01-10-2012, 12:46 PM
Downstream processing
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The various stages of processing that occur after the completion of the fermentation or bioconversion stage, including separation, purification, and packaging of the product
Stages in Downstream Processing
Removal of insoluble's
Product Isolation
Product Purification
Product Polishing
Removal of insoluble's
capture of the product as a solute in a particulate-free liquid
Example
separation of cells, cell debris or other particulate matter from fermentation broth containing an antibiotic.
Typical operations
Filtration
A mechanical operation used for the separation of solids from fluids (liquids or gases) by interposing a medium to fluid flow through which the fluid can pass, but the solids in the fluid are retained.
Filter media
two main types of filter media are
solid sieve which
-traps the solid particles
bed of granular materials
-retains the solid particles
Centrifugation
use of the centrifugal force for the separation of mixtures
More-dense components migrate away from the axis of the centrifuge
less-dense components migrate towards the axis.
Flocculation
process where a solute comes out of solution in the form of flocs or flakes.
Particles finer than 0.1 µm in water remain continuously in motion due to electrostatic charge which causes them to repel each other
Once their electrostatic charge is neutralized (use of coagulant) the finer particles start to collide and combine together .
These larger and heavier particles are called flocs.
Product Purification
To separate contaminants that resemble the product very closely in physical and chemical properties.
Expensive and require sensitive and sophisticated equipment.
Crystallization
process of formation of solid crystals precipitating from a solution, melt or more rarely deposited directly from a gas.
chemical solid-liquid separation technique, in which mass transfer of a solute from the liquid solution to a pure solid crystalline phase occurs.