Bioreactor Analysis and OperationChapter 9&10 (textbook)
- Overview of bioreactors
- Modified batch and continuous reactors
- Scale up/down
- Immobilized cell systems
- Operation consideration
- Sterilization
- Bioreactor Instrumentation and control
- Fermentation processes
- solid state: water content: 40~ 80%, mostly mold fermentation on agriculture products and
food: rice, wheat, barley, corn and soybean.
e.g.rotary drum fermentator
- submerged systems: water content > 95%
e.g. bacteria, yeast.
Bioreactor Analysis and Operation
- Overview of bioreactors for submerged system
- Classification:
operation modes:- batch: stirred tank- continuous: chemostat, fluidized-bed- modified types of the above modes:
fed-batch, chemostat with recycle, multi-stage continuous reactors
Oxygen supply:- aerobic: airlift- anaerobic
Form of biocatalyst:- free cell (enzyme)- immobilized cell (enzyme)packed-bed, membrane reactor
Bioreactor Analysis and Operation
Industrial Bioreactor
Glacial Lakes Energy in Watertown, South Dakota
47+ million gallon per year ethanol production .
World's Largest Industrial Fermenter (Chem. Eng. News,10-Apr-78)
The fermenter is 200' high and 25 ft diam.
Requirements for Cultivation Methods
• Biomass concentration which must remain high • Sterile conditions being maintained • Effective agitation so that the distribution of
substances in the reaction is uniform • Heat removal • Creation of the correct shear conditions - high
may damage cells, low may lead to flocculation or growth on wall and stirrer
Chemostat with Cell Recycle- To keep the cell concentration higher than the normal steady-state level in a chemostat.
- To increase the cell and growth-associated product yield.
- For low-product-value processes: e.g. waste treatment.
fuel ethanol
,
X1, S
v
Chemostat with Cell RecycleCell mass balance (qp=0, kd ≈0, X0=0, Monod equation is applied):
A chemostat can be operated at dilution rates higher than the specific growth rate when cell recycle is used.
where µ=µnet=µg-kd
Chemostat with Cell Recycle
When kd=0
Chemostat with Cell RecycleMass balance on growth-limiting substrate (qp=0, kd ≈0, X0=0,
Monod equation is applied):
])1(
)1([
)]1(1[X ,
1
)(X
,)]1(1[ Since
)(D
X
0,dS/dt state,steady At
)1(1
010
1
01
10
//
/
/
CD
CDKS
C
Y
C
SSY
DC
SSY
dt
dSVFS
YXVFSFS
m
s
g
g
g
M
SX
M
SX
M
SX
M
SX
)1(
)1(
CDm
CDsKS
Chemostat with Cell Recycle
No recycle
µm=1.00h-1, S0=2.0g/l, Ks=0.01 g/l, Yx/s=0.5 g/g, concentration factor C=2.0 and recycle ratio α=0.5
Chemostat with Cell RecycleCell mass balance around the cell separator.
X1, S
v
F
V
XFCXFXFX
)1(
separator cell
separator cellin timeresidence average The2121)1(
Example-Chemostat with Cell RecycleOrganisms are cultured in a chemostat with cell recycle. The
system is operated under glucose limitation.
0K 0,X 0.7,α 1.5,C 1g/L,Ks
,0.2hμ substrate; cells/g 0.5gdwY
glucose/L g 10S 1000ml,V ml/h, 100F
d0
1m
MX/S
0
Determine specific growth rate μnet, S in the reactor effluent, cell concentration in the recycle stream (CX1) and in the concentrator effluent (X2)
If the concentrator has a volume of 300 mL, what is the residence time in it?
Fed-BatchNutrients are continuously or semi-continuously fed,
while effluent is removed discontinuously.
- overcome substrate inhibition or catabolite repression by intermittent feeding of substrate by maintaining low substrate concentration.for production of secondary metabolites e.g. antibiotics, lactic acid, E. Coli making proteins from recombinant DNA technology.
Fed-Batch Analysis of fed-batch with substrate continuously fed and no output: t=0, V0=0, F is constant.
D
DK
m
s
SThen
At quasi steady state, S added=S consumed, X, S, P concentrations are constant.
)(
dt
XVdXVFX netO
then,)(
sincedt
dVX
dt
dXV
dt
XVd
DV
F
dt
dV
Vdt
dVXXV netnet
1
tD
D
FtV
F
V
F onet
00 1
Ftdt
dV oVV F Volume:
Cell mass balance:
0K if d
SK
SD
s
mnet
dt
dVX
dt
dXVXVFX netO
(Monod growth model applied)
Fed-Batch
where S≈0
where Xt=Xt0 at t=0
M
M
assuming X≈Xm
Fed-Batch
at Pt=Pt0, t=0
(g)
qp (i.e. g product/g cells-min)
Fed-Batch
Example: Fed- BatchIn a fed-batch culture operating with intermittent
addition of glucose, the value of V is given at time t=2hr, when the system is at quasi-steady state.
cells g 03X 1g/L,.0Ks
,0.3hμ glucose; cells/g 0.5gdwY
glucose/L g 100S 1000ml,V ml/h, 200F
0t
1m
MX/S
0
dt
dV
Determine V0.
At t=2 hr, find S, X and Xt and P at quasi-steady state if qp=0.2 g product/g cells-h, P0=0.