Biomedical Engineering Reference
In-Depth Information
TABLE 18.4
Typical Respiration Rates of Microbes and Cells in Culture
Organism
m
O
2
, mmol-O
2
/(g-dw h)
Bacteria
10
e
12
E. coli
Azotobacter sp.
30
e
90
Streptomyces sp.
2
e
4
Yeast
S. cerevisiae
8
Molds
Penicillium sp.
3
e
4
Aspergillus niger
ca. 3
Plant cells
Acer pseudoplatanus (sycamore)
0.3
Saccharum (sugar cane)
1
e
3
Animal cells
10
12
mol-O
2
/(h
$
cell)
HeLa
0.4
10
12
mol-O
2
/(h
$
cell)
Diploid embryo WI-38
0.15
where P
u
is the power requirement for ungassed vessel (i.e. in the absence of aeration or
airflow into the reactor).
K
L
a is dependent on the media, salts, surfactants, pressure, and temperature making it
difficult to predict. K
L
a is however measurable. Four approaches are generally used to
measure K
L
a: unsteady state, steady state, dynamic, and sulfite test. The reactor is filled
with water or medium and sparged with nitrogen to remove oxygen. The air is introduced
and DO is monitored until the bioreactor is nearly saturated.
In the case of no consumption of oxygen in the reactor, mass balance of oxygen in the
reactor leads to
d
C
L
d
t
¼ K
L
aðC
C
L
Þ
(18.5a)
which can be integrated to yield
C
L
¼ C
ðC
C
L
0
ÞexpðK
L
a$tÞ
(18.5b)
The DO changes exponentially with time for unsteady-state accumulation of oxygen. This is
the theoretical basis for unsteady-state method of measuring the oxygen transfer coefficient.
It is the simplest and easiest one to implement.
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