This set of Bioprocess Engineering MCQs focuses on “Kinetics of Cell Substrate Uptake in Cell Culture”.
1. Is substrate only needed for product formation?
a) True
b) False
View Answer
Explanation: In some cultures there is no extracellular product formation; for example, biomass itself is the product in manufacture of bakers’ yeast and single-cell protein. In the absence of product formation, we assume that all substrate entering the cell is used for growth and maintenance functions.
2. If the external supply is exhausted will there be exhaustion of maintenance energy?
a) True
b) False
View Answer
Explanation: There is substrate uptake as long as there is external substrate available; when the substrate is exhausted maintenance energy is generally supplied by endogenous metabolism.
3. The supply of substrate for production and maintenance is different.
a) True
b) False
View Answer
Explanation: Substrate consumed for maintenance does not contribute to growth; it therefore constitutes a separate substrate flow into the cell. In contrast, when production is not linked or only partly linked to energy metabolism, all or some of the substrate required for product synthesis is additional to, and separate from, that needed for growth and maintenance.
4. What is the growth condition for Saccharomyces cerevisiae with glucose as energy source?
a) Aerobic
b) Anaerobic
c) Tryptophan limited
d) Glucose limited
View Answer
Explanation: Yeast belongs to the class of Protoascomyceten and more specifically to the physiological class of Saccharomyces Cerevisiae. Saccharomyces Cerevisiae is crabtree positive yeast, which is sensitive to high substrate concentrations that results in the reduction of the oxygen uptake rate. As a result glucose is metabolized to ethanol. This metabolic pathway can be reduced by introduction of a regulated feed procedure adapted to the specific growth rate of the yeast.
5. What is the growth condition for Penicillium chrysogenum with glucose as energy source?
a) Aerobic
b) Anaerobic
c) Tryptophan limited
d) Glucose limited
View Answer
Explanation: Penicillin was the first important commercial product produced by an aerobic, submerged fermentation. Penicillin is produced by the fungus Penicillium chrysogenum which requires lactose, other sugars, and a source of nitrogen (in this case a yeast extract) in the medium to grow well.
6. In which phase Penicillin is produced?
a) Lag phase
b) Log phase
c) Exponential phase
d) Stationary phase
View Answer
Explanation: Like all antibiotics, penicillin is a secondary metabolite, so is only produced in the stationary phase.
7. Which type of fermenter and process does Penicillin production requires?
a) Batch fermenter and fed-batch process
b) Batch fermenter and batch process
c) Continuous fermenter and fed-batch process
d) Continuous fermenter and batch process
View Answer
Explanation: It requires a batch fermenter, and a fed batch process is normally used to prolong the stationary period and so increase production.
8. A completely mixed continuous stirred-tank reactor for the cultivation of cells is called?
a) Turbidostat
b) Chemostat
c) Haemostat
d) Thermostat
View Answer
Explanation: A completely mixed continuous stirred-tank reactor for the cultivation of cells are called chemostats. Chemostat controls flow rate and concentration of growth-limiting nutrient of liquid medium entering and exiting a growth chamber (bioreactor).
9. Which of the following equation describes the relationship between μ and residual growth limiting substrate?
a) Eyring equation
b) Van’t Hoff equation
c) Arrhenius equation
d) Monad equation
View Answer
Explanation: The decrease in growth rate and the cessation of growth due to the depletion of substrate, may be described by the relationship between μ and the residual growth limiting substrate. This relationship is represented by an equation given by Monad in1942 which is known as Monad equation.
10. The monod equation is based on which type of kinetics?
a) Zero order kinetics
b) First-order kinetics
c) Second order kinetics
d) First-zero order kinetics
View Answer
Explanation: Biochemical reactions involving a single substrate are often assumed to follow Michaelis–Menten kinetics, without regard to the model’s underlying assumptions. The Michaelis-Menten relationship for the effect of substrate concentration on the rate of an enzyme catalysed reaction is given by the equation:
\(V = \frac{V_{max}S}{(S+K_m)}\)
where V = rate of reaction, Vmax = maximal rate of reaction, S = substrate concentration, and Km = substrate concentration at which reaction rate = 0.5 Vmax.
The analogous Monod equation for effect of substrate concentration on the specific growth rate of a microorganism is as follows:
\(\mu = \frac{\mu_{max}S}{(S+K_s)}\)
where μ = specific growth rate, μmax = maximum specific growth rate in absence of substrate limitation, S = concentration of growth limiting substrate, Ks = substrate concentration which allows the organism to grow at 0.5 μmax.
11. Logistic growth model describes which type of growth?
a) Product- based growth
b) Non-growth
c) Substrate-based growth
d) Maintenance-based growth
View Answer
Explanation: Logistic growth model describes the Substrate-based growth. It is used from beginning of exponential phase through end of max population (or stationary phase).
Modification of unlimited growth eqn:
dX/dt = μm X[1 – X/Xf]
Where, Xf = max population size or concentration
Term [1 – X/Xf] describes reduction of specific growth rate as exponential growth phase gives way to retardation phase.
12. What do you mean by the low Ks value?
a) Low affinity for the limiting substrate
b) Medium affinity for the limiting substrate
c) High affinity for the limiting substrate
d) No affinity for the limiting substrate
View Answer
Explanation: If the organism has a very high affinity for the limiting substrate (a low Ks value) the growth rate will not be affected until the substrate concentration has declined to a very low level. Thus, the deceleration phase for such a culture would be short.
13. The biomass concentration is at the highest level in which phase?
a) Lag phase
b) Log phase
c) Exponential phase
d) Stationary phase
View Answer
Explanation: The biomass concentration at the end of the exponential phase is at its highest level. Therefore the decline in substrate concentration will be very rapid so that the time period during which the substrate concentration is close to Ks is very short.
14. Which of the following phase is known as the “Maximum population phase”?
a) Lag phase
b) Log phase
c) Exponential phase
d) Stationary phase
View Answer
Explanation: The stationary phase in batch culture is that point where the growth rate has declined to zero. This phase is also known as the maximum population phase.
15. Monod and Michealis-Menten kinetics are same.
a) True
b) False
View Answer
Explanation: Difference between the two types of kinetics (Monod and Michaelis-Menten):
– Michaelis-Menten – quantity of reactive material (enzyme) is constant
– Monod – quality of reactive material (cells) is increasing.
Sanfoundry Global Education & Learning Series – Bioprocess Engineering.
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