3lecture types 2

8/7/2019 3lecture Types 2

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P.V.S.YUGANDHARM.Tech ( Biotech)

BIOREACTORBIOREACTOR

TYPES -II


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Airlift bioreactor

An air-lift reactor is divided into three regions:the air-riser, down-comerand disengagement

zone. The region into which bubbles are sparged is

called the air-riser. The air-riser may be on theinside or the outside of the draft-tube. The latter

design is preferred for large scale fermenters as itprovides better heat transfer efficiencies.


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Airlift bioreactor

The rising bubbles in the air-riser cause the liquidto flow in a vertical direction. To counteract theseupward forces, liquid will flow in a downwarddirection in the down-comer. This leads to liquidcirculation and thus improved mixing efficienciesas compared to bubble columns.

The enhanced liquid circulation also causesbubbles to move in a uniform direction at arelatively uniform velocity. This bubble flow

pattern reduces bubble coalescence and thusresults in higher kLa values as compared tobubble column reactors.


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Immobilized Cell

Reactors


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Fixed bed reactors

In fixed bed fermenters, the cells are

immobilized by absorption on or

entrapment in solid, non-moving solid

surfaces.


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In one type of fixed bed fermenter, the

cells are immobilized on the surfaces of

immobile solid particles such as

>plastic blocks

>concrete blocks

>wood shavings or

>fibrous material such as plastic or glass

wool.

*In other types of fixed-bed fermenters, the

cells are immobilized in solidified gels

such as agar or carrageenin.


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**Industrial applications of fixed

bed reactors includewaste water treatment

production of enzymes andamino acids

steroid transformations


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Cellrecyclesystems

In a fermenter with cell recycle the cellsare separated from the effluent and then

recycled back to the fermenter; thusminimizing cell removal from thefermenter

Cell recycle is used in activated sludgesystems. A portion of the cells areseparated in a settling tank and returned tothe activated sludge fermenter.


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Packed and Trickle bed

Bioreactors Packed bed reactors often suffer from

problems caused by poor mass transferrates and clogging. Despite this they areused commercially with enzymatically

catalysts and with slowly or non-growingcells.

Trickle bed reactors are a class of packedbed reactors in which the medium flows(or trickles) over the solid particles. Inthese reactors, the particles are notimmersed in the liquid. They are used

widely in aerobic treatment of sewage.


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Fluidized bed reactors

Fluidized bed bioreactors are an example

of reactors in which mixing is assisted by

the action of a pump. In a fluidized bed

reactor, cells or enzymes are immobilized

in and/or on the surface of light particles.


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Aerationand Agitationin

Animal Cell Bioreactors

Animal cells fragilecan be easilydamaged

In mammalian cell culture the objectives ofmaximizing oxygen transfer must bebalanced by the need to maintain cellintegrity. Fortunately, mammalian cellgrowth rates are considerably slower thanthose of most aerobic microorganisms andoxygen transfer requirements are therefore

also proportionately lower.


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Methodsofminimizingcell damage

Bubblefreeoxygenation - External

oxygenation

A more commonly used and effective

method of bubble free oxygenation is to

use a separate oxygenation chamber: Themediumisoxygenated inaseparateunit

whichcaneither beastirred tankreactorora

staticmixer. Theoxygenated medium is

pumped intothe bioreactorwhiletheoxygen

depleted medium ispumped backintothe

oxygenationunit


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Thesameprinciplecan beused

withimmobilized cellculturessuchasfluidized bed and fibre

bed reactors.


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3lecture types 2

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