Fed Batch - Mass and Kinetic Balances Flashcards

1
Q

What is the primary characteristic of a Fed Batch fermentation process?

A

There is flow in but no flow out. Thus volume changes.

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2
Q

Why use a Fed Batch process?

A

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)

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3
Q

What are common products produced by a fed-batch process?

A

Bakers yeast, antibiotics, pharmaceutical proteins

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4
Q

In order to keep the dilution rate constant, what do we do?

A

We change the feed flow rate exponentially so that D = F/V is constant.

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5
Q

What happens is the feed flow rate is linear?

A

The specific growth rate decreases

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6
Q

What is the equation for the feed flow rate with time?

A

F(tP) = [(Ysx u)/(csf - cs)]Vo xo e^(u t)

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7
Q

What are the limitation to how long a fed-batch can run?

A

1) Air mass transfer (DO, OUR)
2) Cooling of the fermenter
3) Volume of the fermenter

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8
Q

How can a fed-batch be operated “continuously”?

A

Through a repeated fed-batch process where some of the broth is drained off periodically.

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9
Q

When is linear feed flow used?

A

When mass transfer and cooling are issues

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10
Q

What other option can be used with the feed flow to address issues?

A

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.

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