MCQOPTIONS
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MCQOPTIONS
This section includes 108 Mcqs, each offering curated multiple-choice questions to sharpen your Microbiology knowledge and support exam preparation. Choose a topic below to get started.
| 51. |
Which of the following will have the largest interfacial area per unit volume? |
| A. | A bubble with a diameter of 1 mm |
| B. | A bubble with a diameter of 5 mm |
| C. | A bubble with a diameter of 15 mm |
| D. | A bubble with a diameter of 50 mm |
| Answer» B. A bubble with a diameter of 5 mm | |
| 52. |
For laminar flow, Reynolds number is correlated with power number as (where K, a constant which depends on the container geometry and shape of stirrer; Rei is Reynolds number for agitator; Di, stirrer diameter and N, stirrer speed) |
| A. | Np = K(Rei)¹ |
| B. | Np = N2Di(Rei)¹ |
| C. | Np = K(Rei) |
| D. | Np = KNDi(Rei)² |
| Answer» B. Np = N2Di(Rei)¹ | |
| 53. |
Power number (Np) is also known as |
| A. | Froude's number |
| B. | Bond's number |
| C. | Newton's number |
| D. | Rayleigh's number |
| Answer» D. Rayleigh's number | |
| 54. |
An aerated bioreactor will increase oxygen transfer rates with the addition of detergents because it |
| A. | enhances bubble coalescence |
| B. | causes bubbles to expand |
| C. | discourages bubble coalescence |
| D. | increases the surface tension of the liquid |
| Answer» D. increases the surface tension of the liquid | |
| 55. |
Henry's law relates |
| A. | the partial pressure of oxygen and the saturation concentration of oxygen in the liquid |
| B. | the oxygen transfer rate and the bubble size |
| C. | the oxygen transfer rate and the temperature |
| D. | the oxygen transfer rate to the partial pressure of oxygen in the liquid |
| Answer» B. the oxygen transfer rate and the bubble size | |
| 56. |
Which of the following would be best described as an axial flow impeller? |
| A. | An impeller with blades pitched at 45° to the vertical |
| B. | An impeller which directs liquid flow towards the base of the reactor |
| C. | Both (a) and (b) |
| D. | An impeller with blades pitched at 75° to the vertical |
| Answer» D. An impeller with blades pitched at 75° to the vertical | |
| 57. |
If liquid density and viscosity remains constant, then the Reynolds number in a stirred tank reactor will vary with the |
| A. | square root of the impeller diameter |
| B. | impeller diameter |
| C. | cube of the impeller diameter |
| D. | square of the impeller diameter |
| Answer» E. | |
| 58. |
Which of the following is not classified as an axial flow impeller? |
| A. | A marine impeller |
| B. | A propeller |
| C. | A hydrofoil impeller |
| D. | A Rushton turbine |
| Answer» E. | |
| 59. |
At 25°C, the saturation concentration of oxygen in water is 1.26 mmol/l and the partial pressure of oxygen is 1 atm. The Henry\'s law constant will be |
| A. | 0.207atml/mmol |
| B. | 0.793atml/mmol |
| C. | 8.74 atml/mmol |
| D. | 1.26 atml/mmol |
| Answer» C. 8.74 atml/mmol | |
| 60. |
In the design of a paddle agitator, the ratio of paddle diameter to tank diameter is normally taken as |
| A. | 0.8 |
| B. | 0.5 |
| C. | 0.2 |
| D. | 0.3 |
| Answer» B. 0.5 | |
| 61. |
Higher temperatures affect oxygen transfer rates by |
| A. | lowering KLa but increasing C*o |
| B. | increasing KLa but lowering C*o |
| C. | lowering KLa and lowering Co |
| D. | increasing KLa and increasing Co |
| Answer» C. lowering KLa and lowering Co | |
| 62. |
A cylindrical reactor has a liquid volume of 100,000 litres. It has an aspect ratio the ratio of the channel height to width of 1:1. The height of the liquid in the reactor will be approximately: |
| A. | 3.0 m |
| B. | 1.0 m |
| C. | 7.0 m |
| D. | 5.0 m |
| Answer» E. | |
| 63. |
Swirling and vortex formation can be prevented by |
| A. | using diffusion ring with turbines |
| B. | using baffles |
| C. | none of these |
| D. | both ( and ( |
| Answer» E. | |
| 64. |
Which of the following would be best described as a radial flow impeller? |
| A. | A Rushton turbine |
| B. | An impeller with blades pitched at 45° to the vertical |
| C. | An impeller which directs liquid flow towards the base of the reactor |
| D. | Both ( and ( |
| Answer» B. An impeller with blades pitched at 45° to the vertical | |
| 65. |
Detergent like substances produced by microorganisms during a fermentation will lead to |
| A. | accumulate at the gas liquid interface |
| B. | decrease the surface tension of the liquid |
| C. | all of the above |
| D. | decrease the rate of bubble coalescence |
| Answer» D. decrease the rate of bubble coalescence | |
| 66. |
The oxygen transfer rate in a bioreactor will increase if |
| A. | antifoam is added |
| B. | oil is added |
| C. | increase in the reactor temperature |
| D. | detergent like molecules are added |
| Answer» E. | |
| 67. |
The power consumption in a stirring vessel can be assessed by using a |
| A. | strain gauge attached to agitator shaft |
| B. | dynamometer |
| C. | all of these |
| D. | watt meter attached to agitator motor |
| Answer» D. watt meter attached to agitator motor | |
| 68. |
A microbial population in a suspension culture will only be limited by oxygen availability if the dissolved oxygen |
| A. | concentration is greater than the critical concentration |
| B. | concentration is less than the critical concentration |
| C. | levels are equal to saturation oxygen level |
| D. | levels are greater than the saturation concentration of oxygen |
| Answer» C. levels are equal to saturation oxygen level | |
| 69. |
Power consumption by agitation is |
| A. | a function of operating conditions |
| B. | a function of physical properties |
| C. | all of the above |
| D. | a function of vessel and impeller geometry |
| Answer» D. a function of vessel and impeller geometry | |
| 70. |
The range of width for the baffle in the fermenter is __________ times of vessel diameter |
| A. | 1/8 to 1/10 |
| B. | 1/10 to 1/12 |
| C. | none of these |
| D. | 1/5 to 1/8 |
| Answer» C. none of these | |
| 71. |
The dynamic technique is based on the |
| A. | change of the oxygen concentration |
| B. | oxygen material balance in an aerated batch fermenter during the growth of microorganisms |
| C. | oxygen material balance in a fermenter |
| D. | oxidation of the sodium sulfite to sodium sulfate |
| Answer» C. oxygen material balance in a fermenter | |
| 72. |
Impeller damage can be minimized by |
| A. | using radial flow impellers |
| B. | using specially designed axial flow impellers |
| C. | all of the above |
| D. | using Intermig impellers |
| Answer» C. all of the above | |
| 73. |
The maximum solubility of the alkane in the medium is 5 ppm. If the actual dissolved concentration of the alkane in the medium is 1 ppm. what conclusion may be drawn? |
| A. | The growth rate is limited by the intrinsic kinetic properties of the cells and not by mass transfer |
| B. | The growth rate is limited by the rate of mass transfer of the alkane into the fermentation medium |
| C. | No conclusion on the growth rate can be withdrawn |
| D. | The growth rate is neither mass transfer nor kinetically limited |
| Answer» D. The growth rate is neither mass transfer nor kinetically limited | |
| 74. |
Which have the maximum resistance while transferring carbon dioxide from the bulk liquid to an air bubble? |
| A. | Moving through the bubble boundary layer |
| B. | Moving through the gas liquid interface |
| C. | Moving through the bulk liquid |
| D. | Moving across the cell membrane |
| Answer» B. Moving through the gas liquid interface | |
| 75. |
Flooding is a condition/phenomenon which occur in a bioreactor when |
| A. | The fermenter medium spills out the reactor due to foaming |
| B. | The air escapes without being distributed by the agitator |
| C. | None of the above |
| D. | The volume of foam is more than the volume of broth |
| Answer» C. None of the above | |
| 76. |
Which of the following will have the highest surface area available for oxygen transfer? |
| A. | A standing test tube |
| B. | A shake flask |
| C. | A sparged stirred tank reactor agitated at 400 rpm |
| D. | A non-sparged stirred tank reactor agitated at 400 rpm |
| Answer» D. A non-sparged stirred tank reactor agitated at 400 rpm | |
| 77. |
What is the ratio of depth of liquid in vessel to the diameter of tank (H:Dt)? |
| A. | 0.0840277777777778 |
| B. | 0.0423611111111111 |
| C. | none of these |
| D. | 0.167361111111111 |
| Answer» C. none of these | |
| 78. |
Larger propellers turn at the speed of |
| A. | 150 to 300 rpm |
| B. | 20 to 150 rpm B |
| C. | 1150 rpm |
| D. | 400 to 800 rpm |
| Answer» E. | |
| 79. |
When the height of an aerated bioreactor is increased, it will increase the oxygen transfer rate by |
| A. | decreasing the saturation concentration of oxygen in the reactor |
| B. | increasing the partial pressure of oxygen at the base of the reactor |
| C. | all of the above |
| D. | decreasing the gas-holdup |
| Answer» C. all of the above | |
| 80. |
To increase the oxygen transfer rate in a shake flask culture system, which of the following (s) is/are followed? |
| A. | Stirrer speed is increased |
| B. | Liquid volume in the flask is reduced |
| C. | All of the above |
| D. | Baffled flasks are used |
| Answer» D. Baffled flasks are used | |
| 81. |
Main reason for using baffles in stirred tank reactors are |
| A. | baffles will allow axial mixing to occur even with radial flow impellers |
| B. | baffles permit turbulence conditions to arise at low stirrer speed |
| C. | baffles prevent turbulent conditions in stirred tank reactors |
| D. | both ( and ( |
| Answer» E. | |
| 82. |
During aeration, a cylindrical reactor had a height of 10 m. Without aeration, the height was 7.5 m. Under these aeration and mixing conditions, the gas hold up in the reactor is |
| A. | 0.75 |
| B. | 1 |
| C. | 0.25 |
| D. | 0.5 |
| Answer» D. 0.5 | |
| 83. |
Henry\'s law relates |
| A. | the oxygen transfer rate and the bubble size |
| B. | the partial pressure of oxygen and the saturation concentration of oxygen in the liquid |
| C. | the oxygen transfer rate to the partial pressure of oxygen in the liquid |
| D. | the oxygen transfer rate and the temperature |
| Answer» C. the oxygen transfer rate to the partial pressure of oxygen in the liquid | |
| 84. |
The power required by an impeller in a gas sparged system compare to the power required by impeller operating at same speed in a gas free liquid is usually |
| A. | higher |
| B. | lesser |
| C. | may be lesser or higher depending upon the geometry |
| D. | same |
| Answer» D. same | |
| 85. |
Vortexing in stirred tank reactors can be prevented by |
| A. | shifting the impeller to an off-centre position |
| B. | installing baffles in the reactor |
| C. | using axial flow impellers |
| D. | Both ( and ( |
| Answer» E. | |
| 86. |
Which of the following stirrer requires least amount of energy for same yield? |
| A. | Intermig |
| B. | Mig |
| C. | Disc |
| D. | Turbine |
| Answer» B. Mig | |
| 87. |
The rate limiting step in the movement of oxygen from the gas phase in a bubble to the cell is the movement of oxygen molecules through |
| A. | bubble boundary layer |
| B. | gas-liquid interface |
| C. | gas phase |
| D. | bulk liquid |
| Answer» B. gas-liquid interface | |
| 88. |
During fermentation, the saturation concentration of oxygen was reduced from 7 ppm. to 1 ppm. Which one of the following conclusions can be drawn? |
| A. | Microbial growth is not oxygen limited since the oxygen concentration is lesser than the saturation concentration |
| B. | Microbial growth is oxygen limited since the oxygen concentration is lesser than the saturation concentration |
| C. | No conclusion can be drawn |
| D. | Experimental error leads to the reduction |
| Answer» D. Experimental error leads to the reduction | |
| 89. |
Which of the following is correct for the off-centre impellers? |
| A. | Off-centre impellers should only be used with reactors with volumes less than 10 m3 |
| B. | Off-centre impellers can be used with any size reactor |
| C. | Off-centre impellers can be used when volume is greater than 10 m3 |
| D. | The impeller should never be placed in an off-centre position |
| Answer» B. Off-centre impellers can be used with any size reactor | |
| 90. |
Froude number is avoided in calculation of power requirements for low viscosity liquid mixing systems when |
| A. | Reynolds number is less than 300 |
| B. | baffled systems are used |
| C. | none of these |
| D. | both (and( |
| Answer» E. | |
| 91. |
Gas hold up, characterizing the hydrodynamics in a fermenter, mainly depends on the |
| A. | power consumption |
| B. | superficial gas velocity |
| C. | gas concentration |
| D. | Both ( and ( |
| Answer» E. | |
| 92. |
Which of the following is not considered among the three best-known theories of interphase mass transfer? |
| A. | penetration theory |
| B. | two-film theory |
| C. | Calderbank and Moo-Young theory |
| D. | surface renewal theory |
| Answer» D. surface renewal theory | |
| 93. |
Pure oxygen, if used instead of air will increase oxygen transfer rates because |
| A. | the bubble size is smaller |
| B. | the saturation concentration of oxygen is higher |
| C. | the partial pressure of oxygen in the gas phase is lower |
| D. | the oxygen transfer coefficient is larger |
| Answer» C. the partial pressure of oxygen in the gas phase is lower | |
| 94. |
Small propellers turn at the speed of either |
| A. | 150 or 300 rpm |
| B. | 20 or 150 rpm |
| C. | 1150 rpm or 1750 rpm |
| D. | 400 or 800 rpm |
| Answer» D. 400 or 800 rpm | |
| 95. |
Which of the following is most likely to cause an increase in the rate of oxygen transfer into a particular aerated fermentation system? |
| A. | Increase in temperature |
| B. | Addition of antifoams |
| C. | Both ( and ( |
| D. | Increase in stirrer speed |
| Answer» E. | |
| 96. |
A typical ceiling fan would be best described as a(n) |
| A. | axial flow impeller |
| B. | radial flow impeller |
| C. | Rushton turbine |
| D. | intermig impeller |
| Answer» B. radial flow impeller | |
| 97. |
A flooded impeller will lead to poor oxygen transfer rates because |
| A. | bubbles tend to break down too rapidly under high shear conditions |
| B. | bubbles tend to coalesce under the impeller |
| C. | the cells clog up the surface of the bubble |
| D. | bubbles tend to move too quickly through the bulk liquid |
| Answer» C. the cells clog up the surface of the bubble | |
| 98. |
What is the ratio of diameter of impeller to the diameter of tank (Da:Dt)? |
| A. | 0.0840277777777778 |
| B. | 0.04375 |
| C. | 0.0451388888888889 |
| D. | 0.167361111111111 |
| Answer» C. 0.0451388888888889 | |
| 99. |
Which of the following best explains the reasons for using axial flow impellers in crystallization and precipitation reactions? |
| A. | Crystals and precipitates are thoroughly broken down, so as to ensure easy separation of the solids from the mother liquor |
| B. | Crystal and precipitates are not too small, so as to ensure easy separation of the solids from the mother liquor |
| C. | Axial flow impellers provide low shear, energy efficient mixing conditions |
| D. | Both ( and ( |
| Answer» C. Axial flow impellers provide low shear, energy efficient mixing conditions | |
| 100. |
Which of the following impellers are used for wide range of viscosities? |
| A. | turbines |
| B. | paddles |
| C. | none of these |
| D. | propellers |
| Answer» B. paddles | |