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.