{22.33}O_{6}N_{1.667}$

Explanation

GATE→2022→Fundamentals of Biological Engineering→Bioreaction Engineering

Q34

NAT[1 Mark]

A microorganism is grown in a batch culture using glucose as a carbon source. The apparent growth yield is $0.5\frac{\text{g biomass}}{\text{g substrate}}$. The initial concentrations of biomass and substrate are $2\text{ g L}^{-1}$ and $200\text{ g L}^{-1}$, respectively. Assuming that there is no endogenous metabolism, the maximum biomass concentration that can be achieved is $\text{g L}^{-1}$

Explanation

GATE→2022→Fundamentals of Biological Engineering→Bioreaction Engineering

Q35

NAT[1 Mark]

The degree of reduction of lactic acid $(C_{3}H_{6}O_{3})$ is

Explanation

GATE→2022→Fundamentals of Biological Engineering→Bioreaction Engineering

Q36

NAT[1 Mark]

The specific growth rate of a yeast having a doubling time of 0.693 h (rounded off to nearest integer) is $\text{h}^{-1}$

Explanation

GATE→2022→Fundamentals of Biological Engineering→Bioreaction Engineering

Q37

NAT[1 Mark]

A fermentation broth of density $1000~\text{kg m}^{-3}$ and viscosity $10^{-3}~\text{kg m}^{-1}\text{s}^{-1}$ is mixed in a 100 L fermenter using a 0.1 m diameter impeller, rotating at a speed of $2~\text{s}^{-1}$. The impeller Reynolds number is

Explanation

GATE→2022→Fundamentals of Biological Engineering→Bioreaction Engineering

Q38

MSQ[2 Marks]

Which of the following statements are CORRECT for an enzyme entrapped in a spherical particle?

(A)

Effectiveness factor is ratio of the reaction rate with diffusion-limitation to the reaction rate without diffusion-limitation

(B)

Internal diffusion is rate-limiting at low values of Thiele modulus

(C)

Effectiveness factor increases with decrease in Thiele modulus

(D)

Internal diffusion-limitation can be reduced by decreasing the size of the particle

Explanation

GATE→2022→Fundamentals of Biological Engineering→Bioreaction Engineering

Q39

NAT[2 Marks]

Figure below depicts simplified metabolic and transport reactions taking place in the production of B from A in a cell... Under pseudo-steady-state condition, the following reaction fluxes are available: $r_{3}=1$ and $r_{6}=1$. The transport flux of B, $r_{4}$, is

Explanation

GATE→2022→Fundamentals of Biological Engineering→Bioreaction Engineering

Q40

NAT[2 Marks]

The amount of biomass in a reactor at the end of the batch process is 50 g. Fed-batch operation is initiated by feeding the substrate solution at a constant rate of $1~\text{L h}^{-1}$. The concentration of substrate in the feed is $50~\text{g L}^{-1}$. The maximum biomass yield $(Y_{XS}^{M})$ is $0.4~\frac{\text{g substrate}}{\text{g biomass}}$? Wait, unit in text: 0.4 g substrate / g biomass or g biomass / g substrate. Assuming standard yield definition: $\Delta X = Y_{X/S} \times S_{fed} \times F \times \Delta t$. $50 + 0.4 \times 50 \times 1 \times 5 = 150 \text{ g}$.

Explanation

GATE→2022→Fundamentals of Biological Engineering→Bioreaction Engineering

Q41

NAT[2 Marks]

An enzyme catalyzes the conversion of substrate A into product B. The rate equation for this reaction is $$-r_{A}=\frac{C_{A}}{5+C_{A}}~\text{mol L}^{-1}\text{min}^{-1}$$ Substrate A at an initial concentration of $10~\text{mol L}^{-1}$ enters an ideal mixed flow reactor (MFR) at a flow rate of $10~\text{L min}^{-1}$. The volume of the MFR required for 50% conversion of substrate to product is L.

Explanation

GATE→2022→Fundamentals of Biological Engineering→Bioreaction Engineering

Q42

NAT[2 Marks]

Liquid-phase mass transfer coefficient $(k_{L})$ is measured in a stirred tank vessel using steady-state method by sparging air. Oxygen uptake by the microorganism is measured. The bulk concentration of $O_{2}$ is $10^{-4}~\text{mol L}^{-1}$. Solubility of $O_{2}$ in water at $25^{\circ}\text{C}$ is $10^{-3}~\text{mol L}^{-1}$. If the oxygen consumption rate is $9\times10^{-4}~\text{mol L}^{-1}\text{s}^{-1}$ and interfacial area is $100~\text{m}^{2}/\text{m}^{3}$, the value of $k_{L}$ is $\text{cm s}^{-1}$.

Explanation

GATE→2022→Fundamentals of Biological Engineering→Bioreaction Engineering

Q43

NAT[2 Marks]

Consider the growth of S. cerevisiae under aerobic condition in a bioreactor and the specific growth rate of yeast is $0.5~\text{h}^{-1}$. The overall reaction of the process is $$2C_{6}H_{12}O_{6}+0.2NH_{3}+10.35O_{2}\rightarrow CH_{1.8}O_{0.5}N_{0.2}+0.2C_{2}H_{6}O+10.6CO_{2}+10.8H_{2}O$$ The heat of combustion values for different compounds are tabulated. The specific rate of heat production (rounded off to nearest integer) is $\text{kJ mol}^{-1}\text{h}^{-1}$ (per mole of substrate or biomass basis as per standard stoichiometric enthalpy balance).

Explanation

GATE→2022→Fundamentals of Biological Engineering→Bioreaction Engineering

Q44

NAT[2 Marks]

A bacterial strain is grown in nutrient medium at $37^{\circ}\text{C}$ under aerobic conditions. The medium is inoculated with $10^{2}$ cells from a seed culture. If the number of cells in the culture is $10^{5}$ after 10 hours of growth, the doubling time of the strain (rounded off to nearest integer) is h.

Explanation

Upstream and Downstream Processing

32 Questions

GATE→2026→Fundamentals of Biological Engineering→Upstream and Downstream Processing

Q45

MCQ[1 Mark]

The transfer function of a Proportional-Integral (PI) controller $G_{C}(s)$ is given by $G_{C}(s)=K_{C}(1+\frac{1}{\tau_{I}s})$ where $K_{C}$ is the controller gain, $\tau_{I}$ is the controller integral time constant and s is the Laplace variable. The role of the integral component of the controller is to

(A)

integrate the difference between the process and manipulated variable

(B)

integrate the difference between the set point and disturbance variable

(C)

integrate the difference between the set point and the measured variable

(D)

integrate the difference between the input and output variable

Explanation

GATE→2026→Fundamentals of Biological Engineering→Upstream and Downstream Processing

Q46

MCQ[2 Marks]

In the open-loop process shown in the figure, the input $U(s)$, the transfer function $G_{p}(s)$ and the output $Y(s)$ are given in the Laplace domain in terms of the Laplace variable s. For this process, which of the following is true? (where M, $\tau_{p}$, $K_{P}$, are the magnitude of the input, the characteristic time and the gain for the process, respectively) $$U(s)=\frac{M}{s}, \quad G_{p}(s)=\frac{K_{p}}{\tau_{p}s+1}$$

(A)

$y(t)=K_{p}(1-e^{-t/\tau_{p}})$

(B)

$y(t)=MK_{p}(1-e^{-t/\tau_{p}})$

(C)

$y(t)=K_{p}(M-e^{-t/\tau_{p}})$

(D)

$y(t)=K_{p}(1-Me^{-t/\tau_{p}})$

Explanation

GATE→2026→Fundamentals of Biological Engineering→Upstream and Downstream Processing

Q47

MSQ[2 Marks]

For a Newtonian fluid, a plot of shear stress (on Y axis) against shear rate (on X axis) will result in a straight line

(A)

parallel to the X axis

(B)

parallel to the Y axis

(C)

with a negative slope

(D)

with a positive slope

Explanation

GATE→2026→Fundamentals of Biological Engineering→Upstream and Downstream Processing

Q48

MSQ[2 Marks]

For a liquid flowing in a circular cross section pipe, the transition from laminar to turbulent flow will NOT depend on which of the following factor(s)?

(A)

The diameter of the pipe

(B)

The length of the pipe

(C)

The linear velocity of the liquid

(D)

The viscosity of the liquid

Explanation

GATE→2026→Fundamentals of Biological Engineering→Upstream and Downstream Processing

Q49

NAT[2 Marks]

A heat exchanger during operation in a bioprocess has a steady temperature of $90^{\circ}\text{C}$. After completion of its operation, it was shut down and it was observed that the rate of decrease of temperature at any time was directly proportional to the difference $T(t)-30^{\circ}\text{C}$, where $T(t)$ denotes temperature at time t. It was observed that it took 30 min for the temperature to drop to $70^{\circ}\text{C}$. The temperature after 51.5 min will be $^{\circ}\text{C}$. (rounded off to the nearest integer)

Explanation

GATE→2026→Fundamentals of Biological Engineering→Upstream and Downstream Processing

Q50

NAT[2 Marks]

A batch sterilizer is being operated at $121^{\circ}\text{C}$ for sterilizing a medium containing microbial cells. Assume that the thermal deactivation of cells is a first order process with a death rate constant of $0.69\text{ min}^{-1}$ at $121^{\circ}\text{C}$. If the initial concentration of microbes in the medium is $10^{10}\text{ cells m}^{-3}$, the time taken to reduce the microbial load to a final concentration of $10\text{ cells m}^{-3}$ is min. (rounded off to the nearest integer)

Explanation

GATE→2026→Fundamentals of Biological Engineering→Upstream and Downstream Processing

Q51

NAT[2 Marks]

A packed bed bioreactor with length 1 m and inside diameter 10 cm has liquid flowing at an interstitial velocity of $1~\text{cm s}^{-1}$. Given a volumetric flow rate of $0.025~\text{L s}^{-1}$, the void fraction of the packed bed is (rounded off to two decimal places)

Explanation

GATE→2025→Fundamentals of Biological Engineering→Upstream and Downstream Processing

Q52

MSQ[1 Mark]

Which of the following separation processes is/are based on molecular size?

(A)

Size-exclusion chromatography

(B)

Ion exchange chromatography

(C)

Membrane ultrafiltration

(D)

Ultracentrifugation

Explanation

GATE→2025→Fundamentals of Biological Engineering→Upstream and Downstream Processing

Q53

MSQ[1 Mark]

Which of the following fluids exhibit(s) non-Newtonian behaviour at $25^{\circ}\text{C}$?

(A)

Toothpaste

(B)

Mercury

(C)

Brine

(D)

Blood plasma

Explanation

GATE→2025→Fundamentals of Biological Engineering→Upstream and Downstream Processing

Q54

MSQ[1 Mark]

A recombinant protein is secreted extracellularly in soluble form by an E. coli culture. Which of the following downstream processes is/are involved in the purification of the extracellular secreted protein?

(A)

Cell disruption

(B)

Membrane ultrafiltration

(C)

Solubilisation of inclusion bodies

(D)

Liquid chromatography

Explanation

GATE→2025→Fundamentals of Biological Engineering→Upstream and Downstream Processing

Q55

NAT[1 Mark]

For a mechanically reversible isobaric process taking place in a closed system involving 5 moles of an ideal gas, the temperature increases from an initial value of 300 K to a final value of 450 K. If the specific heat capacity at constant volume $(C_{v})$ is given as $12.5~\text{J mol}^{-1}\text{K}^{-1}$ and gas constant is $8.314~\text{J mol}^{-1}\text{K}^{-1}$, the amount of heat transferred to the system will be J. (Round off to the nearest integer)

Explanation

GATE→2025→Fundamentals of Biological Engineering→Upstream and Downstream Processing

Q56

MCQ[2 Marks]

A thermometer measuring body temperature follows a first-order response with a time constant of 40 seconds. The instrument will reach 95% of its steady-state output at seconds. (Round off to the nearest integer)

(A)

60

(B)

80

(C)

120

(D)

160

Explanation

GATE→2025→Fundamentals of Biological Engineering→Upstream and Downstream Processing

Q57

MCQ[2 Marks]

The output $y(t)$ of a first-order process is governed by the following differential equation $$\tau_{p}\frac{dy}{dt}+y=K_{p}f(t)$$ where $\tau_{p}$ is a non-zero time constant, $K_{p}$ is the gain and $f(t)$ is the input with $f(0)=0$. Assume $y(0)=0$. The transfer function for this process is (consider s as the independent variable in the Laplace domain)

(A)

$\frac{K_{p}}{\tau_{p}s+1}$

(B)

$\frac{\tau_{p}}{K_{p}s+1}$

(C)

$\frac{\tau_{p}}{K_{p}(s+1)}$

(D)

$\frac{K_{p}}{\tau_{p}(s+1)}$

Explanation

GATE→2025→Fundamentals of Biological Engineering→Upstream and Downstream Processing

Q58

NAT[2 Marks]

A binary mixture of benzene and toluene under vapour-liquid equilibrium at $80^{\circ}\text{C}$ follows ideal Raoult's law. At this condition, the saturation pressures of benzene and toluene are 101 kPa and 40 kPa, respectively. If the mole fraction of benzene in the liquid phase is 0.6, the corresponding mole fraction of benzene in the vapour phase will be (Round off to two decimal places)

Explanation

GATE→2025→Fundamentals of Biological Engineering→Upstream and Downstream Processing

Q59

NAT[2 Marks]

A hot, freshly-sterilised fermentation medium is cooled in a double-pipe heat-exchanger. The medium enters the inner pipe of the exchanger at $95^{\circ}\text{C}$ and leaves the exchanger at $40^{\circ}\text{C}$. Cooling water, flowing counter-currently to the medium, enters the annulus of the exchanger at $15^{\circ}\text{C}$ and leaves the exchanger at $45^{\circ}\text{C}$. The overall heat transfer coefficient is 1350~\text{W m}^{-2}^{\circ}\text{C}^{-1}. The rate of heat transfer per unit area will be $\text{W/m}^{2}$. (Round off to the nearest integer)

Explanation

GATE→2024→Fundamentals of Biological Engineering→Upstream and Downstream Processing

Q60

MCQ[1 Mark]

In adsorption chromatography, the adsorption of uncharged solute molecules onto a silica-based stationary phase is by

(A)

covalent bonds

(B)

electrostatic interactions

(C)

ionic bonds

(D)

van der Waals forces

Explanation

GATE→2024→Fundamentals of Biological Engineering→Upstream and Downstream Processing

Q61

MCQ[1 Mark]

The transfer function of a process is $G(s)=\frac{K_{p}}{\tau_{p}s+1},$ where $K_{p}$ is the gain and $\tau_{p}$ is the time constant. This is a

(A)

first order process

(B)

multi-capacity

(C)

purely capacitive

(D)

second order

Explanation

GATE→2024→Fundamentals of Biological Engineering→Upstream and Downstream Processing

Q62

MCQ[1 Mark]

Which one of the following statements is correct in the context of thermodynamics?

(A)

In a closed system, neither mass nor energy is transferred across the system boundary

(B)

In a closed system, both mass and energy can be transferred across the system boundary

(C)

The total energy of the system is the sum of kinetic and potential energies

(D)

In a closed system, only energy can be transferred across the system boundary and not mass

Explanation

GATE→2024→Fundamentals of Biological Engineering→Upstream and Downstream Processing

Q63

NAT[1 Mark]

The decimal reduction time of a microbe during sterilization at $120^{\circ}\text{C}$ with a first order thermal death rate constant of $1\text{ min}^{-1}$ will be min (rounded off to 1 decimal place).

Explanation

GATE→2024→Fundamentals of Biological Engineering→Upstream and Downstream Processing

Q64

NAT[2 Marks]

Fermentation medium is cooled from $121^{\circ}\text{C}$ to $30^{\circ}\text{C}$ in a double pipe heat exchanger. If cold water is flowing in the counter-current direction and is heated from $10^{\circ}\text{C}$ to $70^{\circ}\text{C}$, then the Log-Mean Temperature Difference (LMTD) is $^{\circ}\text{C}$ (rounded off to the nearest integer).

Explanation

GATE→2023→Fundamentals of Biological Engineering→Upstream and Downstream Processing

Q65

NAT[2 Marks]

Aqueous two-phase extraction is used to recover $\alpha$-amylase from a solution. A polypropylene glycol-dextran mixture is added and the solution separates into upper and lower phases. The partition coefficient is 4.0 and the ratio of upper to lower phase volume is 5.0. The enzyme recovery or yield (in percentage, rounded off to the nearest integer) is

Explanation

GATE→2023→Fundamentals of Biological Engineering→Upstream and Downstream Processing

Q66

NAT[2 Marks]

E. coli cultivated at 298 K uptakes an uncharged compound (A) by passive diffusion. The intracellular and extracellular concentrations of A are 0.001 M and 0.1 M, respectively. If the value of the ideal gas constant R is $1.9872\text{ cal.mol}^{-1}\text{K}^{-1}$, the free-energy change (in $\text{kcal.mol}^{-1}$) for this passive diffusion of A (rounded off to two decimal places) is

Explanation

GATE→2023→Fundamentals of Biological Engineering→Upstream and Downstream Processing

Q67

NAT[2 Marks]

The values of the consistency index 'K' and the flow behavior index 'n' of a dilatant fluid are 0.415 (in CGS units) and 1.23, respectively. The value of the apparent viscosity (in $\text{g.cm}^{-1}.\text{s}^{-1}$) of this fluid at a shear rate of $60\text{s}^{-1}$ (rounded off to the nearest integer) is

Explanation

GATE→2023→Fundamentals of Biological Engineering→Upstream and Downstream Processing

Q68

NAT[2 Marks]

An evaporator is insulated using glass wool material of 0.15 m thickness. The inner most surface and the outer surface of the insulation are at $700^{\circ}\text{C}$ and $80^{\circ}\text{C}$, respectively. The mean thermal conductivity of the glass wool under these conditions is $0.29\text{ W.m}^{-1}\text{K}^{-1}$. The rate of heat loss (in W) through $1.2~\text{m}^{2}$ of the evaporator wall surface (rounded off to the nearest integer) is

Explanation

GATE→2023→Fundamentals of Biological Engineering→Upstream and Downstream Processing

Q69

NAT[2 Marks]

A proportional controller is used to control the temperature of an autoclave from $60^{\circ}\text{C}$ to $130^{\circ}\text{C}$. If the proportional band setting of the controller is 25%, the proportional gain value is

Explanation

GATE→2022→Fundamentals of Biological Engineering→Upstream and Downstream Processing

Q70

MCQ[1 Mark]

For a double-pipe heat exchanger, the inside and outside heat transfer coefficients are 100 and 200 W $m^{-2}K^{-1}$, respectively. The thickness and thermal conductivity of the thin-walled inner pipe are 1 cm and 10 $W~m^{-1}K^{-1}$, respectively. The value of the overall heat transfer coefficient is $W~m^{-2}K^{-1}$

(A)

0.016

(B)

42.5

(C)

62.5

(D)

310

Explanation

GATE→2022→Fundamentals of Biological Engineering→Upstream and Downstream Processing

Q71

MCQ[1 Mark]

Match the media component (Column I) with its role (Column II). **Column I** P. Sucrose Q. Zinc chloride R. Ammonium sulphate S. Silicone oil **Column II** 1. Anti-foam agent 2. Nitrogen source 3. Carbon source 4. Trace element

(A)

P-1, Q-2, R-3, S-4

(B)

P-2, Q-1, R-3, S-4

(C)

P-3, Q-2, R-4, S-1

(D)

P-3, Q-4, R-2, S-1

Explanation

GATE→2022→Fundamentals of Biological Engineering→Upstream and Downstream Processing

Q72

NAT[1 Mark]

For a pure species, the slope of the melting line $\frac{dP}{dT}$ at $-2^{\circ}\text{C}$ is $-5.0665\times 10^{6}~\text{Pa K}^{-1}$. The difference between the molar volumes of the liquid and solid phase at $-2^{\circ}\text{C}$ is $-4.5\times 10^{-6}~\text{m}^{3}\text{mol}^{-1}$. The value of the latent heat of fusion (rounded off to nearest integer) is $J~mol^{-1}$

Explanation

GATE→2022→Fundamentals of Biological Engineering→Upstream and Downstream Processing

Q73

MCQ[2 Marks]

Match the stationary phase (Column I) with its corresponding chromatography technique (Column II). **Column I** P. Protein A Q. Sephadex R. Phenylsepharose S. Diethylaminoethyl cellulose **Column II** 1. Size exclusion chromatography 2. Ion-exchange chromatography 3. Affinity chromatography 4. Hydrophobic interaction chromatography

(A)

P-1, Q-4, R-2, S-3

(B)

P-3, Q-1, R-4, S-2

(C)

P-3, Q-4, R-2, S-1

(D)

P-4, Q-1, R-3, S-2

Explanation

GATE→2022→Fundamentals of Biological Engineering→Upstream and Downstream Processing

Q74

MCQ[2 Marks]

Which of the following statements are CORRECT for a controller? P. In a proportional controller, a control action is proportional to the error Q. In an integral controller, a control action is proportional to the derivative of the error R. There is no "offset" in the response of the closed-loop first-order process with a proportional controller S. There is no "offset" in the response of the closed-loop first-order process with a proportional-integral controller

(A)

P and Q only

(B)

P and R only

(C)

P and S only

(D)

Q and S only

Explanation

GATE→2022→Fundamentals of Biological Engineering→Upstream and Downstream Processing

Q75

NAT[2 Marks]

Consider a piston-cylinder assembly... The cylinder contains 1 mole of an ideal gas at 300 K and the piston is held initially at the position $z_{1}$ using a stopper. After the stopper is removed, the piston suddenly rises against atmospheric pressure $(1.013\times 10^{5}~\text{Pa})$ to the new position $z_{2}$ where it is held by another stopper. The heat capacity $(C_{v})$ of the gas is $12.5~\text{J mol}^{-1}\text{K}^{-1}$. The cross-sectional area of the cylinder is $10^{-3}~\text{m}^{2}$. If $z_{2}-z_{1}=1$ m, the final temperature of the gas (rounded off to nearest integer) is K.

Explanation

GATE→2022→Fundamentals of Biological Engineering→Upstream and Downstream Processing

Q76

NAT[2 Marks]

A pilot sterilization was carried out in a vessel containing $100~\text{m}^{3}$ medium with an initial spore concentration of $10^{8}$ spores/ml. The accepted level of contamination after sterilization is 1 spore in the entire vessel. The specific death rate constant for the spore is $2~\text{min}^{-1}$ at $121^{\circ}\text{C}$. Assuming no death takes place during the heating and cooling cycles, the holding time at $121^{\circ}\text{C}$ (rounded off to nearest integer) is min.

Explanation