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Biochemical Engineering Objective Questions { Fermentation Reactors }

15. In aerobic yeast fermentation for production of citric acid from alkanes using a fed-batch culture, why alkanes are slowly fed to the yeast?
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
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16. A continuous reactor has a dilution rate of 0.5 h-1. Its residence time would be
B.ln(2) x 0.5
C.0.5 h
D.2 h
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17. Which of the following is used to calculate mass of substrate in the reactor?
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
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18. If biomass yields are constant, then the biomass productivity of a culture grown in continuous reactor will
A.always decrease with dilution rate
B.increase with dilution rate until washout
C.remain constant irrespective of the dilution rate
D.decrease with dilution rate until washout
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19. Low dissolved oxygen concentrations leads to
A.low biomass yields
B.high biomass yields
C.no effect on biomass yields
D.none of the above
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20. In a continuous reactor, the medium contains 40 g.l-1 of maltose and the medium flow rate is 10 litres per hour and the effluent contains 20 g.l-l of lactate. What is the productivity of lactate production from this reactor?
A.50 g maltose.l-1
B.50 g lactate.l-1
C.200 g maltose.l-1
D.200 g lactate.l-1
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21.  A fed-batch reactor containing 1 g.l-1 of substrate in 2 litre of medium. It is fed with 1 g.l-l of substrate at the rate of 1 litre per hour. After 10 hours, the concentration of substrate in the reactor was 0.5 g.l-1 . The mass of substrate that was used by the culture in the reactor was
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