BIOREACTOR DESIGNYUSRON SUGIARTO

Bioreactor: device, usually a vessel, used to direct the activity ofa biological catalyst to achieve a desired chemicaltransformation.

Product

Bioreactor

Recycle

Product

separation & purification

Nutrients tank

Waste

Input

Pre-filtration

Fermenter: type of bioreactor in which the biocatalyst is a living cell.

What is a bioreactor?

WHAT IS BIOREACTOR DESIGN?

Biotechnology:Application-oriented integration of biodisiplinesand engineering

WHAT IS THE AIM OF BIOREACTOR DESIGN?

MINIMIZATION OF THE COSTS OF THE PERTINENT PRODUCT WHILE RETAINING THE DESIRED QUALITY AND THIS WITHIN THE BIOLOGICAL AND TECHNOLOGICAL CONSTRAINTS.

1. Aerobic bioreactor: Need adequate mixing and aeration

2. Anaerobic bioreactor: no need for sparging or agitation

Challenges in Bioreactor Design

REACTOR BIOREACTOR

any manufactured or engineered device or system that supports a biologically active environment.

vessels designed to contain chemical reactions a vessel in which a chemical process is carried out which involves organisms or biochemically active substances derived from such organisms

The design of a chemical reactor deals with multiple aspects of chemical engineering.

REACTOR CONCEPTS

• The batch reactor

• The fed batch reactor

• The continuous flow, stirred tank reactor (CSTR)

• The plug flow reactor

1. Bioreactor configurations

2. Bioreactor operation modes

3. Practical considerations for bioreactor design

Outline of Lecture

BIOREACTOR TYPES

• The stirred vessel

• The bubble colomn

• The air lift

• The packed bed

Bioreactor Configurations1. Stirred tank

Mixing method: Mechanical agitation

•Baffles are usually used to reduce vortexing

• Applications: free and immobilized enzyme reactions

•High shear forces may damage cells

•Require high energy input

Bioreactor Configurations2. Bubble column

Mixing method: Gas sparging• Simple design•Good heat and mass transfer•Low energy input

Gas-liquid mass transfer coefficients depend largely on bubble diameter and gas hold-up.

Bioreactor Configurations3. Airlift reactor

Mixing method: airlift• Compared to bubble column reactors, in an airlift reactors, there are two liquid steams: up-flowing and down-flowing steams. Liquid circulates in an airlift reactor as a result of density difference between riser and downcomer.

Bioreactor Configurations4. Packed-bed reactor

Packed-bed reactors are used with immobilized or particulate biocatalysts.

Medium can be fed either at the top or bottom and forms a continuous liquid phase.

Bioreactor Configurations5. Trickle-bed reactor

The trickle-bed reactor is another variation of the packed bed reactors.

Liquid is sprayed onto the top of the packing and trickles down through the bed in small rivulets.

Bioreactor Configurations6. Fluidized bed reactor

When the packed beds are operated in upflow mode, the bed expands at high liquid flow rates due to upward motion of the particles.

1. Bioreactor configurations

3. Practical considerations for bioreactor design

Outline of Lecture

Bioreactor Operation Modes1. Batch Operation

A batch bioreactor is normally equipped with an agitator to mix the reactant, and the pH of the reactant is maintained by employing either buffer solution or a pH controller

trCCC

CK ss

s

sm max0

0ln Change of Cs with time, t

Batch operation with stirring

•A foam breaker may be installed to disperse foam

Sm

Ss

CK

Cr

dt

dCr

max

Substraterate

Biocatystconcentration

Bioreactor Operation Modes2. Plug-flow mode

In a plug-flow reactor, the substrate enters one end of a cylindrical tube with is packed with immobilized enzyme and the product steam leaves at the other end.

trCCC

CK ss

s

sm max0

0ln

F, Cs0 F, Cs

t = 0F

V

An ideal plug-flow reactor can approximate the long tube,

packed-bed and hollow fiber or multistaged reactor

Residence time

Continuous operation without stirring

V

Bioreactor Operation Modes3. Continuous stirred-tank

A continuous stirred-tank reactor (CSTR) is an ideal reactor which is based on the assumption that the reactants are well mixed.

Continuous operation with

stirring

F, Cs0

F, CsV

Bioreactor Operation Modes3. Continuous stirred-tank reactor-Con.

dt

dCVVrFCFC s

sss 0

F, Cs0

F, CsV

Mass balance of substrate:

onAccumulati n ConsumptioOutput -Input

0dt

dCsSteady state:

Michaelis-Menten rate:

Sm

S

CK

Crr

max

0max0

sm

sss

CK

CrVFCFC

Bioreactor Operation Modes3. Continuous stirred-tank reactor-Con.

ss

sms

CC

CrKC

0

max

F, Cs0

F, CsV

Mass balance of substrate:

0max0

sm

sss

CK

CrVFCFC

smss

s

CKCC

Cr

V

F

0

max

1

V

F

1. Bioreactor configurations

2. Bioreactor operation modes

3. Practical considerations for bioreactor design

Outline of Lecture

kcalYCVq

1

Heat production rate:

q : heat production rate, kcal/ls

V: reactor liquid volume, l

: specific growth rate, s-1

C: biomass concentration (g/l)

Ykcal: a yield coefficient given as grams of cells formed per kcal energy released, g cells/kcal

Heat load: Heat load is determined by energy balances

Practical Issues for Bioreactors- Temperature Control (Heat Load)

Popular method

Practical Issues for Bioreactors-Temperature control (heat transfer)

Heat transfer surface area: 1. Low in (a) external jacket and (b) external coil for small reactors2. High in (c) internal helical coil and (d) internal baffle coil for large reactors3. Easily adjustable in (e) a separate external heat exchange unit

Difficult to cleanEasily fouled by cell

growth on the surface

No cleaning problem

• Sterility requirement

• Shear forces imposed on cells

• Depletion of oxygen

1. Biological reactions almost invariably are three-phase reactions (gas-liquid-solid). Effective mass transfer between phases is often crucial. For example, for aerobic fermentation, the supply of oxygen is critical.

HPCgAA

* gAAlA CCKJ *

The equation governing the oxygen transfer rate is:

Agitation:

•Mechanical stirring (for small reactors, and/or viscous liquids, low reaction heat)

•Air-driven agitation (for large reactors and/or high reaction heat)

Practical Issues for Bioreactors-Agitation (gas transfer)

1. Mechanical foam breaker (a supplementary impeller)

2. Chemical antifoam agents (may reduce the rate of oxygen transfer)

Practical Issues for Bioreactors- Foaming removal

1. Aseptic operation (3-5% of fermentations in an industrial plant are lost due to failure of sterilization.

2. Construction materials (glass for small bioreactors, e.g., < 30 liters and corrosion-resistant stainless steel for large reactors)

3. Sparage design (three designs: porous, orifice and nozzle)

4. Evaporation control due to dry air input

Practical Issues for Bioreactors- Other issues

Summary of Lecture

1. Bioreactor configurations

2. Bioreactor operation modes

3. Practical considerations for bioreactor design

BIOREACTOR DESIGN

1. MIXING

2. HOLD UP

3. MASS TRANSFER

4. FOAM

5. HEAT TRANSFER

6. POWER CONSUMPTION

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