8. The range of width for the baffle in the fermenter is __________ times of vessel diameter
A.1/10 to 1/12
B.1/8 to 1/10
C.1/5 to 1/8
D.none of these

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9. The average concentration of oxygen in the boundary layers surrounding the bubbles (Co*) in a reactor is normally determined by
A.ultra-small dissolved oxygen probes
B.laser based photographic systems
C.measuring the steady state concentration of oxygen in the bulk liquid prior to inoculation of the reactor
D.measuring the steady state concentration of oxygen in the bulk liquid after inoculation of the reactor

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10. Why vortexing is undesirable in the agitation of biological systems?
A.The collision between the cells, impeller and air bubbles will lead to cell damage
B.Poor mixing despite the use of high stirrer speeds
C.Mixing will not be in the turbulent region
D.All of the above

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11.  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.gas-liquid interface
B.bubble boundary layer
C.bulk liquid
D.gas phase

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12. Penetration theory assumes that turbulent eddies travel from the bulk of the phase to the interface where they remain constant for a constant exposure time (te). The model correlating KL, mass transfer coefficient and DAB, diffusivity can be expressed as
A.KL = 2(DAB/πte)0.25
B.KL = 2(DAB/πte)0.5
C.KL = 2(DAB/πte)0.75
D.KL = 2(DAB/πte)

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13. The oxygen uptake requirements of a microbial population is characterized by the following parameters: μm = 0.2 h-1, K0 = 0.2 mg O2.l-1, Y0 = 0.5 mg dry weight/mg O2 and C0,crit=0.8 mg.l-1 The required concentration of cells is 1000 mg.l-1 and the saturation oxygen concentration of the medium is 5.8 mg.l-1. The required KLa must be greater than
A.64 h-1
B.32 h-1
C.16 h-1
D.8h-1

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14. Which have the maximum resistance while transferring carbon dioxide from the bulk liquid to an air bubble?
A.Moving through the gas liquid interface
B.Moving through the bubble boundary layer
C.Moving across the cell membrane
D.Moving through the bulk liquid

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