Fermentation Reactors

Q1: Mixing in an anaerobic sludge blanket reactor is due to

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

Q2: On a glucose medium, the growth of an organism is characterized by the following Monod model and stoichiometric parameters μm = 0.3 h-1, Ks =0.05 g.l-1 and Yxs = 0.3 g.g-1 When this organism is grown in a 2 litre continuous on a medium containing 10 g.l-1 of glucose added at 1 l.h-1, the steady state concentration of biomass in the reactor will be

A 0 g.l-1

B 0.4 g.l-1

C 0.5 g.l-1

D 10 g.l-1

Q3: The lowest biomass yield in a culture of Escherichia coli will be in

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

Q4: 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?

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

Q5: 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

A decrease abruptly

B increase

C increase drastically

D be zero

Q6: Mixing per unit volume is observed to be poorest in

A continuous packed bed reactor

B continuous fluidized bed bioreactor

C continuous airlift bioreactor

D none of the above

Q7: A chemostat has a liquid volume of 2 litres and is being fed at a rate of 4 litres per hour. Dilution rate for this reactor will be

A 2 litres

B 2 litres per hour

C 2 h-1

D 4 litres per hour

Q8: Which of the following would not be subjected to the "glucose effect"?

A Aspergillus fumigatus

B Saccharomyces cerevisiae

C Escherichia coli

D Aspergillus niger

Q9: 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

Q10: A culture system with constant environmental conditions maintained through continual provision of nutrient and removal of wastes is called __________ culture system.

A continuous

B batch

C fed-batch

D semi continuous

Q11: A continuous bioreactor in which only the flow rate is used to control the rate of cell or product productivity is called

A turbidostat

B chemostat

C level stat

D pH

Q12: The continuous cultures are not widely used in industry because

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

Q13: The lowest yield of ATP /is in

A fermentation

B aerobic respiration

C anaerobic respiration

D same in (a), (b) and (c)

Q14: Fluidized bed bioreactors provide higher mass transfer rates than packed bed bioreactors because

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

Q15: Fed batch reactors is used to produce vinegar because

A it can maintain low ethanol concentrations

B it can maintain low acetic acid concentrations

C acetic acid bacteria tend to ferment at high ethanol concentrations

D all of the above

Q16: The main reason for production of antibiotics in fed batch reactors is

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

Q17: A fed-batch reactor initially contains 2 litre of medium. If it was fed at 1 litre per hour, then after 10 hours, the volume of the reactor will be

A 1 litre

B 2 litre

C 3 litre

D 13 litre

Q18:Bacillus sp. produces an antibiotic only during the stationary phase when grown in a batch culture. If grown in a 5 litre continuous culture, the steady state productivity of the antibiotic

A will increase until the culture washes out

B will decrease after washout

C will be zero

D will be infinite

Q19: 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

Q20: Unsteady state mass balance for dynamic model of continuous stirred tank reactor (CSTR) is

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

Q21: The growth of an organism on glucose is described by the following Monod model parameters: μm = 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

A 0 g.l-1

B 0.5 g.l-1

C 1.0 g.l-1

D 10 g.l-1

Q22: Which of the statement is true for continuous reactor at steady state?

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

Q23: In a fluidized bed reactor, the function of the disengagement zone is to

A reduce loss of particles from the reactor

B reduce the velocity of the particles near the surface of the reactor

C reduce foaming problems

D all of the above

Q24: A continuous reactor has a dilution rate of 0.5 h-1. Its residence time would be

A ln(2)/0.5

B ln(2) x 0.5

C 0.5 h

D 2 h

Q25: Formation of end product by Lactococcus lactis will become non-growth associated as lactic acid accumulates because

A cells will redirect ATP to anabolism

B cells will redirect NAD+ to anabolism

C cells will redirect ATP to facilitate the diffusion of lactic acid and H+ out of the cells

D cells will redirect ATP to the active transport of lactic acid and H+ out of the cells

Q26: Yield coefficient represents

A total biomass or product produced

B conversion efficiency of a substrate into product

C conversion rate of a substrate into biomass or product

D production time of biomass or product

Q27: Mixing profiles closest to plug flow are observed in

A continuous packed bed reactor

B stirred tank reactor with biomass recycles

C continuous fluidized bed bioreactor

D all of these

Q28: For organisms growing in a chemostat, the specific growth rate

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

Q29: 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

A 2g

B 6g

C 8g

D 12g

Q30: Immobilized cell reactors for wastewater treatment have the advantage of having/being

A higher cell concentration

B more stable and prevent washout

C higher dilution rate before the cells washout

D all of the above

Q31: 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

Q32: 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

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

Q33: 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

Q34: When a culture of fermenting yeast becomes metabolically uncoupled, ethanol

A becomes a secondary metabolite

B production becomes growth associated

C production becomes non-growth associated

D becomes a growth nutrient

Q35: 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

A decrease with time

B increase with time

C be constant

D change randomly with time

Q36: In fed-batch fermentation, mass of substrate utilized is calculated using the relationship

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

Q37: Toxins accumulated in a reactor can lead to low biomass yields probably due to which of the following?

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

Q38: When two populations compete for a single growth limiting substrate in a continuous fermenter, which organism would not be washed out?

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

Q39: A continuous reactor at steady state contains 0.04 g.l-1 of biomass and 0.02 g.l-1 of phenol. The feed contained 0.1 g.l-1 of phenol. The biomass yield would be

A 0.4 g.g-1

B 0.5 g.g-1

C 1.0 g.g-1

D 5.0 g.g-1

Q40: 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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