11. 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

12. 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

13. 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

14. 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

15. In aerobic yeast fermentation for the 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