Downstream processing

Submitted to : Dr. Dinesh Kumar chatanta

Submitted by: Pritika

Downstream processing :

Process including separation and purification.

Also known as product recovery. Material-upstream-finished products.

Stages in downstream processing :

Removal of insolubles Product isolation Product purification Product polishing

Removal of insolubles

The first step and involves the capture of the product as a solute in a particulate-free liquid.

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

Typical operations to achieve this are : filtration, 

centrifugation, 

sedimentation, precipitation, flocculation,

Filteration: The mechanical or physical operation

which is used for the separation of solids from fluids (liquids or gases) by interposing a medium through which only the fluid can pass.

Centrifiugation : Process which involves the use of the

centrifugal force for the sedimentation of heterogeneous mixtures with a centrifuge, used in industry and in laboratory settings. This process is used to separate two immiscible liquids.

Sedimentation : Tendency for particles in suspension to

settle out of the fluid in which they are entrained, and come to rest against a barrier. This is due to their motion through the fluid in response to the forces acting on them: these forces can be due to gravity, centrifugal acceleration or electromagnetism. 

Floculation :

Process wherein colloids come out of suspension in the form of floc or flake; either spontaneously or due to the addition of a clarifying agent. 

Product isolation

The removal of those components whose properties vary markedly from that of the desired product.

For most products, water is the chief impurity and isolation steps are designed to remove most of it, reducing the volume of material to be handled and concentrating the product. 

Solvent extraction, adsorption, ultrafiltration, and precipitation are some of the unit operations involved.

Extraction :

Separation process consisting in the separation of a substance from a matrix.

It includes Liquid-liquid extraction, and Solid phase extraction.

Adsorption : The adhesion of atoms, ions, or molecules

from a gas, liquid, or dissolved solid to a surface.

This process creates a film of the adsorbate on the surface of the adsorbent. 

Ultrafilteration :

Separation process for sperating gaseous or liquid stream use membrane technology.

Pore size 0.001-0.01μm . Separate concentrate and purification

of dissolved and suspended constituent according to their relative molecular size.

Mainly used in dairy industry.

Product purification

Done to separate those contaminants that resemble the product very closely in physical and chemical properties.

Consequently steps in this stage are expensive to carry out and require sensitive and sophisticated equipment.

This stage contributes a significant fraction of the entire downstream processing expenditure.

Operations include affinity, size exclusion chromatography, crystallization and fractional precipitation.

Affinity chromatography : Method of separating biochemical

mixtures based on a highly specific interaction such as that between antigen and antibody, enzyme and substrate, or receptor and ligand.

Size exclusion chromatography : Method in which molecules in solution

are separated by their size, and in some cases molecular weight.

Crystallisation :

A chemical solid–liquid separation technique, in which mass transfer of a solute from the liquid solution to a pure solid crystalline phase occurs.

formation of solid crystals precipitating from a solution, melt or more rarely deposited directly from a gas.

Product polishing

The final processing steps which end with packaging of the product in a form that is stable, easily transportable and convenient.

Crystallization,desiccation, lyophilization and spray drying are typical unit operations.

Depending on the product and its intended use, polishing may also include operations to sterilize the product and remove or deactivate trace contaminants which might compromise product safety. Such operations might include the removal of viruses or depyrogenation.

Dessication

The state of extreme dryness, or the process of extreme drying.

A desiccant is a hygroscopic (attracts and holds water) substance that induces or sustains such a state in its local vicinity in a moderately sealed container.

Spray Drying

Method of producing a dry powder from a liquid or slurry by rapidly drying with a hot gas.

This is the preferred method of drying of many thermally-sensitive materials such as foods and pharmaceuticals.