3rd

Question 1

The function of the disengagement zone in an
airlift fermenter is to

Answer 1

• prevent CO2 rich bubbles from entering the downcomer
• reduce the velocity of the bubbles
• reduce liquid loss as aerosols

Question 2

Stationary phase is described as

Answer 2

no further increase in the cell population
after a maximum value

Question 3

In the accelerated phase, cell starts to

Answer 3

increase and the division rate increases to
reach a maximum

Question 4

The Monod model predicts that the specific
growth rate

Answer 4

will increase with the concentration of the growth limiting substrate until it reaches a maximum value

Question 5

A mixed fermentation is one, which produces

Answer 5

both acid and alcohol

Question 6

The function of a mechanical seal is to

Answer 6

• prevent contaminants entering the reactor
• prevent cells from leaving the reactor

Question 7

The phenomenon in which substrates are used in a sequential manner is known as

Answer 7

diauxie

Question 8

The dilution rate, D is defined as (where F = volumetric flow rate, VR= total volume of culture in the reactor and μ specific growth rate)

Answer 8

F/VR

Question 9

Diauxie is

Answer 9

the stagewise uptake of nutrients

Question 10

An open system in which the growth rate is maintained by adding a nutrient (present in
limiting quantities) at the same rate as that medium containing micro-organism is removed is called

Answer 10

Chemostat

Question 11

In the death phase

Answer 11

nutrients available for the cells are depleted
and begin to die

Question 12

The maximum specific growth rate of an
organism depends on

Answer 12

medium composition
temperature
pH

Question 13

Which of the following is not correct for the Monod model and the Michaelis Menten Model

Answer 13

a. The Michaelis Menten Model was derived from a curve fitting exercise
b. The Michaelis Menten model was derived from an analysis of the mechanism of microbial growth
c. The Monod model was derived from an analysis of the mechanism of microbial growth

Question 14

Bubble column reactor has

Answer 14

large height to diameter ratio

Question 15

Why a T-flask used in small-scale cell culture is incubated in a horizontal position

Answer 15

• To save space
• To increase the surface area of the liquid-air
  interface

Question 16

An open system in which the growth rate is maintained by the removal and addition of media at such a rate as to maintain a constant cell density is called a

Answer 16

Turbidostat

Question 17

Wash out in steady state fermentation occurs
when

Answer 17

dilution rate is higher than the maximum
specific growth rate

Question 18

Fermenter should be filled with medium upto

Answer 18

75-80%

Question 19

Bacterial growth curve is obtained by plotting

Answer 19

log of number of cells versus time

Question 20

When intracellular enzymes of whole cells are to be used in a bio-conversion process, it is often necessary to____________the cells.

Answer 20

Permeabilize

Question 21

Heat transfer rates (per unit volume) will be
lowest in

Answer 21

Continuous packed bed reactor

Question 22

The function(s) of the draft tube in an airlift
bioreactor is

Answer 22

• to reduce bubble coalescence
• to improve circulation
• to even out shear conditions throughout the reactor

Question 23

The Monod Model relates

Answer 23

specific growth rate to the substrate
availability

Question 24

The height to diameter ratio (H/D) for the
column fermenters is

Answer 24

> 3

Question 25

The high oxygen transfer efficiencies of airlift
bioreactors is due to

Answer 25

• the large aspect ratio of the reactor, which leads to a high gas hold-up
• the large aspect ratio of the reactor, which leads to a high oxygen solubility at the base of the reactor
• the draft tube, which reduces bubble
  coalescence in the reactor

Question 26

The maximum specific growth rate (μm) of an organism in batch culture is equal to slope of a plot of

Answer 26

In [biomass] against time for exponential
phase data only

Question 27

The region of an airlift bioreactor in which the liquid travels in a downward direction is called the

Answer 27

Downcomer

Question 28

Population doubling time, td can be expressed as (where μ is the specific growth rate.)

Answer 28

ln2/μ

Question 29

A higher Ks value of Monod’s equation means

Answer 29

greater affinities to substrate

Question 30

The increased air flow rate in bubble column fermenter can cause excessive foaming and
high retention of air bubbles in the column which

Answer 30

decreases the productivity of the fermenter

Question 31

Which of the following is correct for the prediction of time requirement in a batch fermenter?

Answer 31

• Carrying out experiments
• Mathematical modelling of the
  fermentation process

Question 32

In an airlift bioreactor, the spent gases released from the liquid are called

Answer 32

disengagement zone

Question 33

The contents in jet loop reactor are mixed
through

Answer 33

external pumping

Question 34

The specific growth rate (μ) is defined as

Answer 34

the rate of individual cells division or increase in their biomass

Question 35

The number of baffles in a standard stirred tank
bioreactor is

Answer 35

4

Question 36

In the stationary phase

Answer 36

growth rate is equal to death rate

Question 37

Which of the following is an example of a
mathematical model?

Answer 37

• Volume of cuboid = length x breadth x height
• The Monod Model
• The Michaelis Menten Equation

Question 38

Biomass concentrations during fermentation is

Answer 38

• diluting the samples to optical density less than 0.3
• monitored by controlling the changes in biomass concentrations
• considering that optical density is
  proportional to the surface area of the biomass in the sample

Question 39

Chemostats work on the principle of

Answer 39

maintaining uniform nutrients
concentration

Question 40

During the exponential phase the maximum specific growth rate equals specific growth rate as

Answer 40

concentration of growth limiting substrate is much greater than the Monod constant