Low-cost aqueous two-phase system for

Szlag, D. C. Giuliano, K. A. "A Low-cost Aqueous Two Phase System for Enzyme Extraction" Biotechnology Techniques. 1988, 2, 4, pp 277-282. 

A Low-Cost Aqueous Two-Phase System for Affinity Extraction... 

Szlag DC, Giuhano A, and Snyder SM, A low-cost aqueous two phase system for affinity extraction. In Hamel JFP, Hunter JB, and Sikdar SK, eds. Doivnstream Processing and Bioseparation, Recovery and Purification of Biological Products. ACS Symp. Ser. 419, ACS Press, Washington, 1990 pp. 71-86. 

SZL Szlag, D.C. and Giuliano, K.A., A low-cost aqueous two phase system for enzyme extraction, Biotechnol. Techn., 2, 111, 1988. 

A prehminary study of the use of larch AGs in aqueous two-phase systems [394] revealed that this polysaccharide provides a low-cost alternative to fractionated dextrans for use in aqueous two-phase, two-polymer systems with polyethylene glycol (PEG). The narrow molecular-weight distribution (Mw/Mn of 1-2) and low viscosity at high concentration of AG can be exploited for reproducible separations of proteins under a variety of conditions. The AG/PEG systems were used with success for batch extractive bioconversions of cornstarch to cyclodextrin and glucose. 

Low-cost maltodextrins (Mavg = 1200,1800,3600) can be combined with polyethylene glycol (PEG) to form aqueous two-phase systems which are useful for protein separations. The physical characteristics of these maltodextrin/FEG systems are similar in many respects to dextran/FEG systems. Maltodextrins are currently available for a hundredth of the cost of fractionated dextran making the large scale application of polymer-polymer aqueous two-phase extractions more likely. The physical characteristics of the maltodextrin/FEG two-phase systems are described in this paper along with their application towards the purification of yeast alcohol dehydrogenase. 

The main drawback to the widespread use of polymer-polymer aqueous two-phase extraction has been the high cost of fractionated dextran. Crude dextran has been used with some success for the purification of enzymes but is much too viscous for many applications. Conversely, polymer-salt systems have relatively low viscosities, separate rapidly, and are inexpensive. Unfortunately, they lack selectivity and cannot be used for affinity partitioning in most cases since the high salt concentrations interfere with the protein-ligand interaction. The starch derivatives are reasonable alternatives for bottom phase polymers but have been hampered by low solubilities and the tendency for gel formation. Tjemeld has reported that chemically modified starches i.e. hydroxypropyl starch... 

The MD/PEG system offers the combined advantages of low-cost, reduced lower phase viscosities and high density differences for inexpensive polymer-polymer affinity partitioning. When coupled with low-cost affinity ligands i.e. triazine dyes, two-phase aqueous affinity partitioning could be used as the first step in a separation train for the recovery of industrially important enzymes. The bottom phase, which is generally considered to be a waste stream and non-recyclable if dextran or salt is used could be used as a substrate for additional fermentations if maltodextrin is used, thereby aiding the overall economics of the process. 

Aqueous biphasic systems offer the potential for highly selective and low-cost separations. Aqueous biphasic extraction for soil decontamination is based on the selective partitioning of either dissolved solutes or ultrafine particulates between two immiscible aqueous phases. Both soluble and particulate uranium contaminants can be separated from soil using this technique. Aqueous biphasic extraction may also have application for separation of plutonium and thorium from soil or waste. 

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