Agitation And Aeration

Question: An aerated bioreactor will increase oxygen transfer rates with the addition of detergents because it
[A].

enhances bubble coalescence

[B].

causes bubbles to expand

[C].

discourages bubble coalescence

[D].

increases the surface tension of the liquid

Answer: Option C

Explanation:

No answer description available for this question.

Question: A microbial population in a suspension culture will only be limited by oxygen availability if the dissolved oxygen
[A].

concentration is less than the critical concentration

[B].

concentration is greater than the critical concentration

[C].

levels are greater than the saturation concentration of oxygen

[D].

levels are equal to saturation oxygen level

Answer: Option A

Explanation:

No answer description available for this question.

Question: The addition of antifoams to an aerated bioreactor will decrease oxygen transfer rates because antifoams
[A].

increase the tendency of bubbles to coalesce

[B].

tend to accumulate in the gas liquid interface

[C].

reduce the surface tension of the liquid

[D].

All of the above answers

Answer: Option D

Explanation:

No answer description available for this question.

Question: Which of the following will have the largest interfacial area per unit volume?
[A].

A bubble with a diameter of 1 mm

[B].

A bubble with a diameter of 5 mm

[C].

A bubble with a diameter of 15 mm

[D].

A bubble with a diameter of 50 mm

Answer: Option A

Explanation:

No answer description available for this question.

Question: The main function of the dimples provided in the cooling jacket is to
[A].

increase the level of turbulence of the cooling water in the jacket

[B].

increase the residence time of the cooling water in the jacket

[C].

increase the cooling water-jacket wall boundary layer size

[D].

all of the above

Answer: Option A

Explanation:

No answer description available for this question.

Question: 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

Answer: Option B

Explanation:

No answer description available for this question.

Question: During fermentation, the saturation concentration of oxygen was reduced from 7 ppm. to 1 ppm. Which one of the following conclusions can be drawn?
[A].

Microbial growth is oxygen limited since the oxygen concentration is lesser than the saturation concentration

[B].

Microbial growth is not oxygen limited since the oxygen concentration is lesser than the saturation concentration

[C].

Experimental error leads to the reduction

[D].

No conclusion can be drawn

Answer: Option D

Explanation:

No answer description available for this question.

Question: If the stirring speed increased from 300 to 500 rpm leads to an increase in the reaction rate by two folds. Then it may be concluded that
[A].

the reaction was mass transfer limited at 300 rpm

[B].

the reaction was mass transfer limited at 500 rpm

[C].

the reaction did not involve any mass transfer step

[D].

the movement of molecules in the reactor at 300 rpm occurred due to diffusion alone

Answer: Option A

Explanation:

No answer description available for this question.

Question: 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

Answer: Option C

Explanation:

No answer description available for this question.

Question: The maximum solubility of the alkane in the medium is 5 ppm. If the actual dissolved concentration of the alkane in the medium is 1 ppm. what conclusion may be drawn?
[A].

The growth rate is limited by the rate of mass transfer of the alkane into the fermentation medium

[B].

The growth rate is limited by the intrinsic kinetic properties of the cells and not by mass transfer

[C].

The growth rate is neither mass transfer nor kinetically limited

[D].

No conclusion on the growth rate can be withdrawn

Answer: Option D

Explanation:

No answer description available for this question.