Sterilization Multiple Choice Questions
1. The mechanical means of accomplishing sterilization of fermentation media/equipment is
a. ultrasonic
b. radiation
c. chemical agents
d. none of these
2. Typical aeration rates for aerobic fermentation are
a. 0 – 0.5 vvm
b. 0.5 – 1.0 vvm
c. 1.0 – 1.5 vvm
d. 1.5 – 2.0 vvm
3. The K used in the equation for X10=2.303/K depends upon
a. nature of the filter material
b. linear velocity of the air passing through filter
c. both (a) and (b)
d. thickness of the filter
4. The radius of the filter with a depth of 14 cm required for a volumetric airflow rate of 10 m3/min is approximately
a. 1.6 m
b. 0.6 m
c. 3
d. 6 m
5. The moist heat is more effective than the dry heat because the intrinsic heat resistance of vegetative cells is greatly
a. increased in a dry state
b. decreased in a dry state
c. increased in a wet state
d. decreased in a wet state
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
7. The reduction of number of cells from 1010 to one will result into the del factor (Δ) of
1
10
23
103
8. Sterilization can be carried out by
heat
radiation
chemical agents
all of these
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
10. The heated medium passes through a holding section, which is usually maintained in
adiabatic conditions
isothermal conditions
isotropic conditions
isobaric conditions
11. The highest temperature which appears to be feasible for batch sterilization is
121°C
100°C
105°C
130°C
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
13. The collection efficiency by impaction increases with
increasing particle diameter
increasing air flow velocity
both (1) and (2)
increasing particle size
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
15. The heat conduction in dry air is
less rapid than in steam
more rapid than in steam
similar to steam
none of these
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
17. In sterilization process, spore of which of the following organism is considered as control?
Bacillus subtilis
Clostridium botulinum
Bacillus stearothermophilus
Aspergillus niger
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
19. The typical size of particles collected by diffusion mechanism is
<0.25μm
<0.5μm
<0.75μm
<1μm
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%
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
22. The collection efficiency by interception increases with the
increasing particle diameter
increasing air flow velocity
both (1) and (2)
increasing particle size
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
24. The mechanism of air filtration in fibrous filter is
electrostatic attraction
impaction
interception
all of these
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)
26. For the turbulent flow, the dispersion coefficient is correlated as a function of
Reynolds number
Sherwood number
Schmidt number
Grashof number
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
28. The filter material used for air filtration system is/are
glass wool
glass fibre
norite
all of the above
29. The deviation from ideal plug flow due to axial mixing can be described by the
dispersion model
Langmuir model
Friedlander model
Pasceri model
30. The collection efficiency by diffusion increases with
decreasing particle size
decreasing air velocity
both (1) and (2)
increasing particle size
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
32. The sterilization method depends
nature of additive
volume and feed rate
both (1) and (2)
none of these
33. The specific death rate of an organism can be expressed as
ln 2/D
D/ln2
D.ln2
0.3/ln2
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
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
36. The del factor (Δ) increases as the final number of cells
decreases
increases
zero
constant