Agitation and Aeration MCQs

Question 1

Detergent like substances produced by microorganisms during a fermentation will lead to

Accepted Answer

all of the above

Answer

decrease the surface tension of the liquid

Answer

accumulate at the gas liquid interface

Answer

decrease the rate of bubble coalescence

Question 2

A cylindrical reactor fitted with Rushton Turbine has a liquid volume of 100,000 litres. It has an aspect ratio (the ratio of the channel height to the width) of 2:1. The diameter of the impeller should be approximately:

Accepted Answer

1.3 m

Answer

3.3 m

Answer

5.3 m

Answer

7.3 m

Question 3

In the bubble boundary layer, oxygen concentration can be determined by measuring

Accepted Answer

the steady state oxygen concentration in a mixed aerated reactor before inoculation

Answer

the steady state oxygen concentration in a mixed aerated reactor after inoculation

Answer

the steady state oxygen concentration in the boundary layer using a micro-probe

Answer

volume of oxygen supplied

Question 4

Impeller damage can be minimized by

Accepted Answer

using specially designed axial flow impellers

Answer

using radial flow impellers

Answer

using Intermig impellers

Answer

all of the above

Question 5

To increase the oxygen transfer rate in a shake flask culture system, which of the following (s) is/are followed?

Accepted Answer

All of the above

Answer

Liquid volume in the flask is reduced

Answer

Stirrer speed is increased

Answer

Baffled flasks are used

Question 6

What is/are the major difference(s) between disc and turbine type stirrer?

Accepted Answer

Both (a) and (b)

Answer

Blades in disc type are projected out beyond the edge of disc while blades are curved one in turbine type

Answer

Turbine type requires 50 % less air than disc type for the same yield and energy consumption

Answer

Number of blades in the stirrer

Question 7

In the design of a paddle agitator, the ratio of paddle diameter to tank diameter is normally taken as

Accepted Answer

0.8

Answer

0.1

Answer

0.25

Answer

0.5

Question 8

The oxygen absorption rate can be determined by

Accepted Answer

all of these

Answer

sodium sulfite oxidation method

Answer

dynamic gassing out technique

Answer

direct measurement

Question 9

Industrial paddle agitators turn at the speed of

Accepted Answer

20 and 150 rpm

Answer

150 and 300 rpm

Answer

400 and 800 rpm

Answer

1150 rpm