When a culture of fermenting yeast becomes metabolically uncoupled, ethanol beco

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Question
When a culture of fermenting yeast becomes metabolically uncoupled, ethanol
Options
A. becomes a secondary metabolite
B. production becomes growth associated
C. production becomes non-growth associated
D. becomes a growth nutrient

Correct Answer

production becomes non-growth associated

Fermentation Reactors problems

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1. The main reason for production of antibiotics in fed batch reactors is
Options
A. the presence of precursors is often toxic to the cells
B. higher yields when cells enter the stationary phase
C. higher yields when cell growth slows
D. all of the above

2. The lowest biomass yield in a culture of Escherichia coli will be in
Options
A. an aerated batch culture containing a initial high concentration of glucose
B. an aerated batch reactor containing an initial low concentration of glucose
C. an aerated fed-batch reactor having a low glucose concentration
D. an aerated continuous reactor having a low glucose concentration

3. In batch culture, protogon is produced from peptone during the stationary phase with a yield of 0.4 protogon mg per g of peptone. If it is to be produced in a chemostat at a dilution rate of 0.5 h^-1 from a medium containing 10 g.l^-1 of peptone, then the rate of protogon synthesis would be
Options
A. 0 g.l^-1h^-1
B. 0.5 g.l^-1h^-1
C. 1 g.l^-1h^-1
D. 2 g.l^-1h^-1

4. Unsteady state mass balance for dynamic model of continuous stirred tank reactor (CSTR) is
Options
A. time rate of total amount in rector = rate of addition to reactor -rate of removal + rate of formation
B. total amount in rector = rate of addition to reactor - rate of removal + rate of formation
C. rate of total amount in rector = rate of addition to reactor - rate of removal + rate of formation
D. none of the above

5. The cellular productivity in a continuous stirred tank fermenter (CSTF) increases with an increase in the dilution rate and reaches a maximum value. If the dilution rate is increased beyond the maximum point, the productivity will
Options
A. decrease abruptly
B. increase
C. increase drastically
D. be zero

6. For organisms growing in a chemostat, the specific growth rate
Options
A. cannot be determined
B. can be determined from the dilution rate
C. equals to the maximum specific growth rate of the culture
D. none of the above

7. Mixing profiles closest to plug flow are observed in
Options
A. continuous packed bed reactor
B. stirred tank reactor with biomass recycles
C. continuous fluidized bed bioreactor
D. all of these

8. Toxins accumulated in a reactor can lead to low biomass yields probably due to which of the following?
Options
A. NAD⁺ is diverted away from homeostasis to anabolism
B. ATP is diverted away from homeostasis to anabolism
C. NAD⁺ is diverted away from anabolism to homeostasis
D. ATP is diverted away from anabolism to homeostasis

9. The continuous cultures are not widely used in industry because
Options
A. they are not suited for the production of secondary metabolites
B. contamination or mutation can have a disastrous effect on the operation
C. the government will not approve the licensing of pharmaceuticals produced in continuous cultures
D. all of the above

10. Saccharomyces cerevisiae produces high biomass yields at low glucose concentrations and high dissolved oxygen concentrations. Which of the following should be followed for maximizing its biomass productivity?
Options
A. Batch fermenter with a high initial glucose concentration
B. Continuous fermenter with a low initial glucose concentration
C. Fed batch fermenter
D. All of the above

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