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BIOREACTION AND BIOREACTOR
By: Mdm. Noor Amirah Abdul Halim
WHAT IS BIOREACTOR?
 A special reactor that sustains and supports life for cells and tissue cultures.
 Used in industrial processes to produce pharmaceuticals, vaccines, or antibodies
 Bioreactors are commonly employed in the food and fermentation industries, in
waste treatment, and in some biomedical operations - the heart of any industrial
fermentation process.
 The advantages are mild reaction conditions, high yields and stereospecific
compounds.
 Bioreactors supply a homogeneous (same throughout) environment by constantly
stirring the contents.
 Bioreactors give the cells a controlled environment by ensuring the same
temperature, pH, and oxygen levels.
BIOREACTOR AND ITS PARTS
THE CELL
THE CELL
 A cell uses its nutrients to produce energy and more
cells.
 The cell consists of a cell wall and an outer membrane
that encloses cytoplasm containing a nuclear region and
ribosomes.
 The cell wall protects the cell from external influences.
 The cell membrane provides for selective transport of
materials into and out of the cell
CELL GROWTH
 The growth of an aerobic organism follows the equation;
SUBSTRATE
STAGES OF CELL GROWTH
RATE LAW FOR BIOREACTOR
 The most commonly used expression is the Monod equation for
the exponential growth
 The specific growth rate can be expressed as;
 Thus,
RATE LAW FOR BIOREACTOR
 For most of the bacteria, Ks is small (
)
Thus, it can be neglected to give;
Growth rate, rg depends on the nutrient concentration (Cs)
INHIBITION OF THE GROWTH RATE (rg)
 In many systems, product inhibits the growth rate.
 Wine production is an example where fermentation of
glucose to produce ethanol is inhibited by the product
ethanol (ethanol kills the yeast)
TESSIER AND MOSER EQUATION
 Tessier & Moser equations are another equation used to
describe the cell growth rate. They fit the experimental data
better.
TESSIER
 𝜆 and k are empirical constants
MOSER
CELL DEATH RATE (rd)
 The cell death is a result of;
- harsh environments
- depletion of nutrients
- presence of toxic substance
 The rate law for cell death is given by;
EFFECT OF TEMPERATURE
The cell growth at
temperature =T
STOICHIOMETRY FOR BIOREACTIONS
RATE OF PRODUCT FORMATION (rp)
 Product formation can take place during different phases of
the cell growth cycle. When product formation only occurs
during the exponential growth phase, the rate of product
formation is:
Rate of product
formation (rp)
during growth
phase
Rate of product
formation (rp)
during stationary
phase
MASS BALANCES
Batch operation
Cell
Substrate
Growth phase
stationary
phase
Product
Chemostat
DESIGN EQUATION
 CSTR (chemostat)
The case where the volumetric flow rates in and out are the
same and no live cells enter the chemostat
 Dilution rate
Dilution rate is a parameter used in bioreactor. It is reciprocal
of space time
 CSTR Mass Balance
 Using Monod Eqn;the growth rate,rg
 For steady state operation;
 Mass flowrate of cells out of the system, Fc
Neglect death rate
Divide by Cc V,
The specific growth rate of the cell can
be controlled by the dilution rate,D
 From Monod Equation,
If a single nutrient is limiting,
- cell growth is the only process to substrate consumption.
-cell maintenance is neglected.
Then,
WASH OUT
To learn the effect of increasing the dilution rate;
Assume;
the dilution rate at which wash-out will occur is:
 D for the maximum cell production:
{Cell production per unit volume is the
mass flow rate of cells out of the reactor} :
Exercise
Cell growth takes place in bioreactors called chemostat. A substrate such as
glucose is used to grow cells and produce a product which is CO2.
Glucose
cell
More cells + CO2
By assuming 1 mole of glucose (180g/dm3) reacts, to produce 0.909
mol/dm3 of cells (MW: 91.34 g/mol) and 1.47 mol/dm3 of CO2 Calculate:
(a) The yield coefficient YC/S
(b) The yield coefficient ,Y c/p
(c) The rate of cell growth rg ( k = 1.3 h-1 and μmax = 2.2 x 10-5 s-1)
(d) The rate of product formation, rp during the exponential growth
(e) The rate of substrate consumption (-rs) during the exponential growth
(m = 0.05 h-1)