Answer for question 3?
You are designing a recombinant yeast production system and need to determine the oxygen uptake rate (OUR) of the cells that you will be growing, as well as the oxygen transfer rate (OTR) of the medium. You carry out some unsteady state studies and obtain the following data:
OUR Study Time [0] (min) mg/L)
0 7.38
3.0 4.70
6.0 2.15
7.5 0.85
8.4 0.02
OTR Study Time [0] (min) (mg/L)
0 0
2.5 3.52
5.0 5.40
7.5 6.35
10 6.82
The OUR study was carried out in a bioreactor with 0.2 g/L of cells. The OTR study did not involve any cells. Both studies were carried out using air as the gas. The critical dissolved oxygen concentration for these cells is 0.2 mg/L. For oxygen in air, the partial pressure is 0.21 atm and the solubility in water at 25C, 1 atm is 7.3 mg/L.
a) (5 Points) Carry out an oxygen balance on the reactor and develop a linear equation which can be used to determine the OUR value for the cells (Since this is unsteady state, there will be an accumulation term in your balance which is dCi/dt, where Ci is the concentration of oxygen).
b) (5 Points) Using the OUR data, plot the equation derived in (a) and determine the value of OUR (mg O/g min) for these cells.
c) (5 Points) Carry out an oxygen balance on the reactor and develop a linear equation which can be used to determine the kia value for this system.
d) (5 Points) Using the OTR data, plot the equation derived in (c) and determine the value of kia (min^-1) for this bioreactor.
e) (5 Points) If oxygen is known to limit biomass production, calculate the maximum cell concentration (g/L) that could be supported in this system.
f) (5 Points) If you replace the air in this system with a mixture that contains 50% oxygen, determine the cell concentration that could be supported.
