ICAR Research Data Repository for Knowledge Management

In the recent years there have been tremendous efforts by research and industrial community for the production of biochemicals through application of fermentation technology and cell culture. However, the technology for downstream processing (DSP) of biological products from the media/broth has not kept pace with the advances in upstream operations involving bioreactors, despite the fact that in many cases DSP contributes major share of the final product cost. The separation of many biochemicals from the product stream is still performed by batch mode small-scale processes such as column chromatography, salt and solvent precipitation and electrophoresis for which scale-up poses considerable problems, making them uneconomical at large-scale unless the product is of high value. Affinity-based chromatographic separations though have excellent selectivity and have been carried out in large scale, for the most part such systems operate discontinuously and is very expensive, which in turn makes the product also expensive. The economy of scale has not often been realized. Therefore, current research in the area of DSP is directed towards the development of efficient and scalable alternative bioseparation processes with potential for continuous operation. Liquid-liquid extraction (LLE) is a traditional chemical engineering unit operation for which the design and scale-up of both batch as well as continuous processes are already accomplished. Unlike affinity chromatography and precipitation, LLE is well known to be operative on continuous mode at large scale with high throughputs. The process is easy to operate and high flexible. LLE using organic/aqueous phase has been employed in many chemical industries. However, this technique with all its advantages has not gained wide industrial recognition in the field of biotechnology, mainly due to the poor solubility of proteins in organic solvents and the tendency of organic solvents to denature the proteins. In recent years LLE using the aqueous two-phase systems (ATPS) has been recognized as a superior and versatile technique for DSP of biomolecules, and a wealth of information has been reported in the literature on various aspects of aqueous two-phase extraction (A TPE) for the isolation and concentration of proteins, enzymes and other biological materials. The major advantages of A TPE include high capacity, biocompatible environment, low interfacial tension, high yield, lower process time as well as energy, and high selectivity. Further, it offers ease of scaleup, continuous operation and most importantly, allows easy adaptation of the equipment and the methods of conventional organic-aqueous phase extraction used in the chemical industry. However, ATPE is not selective enough to provide the extreme purity usually desired. It is recognized as a primary purification step in the overall process of enzyme/protein purification in which the final purification is achieved by methods such as chromatography, or crystallization. This technique is also effective in the removal of contaminating material such as polysaccharides and nucleic acids.