Bioprocess Engineering Multiple Choice Questions on “Fed Batch Culture”.
1. A concentrated solution of the limiting substrate is added in fed-batch at a rate?
A. Greater than the solution of the limiting substrate and the same medium used to establish the batch culture
B. Less than the solution of the limiting substrate and the same medium used to establish the batch culture
C. Equal to the solution of the limiting substrate and to the same medium used to establish the batch culture
D. Negligible to the solution of the limiting substrate and to the same medium used to establish the batch culture
Answer: B
Explanation: A concentrated solution of the limiting substrate is added in fed-batch at a rate less than the solution of the limiting substrate and the same medium used to establish the batch culture, resulting in an increase in volume.
2. Which of the following Fed-batch system is described as a fixed volume?
A. The same medium used to establish the batch culture
B. A solution of the limiting substrate
C. A concentrated solution of the limiting substrate
D. A very concentrated solution of the limiting substrate
Answer: D
Explanation: A very concentrated solution of the limiting substrate added at a rate less than the same medium used to establish the batch culture, a solution of the limiting substrate and a concentrated solution of the limiting substrate, resulting in an insignificant increase in volume.
3. What do you mean by “Quasi steady state”?
A. Cell concentration remains virtually constant
B. Cell concentration is virtually variable
C. Total biomass remains constant with time
D. Total biomass decreases with time
Answer: A
Explanation: The total biomass in the culture (X) increases with time, cell concentration (x) remains virtually constant, that is dx/dt ≅ 0 and therefore μ ≅ D. This situation is termed as a quasi steady state.
4. Quasi – steady state in fed batch is when?
A. Growth rate remains constant
B. Dilution remains constant
C. Growth rate changes variably
D. μ remains constant
Answer: C
Explanation: The major difference between the steady state of a chemostat and the quasi steady state of a fed batch culture is that μ is constant in the chemostat but decreases in fed-batch. However, in the genuine steady state of a chemostat, dilution rate and growth rate are constant whereas in a fed-batch quasi steady state they change over the time of fermentation.
5. In a fixed-volume fed- batch culture μ declines when?
A. Biomass increases
B. Biomass decreases
C. Biomass remains constant
D. Biomass is equal to zero
Answer: A
Explanation: The μ declines when the limiting substrate concentration remains virtually constant, biomass increases and the concentration of the non-limiting nutrients declines.
6. Dilution refilling is done with______
A. Non- sterile water
B. Sterile water
C. Microbes
D. Waste
Answer: B
Explanation: Dilution would be achieved by withdrawing culture and refilling to the original level with sterile water or medium not containing the feed substrate.
7. What will be the condition when pH will be high?
A. Glucose is low
B. Glucose is equal with biomass concentration
C. Glucose is high with biomass concentration
D. Excess of glucose
Answer: A
Explanation: Glucose starvation may result in the organic nitrogen in the medium being used as a carbon source, resulting in high pH and inadequate biomass formation.
8. Fed-batch culture is superior to conventional batch culture.
A. True
B. False
Answer: A
Explanation: The advantage of the fed-batch culture is that one can control concentration of fed-substrate in the culture liquid at arbitrarily desired levels (in many cases, at low levels). Generally speaking, fed-batch culture is superior to conventional batch culture when controlling concentrations of a nutrient (or nutrients) affect the yield or productivity of the desired metabolite.
9. Fed-batch culture is not used for substrate inhibition.
A. True
B. False