Sterilization Questions and Answers

Multiple Choice Questions and Answers on Sterilization

Question 1 : Typical aeration rates for aerobic fermentation are

  1. 0 – 0.5 vvm
  2. 0.5 – 1.0 vvm
  3. 1.0 – 1.5 vvm
  4. 1.5 – 2.0 vvm

Answer : 2

Question 2 : The K used in the equation for X10=2.303/K depends upon

  1. nature of the filter material
  2. linear velocity of the air passing through filter
  3. both (a) and (b)
  4. thickness of the filter

Answer : 3

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

  1. ultrasonic
  2. radiation
  3. chemical agents
  4. 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. 1.6 m
  2. 0.6 m
  3. 3
  4. 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

  1. increased in a dry state
  2. decreased in a dry state
  3. increased in a wet state
  4. decreased in a wet state

Answer : 1

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

  1. first order chemical reaction
  2. zero order chemical reaction
  3. second order chemical reaction
  4. 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. 1
  2. 10
  3. 23
  4. 103

Answer : 3

Question 8 : Sterilization can be carried out by

  1. heat
  2. radiation
  3. chemical agents
  4. all of these

Answer : 4

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

  1. Stokes and Reynolds number
  2. Stokes and Schmidt number
  3. Grashoff and Reynolds number
  4. Stokes and Grashof number

Answer : 1

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

  1. adiabatic conditions
  2. isothermal conditions
  3. isotropic conditions
  4. isobaric conditions

Answer : 1

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

  1. 121°C
  2. 100°C
  3. 105°C
  4. 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)

  1. ηimp = 0.075NSt1.2
  2. ηimp = 0.75NSt1.2
  3. ηimp = 0.25NSt1.2
  4. ηimp = 0.025NSt1.2

Answer : 1

Question 13 : The collection efficiency by impaction increases with

  1. increasing particle diameter
  2. increasing air flow velocity
  3. both (1) and (2)
  4. 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. 1 – ηimpηintηdif
  2. 1 – (1 – ηimp)(1 – ηint)( 1 – ηdif)
  3. 1 – ( ηimpηint/ηdif)
  4. None of the above

Answer : 1

Question 15 : The heat conduction in dry air is

  1. less rapid than in steam
  2. more rapid than in steam
  3. similar to steam
  4. 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

  1. 0.5
  2. 0.75
  3. 0.87
  4. 0.37

Answer : 1

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

  1. Bacillus subtilis
  2. Clostridium botulinum
  3. Bacillus stearothermophilus
  4. 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‘)

  1. Jn = –dcn/dx
  2. Jn = dcn/dx
  3. Jn = –D dcn/dx
  4. Jn = D dcn/dx

Answer : 3

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

  1. <0.25μm
  2. <0.5μm
  3. <0.75μm
  4. <1μm

Answer : 2

Question 20 : The X90 value for a filtration system is

  1. the time required to reduce microbial population by 90%
  2. the time required to traverse survivor curve by one log cycle
  3. the depth required to reduce population by 90%
  4. the depth of the filter required to reduce population by 99%

Answer : 3

Question 21 : The value of K

  1. increases with increase in air velocity
  2. decreases with increase in air velocity
  3. increases to an optimum with increase in air velocity and decreases on further increase of air velocity
  4. none of these

Answer : 3

Question 22 : The collection efficiency by interception increases with the

  1. increasing particle diameter
  2. increasing air flow velocity
  3. both (1) and (2)
  4. 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

  1. larger heat transfer area
  2. smaller heat transfer area
  3. lesser cost
  4. more number of plates

Answer : 1

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

  1. electrostatic attraction
  2. impaction
  3. interception
  4. 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)

  1. V = V0/(1-α)
  2. V-V0 = 1 – α
  3. V = V0(1 – α)
  4. V = V0/(1 + α)

Answer : 1

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

  1. Reynolds number
  2. Sherwood number
  3. Schmidt number
  4. Grashof number

Answer : 1

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

  1. Δoverall = Δheating + Δholding– Δcooling
  2. Δoverall = Δheating + Δholding+ Δcooling
  3. Δoverall = Δheating – Δholding+ Δcooling
  4. Δoverall = Δheating – Δholding– Δcooling

Answer : 2

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

  1. glass wool
  2. glass fibre
  3. norite
  4. all of the above

Answer : 4

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

  1. dispersion model
  2. Langmuir model
  3. Friedlander model
  4. Pasceri model

Answer : 1

Question 30 : The collection efficiency by diffusion increases with

  1. decreasing particle size
  2. decreasing air velocity
  3. both (1) and (2)
  4. increasing particle size

Answer : 3

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

  1. lower pressure drop and are less liable to wetting or combustion
  2. more pressure drop and are less liable to wetting or combustion
  3. lower pressure drop and are more liable to wetting or combustion
  4. more pressure drop and are more liable to wetting or combustion

Answer : 1

Question 32 : The sterilization method depends

  1. nature of additive
  2. volume and feed rate
  3. both (1) and (2)
  4. none of these

Answer : 3

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

  1. ln 2/D
  2. D/ln2
  3. D.ln2
  4. 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)

  1. dp/Dc
  2. dp x Dc
  3. dp/Dc x 100
  4. dpDc/100

Answer : 1

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

  1. Δ = A.t. e-E/RT
  2. Δ = 1/(A.t. e-E/RT)
  3. Δ = A.t. eE/RT
  4. Δ = A.t.T

Answer : 1

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

  1. decreases
  2. increases
  3. zero
  4. constant

Answer : 1