This set of Bioseparation Technology Multiple Choice Questions & Answers (MCQs) focuses on “Cell Disruption using Bead Mill”.

1. What is the principle of cell disruption using bead mill?

a) Grinding action of rolling beads

b) Heat generated by the mill

c) Pressing of cells against the bead

d) Vessel of mill

View Answer

Explanation: The grinding action of rolling beads leads to cell disruption using rolling beads and the impact of cascading beads breaks the cell. When the beads press against the cell along with the cascading beads, the cells are grinded resulting in the disruption and the cell components along with the desired product are brought into the fermentation broth for further purification.

2. What is the major component of the bead mill equipment?

a) Tubular vessel made of plastic

b) Tubular vessel made of metal or glass

c) Circular vessel made of metal or glass

d) Circular vessel made of plastic

View Answer

Explanation: The bead mill consists of tubular vessel which is made up of either metal or glass. The vessel contains the cell suspension along with the beads and the vessel is rotated about its axis as a result the beads roll from one direction to another leading to grinding of cells.

3. What is the cause of cascading back of beads?

a) Low rotation speed of tubular vessel

b) High Speed of beads in the vessel

c) High rotation speed of tubular vessel

d) Low speed of beads in the vessel

View Answer

Explanation: The high rotation speed of the tubular vessel allows some of the beads to move up along with the curved wall of the vessel and these beads cascade back on the mass of the beads and cells which leads to grinding of the cells from all the direction and finally the cells get disrupted.

4. Which temperature is suitable for processing of thermolabile materials?

a) High temperature

b) Moderate temperature

c) 100°C

d) Low temperature

View Answer

Explanation: The thermolabile materials can be disrupted and processed at low temperature maintained in the vessel. The low temperature can be maintained by using liquid nitrogen in the tubular vessel during the grinding process. Since the milling process releases more heat which will be harmful for the cell disruption of thermolabile materials as they may be completely denatured therefore use of liquid nitrogen can make the moderate environment within the vessel.

5. What terminology is given to low temperature treatment in bead milling?

a) Cryogenic bead milling

b) Cryptogenic

c) Cryopreservation

d) Cryotherapy

View Answer

Explanation: The term cryogenic means maintaining low temperature during the production process depending on the behaviour of the material.

6. Which mode of operation is suitable for disruption of yeast cells in bead milling?

a) Continuous

b) Batch or continuous

c) Batch

d) Fed batch

View Answer

Explanation: The bead mill operates at either batch mode or continuous mode depending on the amount of cells suspension. Small scale unit can be operated using continuous mode and it can disrupt some kg of yeast cells at hourly basis.

7. Cell disruption does not involve particle size reduction and do not have particle similarity in grinding.

a) True

b) False

View Answer

Explanation: Cell disruption involves the size reduction of particles during the grinding process using bead mills. The beads crush the particles which lead to breaking of each particle into smaller particle this shows reduction in size, ultimately the particles get disrupted and the desired product gets suspended in the cell suspension.

8. Which law is associated with the grinding of particles in bead mills?

a) Fick’s law

b) Netwon’s law

c) Kick’s law

d) Law of thermodynamics

View Answer

Explanation: The Kick’s law is associated with the grinding of particles in the bead mill. It states that the amount of energy required for the reduction of size of particle is directly proportional to the size reduction ratio.

9. What is the equation for Kick’s law of grinding?

a) –\(\frac{dE}{dr}\) = \(\frac{K_K f_c}{r}\)

b) \(\frac{dE}{dr}\) = –\(\frac{K_K f_c}{r}\)

c) \(\frac{dE}{dr}\) = \(\frac{f_c}{rK_K}\)

d) \(\frac{dE}{dr}\) = \(\frac{K_K f_c}{r}\)

View Answer

Explanation: \(\frac{dE}{dr}\) = –\(\frac{K_K f_c}{r}\) is the equation of Kick’s law of grinding where, r is the radius of particle, E is the energy, K

_{K}is the Kick’s coefficient, f

_{c}is the crushing strength of the beads in the bead mill.

10. Kick’s coefficient is dependent on ___________

a) Equipment and operating conditions

b) Type of equipment

c) Type of operation

d) Operating conditions

View Answer

Explanation: Kick’s coefficient is dependent on the equipment and the operating conditions. The type of equipment is an important factor for the reduction of size of the desired particle; the operating conditions play a vital role in cell disruption. Depending on the material being crushed, the operating condition is applied. For example, thermolabile materials are given cryogenic environment for disruption.

11. The integrating equation for size reduction from r_{1} to r_{2} is __________

a) E = f_{c} ln(\(\frac{r_1}{r_2}\))

b) E = K_{K} f_{c} ln(\(\frac{r_1}{r_2}\))

c) E = K_{K} ln(\(\frac{r_1}{r_2}\))

d) E = ln(\(\frac{r_1}{r_2}\))

View Answer

Explanation: The integrating equation for size reduction from r

_{1}to r

_{2}is E = K

_{K}f

_{c}ln(\(\frac{r_1}{r_2}\)). The other equations do not have sufficient parameters for the use of Kick’s law since Kick’s law is the ratio of size reduction of particle with respect to the crushing strength of the bead and the kick’s coefficient.

12. What is the other law of grinding apart from Kick’s law?

a) Fick’s law

b) Netwon’s law

c) Rittinger’s law

d) Kick’s law

View Answer

Explanation: The other law of grinding apart from Kick’s law is Rittinger’s law. It states that the amount of energy which is needed for the reduction of size is directly proportional to the change in the surface area of the particle.

13. What is the equation for Rittinger’s law?

a) \(\frac{dE}{dr}\) = \(\frac{K_K f_c}{r}\)

b) –\(\frac{dE}{dr}\) = \(\frac{K_K f_c}{r}\)

c) \(\frac{dE}{dr}\) = –\(\frac{K_K f_c}{r}\)

d) \(\frac{dE}{dr}\) = \(\frac{K_R f_c}{r^2}\)

View Answer

Explanation: The equation for Rittinger’s law is \(\frac{dE}{dr}\) = \(\frac{K_R f_c}{r^2}\) where, K

_{R}is the Rittinger’s coefficent. \(\frac{dE}{dr}\) = \(\frac{K_K f_c}{r}\) is Kick’s law equation. –\(\frac{dE}{dr}\) = \(\frac{K_K f_c}{r}\), \(\frac{dE}{dr}\) = –\(\frac{K_K f_c}{r}\) are the incorrect form of the equation.

14. The integrating equation for size reduction using Rittinger’s law from r_{1} to r_{2} is ______

a) E = K_{R}f_{c} ln(\(\frac{1}{r_1} – \frac{1}{r_2}\))

b) E = K_{K} ln(\(\frac{r_1}{r_2}\))

c) E = K_{K}f_{c} ln(\(\frac{r_1}{r_2}\))

d) E = f_{c} ln(\(\frac{1}{r_1} – \frac{1}{r_2}\))

View Answer

Explanation: The integrating equation for size reduction using Rittinger’s law from r

_{1}to r

_{2}is E = K

_{R}f

_{c}ln(\(\frac{1}{r_1} – \frac{1}{r_2}\)). E = K

_{R}f

_{c}ln(\(\frac{1}{r_1} – \frac{1}{r_2})\) is the integrating equation for Kick’s law. The other two equations are inappropriate form of equation which does not fulfil the requirements of the coefficients and the crushing strength of the material used for crushing the cells.

15. Calculate the requirement of energy to reduce the average radius from 9 microns to 6 micron for the mass of *Penicillium* in the bead mill. The average initial radius are 9, 8, 7, 6, 5 and the final radius are 9, 8, 7, 6, 5, 4 microns and the energy required are 2.5, 3.8, 4.5, 7.9, 15.4, 21.4 Joules respectively. Given : K_{R}f_{c} = 180 × 10^{-6} J – m.

a) 10.02J

b) 16J

c) 30.02J

d) 20.02J

View Answer

Explanation: The energy required for the size reduction will be dependent on Rittinger’s law as it gives the idea of energy which is required for crushing the particle is directly proportional to the new surface been created as a result of cell disruption. So, K

_{R}f

_{c}= 180 × 10

^{-6}J – m.

E = K

_{R}f

_{c}ln(\(\frac{1}{r_1} – \frac{1}{r_2}\)) ∴ E = 180 × 10

^{-6}(\(\frac{1}{5 × 10^{-6}} – \frac{1}{9 × 10^{-6}}\)) = 16 J.

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