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8/3/2019 MT Seminar
1/21
BIOSENSORS IN MONITORING
OF BIOPROCESS
SAJINA.KUMARI.S
3rd sem biotechnology
8/3/2019 MT Seminar
2/21
Fermentation process are complex
systems, with many interacting variables Continuous monitoring of parameters such
as pH , temperature , and dissolved
oxygen levels, with direct feedback to
control systems, is standard even in the
smallest bioreactors and the enabling
technologies
Monitoring of other parameters, such asthe levels of substrates and products
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BIOSENSORS IN PROCESS
MONITORING The common theme is that a biosensors
couples a biological element , which
provides specific recognition of the targetanalyte, to a transducer, which generates
an electrical signal
Electrical signal can be directed to a digital
readout, or can be logged or used as an
input to a control system
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The biological recognition element may be
an enzyme, an antibody or similar bindingmolecule, or a living cell
Transducer may detect a redox reaction,light emission, altered levels of an ion, a
luminescent or fluorescent signal, or achange in mass associated with a surface
The aim of a biosensor is to provide arapid, highly specific, quantitativeresponse , with a minimal or zerorequirement for sample preprocessing
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The main types of recognition element
used are enzymes and antibodies
Biosensors are also applied to the
detection of many other analytes in the
clinical samples, pollutants, food industry,
metabolites during fermentation process
FIA automatic abstraction of samples
from the test system and their injection into
flow of a carrier liquid, which is constantlypassed through the detection element
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TRANSDUCTION METHODS
Amperometric - electrode is held poised at
a constant voltage relative to a reference
electrode usually Ag/AgC
l) by the use of acircuit known as a potentiostat
Potentiometric an ion selective electrode
is used, and the build-up of the appropriate
ion causes a change in potential with verylittle current flow
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Thermal- extremely sensitive temperature
sensing element (thermistor) used to
detect the increase in temperature due to
heat released by an enzyme- catalyzed
reaction
Optical- based on the transmission of lightalong an optical fiber to a detector.
Surface Plasmon Resonance(SPR)-It is
applied to the detection of small changesin mass due to ligand binding in a film of
immobilized antibodies
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Piezoelectric- In
this case, the film
is immobilized on
the surface of a
piezoelectric
crystal such asquartz, detection
based on changes
in the mechanicalproperties of the
surface film as its
mass increases.
8/3/2019 MT Seminar
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CATALYTIC BIOSENSORS: Enzymes
as Biological Sensing Elements
Enzymes form most widely used
Biosensors- Oxidoreductase : oxidize orreduce the substrate , they are involved in
the movement of electrons and lend to
amperometric detection methods
Some cases enzyme based system
require additional small molecules such as
co-factors or co-substrates
8/3/2019 MT Seminar
11/21
AFFINITY BIOSENSORS: Antibodies as
Biological Detection Elements
Biosensors based on antibodies are
sometimes immunosensors Two types of Label-based assay
Sandwitch assay
Competitive assays
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IMMOBILIZATIONOF THE BIOLOGICAL
RECOGNITION ELEMENT
ADSORPTION- enzyme or antibody exposed
to the surface and attaches by adsorption
RETENTION WITHIN A MEMBRANE-BOUNDED
COMPARTMENT-electrode surrounded by
dialysis membrane, enzyme solution is
contained between this and anotherdialysis membrane
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INDIRECT AFFINITY SENSORS-Optical and
Electrical biosensors based on antibodies
Use of antibodies labeled with horseradish
peroxidase (HRP), such antibodies areused for colorimetric or fluorimetric
detection based on reaction of HRP with
luminol or chromogenic substrates( 4-amino-phenazone
When used in biosensors it can be
detected optically by chemiluminescence
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Using aptamersrather than using a
antibodies in a sandwich-type assay The captured aptamer was immobilized on
a gold electrode surface, and the detection
aptamer was labeled with PQQ-dependent
glucose dehydrogenase .
Amout of enzyme captured near the
electrode surface was detected
amperometrically following the addition ofglucose
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DIRECT AFFINITY DETECTION USING
SURFACE PLASMON RESONANCE ANDPIEZOELECTRIC BIOSENSORS
Here the binding of ligand to immobilizedcapture molecules is detected directly by
monitoring the amount of mass associated
with the capture surface
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Atttachment of large ligands to the capture
molecules increases the mass of the filmto a detectable degree
The main method used for such systems
are surface plasmon resonance(SPR) and
piezoelectric transduction, mainly quartz
crystal microbalance(QCM)
Surface Plasmon Resonance(SPR) is an
effect in which a beam of laser light isshown through a transparent medium
coated with a thin film of gold, with a fluid
layer on the other side of the gold film.
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Some reports have also described
integration of multiple sensors of differenttypes in a single chip
For eg: construction of an SPR
immunosensors chip for human IgG, alsobearing integrated amperiometric sensors
for glucose and lactate ; this was used for
simultaneous on-line monitoring of
glucose, lactate, and IgG in a cell culture
bioreactor
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Acoustic wave (piezoelectric) systems
used to measure mass changes due to
ligand binding in a film of immobilized
antibody
This detection is based on changes in the
nature of vibration of a piezoelectricmaterial such as quartz when an electrical
potential is applied
In this case, the antibody film isimmobilized on the surface of a
piezoelectrical crystal
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REFERENCES
Principlesoffermentationtechnology-
PeterF. Stanbury, Allan Whitaker
Fermentationmicrobiologyandbiotechnology- Mansi El-Mansi, Charles
F. A. Bryce