By: Mdm. Noor Amirah Abdul Halim BIOREACTION AND
BIOREACTOR
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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. 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.
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BIOREACTOR AND ITS PARTS
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THE CELL
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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 THE CELL
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CELL GROWTH The growth of an aerobic organism follows the
equation; SUBSTRATE
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STAGES OF CELL GROWTH
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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,
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For most of the bacteria, Ks is small ( ) Thus, it can be
neglected to give; Growth rate, r g depends on the nutrient
concentration (C s ) RATE LAW FOR BIOREACTOR
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INHIBITION OF THE GROWTH RATE (r g ) 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)
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TESSIER AND MOSER EQUATION Tessier & Moser equations are
another equation used to describe the cell growth rate. They fit
the experimental data better. and k are empirical constants TESSIER
MOSER
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CELL DEATH RATE (r d ) 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;
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EFFECT OF TEMPERATURE The cell growth at temperature =T
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STOICHIOMETRY FOR BIOREACTIONS
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RATE OF PRODUCT FORMATION (r p ) 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:
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Rate of product formation (r p ) during growth phase
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Rate of product formation (r p ) during stationary phase
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MASS BALANCES
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Batch operation Cell
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Substrate Growth phase stationary phase
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Product
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Chemostat
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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
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CSTR Mass Balance Using Monod Eqn;the growth rate,r g
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For steady state operation; Mass flowrate of cells out of the
system, Fc Divide by Cc V, Neglect death rate The specific growth
rate of the cell can be controlled by the dilution rate,D The
specific growth rate of the cell can be controlled by the dilution
rate,D
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From Monod Equation, If a single nutrient is limiting, - cell
growth is the only process to substrate consumption. -cell
maintenance is neglected. Then,
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WASH OUT To learn the effect of increasing the dilution rate;
Assume; the dilution rate at which wash-out will occur is:
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D for the maximum cell production: {Cell production per unit
volume is the mass flow rate of cells out of the reactor} :
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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 + CO 2 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 Y C/S (b) The yield coefficient, Y c/p (c) The
rate of cell growth r g ( k = 1.3 h-1 and max = 2.2 x 10-5 s-1) (d)
The rate of product formation, r p during the exponential growth
(e) The rate of substrate consumption (-r s ) during the
exponential growth (m = 0.05 h-1) Exercise