A production strain of L-threonine was derived from fermentation of Escherichia coli (E. Coli). A biochemical engineer has determined the cell growth, product formation and substrate consumption. The data were tabulated in Table 1. Moreover, the dissolved oxygen concentration was measured to estimate the oxygen uptake rate and volumetric oxygen transfer coefficient (ka) in this system. a) Estimate the volumetric oxygen transfer coefficient (k, a) for the fermentation process. The critical oxygen concentration must be above 10% of the saturation level. Given that the yield of oxygen coefficient is 0.45 g cell/g O2 and oxygen solubility is 7.5 mg/L at cell concentration of 60 g/L.

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A production strain of L-threonine was derived from fermentation of Escherichia coli (E.Coli).
A biochemical engineer has determined the cell growth, product formation and substrate
consumption. The data were tabulated in Table 1. Moreover, the dissolved oxygen
concentration was measured to estimate the oxygen uptake rate and volumetric oxygen
transfer coefficient (k, · a) in this system.
a) Estimate the volumetric oxygen transfer coefficient (kL · a) for the fermentation process.
The critical oxygen concentration must be above 10% of the saturation level. Given that
the yield of oxygen coefficient is 0.45 g cell/g O2 and oxygen solubility is 7.5 mg/L at cell
concentration of 60 g/L.
b) Determine the maximum concentration of E.coli that can be sustained in the fermenter
under steady-state condition if the specific rate of oxygen consumption in (a) is doubled.
Conclude your finding.
Table 1: Cell growth, substrate concentration and product formation data.
Time
E.Coli
Dissolved
Охудen
(mg/L)
Glucose
Threonine
(h)
concentration
concentration
Concentration
(g/L)
(g/L)
(g/L)
1
45
7.87
2
43
7.76
12
6.
41
1
6.38
18
15
36
3
4.78
24
30
30
29
2.99
30
45
22
57
1.98
36
54
16
76
2.89
42
58
9.
91
4.48
48
60
98
6.47
54
60
0.2
100
7
60
60
0.1
101
7.01
Transcribed Image Text:A production strain of L-threonine was derived from fermentation of Escherichia coli (E.Coli). A biochemical engineer has determined the cell growth, product formation and substrate consumption. The data were tabulated in Table 1. Moreover, the dissolved oxygen concentration was measured to estimate the oxygen uptake rate and volumetric oxygen transfer coefficient (k, · a) in this system. a) Estimate the volumetric oxygen transfer coefficient (kL · a) for the fermentation process. The critical oxygen concentration must be above 10% of the saturation level. Given that the yield of oxygen coefficient is 0.45 g cell/g O2 and oxygen solubility is 7.5 mg/L at cell concentration of 60 g/L. b) Determine the maximum concentration of E.coli that can be sustained in the fermenter under steady-state condition if the specific rate of oxygen consumption in (a) is doubled. Conclude your finding. Table 1: Cell growth, substrate concentration and product formation data. Time E.Coli Dissolved Охудen (mg/L) Glucose Threonine (h) concentration concentration Concentration (g/L) (g/L) (g/L) 1 45 7.87 2 43 7.76 12 6. 41 1 6.38 18 15 36 3 4.78 24 30 30 29 2.99 30 45 22 57 1.98 36 54 16 76 2.89 42 58 9. 91 4.48 48 60 98 6.47 54 60 0.2 100 7 60 60 0.1 101 7.01
Useful equation
kL a[C* – C¿]
The rate of oxygen transfer, OTR
The oxygen uptake rate,
HgX
OUR =
902 *
where
is the oxygen transfer coefficient (cm/hr)
is the gas-liquid interfacial area (cm?/cm³)
kL
а
kL·a is the volumetric oxygen transfer coefficient
C*
is the saturated DO concentration (mg/L)
is the actual DO concentration in the broth (mg/L)
is the specific rate of oxygen consumption (mg Oz/g dw cells.hr)
CL
902
is specific growth rate (hr')
Hg
is the yield coefficient on oxygen (g dw cells/g O2)
X
is cell concentration (g dw cell/L)
Transcribed Image Text:Useful equation kL a[C* – C¿] The rate of oxygen transfer, OTR The oxygen uptake rate, HgX OUR = 902 * where is the oxygen transfer coefficient (cm/hr) is the gas-liquid interfacial area (cm?/cm³) kL а kL·a is the volumetric oxygen transfer coefficient C* is the saturated DO concentration (mg/L) is the actual DO concentration in the broth (mg/L) is the specific rate of oxygen consumption (mg Oz/g dw cells.hr) CL 902 is specific growth rate (hr') Hg is the yield coefficient on oxygen (g dw cells/g O2) X is cell concentration (g dw cell/L)
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