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fresh nutrient medium is continually supplied to a well-stirred culture and products and cells are simultaneously withdrawn.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.

A continuous-culture laboratory setup medium Products, cells

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.

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); V R is the culture volume (l) (constant); X is the cell concentration (g/l); P is the extracellular product (g/l); µ g and k d are growth rate and endogenous rate constant, respectively (h -1 ). Subscript 0 denotes the parameters at the feed medium. q p is the specific rate of extracellular product formation (g P/g cells-h) Y p/s is the product yield coefficient (g P/g S).

Cell Growth in Ideal Chemostat At steady state, X 0 =0, k d ≈ 0, q p =0, Monod equation applied,

Cell Growth in Ideal Chemostat At steady state, X 0 =0, k d ≈ 0, q p =0, Monod equation applied, Cell Productivity: DX D=F/V R, is dilution rate (1/time), the reciprocal of residence time. Assign. Q 6.13, q o 2

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

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

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

Cell Growth in Ideal Chemostat At steady state, X 0 =0, k d > 0, q p =0, Monod equation applied,

Cells Growth in Continuous Culture Ideal Chemostat Endogenous metabolism (X 0 =0, k d > 0, q p =0) is considered Equation summary Productivities: DX

Cells Growth in Continuous Culture Ideal Chemostat Endogenous metabolism (X 0 =0, k d > 0, q p =0) is considered

Cells Growth in Continuous Culture Ideal Chemostat Endogenous metabolism (X 0 =0, k d > 0, q p =0) is considered.

Cell Growth in Ideal Chemostat At steady state, X 0 =0, k d >0, q p >0, Monod equation applied, 0 0 0

Cells Growth in Continuous Culture Ideal Chemostat Endogenous metabolism (k d > 0, q p > 0) is considered Productivities: DP, DX Equation summary: Use graphical method to determine the optimum DP, DX.

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

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

Summary of Growth Kinetics - Monod equation : -Cell growth in continuous culture : q p =0, k d ≈0, X 0 =0, Monod equation is applied: Productivity: DX

Summary of Growth Kinetics -Cell growth in continuous culture : q p =0, k d >0, X 0 =0, Monod equation is applied: Productivities: DP, DX

Summary of Growth Kinetics -Cell growth in continuous culture : q p >0, k d >0, X 0 =0, Monod equation is applied: Productivities: DP, DX