Scale-up of Aerobic bioreactors

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Scale-up of Aerobic bioreactors
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Aerobic bioreactors

• Most of the industrial bioprocesses are aerobic
• Oxygen is an important nutrient for microorganism
  for growth
• The oxygen transfer rate can control the overall
  rate of the bioprocess in aerobic bioreactors

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Widely used types are
Stirred tank reactor
Air lift column
Bubble column
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Parameters affecting the Oxygen transfer rate

• the system physical properties
• the biochemical properties
• the operational conditions(gas flow rate, stirrer
  tip speed)
• the geometrical parameters of bioreactor (kind
  and size of bioreactor, design and number of
  stirrers, etc.)
• The parameters in the first two groups are
  determined by the nature of the system and can
  not be altered freely the last two groups depend
  on the process parameters and on the device used

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Steps of scale up

• Find geometric parameters of the larger scale
  bioreactor
• Stirred tank reactor
• Vessel diameter, Height, Impeller diameter
• Bubble column
• Height, Diameter
• Use scale up criteria to determine operational
  parameters of the larger scale
• Stirred tank reactor
• Impeller speed, Air flow rate
• Bubble column
• Air flow rate

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Geometric correlations of a stirred tank reactor

• For Turbine blade impellers

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Scale-up criteria

• Constant volumetric mass transfer
  coefficient(KLa)
• Constant power consumption per unit volume(P/V)
• Constant impeller tip speed(?ND)
• Constant Reynolds number(Re)
• Constant dissolved oxygen concentration (CO2)

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Scale-up criteria
Percentage of each criteria used in fermentation
industry
(Garcia Gomez, 2009)
9
Scale-up criteria
(Garcia and Gomez,2009)
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Constant tip speed

• N1 Impeller speed of small bioreactor
• N2 Impeller speed of Large bioreactor
• Di1 Impeller diameter of small bioreactor
• Di2 Impeller diameter of large bioreactor

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Constant Reynolds number

• N Impeller speed
• D Impeller diameter
• ?L Density of the liquid
• µLViscosity of the liquid

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Constant Power consumption per unit volume
(Rushtons equation)
Ungassed power consumption ,
Np
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Constant Power consumption per unit volume
(Rushtons equation)
Ungassed power consumption ,
Gassed power consumption ,
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Constant Power consumption per unit volume
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• Constant volumetric mass transfer coefficient
  (kLa)
• There are large no.of empirical correlations
• Ex empirical correlations to determine Kla for
  Newtonian fluids in stirred tank reactors

(Garcia and Gomez,2009)