Fermentor design

Design of fermentor

2. TheFermentationreactiontakesplaceina
closedcontainercalledFermentor.
Twotypes-OpenandClosed

6. ConstructionmaterialsofFermentorwilldiffer
withSmallscale,PilotandLargescale.Glass
(borosilicateglass)orstainlesssteelforsmall
scaleprocess.Stainlesssteel(>4%chromium),
Mildsteel(coatedwithglassorepoxymaterial),
Wood,PlasticorConcreteforPilotandLarge
scaleprocess.

8. FermentorhavemechanicallymovingAgitators
orImpellerswithinabaffledcylindricalvessel.
Bafflesareusuallyflatverticalplateswhose
widthisaboutone-tenthofthevesseldiameter.
Normally,4–6baffleplatesarefittedtothe
insidevesselwallstoaidmixingandmass
transferbyincreasingturbulence,preventing
vortexformationandeliminating‘deadspaces’.

10. WithineachvesseltheImpellerisconnectedtoan
externalmotorwhichdrivesthestirrersystem.
Theagitatorassembly,includingtheseal,isoftena
potentialrouteofcontamination.Topreventthis
problem,theShafthastopassintothefermentor
throughasetofasepticStirrershaftseals.

12. TheSterileair(Oxygen)requiredforthe
fermentationprocessarepassedtothe
FermentorthroughSparger.
SampleAdditionPortandSterileGas
Exhaustarepresentonthetopregionof
Fermentor.
Water/SteamInandWater/SteamOutare
presentonthebothsidesoftheFermentor.
HarvestPortispresentonthebottomregion
ofFermentor.

14. SelectionofMicrobialStrains:Selectionofappropriate
strainofparticularspeciesofmicroorganismsisvery
importantforfermentationprocess.Themicroorganisms
whichareinvolvedinleachingofmetalsshouldbe
avoidedandthefermentorshouldbesterilizedbefore
Fermentationprocess.
pH–Mostofthemicroorganismsemployedin
fermentationgrowoptimallybetweenpH5.5to8.5.in
thebioreactor,asthemicroorganismsgrow,theyrelease
metabolitesintothemediumwhichchangepH.
Therefore,thepHofthemediumshouldbecontinuously
monitoredandmaintainedatoptimumlevel.Thiscan
bedonebyadditionofacid(Con.HCl)oralkalibase
(NaOH).

15. Temperature–Temperaturecontrolisessentialforthe
fermentationprocess.Lowertemperaturecausesreduced
productformationwhilehighertemperatureaffectsthe
growthofmicroorganisms.Thebioreactorarenormally
equippedwithheatingandcoolingsystemthatcanbe
usedaspertherequirement.
DissolvedOxygen–Continuoussupplyofoxygeninthe
formofsterilizedairisdonetotheculturemedium.This
iscarriedoutbyintroducingairintothebioreactorinthe
formofbubbles.ContinuousmonitoringofDissolved
oxygenconcentrationisdoneinthebioreactorforoptimal
productformation.
NutrientConcentration–Thenutrientconcentrationina
Bioreactorshouldbelimited.Limitingconcentrationof
nutrientsisadvantageousforoptimalproductformation
butthehighnutrientconcentrationareoftenassociated
withinhibitoryeffectonmicrobialgrowth.

16. AdequatemixingorAgitation–Continuousand
adequatemixingofthemicrobialcultureensures
optimalsupplyofnutrientsandoxygen,besides
preventingaccumulationoftoxicmetabolicby-
products.Goodmixing(Agitation)alsocreates
favourableenvironmentformicrobialgrowthandgood
productformation.However,excessiveAgitationmay
damagemicrobialcellsandincreasethetemperatureof
themedium,besidesincreasedfoamformation.
Foamformation–Themediausedinindustrial
fermentationisgenerallyrichinprotein.Whenagitated
duringaeration,itinvariablyresultsinformationof
foam.Antifoamchemicals(MineraloilsorVegetable
oils)aregenerallyusedtolowerthesurfacetensionof
themedium.Sometimes,Mechanicalfoambreakersare
fittedatthetopofthebioreactortobreakthefoam
bubbles.