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 X10=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 m3/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 1010 to one will result into the del factor (Δ) of
- 1
- 10
- 23
- 103
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 NSt is the Stokes number)
- ηimp = 0.075NSt1.2
- ηimp = 0.75NSt1.2
- ηimp = 0.25NSt1.2
- ηimp = 0.025NSt1.2
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 ηimp,ηint,ηdif are the efficiencies by impaction, interception and diffusion respectively)
- 1 – ηimpηintηdif
- 1 – (1 – ηimp)(1 – ηint)( 1 – ηdif)
- 1 – ( ηimpηint/ηdif)
- 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 Jn is flux component ‘n‘, cn is concentration of’n‘)
- Jn = –dcn/dx
- Jn = dcn/dx
- Jn = –D dcn/dx
- Jn = D dcn/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 X90 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 V0 is undisturbed fluid velocity)
- V = V0/(1-α)
- V-V0 = 1 – α
- V = V0(1 – α)
- V = V0/(1 + α)
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
- Δoverall = Δheating + Δholding– Δcooling
- Δoverall = Δheating + Δholding+ Δcooling
- Δoverall = Δheating – Δholding+ Δcooling
- Δoverall = Δheating – Δholding– Δcooling
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 dp is the particle diameter and Dc cylindrical collection diameter)
- dp/Dc
- dp x Dc
- dp/Dc x 100
- dpDc/100
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. eE/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