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BIOREACTION AND BIOREACTOR
By Puan Azduwin Khasri
20 NOVEMBER 2012
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 rxn 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
• 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
• Stages of cell growth in a batch reactor;
Phase III: STATIONARY
PHASE
Cells reach a minimum
biological place where
the one or more of the
nutrient are limiting.
Phase I : LAG PHASE
Little increase in cell
PhaseCells
IV: DEATH
conc’n.
are PHASE
A decrease
in live
adjusting
to their
newcell
conc’n occurs.
environment,
synthesizing enzymes,
getting ready
to reproduce.
Phase II: EXPONENTIAL
GROWTH PHASE.
Cell divide at maximum
rate, all of the
enzyme’s pathways are
in place.
RATE LAWS
Monod eqn for exp growth.
• Growth rate, rg depends on the nutrient
concentration (Cs)
INHIBITION OF THE GROWTH RATE
• In many systems, product inhibits the growth
rate. (i.e.; Wine production)
THE MOSER AND TESSIER
• There are also Tessier & Moser eqns that fit
experimental data better.
TESSIER
MOSER
• 𝜆 and k are empirical constants
Effect of Temperature can be given as
STOICHIOMETRY
• Stoichiometry for cell growth is complex, and varies
with microorganism/nutrient system, and pH, T, etc.
YIELD COEEFICIENT (Cell and substrate);
• Product formation can take place during different phases of the
cell growth cycle if it occurs during the exp growth phase:
• The stoichiometric yield coeff btw product & substrate is
given by:
• Another term is the maintenance utilization term: (to maintain
a cell’s daily activities)
• The rate of substrate consumption
• Neglecting the cell maintenance
Substrate Utilization
If there is production during growth, it is difficult to separate
amount of substrate used in production and growth
The corresponding rate law is
Growth associated product formation in the
growth phase.
Apparently, no net growth during stationary phase
Mass balance
There are two ways that we could account for the growth of
microorganisms. Either no of living cells or mass of the living
cells.
For a CTSR: { called chemostats are the reactors that
contain microorganisms}
Substrate Balance
For a Batch System:
Cell balance
Substrate
DESIGN EQUATION
For a CSTR
The case where the volumetric flow rates in and out
are the same and no live cells enter the chemostat
DILUTION RATE
The dilution rate is reciprocal of the space time,T
CSTR mass balance;
Using Monod Eqn;the growth rate,rg
For steady state operation;
Mass flow rate 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 Eqn;
If a single nutrient is limiting,
- cell growth is the only process to substrate consumption.
- cell maintenance is neglected.
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} :
THE END