#Question id: 14238
#Section 5: Bioprocess Engineering and Process Biotechnology
A genetically-engineered strain of yeast is cultured in a bioreactor at 30⁰C for production of heterologous protein. The oxygen requirement is 80 mmol 1-1 h-I; the critical oxygen concentration is 0.004 mM. The solubility of oxygen in the fermentation broth is estimated to be 10% lower than in water due to solute effects. What mass-transfer coefficient is required if pure oxygen is used instead of air?
#Question id: 14239
#Section 5: Bioprocess Engineering and Process Biotechnology
A 200-1itre stirred fermenter contains a batch culture of
Bacillus subtilis bacteria at 28⁰C Air at 20⁰C is pumped into the vessel at
a rate of 1 vvm; (vvm stands for volume of gas per volume of liquid per
minute). The average pressure in the fermenter is 1 atm. The volumetric flow
rate of off-gas from the fermenter is measured as 189 l min-1. The
exit gas stream is analysed for oxygen and is found to contain 20.1% 02.
The dissolved-oxygen concentration in the broth is measured using an oxygen
electrode as 52% air saturation. The solubility of oxygen in the fermentation
broth at 28⁰C
and 1 atm air pressure is 7.8 x 10-3 kg m-3. Calculate
the oxygen transfer rate_____________
#Question id: 14240
#Section 5: Bioprocess Engineering and Process Biotechnology
A 200-1itre stirred fermenter contains a batch culture of Bacillus subtilis bacteria at 28⁰C Air at 20⁰C is pumped into the vessel at a rate of 1 vvm; (vvm stands for volume of gas per volume of liquid per minute). The average pressure in the fermenter is 1 atm. The volumetric flow rate of off-gas from the fermenter is measured as 189 l min-1. The exit gas stream is analysed for oxygen and is found to contain 20.1% 02. The dissolved-oxygen concentration in the broth is measured using an oxygen electrode as 52% air saturation. The solubility of oxygen in the fermentation broth at 28⁰C and 1 atm air pressure is 7.8 x 10-3 kg m-3. Determine the value of kLa for the system ____________
#Question id: 14241
#Section 5: Bioprocess Engineering and Process Biotechnology
Yeast cells are to be separated from a fermentation broth.
Assume that the cells are spherical with diameter 5 µm and density 1.06 g cm-3.
The viscosity of the culture broth is 1.36 x 10-3 N s m-2.
At the temperature of separation, the density of the suspending fluid is 0.997
g cm-3. 500 litres broth must be treated every hour. Specify Σ
for a suitably-sized disc-stack centrifuge
____________________
#Question id: 14242
#Section 5: Bioprocess Engineering and Process Biotechnology
Small food particles with diameter 10-2 mm and density 1.03 g cm-3 are suspended in liquid of density 1.00 g cm-3. The viscosity of the liquid is 1.25 mPa s. A tubular-bowl centrifuge of length 70 cm and radius 11.5 cm is used to separate the particles. If the centrifuge is operated at 10 000 rpm, estimate the feed flow rate at which the food particles are just removed from the suspension. ____________________
#Question id: 14243
#Section 5: Bioprocess Engineering and Process Biotechnology
A tubular-bowl centrifuge is used to concentrate a suspension of genetically-engineered yeast containing a new recombinant protein. At a speed of 12 000 rpm, the centrifuge treats 3 l broth min-1 with satisfactory results. It is proposed to use the same centrifuge to separate cell debris from homogenate produced by mechanical disruption of the yeast. If the average size of the debris is one-third that of the yeast and the viscosity of the homogenate is five times greater than the cell suspension, what flow rate can be handled if the centrifuge is operated at the same speed? _____________________