Oxygen transfer effects on recombinant benzaldehyde lyase production
Oxygen transfer (OT) effects on benzaldehyde lyase (BAL) production by recombinant Escherichia coli carrying pUC18:: bal gene were investigated on a defined medium with glucose and (NH 4 ) 2 HPO 4 as the sole carbon and nitrogen sources respectively, in 3.0 dm 3 bioreactor systems at six different c...
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Published in | Chemical engineering science Vol. 59; no. 22; pp. 5075 - 5083 |
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Main Authors | , , , |
Format | Journal Article Conference Proceeding |
Language | English |
Published |
Oxford
Elsevier Ltd
01.11.2004
Elsevier |
Subjects | |
Online Access | Get full text |
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Summary: | Oxygen transfer (OT) effects on benzaldehyde lyase (BAL) production by recombinant
Escherichia coli carrying pUC18::
bal gene were investigated on a defined medium with glucose and (NH
4
)
2
HPO
4
as the sole carbon and nitrogen sources respectively, in 3.0
dm
3
bioreactor systems at six different conditions with the parameters, air inlet rate of
Q
O
/
V
R
=
0.5
vvm, and agitation rates of
N
=
250
, 375, 500, 625, 750
min
-
1
and at
Q
O
/
V
R
=
0.7
vvm
,
N
=
750
min
-
1
. Cell concentration (
C
X
), BAL volumetric and specific activities, organic acid concentrations, yield values, maintenance coefficients, oxygen transfer coefficients (
K
L
a
) and oxygen uptake rates (OUR) were determined throughout the bioprocess. Increase in the oxygen transfer rate increased the cell formation up to 0.5
vvm, 500
min
-
1
; however, further increase inhibited cell formation. The highest BAL volumetric activity was obtained at 0.5
vvm, 500
min
-
1
as 860
U
cm
-
3
.
K
L
a
, and enhancement factor
E
(
K
L
a
/
K
L
a
o
)
increased with the cultivation time and agitation rate, their values varied between 0.008–0.046
s
-
1
and 1.00–3.07, respectively. OUR first increased, and then decreased with the cultivation time at all OT conditions, the highest OUR was observed at 0.5
vvm, 500
min
-
1
as 3.6
mmol
m
-
3
s
-
1
at
t
=
8
h
; while the highest specific OUR was obtained at 0.5
vvm, 250
min
-
1
as 0.74
kg
kg
-
1
h
-
1
at
t
=
1
h
. With the increase in
Q
O
/
V
R
and/or
N, Damköhler number
(
Da
)
, that is the OT limitation, decreased. The effectiveness factor (
η
) values were close to 1.0 at medium and high OT conditions at the beginning of the processes as cells consumed oxygen with such a high rate that maximum possible oxygen utilization rate (oxygen demand) value was approached; thereafter,
η
decreased with the increase in cultivation time and
Da, and the decrease rate was higher at lower agitation rates due to the lower
K
L
a
. Oxygen consumption for maintenance (
m
O
) was the highest at 0.5
vvm, 500
min
-
1
and the value was 0.20
kg
kg
-
1
h
-
1
. |
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Bibliography: | ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 |
ISSN: | 0009-2509 1873-4405 |
DOI: | 10.1016/j.ces.2004.07.070 |