## Multiple Choice Questions (MCQ) and Answers on Fermentation Kinetics

**Question 1: A higher K_{s} value of Monod’s equation means**

- greater affinities to substrate
- lower affinities to substrate
- unaffected with the substrate bonding
- lower dissociation constant value

**Answer: 1**

**Question 2: The increased air flow rate in bubble column fermenter can cause excessive foaming and high retention of air bubbles in the column which**

- decreases the productivity of the fermenter
- increases the productivity of the fermenter
- modestly increases the productivity of the fermenter
- does not affect on the productivity

**Answer: 1**

**Question 3: Heat transfer rates (per unit volume) will be lowest in**

- Stirred tank bioreactor with biomass recycle
- Continuous air lift bioreactor
- Continuous packed bed reactor
- Continuous fluidized bed bioreactor

**Answer: 3**

**Question 4: The function(s) of the draft tube in an airlift bioreactor is**

- to reduce bubble coalescence
- to improve circulation
- to even out shear conditions throughout the reactor
- all of the above

**Answer: 4**

**Question 5: The Monod Model relates**

- substrate utilized with the biomass consumption
- specific growth rate to the substrate availability
- yield with the biomass utilization
- the biomass concentration with specific growth rate

**Answer: 2**

**Question 6: The height to diameter ratio (H/D) for the column fermenters is**

- <3
- >3
- <15
- >15

**Answer: 2**

**Question 7: The high oxygen transfer efficiencies of airlift bioreactors is due to**

- 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
- all of the above

**Answer: 4**

**Question 8: The function of a mechanical seal is to**

- prevent contaminants entering the reactor
- prevent cells from leaving the reactor
- both (a) and (b)
- prevent air to enter

**Answer: 3**

**Question 9: The phenomenon in which substrates are used in a sequential manner is known as**

- trans-substrate genesis
- dialism
- diauxie
- multiplicity

**Answer: 3**

**Question 10: The dilution rate, D is defined as(where F = volumetric flow rate, V_{R} = total volume of culture in the reactor and μ specific growth rate)**

*F/V*_{R}*V*/_{R}*F*- μ/
*F* *F*/μ

**Answer: 1**

**Question 11: Why a T-flask used in small-scale cell culture is incubated in a horizontal position?**

- To save space
- To increase the surface area of the liquid-air interface
- Both (a) and (b)
- To increase the rate of oxygen transfer into the liquid

**Answer: 3**

**Question 12: Bubble column reactor has**

- large height to diameter ratio
- small height to diameter ratio
- large diameter to height ratio
- small diameter to height ratio

**Answer: 1**

**Question 13: In the death phase**

- nutrients available for the cells are depleted and begin to die
- the number of viable cells will increase
- nutrients available for cells are replenished and start to multiply
- none of the above

**Answer: 1**

**Question 14: The maximum specific growth rate of an organism depends on**

- medium composition
- temperature
- pH
- All of these

**Answer: 4**

**Question 15: Which of the following is not correct for the Monod model and the Michaelis Menten Model?**

- The Michaelis Menten Model was derived from a curve fitting exercise
- The Michaelis Menten model was derived from an analysis of the mechanism of microbial growth
- The Monod model was derived from an analysis of the mechanism of microbial growth
- All of the above

**Answer: 3**

**Question 16: When intracellular enzymes of whole cells are to be used in a bio-conversion process, it is often necessary to____________the cells.**

- permeabilize
- lyophilize
- heat-kill
- denature

**Answer: 1**

**Question 17: Bacterial growth curve is obtained by plotting**

- number of cells versus time
- number of spores versus time
- log of number of cells versus time
- log of number of cells survived versus time

**Answer: 3**

**Question 18: 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**

- manostat
- chemostat
- turbidostat
- culturostat

**Answer: 3**

**Question 19: Wash out in steady state fermentation occurs when**

- dilution rate is less than maximum specific growth rate
- dilution rate is higher than the maximum specific growth rate
- cell concentration reaches the maximum
- specific growth rate is maximum

**Answer: 2**

**Question 20: Fermentor should be filled with medium upto**

- 65-70%
- 70-75%
- 75-80%
- 80-85%

**Answer: 3**

**Question 21: In the stationary phase**

- growth is proportional to death
- growth rate is equal to death rate
- growth rate is lesser than death rate
- no co-relation exist between death rate and growth rate

**Answer: 2**

**Question 22: Which of the following is an example of a mathematical model?**

- Volume of cuboid = length x breadth x height
- The Monod Model
- The Michaelis Menten Equation
- All of the above

**Answer: 4**

**Question 23: Biomass concentrations during fermentation is**

- 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
- all of the above

**Answer: 4**

**Question 24: Chemostats work on the principle of**

- maintaining constant volume of culture medium
- maintaining continuous flow of nutrients
- maintaining uniform nutrients concentration
- operating at higher pressure

**Answer: 3**

**Question 25: During the exponential phase the maximum specific growth rate equals specific growth rate as**

- concentration of the growth limiting substrate is much less than the monod constant
- concentration of growth limiting substrate is much greater than the monod constant
- specific growth rate increases exponentially
- concentration of the growth limiting substrate is equal to the monod constant

**Answer: 2**

**Question 26: Which of the following is correct for the prediction of time requirement in a batch fermenter?**

- Carrying out experiments
- Mathematical modelling of the fermentation process
- Both (a) and (b)
- It is impossible to predict the time required for fermentation

**Answer: 3**

**Question 27: In an airlift bioreactor, the spent gases released from the liquid are called**

- downcomer
- disengagement zone
- air riser
- flotsam

**Answer: 2**

**Question 28: The contents in jet loop reactor are mixed through**

- compressed air
- a mechanical agitator
- external pumping
- any of these

**Answer: 3**

**Question 29: The specific growth rate (μ) is defined as**

- the concentration of biomass in the reactor
- rate of increase of total biomass in a reactor
- the rate of individual cells division or increase in their biomass
- the rate of cell death

**Answer: 3**

**Question 30: The number of baffles in a standard stirred tank bioreactor is**

- 8
- 6
- 4
- 2

**Answer: 3**

**Question 31: The maximum specific growth rate (μ _{m}) of an organism in batch culture is equal to slope of a plot of**

- In [biomass] against time for exponential phase data only
- In [biomass] against time
- biomass against time
- biomass against time for stationary phase data only

**Answer: 1**

**Question 32: The region of an airlift bioreactor in which the liquid travels in a downward direction is called the**

- downcomer
- disengagement zone
- air riser
- flotsam

**Answer: 1**

**Question 33: Population doubling time, t _{d} can be expressed as (where μ is the specific growth rate)**

- log2/μ
- ln2/μ
- μ/ln2
- μ/log2

**Answer: 2**

**Question 34: The function of the disengagement zone in an airlift fermenter is to**

- prevent CO
_{2}rich bubbles from entering the downcomer - reduce the velocity of the bubbles
- reduce liquid loss as aerosols
- all of the above

**Answer: 4**

**Question 35: A mixed fermentation is one, which produces**

- both alcohol and carbon dioxide
- both acid and carbon dioxide
- both acid and alcohol
- several different kinds of acid

**Answer: 3**

**Question 36: The monod model predicts that the specific growth rate**

- will increase with the concentration of the growth limiting substrate until it reaches a maximum value
- will decrease with the concentration of the growth limiting substrate
- will increase with the concentration of the growth limiting substrate
- does not depend on growth limiting substrate

**Answer: 1**

**Question 37: In the accelerated phase, cell starts to**

- increase and the division rate increases to reach a maximum
- decrease and the division rate increases to reach a maximum
- increase and the division rate decreases to reach a maximum
- increase and the division rate increases to reach a minimum

**Answer: 1**

**Question 38: Stationary phase is described as**

- no further increase in the cell population after a maximum value
- deceleration of growth and division rate after the growth rate reaches a maximum
- acceleration of growth and division rate after the growth rate reaches a maximum
- deceleration of growth and division rate after the growth rate reaches a minimum

**Answer: 1**

**Question 39: 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-organisms is removed is called**

- manostat
- chemostat
- turbidostat
- culturostat

**Answer: 2**

**Question 40: Diauxie is**

- growth factors
- microbiological die off
- the simultaneous uptake of nutrients
- the stagewise uptake of nutrients

**Answer: 4**