Lecture 5: bioreactor operations
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Modes of Bioreactor Operations
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Batch Culture
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Simple batch
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Fed-batch
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Continuous Culture
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Chemostat
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Perfusion
Cell retention using cell entrapment
Cell retention using cell retention devices
Internal vs external cell retention
Open vs closed cell retention systems
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Semi-continuous
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Harvest Refeed (with cell retention)
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Draw and refill a.k.a repeated batch (no cell retention)
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Mixed mode
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Perfused fed-batch
Many Commercial Options for Cell Culture Production Systems
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Roller bottles – Epogen (red blood cells) by Amgen
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Batch stirred tank reactor – Avonex by Biogen
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Fed-batch stirred tank reactor
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Zenapax by Roche
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Herceptin by Genentech
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Many Others
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Airlift bioreactor – Oncoscint by Cytogen/Lonza
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Stirred tank draw and feed (take 80% of the material out then put new media and repeat
the process) or Solara process – Factor VIII by Pfizer (GI, Wyeth)
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Perfusion reactor
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Factor VIII by Bayer
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Reopro by Centocor
Basic Bioreactor Operation Modes
Batch - simple and leave culture in
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Short run, not adding anything, no feeds or anything
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Cell density will go up then go down
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Nutrients are high then lessees as cells are absorbing
Fed batch – have a Concentrated feed
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Have a higher cell density thus increasing product titer
more product
Continuous – adding feed and harvesting at the same time
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Running a long time ( as long as possible)
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Harvest will also contain the cell
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This limits the operations as well because you’re taking the cells out the bioreactor
Perfusion w/ cell bleed – continuous culture with cell retention
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Higher cell density compared to continuous
Batch Operations: Simple Batch and FedBatch
Batch – you have something that makes the cells go down
Bioreactor Operations: Simple Batch Culture
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Placed fresh medium in the bioreactor at start, equilibrate pH, temperature, and dissolved
oxygen
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Seed the bioreactor, typically at 0.2-0.6 MM/mL
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High split ratio* (how much volume is in the medium) is desired (more fresh medium)
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Set batch cycle time (typically 7-10 days)
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Even though it is a batch operation, simple feeds like glucose or glutamine can be added
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Harvest at end of cycle
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Split ratio = Final volume/Seed volume
Comparison of Batch vs. Fed-Batch Cultures Impact of Feeding Strategies on Cell Growth and
Viability
Feeding the culture
Higher cell density
Higher viability (better product quality)
Longer run time
Comparison of Batch vs. Fed-Batch Cultures Impact of Feeding Strategies on Productivity
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4x more titer due to higher cell density, higher viability, and longer run time
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Feeding can also result in higher cell specific productivity
Bioreactor Operations: Fed-batch Culture
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Initiate as a batch culture
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start at a lower volume to accommodate the volume expansion due to feeding
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Feed concentrated nutrients
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Bolus feeding: feed at designated time intervals
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Continuous feeding:
Constant rate (2-10%)
Variable based on cell growth or cellular activity
Calculated to maintain a certain substrate concentration
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