Batch,Fed-batch&continuous fermentation.pdf

Different modes of fermentation

1. Batch, Fed-Batch and
Continuous Fermentation
Dr.DhanyaKC
Assistant Professor, Department of Microbiology
St. Mary’s College, Thrissur-680020, Kerala

2. Batch,FedBatchandContinuousFermentations
Continuous-Opensystem
Mediumcontinuouslyfed
Spentmediumandcellsremovedcontinuously
Volumeremainsconstant
Batch-Closedsystem
Nutrientsinafixedvolume
Furtheradditions-forpHcontrol,aeration,etc.
Fed-batch
Mediumorcomponentsfedcontinuouslyorintermittently
Volumeincreaseswithtime

3. Batchfermentation-Microbialcells-passthroughanumberofphases
•Lagphase
•Logorexponentialphase
•Stationaryphase
•Deathordeclinephase

4. LagPhase
Immediatelyafterinoculation
Noapparentgrowth
Timeofadaptation
Length-reduced–economicalcommercial
Batch fermentation

5. Logarithmicorlogorexponentialphase
Lagandlogphase-trophophase
Productionofprimarymetabolites
Aminoacids,nucleotides,vitamins,citricacid,
aceticacid,ethanol,etc.
Growthrateofcellsincreases-Constant,Maximumrate
dx/dt=µx
x-Concentrationofmicrobialbiomass
µ-Specificgrowthrate
t-Timeinhours
Batch fermentation

6. StationaryPhase-Growthratereduce
Duetosubstratelimitationandtoxinlimitation
Plot-biomassandinitialsubstrateconcentration
Growthindifferentconcentrationsofsubstrates
Initialincreaseinsubstrate-increaseinbiomass
x=Y(S-S
R)
x-concentrationofbiomass
Y-yieldfactor(gbiomass/substrate)
S-initialsubstrateconcentration
S
R-residualsubstrateconcentration
Yieldfactor-efficiencyofsubstrateconversiontobiomass
Batch fermentation

7. Deathordeclinephase-Cessationofgrowth-depletionofsubstrate
Stationaryanddeathphase–idiophase
Secondarymetabolitesareformed
Examples-antibiotics,pigments,toxins,etc
Monodequation
µ=µ
maxs/(K
s+s)
s-Residualsubstrateconcentration
K
s-substrateutilizationconstant
substrateconcentrationwhenµishalfµ
max
Ameasureoftheaffinityforsubstrate
µ-Specificgrowthrate
µ
max–MaximumSpecificgrowthrate
Batch fermentation

8. Deathordeclinephase-Cessationofgrowth-depletionofsubstrate
Stationaryanddeathphase–idiophase
Secondarymetabolitesareformed
Examples-antibiotics,pigments,toxins,etc
Monodequation
µ=µ
maxs/(K
s+s)
s-Residualsubstrateconcentration
K
s-substrateutilizationconstant
substrateconcentrationwhenµishalfµ
max
Ameasureoftheaffinityforsubstrate
µ-Specificgrowthrate
µ
max–MaximumSpecificgrowthrate
Batch fermentation

9. Applicationofbatchfermentation
Variousgrowthconditionsusedforproductionof
Biomass-fastestgrowthrateandmaximumpopulation
1
o
metabolite-extendexponentialphase
2
o
metabolite-shortexponentialphaseandextendedproductionphase
1.Fillingfermenterwithmedium
2.Sterilizationoffermenterandmedium
3.Inoculation
4.Productionphase
5.Harvesting
6.Cleaningofvessel
Disadvantages-Highdowntime-non-productiveperiod

10. Fedbatchfermentation
•Establishedinitiallyinbatchmode
•Fedcontinuouslyorsequentiallywithmedium
•Withoutremovalofculturefluid
i)Samemedium-increaseinvolume
ii)Limitingsubstrate-sameconcentration-increaseinvolume
iii)Limitingsubstrate-concentrated-increaseinvolume
iv)Limitingsubstrate–veryconcentrated-noincreaseinvolume
i),ii)-variablevolumefedbatchsystem
iv)-fixedvolumefedbatchsystem
(iii)-intermediatebetweenthevariableandfixedvolumesystems

11. Continuousfermentation
Freshmediumcontinuouslyadded,Spentbrothandcellsareremoved
Exponentialgrowth-prolonged
Steadystateachieved-newbiomassbalancedbylossofcells
Dilutionrate,D=F/V
FisflowrateandVisthevolumeofvessel
Changeincellmassovertime,dx/dt=growth-output
dx/dt=µx-Dx
Understeadystateconcentrations,dx/dtwillbezero,then
µx=Dx
µ=D

12. Continuousfermentation
Understeadystateconditions
Specificgrowthrateiscontrolledbydilutionrate
Understeadystateconcentrations,dx/dtwillbezero,then
µx=Dx
µ=D
Ifdilutionrateincreaseaboveµmax,completewashoutofcells
Dilutionrateatwhichwashoutisjustavoidediscriticaldilutionrate(D
crit)

13. Monodequation,
µ=µ
maxs/(K
s+s)
Chemostat-Substrateconcentrationiskeptconstant
Turbidostat-Biomassconcentrationiskeptconstant
Atsteadystate,µ=D,so
D=µ
maxŝ/(K
s+ŝ) ŝ-steadystateconcentrationofsubstrate
ŝ=KsD/(µ
max-D)
Substrateconcentrationisinfluencedbydilutionrate
Biomassdependsuponsubstrateconcentrationandtherebyondilutionrate
Continuousfermentation

14. Theconcentrationofcellsinachemostatatsteadystate
ẍ=Y(S
R-S
r)
ẍ-steady-statecellconcentrationinchemostat
S
R-substrateconcentrationofinflowingmedium
Sr-steady-stateresidualsubstrateconcentration
Y-yieldfactor
Biomassconcentrationundersteadystateconditions-controlledby
Substratefeedconcentrationand
Dilutionrate
Continuousfermentation

15. Advantagesanddisadvantagesofcontinuousfermentation
Downtime-muchless-moreeconomic
Easilyautomated-requirelesslabour
Chancesofcontaminationandstraindeterioration–more
Controloperations–complicated
Problemsinlicensingofproduct-can’ttraceproductconsignmenttorawmaterialbatch

16. References
1.IndustrialMicrobiology:AnIntroduction,MJ.Waites,NL.Morgan,JS.
Rockey,GHigton
2.Principlesoffermentationtechnology,PFStanbury,AWhittakker,SJHall,
1995,Butterworth-Heinemannpublications