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Downstream processing ppt





Ideally, extraction and purification process is obtaining
a high quality product as quickly as possible
at an efficient recovery rate
using minimum plant investment
operated at minimal costs.
Choice of recovery product is based of following criteria:-
Intracellular or extracellular location of product
Concentration of product in broth
Physical & Chemical properties of product
Use of that product
Minimal acceptable standard of purity
Magnitude of Bio-Hazard of the product
Impurities in broth
Marketable price for the product

Removal of Microbial Cells & Other Solid Matter

Microbial cells, etc are separated from harvested broth by Filteration or Centrifugation.
Filteration is used to remove cells while heat and floculation treatments are used to increase sedimentation rates.
Method of removal of cell & cell debris include-
Ultrasonic treatment
Magnetic separation
Most frequently used procedure is 2 phase liquid extraction.

Foam Separation

It depends on using methods that exploit differences in surface activity of materials.
The material may be selectively attached or adsorbed to surface of gas bubbles , to be concentrated or separated and finally removed by skimming.
Some materials(Colligends) may be made surface active by surfactants(Collectors).


It can be conducted at various stages of recovery process.
Typical agents used in precipitation-
Acids and Bases
Organic solvents
Non Ionic Polymers
Protein Binding Dyes
Affinity Precipitants


Variety of factors influence choice of equipment to be used for filtration-
Properties of filtrate, particularly Viscosity & Density.
Nature of solid particles
The Solid: Liquid ratio
Need for recovery of Solid or Liquid or both
Scale of operation
Need for Batch or Continuous operation
Need for aseptic operation
Need for pressure or vacuum suction to ensure adequate flow rate of liquid.


Used when filtration is not satisfactory.
According to Stoke s Law, rate of sedimentation of spherical particles suspended in fluid of Newtonian viscosity characteristics is proportional to the square of diameter of particles, thus the rate of sedimentation of particle under gravitational .
Cell aggregation and flocculation
Flocculation is used in effluent treatment for removal of cells and suspended colloidal matter.
Aggregates of cells will sediment fast due to increased diameter of particles.(Stoke s Law)
During flocculation 1 or more mechanisms besides temperature induce cell flocculation-
Neutralization of anionic charges
Reduction in surface hydrophilicity
Use of high molecular weight polymerbridges.

Cell Disruption

Is required to release cell components.
Number of methods have been developed for this purpose.
This process must ensure that liable molecules are not denatured, or hydrolyzed by enzymes present in cell.

Liquid-Liquid Extraction

Separation of component from liquid mixture by treatment with a solvent in which the desired component is soluble.
The specific requirement is that a high percentage extraction of product must be concentrated in smaller volume of solvent.
Solubility characteristic- like dissolves like.
Polar liquids mix with each other and dissolve solids and salts & vice versa.
The dielectric constant D is a measure of the degree of molar polarization of a compound.
This value predicts whether compound is polar or non polar.
D can be measured by determining the electrostatic capacity C of condenser containing the substance between plates. If Co is the value of same condenser when it is completely evacuated then,

Two Phase Aqueous Extraction

Large varieties of natural & synthetic hydrophilic polymers are used to create two (or more) phases.
Phase separation occurs when hydrophilic polymers are added to an aqueous solution and when the concentrations exceed a certain value two immiscible aqueous phases are formed.
Settling time for the two phases can be prolonged, depending on the components used and vessel geometry.
Phase separation can be improved by using centrifugal separators or magnetic separators.


Used to isolate and purify relatively low concentrations of metabolic products.
Depending upon the mechanism used it is divided into following types-
Adsorption Chromatography
Ion Exchange Chromatography
Gel permeation Chromatography
Affinity Chromatography
Reverse Phase Chromatography
High Performance Liquid Chromatography
Downstream processing


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
separation of cells, cell debris or other particulate matter from fermentation broth containing an antibiotic.

Typical operations

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


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.


process where a solute comes out of solution in the form of flocs or flakes.
Particles finer than 0.1 m 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.


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.
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