Biomedical Engineering Reference
In-Depth Information
The productivity of a chemostat for product and biomass can be found from D
P
and
D
X
,respectively.
Figure 12.7
shows the variations of substrate concentration, biomass
concentration, and biomass productivity with dilution rate.
Figure 12.7
(a) shows that
substrates are nearly completely consumed in a chemostat at low dilution rates. Substrate
concentration increases with increasing dilution rate. Different endogeneous growth
needs are illustrated in
Fig. 12.7
: growth rate dependent or growth rate independent.
When death rate is exactly zero, the cell biomass concentration is maximum at low (or
zero) dilution rate. Increasing endogenous needs decreases the cell biomass concentration
especially at low dilution rates. When finite death rate is observed, the cell biomass
concentration is minimal at low dilution rates, reaching zero at zero dilution rate. The
(a)
(b)
1.0
1.0
0.9
0.9
0.8
0.8
0.7
0.7
0.6
0.6
0.5
0.5
0.4
0.4
0.3
0.3
0.2
0.2
0.1
0.1
0.0
0.0
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
D
/
max
D
/
max
(c)
1.0
0.9
0.8
0.7
0.6
K
S
= 0.001
S
0
,
k
d
= 0,
emax
= 0,
K
eS
= 0
0.5
K
S
= 0.05
S
0
,
k
d
= 0,
emax
= 0,
K
eS
= 0
0.4
K
S
= 0.001
S
0
,
k
d
= 0.075
max
,
emax
= 0,
K
eS
= 0
0.3
K
S
= 0.001
S
0
,
k
d
= 0,
emax
= 0.1
max
,
K
eS
= 0.0005
S
0
0.2
0.1
0.0
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
D
/
max
FIGURE 12.7
Variations of substrate concentration (a), biomass concentration and (b), biomass productivity
(c) with dilution rate in a chemostat where growth kinetics is given by
m
G
¼
m
max
S
K
S
þ S
m
net
¼ m
G
m
e
with
and
m
e
¼
m
emax
S
K
eS
þ S
þ k
d
. The solid line is the base case with the growth parameters shown, whereas the dashed lines are
with the change of one parameter from the base case.
Search WWH ::
Custom Search