Fed Batch - Mass and Kinetic Balances Flashcards
What is the primary characteristic of a Fed Batch fermentation process?
There is flow in but no flow out. Thus volume changes.
Why use a Fed Batch process?
1) To reduce the high-substrate inhibiting effect
2) To control the specific growth rate of a microorganism
3) To reach very high titers (compared to continuous especially)
What are common products produced by a fed-batch process?
Bakers yeast, antibiotics, pharmaceutical proteins
In order to keep the dilution rate constant, what do we do?
We change the feed flow rate exponentially so that D = F/V is constant.
What happens is the feed flow rate is linear?
The specific growth rate decreases
What is the equation for the feed flow rate with time?
F(tP) = [(Ysx u)/(csf - cs)]Vo xo e^(u t)
What are the limitation to how long a fed-batch can run?
1) Air mass transfer (DO, OUR)
2) Cooling of the fermenter
3) Volume of the fermenter
How can a fed-batch be operated “continuously”?
Through a repeated fed-batch process where some of the broth is drained off periodically.
When is linear feed flow used?
When mass transfer and cooling are issues
What other option can be used with the feed flow to address issues?
A “less steep” exponential feed is also possible, where the growth rate won’t be constant but also won’t decrease as much as with a linear flow.