A genetically modified yeast is cultivated at pH = 3.3 and temperature = 37°C). Values of substrate flow, F, cell mass concentration, X1, concentration of glucose, S1 (the limiting substrate component), and product concentration, P1, was measures throughout fermentation. The product is a protein - not a primary metabolite - and the substrate utilization for product formation, rS = YX/P,stoich × qp × X, is so low that it can be neglected. All samples were taken after steady state had been established. The feed stream, S0, contains 50.0 g glu/l and no product (P0 = 0), and the working volume, V, is 500 ml. ke = kd = 0.
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F (ml/h)
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50
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100
|
150
|
200
|
250
|
300
|
|
X1 (g DCM/l)
|
17.7
|
21.5
|
23.2
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24.0
|
24.5
|
24.0
|
|
S1 (g glu/l)
|
0.036
|
0.089
|
0.171
|
0.320
|
0.667
|
2.40
|
|
P1 (mg prod/l)
|
115
|
75
|
58
|
48
|
42
|
36
|
a. Explain ke and kd.
b. Examine if the growth if following Monod kinetics and if this is the case determine KS and mMAX.
c. Examine if the substrate utilization kinetics can be expressed by growth constants YX/S,true and mS and if this is the case calculate these constants.
d. At D=0.46 h-1 and same conditions as given above calculate YX/S, rX, rS, rP, and YP/S.