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  • Question
  • Saccharomyces cerevisiae when grown in high glucose concentration medium, the cells activity depends on which of the following?


  • Options
  • A. High concentration of dissolved oxygen
  • B. Low concentration of dissolved oxygen
  • C. No effect of dissolved oxygen
  • D. High concentration of dissolved oxygen and sodium salts

  • Correct Answer
  • No effect of dissolved oxygen 


  • Fermentation Reactors problems


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    • 1. The production of an amylase from starch by Aspergillus niger is often performed in a fed batch fermenter. This is due to the reason that

    • Options
    • A. fed-batch reactor can be used to minimize starch concentrations and prevent a. niger from fermenting
    • B. fed-batch reactor can be used to minimize starch concentrations and thus reduce the viscosity of the medium
    • C. continuous reactor can be used to minimize starch concentrations and their inhibitory effects
    • D. all of the above
    • Discuss
    • 2. In a batch reactor specific growth rate

    • Options
    • A. remains constant throughout the process
    • B. increases exponentially
    • C. changes during the fermentation
    • D. is highest during the stationary phase
    • Discuss
    • 3. The specific growth rate is affected by

    • Options
    • A. sabstrate concentration
    • B. product concentration
    • C. oxygen supply
    • D. all of these
    • Discuss
    • 4. The bubble column fermenter is usually limited to

    • Options
    • A. aerobic fermentations
    • B. anaerobic fermentations
    • C. Both (a) and (b)
    • D. facultative fermentation
    • Discuss
    • 5. The main function(s) of a draft tube in an air lift fermenter is/are to

    • Options
    • A. increase the solubility of oxygen
    • B. distribute shear forces throughout the reactor and minimise bubble coalescence
    • C. concentrate shear forces around the sparger
    • D. concentrate shear forces near the disengagement zone
    • Discuss
    • 6. In a fluidized bed reactor mixing is achieved by

    • Options
    • A. gravity flow of fluid
    • B. upward movement of the incoming feed
    • C. diffusion
    • D. both (a) and (b)
    • Discuss
    • 7. A fed-batch reactor containing 2 litre of medium and 0.1 g.l-l of biomass is fed with a medium containing 1 g.l-1 of substrate at 1 litre per hour. If after 10 hours, the concentration of biomass in the reactor was 0.2 g.l-1, then the biomass produced during the 10 hour period is

    • Options
    • A. 1.5 g
    • B. 2.2 g
    • C. 3.0 g
    • D. 6.0 g
    • Discuss
    • 8. A strain of Escherichia coli has a maximum specific growth rate of 0.8 h-1 on a glucose based medium. If this organism is being grown in a chemostat with a dilution rate of 1.2 h-1, then at steady state the concentration of E. coli in the same medium will

    • Options
    • A. increase
    • B. be zero
    • C. change randomly
    • D. decrease
    • Discuss
    • 9. Which of the following is best described as secondary metabolite?

    • Options
    • A. Acetic acid produced from the oxidation of ethanol
    • B. Ethanol from the fermentation of glucose
    • C. Penicillin
    • D. Citric acid from the partial oxidation of glucose
    • Discuss
    • 10. When the product formation is approximately equal to the rate of cell growth, the pattern of product formation is termed as

    • Options
    • A. uncoupled
    • B. growth associated
    • C. non-growth associated
    • D. metabolically uncoupled
    • Discuss


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