Biosensors
Biosensors = Immobilized enzymes electrodes electrodes, ,
designed for potentiometric or amperometric assay of
substrates
The electrode = an electrochemical sensor in close
contact with a thin permeable membrane, in which the
enzyme is embedded.
Principle:
Enzymatic reaction →→a small molecule is produced or consumed (e.g. 0consumed 02, H , H+, C0 , C02) ) →→detected by the specific
sensor.
The magnitude of the response determines the concentration
of the substrateExamples:
1. Glucose oxidase electrodes = glucose oxidase
layered over a platinum O
O2 electrode.
Glucose conc. inversely proportion to the O
O2 detected
2. Biosensors have been designed is the detection
of pollutants and pathogens
3. Lux operon from Photobacterium = receptor (inducer) +
structural genes for the enzyme luciferase luciferase. .
Pollutant (substrate) + receptor →→activation →→production of luciferaseluciferaseenzyme enzyme
Luciferase + substrate →→EnzymeEnzyme--substrate complexsubstrate complex
(blue blue-green fluorescence fluorescence)
Other applications
IV-Extracellularpolysaccharides (biopolymers)
Microbial cell surface (cell wall and glycocalyx glycocalyx) is rich in
) polysaccharides
Homopolysaccharides (Dextran and cellulose)
Heteropolysaccharides (Xanthan Xanthan)
Advantages:
1. Unique physical properties.
2. Not subjected to crop failure due climatic conditions and
are supplied in constant quality.
IV-Extracellularpolysaccharides (biopolymers)
Dextrancan be produced by:
Direct method:The medium is supplied with enough sucrose (10 %) to support growth and dextransynthesis.
The problem with this method is that during recovery of the product, which depends on precipitation with ethanol, bacteria may be trapped with the product.
The problem with this method is that during recovery of the product, which depends on precipitation with ethanol, bacteria may be trapped with the product.
Indirect method (Enzymatic):The bacteria are allowed to grow in presence of 3% sucrose.
Dextranis recovered by fractional precipitation with increasing amounts of ethanol to obtain the proper molecular weight and higher molecular weight dextranis again hydrolyzed with acid and further fractionated.
V- Primary metabolites
A-Organic acids
Citric acid is produced commercially using mutants of Aspergillusnigerand Aspergilluswentii.
Carbon source pretreatment
Effect of methanol
Phases of fermentation
Surface culture
Submerged culture
Recovery
Carbon source pretreatment
Effect of methanol
Phases of fermentation
Surface culture
Submerged culture
Recovery