# Enzyme Technology Questions and Answers – Immobilized Enzymes – Enzyme Reactors – 1

This set of Enzyme Technology Multiple Choice Questions & Answers (MCQs) focuses on “Immobilized Enzymes – Enzyme Reactors – 1”.

1. A vessel or series of vessels which is used to perform the desired conversion by enzymic means is referred to as ______________
a) centrifuge
b) entrapment
c) biosensors
d) enzyme reactors

Explanation: A vessel or series of vessels which is used to perform the desired conversion by enzymic means is referred to as enzyme reactors. Centrifuge is a vessel used for centrifugation which separates on the basis of the particle size and density difference between the liquid and solid phases. Entrapment is an immobilization method which entraps enzyme in a confined space. Biosensors are analytical devices which converts a biological response into an electrical signal.

2. In which of the enzyme reactors, the enzyme is held within membrane tubes allowing the substrates to diffuse in and the products to diffuse out?
a) Batch membrane reactors
b) Continuous Stirred tank batch reactors
c) Continuous flow membrane reactor
d) Packed bed reactors

Explanation: Batch membrane reactors are those in which the enzyme is held within membrane tubes allowing the substrates to diffuse in and the products to diffuse out. Continuous flow membrane reactor is continuous version of batch membrane reactors. Continuous Stirred tank batch reactors are continuous version of batch stirred tank reactors. Packed bed reactors are those in which there is tank containing a settled bed of immobilised enzyme particles.

3. What does the diagram below represent?

a) Stirred tank batch reactors
b) Continuous Stirred tank batch reactors
c) Batch membrane reactor
d) Continuous flow membrane reactor

Explanation: The above diagram represents a reactor wherein the products are taken out in batches. This type of reactors contains a tank with stirrer for proper mixing between enzyme and substrate and giving products. This kind of reactor is stirred tank batch reactors (STRs). In STRs, enzymes and substrates have identical residence times within the reactor. The operating costs of batch reactors are higher than for continuous processes due to the necessity for the reactors to be emptied and refilled both regularly and often.

4. Which kind of reactor is represented in the following diagram?

a) Continuous flow membrane reactor
b) Continuous Stirred tank batch reactors
c) Stirred tank batch reactors
d) Fluidized bed reactor

Explanation: In the diagram above, it represents a stirred tank reactor with continuous flow of substrate into the reactor and product also is taken out continuously. These reactors consist of heating or cooling coils and baffles too which helps increasing stirring efficiency. It is basically a batch stirred tank reactor running in continuous mode.

5. What does the following equation represent?
$$\frac{V_{max}}{Vol_s} t=[S]_0 X-K_m ln⁡(1-X)$$
a) Miachelis Menten kinetics equation for enzymes
b) Miachelis Menten kinetics equation for immobilized enzymes
c) Miachelis Menten kinetics equation for stirred tank batch reactors
d) Miachelis Menten kinetics equation for non-competitive inhibition

Explanation: The expected productivity of a batch reactor may be calculated by, assuming the validity of the non -reversible Miachelis -Menten reaction scheme with no diffusional control, inhibition or denaturation. The rate of reaction may be expressed in terms of the volume of substrate solution within the reactor and the time as follows:
$$\frac{V_{max}}{Vol_s} t=[S]_0 X-K_m ln⁡(1-X)$$ where,
Vmax = Maximum rate of reaction, Vols = Volume of substrate solution, t = Time, Km = Miachelis Menten constant, S0 = Initial substrate concentration and X = Fractional conversation = 1 – S/S0.

6. Which of these is a disadvantage of membrane reactors?
a) Membranes need to be replaced at regular intervals
b) These may be used in either batch or continuous mode
c) These reactors allow easy removal of enzyme from the product
d) These reactors avoid the costs and problems associated with other methods of immobilization

Explanation: Advantages of membrane reactors are as follows:
* These may be used in either batch or continuous mode.
* These reactors allow easy removal of enzyme from the product.
* These reactors avoid the costs and problems associated with other methods of immobilization.
Membrane reactor system may be established. Hence, they may be used for production of enzymes on small scale, especially where multienzyme pathway is involved or regeneration of co-enzyme is needed. The cost of the membranes and their replacement at regular intervals are the major disadvantages of membrane reactor.

7. ____________ is one which expresses the efficiency with which the energy dissipated in producing the fluid flow is used to transport material (and heat) to the catalytic surface.
a) Normalized time
b) Le Goff number
c) Reynolds number
d) Fractional conversion

Explanation: Le Goff number is one which expresses the efficiency with which the energy dissipated in producing the fluid flow is used to transport material (and heat) to the catalytic surface. Fractional conversion is given by X = 1 – S/S0. The normalized time is relative to the time that would be required to convert all the substrate if the enzyme acted at Vmax throughout, the actual time for complete conversion. Reynolds number relates to inertial force due to flow of solution to the viscous force resisting that flow.

8. Packed bed reactor is not referred to as plug flow reactor.
a) True
b) False

Explanation: The above statement is false. Packed bed reactor (PBR) is type enzyme reactor which contains a settled bed of immobilised enzyme particles. PBR is also called plug flow reactor because the material in the reactor flows through it like a plug.

Sanfoundry Global Education & Learning Series – Enzyme Technology.

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