Lecture 5.docx - Lecture 5 bioreactor operations Modes of Bioreactor Operations Batch Culture o Simple batch o Fed-batch Continuous Culture o Chemostat

Lecture 5.docx - Lecture 5 bioreactor operations Modes of...

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Lecture 5: bioreactor operations - Modes of Bioreactor Operations - Batch Culture o Simple batch o Fed-batch - Continuous Culture o Chemostat o Perfusion Cell retention using cell entrapment Cell retention using cell retention devices Internal vs external cell retention Open vs closed cell retention systems - Semi-continuous o Harvest Refeed (with cell retention) o Draw and refill a.k.a repeated batch (no cell retention) - Mixed mode o Perfused fed-batch Many Commercial Options for Cell Culture Production Systems - Roller bottles – Epogen (red blood cells) by Amgen - Batch stirred tank reactor – Avonex by Biogen - Fed-batch stirred tank reactor o Zenapax by Roche o Herceptin by Genentech o Many Others - Airlift bioreactor – Oncoscint by Cytogen/Lonza - 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) - Perfusion reactor o Factor VIII by Bayer o Reopro by Centocor Basic Bioreactor Operation Modes Batch - simple and leave culture in - Short run, not adding anything, no feeds or anything - Cell density will go up then go down - Nutrients are high then lessees as cells are absorbing Fed batch – have a Concentrated feed - Have a higher cell density thus increasing product titer more product Continuous – adding feed and harvesting at the same time - Running a long time ( as long as possible) - 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 - 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 - Placed fresh medium in the bioreactor at start, equilibrate pH, temperature, and dissolved oxygen - Seed the bioreactor, typically at 0.2-0.6 MM/mL - High split ratio* (how much volume is in the medium) is desired (more fresh medium) - Set batch cycle time (typically 7-10 days) - Even though it is a batch operation, simple feeds like glucose or glutamine can be added - Harvest at end of cycle o 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 - 4x more titer due to higher cell density, higher viability, and longer run time - Feeding can also result in higher cell specific productivity Bioreactor Operations: Fed-batch Culture - Initiate as a batch culture o start at a lower volume to accommodate the volume expansion due to feeding - Feed concentrated nutrients o Bolus feeding: feed at designated time intervals o 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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