Stages – PURIFICATION BY CHROMATOGRAPHY
In this downstream processing, the products of fermentation e.g. proteins are perfectly purified. This is where closely related compounds are separated from a mixture. In the stationary phase, the porous compound is balanced with a suitable solvent into which the mixture of the compounds to be separated is put.
The different types of chromatography used in separation are:
Gel filtration –this is where the molecules are separated by shape, weight, and size of the molecule. The gel beads in sponge like structure with pores act as sieves for separation of smaller and bigger molecules. The smaller molecules enter the gel beads and the bigger molecules are left out in the mobile liquid
Ion-exchange chromatography – this involves the separation of downstream processing molecules by their atom charges. Thus the ionic bound molecules can be singled out by changing the pH of the eluent by increasing the concentration of the salt solution.
Affinity chromatography – this is the purification of proteins from a complex mixture and is based on the interaction of a protein with an immobilized antibody or an inhibitor which is used to capture the complementary structures.
Hydrophobic interaction chromatography – this is applicable where the difference in composition of the separation. This decreases the salt concentration, reducing the temperature or decreasing the polarity of the medium.
This refers to the maintenance of activity and stability of biotechnological products during the product storage and distribution. To achieve this most of the water must be removed from the product for a low molecular weight and high concentration. In some cases, downstream processing crystallization is applied by adding salts. Since proteins are subject to loss of biological activity, they have to be stabilized by adding additives that prolong the shelf life of a protein.
In the many forms that proteins are formulated in downstream processing, in form of suspensions, solutions or dry powders, various ways are considered to keep them active e.g. drying gently since most biological products of fermentation are sensitive to heat.