Cells Growth in Continuous Culture

1. Cells Growth in Continuous Culture Continuous culture: fresh nutrient medium is continually supplied to a well-stirred culture and products and cells are simultaneously withdrawn. At steady state, concentrations of cells, products and substrates are constant. In batch culture: the culture environment changes continually. growth, product formation and substrate utilization terminate after a certain time interval.

2. A continuous-culture laboratory setup medium Products, cells

3. Ideal Chemostat Same as perfectly mixed continuous-flow, stirred-tank reactor (CFSTR). - Control elements: pH, dissolved oxygen, temperature - Fresh sterile medium is fed to the completely mixed and aerated (if required) reactor. - Suspension is removed at the same rate. - Liquid volume in the reactor is kept constant.

4. Cell Growth in Ideal Chemostat A material balance on the cell and substrate concentration around the chemostat yields, F is the volumetric flowrate of nutrient solution (l/h); VR is the culture volume (l) (constant); X is the cell concentration (g/l); P is the extracellular product (g/l); µg and kd are growth rate and endogenous rate constant, respectively (h-1). qp is the specific rate of extracellular product formation (g P/g cells-h) Yp/s is the product yield coefficient (g P/g S). Subscript 0 denotes the parameters at the feed medium.

5. Cell Growth in Ideal Chemostat At steady state, X0=0, kd ≈ 0, qp=0 , Monod equation applied, 0 0 0 0 0

6. Cell Growth in Ideal Chemostat At steady state, X0=0, kd ≈ 0, qp=0 , Monod equation applied, Assign. Q 6.13, qo2 Cell Productivity: DX D=F/VR, is dilution rate (1/time), the reciprocal of residence time.

7. Cell Growth in Ideal Chemostat Washed out: If D is set at a value greater than µm (D > µm), the culture cannot reproduce quickly enough to maintain itself. µm = 0.2 hr-1

8. Determination of Monod Parameters In Chemostat: µg=D, varying D obtains D~S Chemostat technique: reliable, constant environment, operation may be difficult.

9. Determination of Monod Parameters Batch: X, S, t → lnX ~ t , get µm (slope) from data in exponential phase.

10. Cell Growth in Ideal Chemostat At steady state, X0=0, kd > 0, qp=0 , Monod equation applied, 0 0 0 0

11. Cells Growth in Continuous CultureIdeal Chemostat Endogenous metabolism (X0=0, kd > 0, qp=0) is considered Equation summary Productivities: DX

12. Cells Growth in Continuous CultureIdeal Chemostat Endogenous metabolism (X0=0, kd > 0, qp=0) is considered

13. Cells Growth in Continuous CultureIdeal Chemostat Endogenous metabolism (X0=0, kd > 0, qp=0) is considered.

14. Cell Growth in Ideal Chemostat At steady state, X0=0, kd >0, qp>0 , Monod equation applied, 0 0 0

15. Cells Growth in Continuous CultureIdeal Chemostat Endogenous metabolism (kd > 0, qp > 0) is considered Equation summary: Productivities: DP, DX Use graphical method to determine the optimum DP, DX.

16. Summary of Growth Kinetics - Autocatalytic reaction: The rate of growth is directly related to cell concentration Net specific growth rate (1/time): - Cell concentration determination - Growth patterns and kinetics in batch culture - lag phase - logrithmic or exponential growth phase: - deceleration phase - stationary phase: endogenous metabolism - death phase

17. Summary of Growth Kinetics • Effect of factors: - Dissolved oxygen: - Temperature, pH, ionic strength, substrate concentration. - Heat evolution:

18. Summary of Growth Kinetics - Monod equation: • Cell growth in continuous culture: • qp=0, kd ≈0, X0=0,Monod equation is applied: Productivity: DX

19. Summary of Growth Kinetics • Cell growth in continuous culture: • qp=0, kd >0, X0=0,Monod equation is applied: Productivities: DP, DX

20. Summary of Growth Kinetics • Cell growth in continuous culture: • qp>0, kd >0, X0=0,Monod equation is applied: Productivities: DP, DX