Wednesday, August 13, 2008 - 8:30 AM
S111
Scale-up considerations related to high viscosity in fungal fermentations
Piet Brocken, DSM Food Specialties B.V., Alexander Fleminglaan 1, PP 624-0295, 2613 AX Delft, Netherlands
For scaling up of viscous fungal fermentation processes a number of additional aspects have to be taken into account. The maximum viscosity that can be handled in a lab scale fermentor is quite limited. E.g. a stirrer speed of 700 rpm is needed in a 20 liter fermentor (turbine diam.: 10 cm) to avoid laminar flow if apparent viscosity is 400 cP (power input > 3 W/kg, Re: 300).
In a large scale fermentor, a Reynolds number of <1000 can only be obtained at extremely high viscosities and low stirrer speeds / power input.
These differences in mixing regime will affect shear rate, morphology, viscosity, growth rate, required dissolved oxygen levels, etc.
To deal with these scale differences in process development and optimization, it is needed to get a good understanding of the critical process parameters.
For that a number of tools can be useful, like the two compartment model and image analysis of morphology. These can help to understand the effect of gradients (oxygen, glucose or other nutrients).
Next to this there are quite a number of process parameters that can be used to try to compensate for the changes in morphology caused by scale effects; like medium composition, inoculum ratio, oxygen enrichment, retrofitting impeller design or to make use of a found correlation between biomass concentration and viscosity / morphology. Scale down experiments should be carefully designed to be able to obtain valuable information for improvements on large scale.
In a large scale fermentor, a Reynolds number of <1000 can only be obtained at extremely high viscosities and low stirrer speeds / power input.
These differences in mixing regime will affect shear rate, morphology, viscosity, growth rate, required dissolved oxygen levels, etc.
To deal with these scale differences in process development and optimization, it is needed to get a good understanding of the critical process parameters.
For that a number of tools can be useful, like the two compartment model and image analysis of morphology. These can help to understand the effect of gradients (oxygen, glucose or other nutrients).
Next to this there are quite a number of process parameters that can be used to try to compensate for the changes in morphology caused by scale effects; like medium composition, inoculum ratio, oxygen enrichment, retrofitting impeller design or to make use of a found correlation between biomass concentration and viscosity / morphology. Scale down experiments should be carefully designed to be able to obtain valuable information for improvements on large scale.
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See more of Invited Oral Papers
See more of The Annual Meeting and Exhibition 2008 (August 10 - 14, 2008)