1 / 18

Measurement of Bioreactor K L a

Measurement of Bioreactor K L a. Motivations. 2. Good example of mass transfer at gas-liquid interface 3. Experience modeling in both semi-empirical and factorial methods. Biotech/pharmaceutical industry employing more Chemical Engineers Process Engineering Validation Management

moe
Download Presentation

Measurement of Bioreactor K L a

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Measurement of BioreactorKLa

  2. Motivations 2. Good example of mass transfer at gas-liquid interface 3. Experience modeling in both semi-empirical and factorial methods • Biotech/pharmaceutical industry employing more Chemical Engineers • Process Engineering • Validation • Management • Pilot testing • Scale-up

  3. Types of Products • Natural Products • Drugs • Penicillin is early example • Taxol • Mupricin • Cyclosporin A, etc. • Foods • Fermented beverages • Fermented dairy products

  4. Types of Products • Transgenic Products • Gene for a therapeutic protein inserted in foreign expression system • Factor IX • a-1-antitrypsin • EPO • Antibodies • antithrombin III • tissue plasminogen activator (TPA) • Interferons, etc.

  5. Expression Systems • Bacterial Cells • Fungal Cells • Plant Cells • Insect Cells • Mammalian Cells

  6. Types of Bioreactors (fermenter)(often depends on shear sensitivity) • Stirred tank • Aerobic or Anaerobic (air-sparged if aerobic) • Most common for bacterial cells • Bubble or airlift column • Good for shear-sensitive cells • Fixed bed systems • Trickle beds, hollow membrane fiber (mammalian cells), etc.

  7. Industrial Stirred Fermenter

  8. Experimental Apparatus

  9. Transport in Bioprocess Systems

  10. Why is KLa Important? • Dissolved oxygen is an important substrate in aerobic fermentations. Since oxygen is sparingly soluble in water, it may be the growth-limiting substrate in these fermentations. For bacteria and yeast cultures, the critical oxygen concentration is about 10% to 50% of the saturated DO (dissolved oxygen concentration).

  11. Equation for Transport Oxygen transfer is usually limited by the liquid film surrounding the gas bubbles: where mO2 is the rate of oxygen transfer per volume of bioreactor (mass O2/ L3 t), kL is the oxygen transport coefficient, [=]L/t, a is the gas-liquid interfacial area per volume of reactor [=] L2/L3, kLa is the volumetric oxygen transfer coefficient [=]1/t, C* is saturated DO (dissolved oxygen) concentration [=] m/L3 (approx. 7 mg/l at 25 deg. C and 1 atm.), CL is the actual DO concentration in the liquid [=] m/L3

  12. Terms affecting rate • KLa • What we are trying to determine and correlate with mixing speed and aeration rate • Two quantities multiplied together • Liquid side (essentially overall mass transfer coefficient) • Total area of bubbles in bioreactor • Can’t be separated

  13. Some Interactions Affecting Oxygen Transport in Aerobic Systems

  14. Terms affecting rate • C* (saturation oxygen concentration; max solubility of the gas in liquid) - Constant at a given T and P - Available in tables (see on-line lab manual) • CL (C(t)) the oxygen concentration at a given time during the run; what we measure - {C*- CL} = “driving force”

  15. Terms affecting rate • KL -mass transfer coefficient • a- interfacial area for mass transfer

  16. Probe response rate needed to get “real” CL(t) value • Gaseous oxygen dissolves in water at bubble interface and disperses in the bioreactor • Dissolved O2 crosses probe membrane at tip. • O2 in probe is sensed and sent to meter 1 2 3 Time constant =1/kLa Time constant =1/kp Fast

  17. Some Interactions Affecting Oxygen Transport in Aerobic Systems

  18. Data Acquisition

More Related