Bioreactor and Sterilization

8/20/2019 Bioreactor and Sterilization

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SSG 2513SSG 2513Introduction of BioprocessIntroduction of Bioprocess

EngineeringEngineering

5.0 Bioreactor selection and optimization5.0 Bioreactor selection and optimization

5.1 Identification of various bioreactor 5.1 Identification of various bioreactor

5.2 Sterilization in bioreactor and bioprocess unit5.2 Sterilization in bioreactor and bioprocess unit

operationsoperations

Goh Kian Mau


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• References:

• Bioprocess Engineering. Shuler. (9.1, 9.2,9.3, 9.5, 15.4.1,10.4)

• Bioprocess Engineering Principles.Pauline M. Doran. (P248.3 B56 1995)

• Operation modes of bioreactors.(TP.248.25.B55 O63 1992)

• Bioreactor Design and product yield

(TP248.25 B55 B56 1992).


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What is bioreactor?

• The bioreactor in which biological/biochemicalreaction takes place occupies a central positionin the chemical process.

• Synonymous for bioreactor: biochemical reactor,biological reactor, fermenter, microbial reactor.

• The reactions happens inside the vessel

because of the presence of either microbialfermentation or enzyme (cell-free) reactions orboth.The cells or enzyme can be in suspension

or immobilized form.• Bioreactors can be operated as aerobic,

anaerobic, or solid state.


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• The bioreactor provides the volume (height, diameter) necessary forthe reaction and holds the amount of catalyst or cells required for thereaction. The energy required to over-come the activation thresholdof each partial reaction is also supplied in the reactor, and the proper

parameters (temperature, concentration, pressure, pH, DO, etc) aremonitored and controlled.


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Bioreactor Configurations

• Batch Stirred Tankonly 70-80% of the volume of stirred

reactors is filled with liquid; this allowsadequate headspace fordisen-gagement (breaking off ) ofdroplets from the exhaust gas and to

accommodate any foam which maydevelop. If foaming is a problem, asupplementary impeller called a foambreaker maybe installed as shown

above. Alternatively, antifoam agentsare added to the broth; becausereduces the rate of oxygen transfer.Normally mechanical foam dispersal isgenerally preferred.


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Batch bioreactor

• Before inoculation (or adding the enzymes),the batch reactor contains a certain volumeof nutrient (or substrate) in suspension.

• After inoculation, the process is leftuntouched, ie no material is added to orremoved from the reactor.

• However, the reactor might be aerated.

• Batch reactors are often referred to as

closed systems.

• The term 'closed' refers to the fact thatmaterial can neither enter nor leave the

reactor. (exceptional: air in and air out)

Exhaust air

(Air out)

Air in


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• In an ideal well-mixedbioreactor, the mixing isassumed to be intenseenough that the fluid ishomogeneous through thereactor.

• no dead zones or clumps

of undissolved solidsubstrate floating aroundand there is no

concentration gradients invessel.

Batch bioreactor-ideal mixing


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Fed batch bioreactor

• The fed-batch reaction (FBR) is a batch

reactor to which, when the nutrientsapproach depletion, fresh nutrients are

added. In other words, the reactor is fed. It

is assumed that the concentration of the

nutrients added is so high that volume

changes are negligible (justifying the batchpart of the name).


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Bubble column

- no mechanical agitation.-aeration and mixing are achieved by gas

sparging; this requires less energy than

mechanical stirring.

-height-to-diameter ratio is usually high to

maximize the aeration mixing

-Advantages of bubble columns include low

capital cost, lack of moving parts, and

satisfactory heat- and mass-transfer

perfor-mance. As in stirred vessels,foaming can be a problem requiring

mechanical dispersal or addition of

antifoam to the medium. (Your imagination

is needed, bubble and foam is different!)


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Bubble column• The oxygen transfer from the air bubble

and the mixing inside the bubble-columndepend entirely on the behaviour of thebubbles released from the sparger.

• Homogeneous flow occurs only at low

gas flow rates and when bubblesleaving the sparger are evenlydistributed across the column cross-section. In homogeneous flow, all

bubbles rise with the same upwardvelocity and there is no backmixing of thegas phase.

• Liquid mixing in this flow regime is alsolimited, arising solely from entrainment inthe wakes of the bubbles. Under normaloperating conditions at higher gasvelocities, large chaotic circulatory flowis develop and heterogeneous flow

occurs as illustrated in figure on the left.


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Airlift bioreactor • Their distinguishing featurecompared with the bubblecolumn is that of liquid flow

are more defined owing tothe physical separation ofup-flowing and down-flowingstreams.

• gas is sparged into a part ofthe vessel section called theriser.

• Gas disengages at the topof the vessel leaving heavierbubble-free liquid torecirculate through thedowncomer.

• Liquid circulates in airliftreactors as a result of thedensity difference betweenthe riser and downcomer.

P k d b d


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Packed-bed

bioreactor • Packed-bed reactors are

used with immobilised or

particulate biocatalysts.

• Medium/buffer can be fed

either at the top or bottomof the column and forms a

continuous liquid phase

between the particles.• Damage due to particle

wear is minimal in packed

beds compared with stirredreactors.

Fl idi d b d


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Fluidized bed

bioreactor

• Normally the vessel is not fullypacked with the bead for the

expansion and movement of thebed.

• When packed beds areoperated in upflow mode with

beads of appropriate size anddensity, the bed expands atliquid flow rates due to upward

motion of the particles.• Because particles in fluidizedbeds are in constant motion,channeling and clogging of the

bed are avoided and air can beintroduced directly into thecolumn.

Trinkle bed


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Trinkle-bed

bioreactor • Trickle-bed reactor is

another variation of

the packed bed.• Liquid is sprayed onto

the top of packing and

trickles down throughthe bed in smallrivulets.

• Air may be introducedat the base. Trickle-bed -bioreactors areused widely foraerobic wastewatertreatment.


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Membrane bioreactor (MBR)• In a membrane reactor continuous processing is

possible if production and separation can beincorporated in one system.

• One application of the membrane bioreactor is to

remove product that is formed, especially for thosethat can inhibit the enzyme reaction.


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Sterilization in bioreactor

• Most bioreactors (especially fermentation process andproduction of pharmaceutical products) outside of thefood and beverage industry are carried out using asepticconditions.

• Most industrial bioreactors are designed for in situ steamsterilisation under pressure. The vessel should have aminimum number of internal structures, ports, nozzles,

connections and other attachments to ensure that steamreaches all parts of the equipment. For effectivesterilisation, all air in the vessel and pipe connectionsmust be displaced by steam.

• Think: In industry, where does the steam supply comefrom?

f


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Example of steam sterilization at the sampling port

of a fermentor • Sampling ports are fitted to fermenters to

allow removal of broth for analysis.• Initially, valves A and D are closed;valves B and C are open to maintain asteam barrier between the reactor andthe outside environ-ment.

• Valve C is then closed, valve B partiallyclosed and valve D partially opened toallow steam and condensate to bleedfrom the sampling port D.

• For sampling, A is opened briefly to coolthe pipe and carry away any condensatethat would dilute the sample; this broth isdiscarded.

• Valve B is then closed and a sample

collected through D. When sampling iscomplete, valve A is closed and Bopened for re-sterilisation of the sampleline; this prevents any contaminantswhich entered while D was open from

travelling up to the fermenter. Valve D isthen closed and valve C re-opened.

Sterilization in other unit operation in


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bioprocess industry

• Heat sterilization• Chemical sterilization (refer to handouts)

• Sterilization using radiation

• -Radiation sterilization is a good alternative forsterilizing disposable medical, laboratory andpharmaceutical products. The radiation that arecommonly are ultraviolet 200-280 nm (UV), β -radiation

and γ -radiation.• In some industries such as the pharmaceutical, high

quality of water (such as RO, milli-Q, water-for-injection (WFI)) is required. Normally, a series offiltration and ion-exchange purification steps areinvolved. High quality water are normally keep inwater tanks before utilize, and these tanks usually are

equipped with UV radiation to avoid the growth ofmicroorganism.


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bioprocess industry• Sterilization by using membrane filter

- All microorganism including viruses have certain sizes.

- The microorganism can simply be removed by usingmembrane filter that has pore size smaller thanmicroorganism. In some application, a series of

membrane filters are used.- Depth filters with bigger pore size (e.g 0.6 µm) may be

used first to remove insoluble particle prior passingthrough membrane filters with smaller pore size (e.g0.45 µm or 0.2 µm). (Think: Why? Check insidetextbook what is the size of common microorganism).


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I like membrane a lot. You must pandai

pandai.


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Bioreactor and Sterilization