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  • Question
  • 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

  • Correct Answer
  • release of gases by the microbial populations 


  • Fermentation Reactors problems


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    • 1. 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
    • 2. 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
    • 3. Saccharomyces cerevisiae is being grown in a chemostat converts glucose to biomass, ethanol, glycerol and carbon dioxide. At steady state, the concentration of glucose, biomass, ethanol and glycerol will

    • Options
    • A. decrease with time
    • B. increase with time
    • C. be constant
    • D. change randomly with time
    • Discuss
    • 4. In fed-batch fermentation, mass of substrate utilized is calculated using the relationship

    • Options
    • A. initial mass of substrate in the reactor + final mass of substrate in the reactor + flow rate x [substrate in the feed]
    • B. initial mass of substrate in the reactor - final mass of substrate in the reactor + flow rate x [substrate in the feed]
    • C. initial mass of substrate in the reactor + final mass of substrate in the reactor - flow rate x [substrate in the feed]
    • D. initial mass of substrate in the reactor + final mass of substrate in the reactor - flow rate
    • Discuss
    • 5. When two populations compete for a single growth limiting substrate in a continuous fermenter, which organism would not be washed out?

    • Options
    • A. Organism maintaining the highest substrate concentration
    • B. Organism maintaining the lowest substrate concentration
    • C. Both (a) and (b)
    • D. Organism maintaining the moderate substrate concentration
    • Discuss
    • 6. 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
    • 7. 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
    • 8. 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
    • Discuss
    • 9. 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
    • 10. 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


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