Functional Solvent Design for Separation of Bioproducts

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According to the development of biotechnology, sufficient separation techniques for bioproducts are strongly required. Among several separation techniques, a purification method due to the partition of bioproducts to aqueous two-phase system seems to be one of promising methods because the aqueous system provides a mild condition. To design the optimum solvent condition, the knowledge of phase behavior of the aqueous two-phase system and the partition coefficient of bioproducts is essentially needed.In the present study, the liquid-liquid equilibria of the dextran-polyethylene glycol- water system were measured at 20゜C. The present liquid-liquid equilibria coincide with the literature values. Further, it is found that the phase behavior of the aqueous two-phase system can be correlated by the Flory-Huggins equation. The reagents used are dextran from Pharmacia Co.Ltd.(Lot No.03375, Mn=24200, T40) and polyethylene glycol supplied by Wako Chemicals, Ltd.(Lot No.AWM2336, Mn=3000, PEG4000). Distilled water from Wako Chemicals, Ltd. was used as pure water.The partition coefficients of -amylase supplied by Wako Chemicals, Ltd.(Bacillus Subtiles, Lot No.PDGO524) to the above aqueous two-phase system were measured. From the present data, it is found that -amylase is distributed mainly to the bottom phase (dextran rich phase). This partition coefficients were correlated by the Flory-Higgins equation. The interaction parameters are found to depend on the molecular weight.