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  • Question
  • In aerobic yeast fermentation for production of citric acid from alkanes using a fed-batch culture, why alkanes are slowly fed to the yeast?


  • Options
  • A. Citric acid is toxic to the cells
  • B. Alkanes cause foaming
  • C. Fast addition of alkanes will inhibit the cells and reduce oxygen transfer rates
  • D. Fast addition of alkanes will cause the cells to grow too quickly

  • Correct Answer
  • Fast addition of alkanes will inhibit the cells and reduce oxygen transfer rates 


  • Fermentation Reactors problems


    Search Results


    • 1. Low dissolved oxygen concentrations leads to

    • Options
    • A. low biomass yields
    • B. high biomass yields
    • C. no effect on biomass yields
    • D. none of the above
    • Discuss
    • 2. Fluidized bed bioreactors provide higher mass transfer rates than packed bed bioreactors because

    • Options
    • A. mixing is higher in fluidized bed bioreactors
    • B. particles move with the fluid in a fluidized bed bioreactor
    • C. immobilized particles are smaller in the fluidized bed bioreactors
    • D. all of the above
    • Discuss
    • 3. Mixing in an anaerobic sludge blanket reactor is due to

    • Options
    • A. rapid change in water temperatures throughout the reactor
    • B. release of gases by the microbial populations
    • C. swimming of microbes
    • D. none of the above
    • Discuss
    • 4. Which of the following is used to calculate mass of substrate in the reactor?

    • Options
    • A. Flow rate x substrate concentration in the reactor
    • B. Volume of reactor x substrate concentration in reactor
    • C. Flow rate x mass of reactor
    • D. Volume of reactor x Flow rate
    • Discuss
    • 5. Which of the statement is true for continuous reactor at steady state?

    • Options
    • A. The rates of biomass, substrate and product concentrations are zero
    • B. Biomass, substrate and product concentrations are zero
    • C. Biomass, substrate and product concentrations do not change with time
    • D. Biomass, substrate and product concentrations change with time
    • Discuss
    • 6. Immobilized cell reactors for wastewater treatment have the advantage of having/being

    • Options
    • A. higher cell concentration
    • B. more stable and prevent washout
    • C. higher dilution rate before the cells washout
    • D. all of the above
    • Discuss
    • 7. The growth of an organism on glucose is described by the following Monod model parameters: ?m = 0.5 h-1 and Ks =0.1 g.l-1, if the concentration of glucose in the feed is 10 g.l-1 and the dilution rate is set to 0.4 h-1, then the steady state concentration of glucose in the effluent will be

    • Options
    • A. 0 g.l-1
    • B. 0.5 g.l-1
    • C. 1.0 g.l-1
    • D. 10 g.l-1
    • Discuss
    • 8. The lowest yield of ATP /is in

    • Options
    • A. fermentation
    • B. aerobic respiration
    • C. anaerobic respiration
    • D. same in (a), (b) and (c)
    • Discuss
    • 9. Which have the maximum resistance while transferring carbon dioxide from the bulk liquid to an air bubble?

    • Options
    • A. Moving through the gas liquid interface
    • B. Moving through the bubble boundary layer
    • C. Moving across the cell membrane
    • D. Moving through the bulk liquid
    • Discuss
    • 10. Penetration theory assumes that turbulent eddies travel from the bulk of the phase to the interface where they remain constant for a constant exposure time (te). The model correlating KL, mass transfer coefficient and DAB, diffusivity can be expressed as

    • Options
    • A. KL = 2(DAB/?te)0.25
    • B. KL = 2(DAB/?te)0.5
    • C. KL = 2(DAB/?te)0.75
    • D. KL = 2(DAB/?te)
    • Discuss


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