Biotechnologies biomolecules separation

Diamond AD, Hsu JT. Aqueous two-phase systems for biomolecule separation. Biotechnology 1992 47 90-135. 

Aqueous two-phase systems are routinely used for enzyme purification. Walter and Johansson7 edited a comprehensive book on the subject entitled Aqueous Two-Phase Systems as Vol. 228 of the series Methods in Enzy-mology published by Academic Press. Another very useful book is the one edited by Walter, Brooks, and Fisher6 entitled Partitioning in Aqueous Two-Phase Systems Theory, Methods, Uses, and Applications to Biotechnology which deals with separations of a variety of biomolecules and bioparticles. 

The immobilization of biomolecules on solid surfaces offers considerable advantages to enzymes in solution. Immobilization via physical attraction is often not reliable because of problems concerning leaching and loss of the biomolecule [1]. Therefore, covalent attachment of the enzymes to solid surfaces is advantageous, especially in biotechnology, where the biomolecule should be separated fix)m the reaction mixture, or for the construction of biosensors, where a biocatalyst would be used in a detector system. 

In applications related to biotechnology, polymeric materials appear very often. A common example is the use of the so-called aqueous two-phase systems for the separation of proteins and other biomolecules.These systems comprise water and two water-soluble polymers such as polyethylene glycol and dextran and form two liquid phases in which the biomolecules are distributed. Salts may be also added. In this case, knowledge of the liquid-liquid equilibria of a very complex system comprising one or two polymers, water, salt, and biomolecules is required for design of this extraction technique. 

Biosensors are the offspring of the first successful marriage between biotechnology and modem electronics. The biomolecules are responsible for the specific recognition of the analyte whereas the physicochemical transducer supplies an electrical output signal which is amplified by the spatially separated electronic component. 

Aqueous two-phase systems are generated by mixing aqueous solutions of two water-soluble polymers, or a polymer and a salt. These systems offer extremely mild conditions for separation of cells, organelles, proteins and other biomolecules, in biochemical processes. Considerable attention has been directed towards the use of the two-phase systems in several areas of biotechnology. The present paper summarizes the state of the art concerning extractive bioconversions for production of small as well as macromolecules, and protein purification using aqueous two-phase system. 

Liquid-liquid extraction is one such method. This technology has been successfully used in separation of compounds in chemical and related industries for many years. However, it is only recently that liquid-liquid extraction technology has been recognized as potentially usefiil in biotechnology [78,79). IWo classes of two-phase extraction system are suitable for biomolecule recovery ... 

The development of techniques and methods for protein purification is very important for bioscience and biotechnology. Various chromatographic techniques with different selectivities are powerful methods for the purification of biomolecules, especially the separation of proteins. 

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