## Multiple Choice Questions and Answers on Sterilization

**Question 1 : Typical aeration rates for aerobic fermentation are**

- 0 – 0.5 vvm
- 0.5 – 1.0 vvm
- 1.0 – 1.5 vvm
- 1.5 – 2.0 vvm

**Answer : 2**

**Question 2 : The K used in the equation for X_{10}=2.303/K depends upon**

- nature of the filter material
- linear velocity of the air passing through filter
- both (a) and (b)
- thickness of the filter

**Answer : 3**

**Question 3 : The mechanical means of accomplishing sterilization of fermentation media/equipment is**

- ultrasonic
- radiation
- chemical agents
- none of these

**Answer : 1**

**Question 4 : The radius of the filter with a depth of 14 cm required for a volumetric airflow rate of 10 m ^{3}/min is approximately**

- 1.6 m
- 0.6 m
- 3
- 6 m

**Answer : 2**

**Question 5 : The moist heat is more effective than the dry heat because the intrinsic heat resistance of vegetative cells is greatly**

- increased in a dry state
- decreased in a dry state
- increased in a wet state
- decreased in a wet state

**Answer : 1**

**Question 6 : The destruction of microorganisms by steam may be described as**

- first order chemical reaction
- zero order chemical reaction
- second order chemical reaction
- none of these

**Answer : 1**

**Question 7 : The reduction of number of cells from 10 ^{10} to one will result into the del factor (Δ) of**

- 1
- 10
- 23
- 10
^{3}

**Answer : 3**

**Question 8 : Sterilization can be carried out by**

- heat
- radiation
- chemical agents
- all of these

**Answer : 4**

**Question 9 : The collection efficiency by the inertial impaction mechanism is the function of**

- Stokes and Reynolds number
- Stokes and Schmidt number
- Grashoff and Reynolds number
- Stokes and Grashof number

**Answer : 1**

**Question 10 : The heated medium passes through a holding section, which is usually maintained in**

- adiabatic conditions
- isothermal conditions
- isotropic conditions
- isobaric conditions

**Answer : 1**

**Question 11 : The highest temperature which appears to be feasible for batch sterilization is**

- 121°C
- 100°C
- 105°C
- 130°C

**Answer : 1**

**Question 12 : Model proposed by the Friedlander, correlating the air filtration efficiency by impaction can be expressed as (where N_{St} is the Stokes number)**

- η
_{imp}= 0.075*N*_{St}^{1.2} - η
_{imp }= 0.75*N*_{St}^{1.2} - η
_{imp}= 0.25*N*_{St}^{1.2} - η
_{imp}= 0.025*N*_{St}^{1.2}

**Answer : 1**

**Question 13 : The collection efficiency by impaction increases with**

- increasing particle diameter
- increasing air flow velocity
- both (1) and (2)
- increasing particle size

**Answer : 3**

**Question 14 : The efficiency of fibrous filter by combined mechanism is given by(where η _{imp},η_{int},η_{dif} are the efficiencies by impaction, interception and diffusion respectively)**

- 1 – η
_{imp}η_{int}η_{dif} - 1 – (1 – η
_{imp})(1 – η_{int})( 1 – η_{dif}) - 1 – ( η
_{imp}η_{int}/η_{dif}) - None of the above

**Answer : 1**

**Question 15 : The heat conduction in dry air is**

- less rapid than in steam
- more rapid than in steam
- similar to steam
- none of these

**Answer : 1**

**Question 16 : For laminar flow of Newtonian fluid through a smooth round pipe, the ratio of average fluid velocity to the maximum velocity is**

- 0.5
- 0.75
- 0.87
- 0.37

**Answer : 1**

**Question 17 : In sterilization process, spore of which of the following organism is considered as control?**

*Bacillus subtilis**Clostridium botulinum**Bacillus stearothermophilus**Aspergillus niger*

**Answer : 3**

**Question 18 : Analogus to the molecular diffusion, the x-directional flux of microorganisms suspended in a medium due to the axial mixing can be represented as (where J_{n} is flux component ‘n‘, c_{n} is concentration of’n‘)**

*J*= –_{n}*dc*/_{n}*dx**J*=_{n}*dc*/_{n}*dx**J*= –_{n}*D dc*/_{n}*dx**J*=_{n}*D dc*/_{n}*dx*

**Answer : 3**

**Question 19 : The typical size of particles collected by diffusion mechanism is**

- <0.25μm
- <0.5μm
- <0.75μm
- <1μm

**Answer : 2**

**Question 20 : The X_{90} value for a filtration system is**

- the time required to reduce microbial population by 90%
- the time required to traverse survivor curve by one log cycle
- the depth required to reduce population by 90%
- the depth of the filter required to reduce population by 99%

**Answer : 3**

**Question 21 : The value of K**

- increases with increase in air velocity
- decreases with increase in air velocity
- increases to an optimum with increase in air velocity and decreases on further increase of air velocity
- none of these

**Answer : 3**

**Question 22 : The collection efficiency by interception increases with the**

- increasing particle diameter
- increasing air flow velocity
- both (1) and (2)
- increasing particle size

**Answer : 4**

**Question 23 : For indirect heating, the plate and frame heat exchanger is generally more effective than the shell and tube heat transfer due to its**

- larger heat transfer area
- smaller heat transfer area
- lesser cost
- more number of plates

**Answer : 1**

**Question 24 : The mechanism of air filtration in fibrous filter is**

- electrostatic attraction
- impaction
- interception
- all of these

**Answer : 4**

**Question 25 : If the packing density (α) is defined as the volume of the fiber unit volume of filter bed, the velocity within the filter void space is equal to (where V is velocity in fluid void space and V_{0} is undisturbed fluid velocity)**

*V*=*V*/(1-α)_{0}*V-V*= 1 – α_{0}*V*=*V*(1 – α)_{0}*V*=*V*/(1 + α)_{0}

**Answer : 1**

**Question 26 : For the turbulent flow, the dispersion coefficient is correlated as a function of**

- Reynolds number
- Sherwood number
- Schmidt number
- Grashof number

**Answer : 1**

**Question 27 : The overall del factor (Δ) may be represented as**

- Δ
_{overall}= Δ_{heating}+ Δ_{holding}– Δ_{cooling} - Δ
_{overall}= Δ_{heating}+ Δ_{holding}+ Δ_{cooling} - Δ
_{overall}= Δ_{heating}– Δ_{holding}+ Δ_{cooling} - Δ
_{overall}= Δ_{heating}– Δ_{holding}– Δ_{cooling}

**Answer : 2**

**Question 28 : The filter material used for air filtration system is/are**

- glass wool
- glass fibre
- norite
- all of the above

**Answer : 4**

**Question 29 : The deviation from ideal plug flow due to axial mixing can be described by the**

- dispersion model
- Langmuir model
- Friedlander model
- Pasceri model

**Answer : 1**

**Question 30 : The collection efficiency by diffusion increases with**

- decreasing particle size
- decreasing air velocity
- both (1) and (2)
- increasing particle size

**Answer : 3**

**Question 31 : Glass fibers are favorable as a filter medium because they give a**

- lower pressure drop and are less liable to wetting or combustion
- more pressure drop and are less liable to wetting or combustion
- lower pressure drop and are more liable to wetting or combustion
- more pressure drop and are more liable to wetting or combustion

**Answer : 1**

**Question 32 : The sterilization method depends**

- nature of additive
- volume and feed rate
- both (1) and (2)
- none of these

**Answer : 3**

**Question 33 : The specific death rate of an organism can be expressed as**

- ln 2/
*D* *D*/ln2*D*.ln2- 0.3/ln2

**Answer : 1**

**Question 34 : The interception efficiency can be expressed as (where d_{p} is the particle diameter and D_{c} cylindrical collection diameter)**

*d*/_{p}*D*_{c}*d*x_{p}*D*_{c}*d*/_{p}*D*x 100_{c}*d*_{p}*D*/100_{c}

**Answer : 1**

**Question 35 : The relationship between the del factor, temperature and time is given as**

- Δ = A.t. e
^{-E/RT} - Δ = 1/(A.t. e
^{-E/RT}) - Δ = A.t. e
^{E/RT} - Δ = A.t.T

**Answer : 1**

**Question 36 : The del factor (Δ) increases as the final number of cells**

- decreases
- increases
- zero
- constant

**Answer : 1**