Cells Growth in Continuous Culture

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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  withdrawn.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.

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A continuous-culture laboratory setup
medium
Products, cells
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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.

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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.
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Cell Growth in Ideal Chemostat
At steady state, X00, kd 0, qp0 , Monod
equation applied,
0
0
0
0
0
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Cell Growth in Ideal Chemostat
At steady state, X00, kd 0, qp0 , Monod
equation applied,
Assign. Q 6.13, qo2
Cell Productivity DX
DF/VR, is dilution rate (1/time), the reciprocal
of residence time.
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Cell Growth in Ideal Chemostat
Washed out If D is set at a value greater than
µm (D gt µm), the culture cannot reproduce quickly
enough to maintain itself.
µm 0.2 hr-1
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Determination of Monod Parameters
In Chemostat µgD, varying D obtains DS
Chemostat technique reliable, constant
environment, operation may be difficult.
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Determination of Monod Parameters
Batch X, S, t ? lnX t , get µm (slope) from
data in exponential phase.
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Cell Growth in Ideal Chemostat
At steady state, X00, kd gt 0, qp0 , Monod
equation applied,
0
0
0
0
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Cells Growth in Continuous CultureIdeal Chemostat
Endogenous metabolism (X00, kd gt 0, qp0) is
considered Equation summary
Productivities DX
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Cells Growth in Continuous CultureIdeal Chemostat
Endogenous metabolism (X00, kd gt 0, qp0) is
considered
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Cells Growth in Continuous CultureIdeal Chemostat
Endogenous metabolism (X00, kd gt 0, qp0) is
considered.
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Cell Growth in Ideal Chemostat
At steady state, X00, kd gt0, qpgt0 , Monod
equation applied,
0
0
0
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Cells Growth in Continuous CultureIdeal Chemostat
Endogenous metabolism (kd gt 0, qp gt 0) is
considered
Equation summary
Productivities DP, DX
Use graphical method to determine the optimum DP,
DX.
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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
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Summary of Growth Kinetics

• Effect of factors
• - Dissolved oxygen

- Temperature, pH, ionic strength, substrate
concentration.
- Heat evolution
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Summary of Growth Kinetics
- Monod equation

• Cell growth in continuous culture
• qp0, kd 0, X00, Monod equation is applied

Productivity DX
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Summary of Growth Kinetics

• Cell growth in continuous culture
• qp0, kd gt0, X00, Monod equation is applied

Productivities DP, DX
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Summary of Growth Kinetics

• Cell growth in continuous culture
• qpgt0, kd gt0, X00, Monod equation is applied

Productivities DP, DX