A Model to Predict the Partition Coefficients of Amino Acids in PEG/Salt Aqueous Two-Phase Systems

Characterization of aqueous two-phase partition systems by distribution analysis of radiolabeled analytes (DARA): application to process definition and control in biorecovery

In this article, we describe a characterization method applicable to aqueous two-phase systems (ATPS) heavily loaded with complex biological feed-stocks. We also studied the partition behavior of mixtures of traceable and quantifiable radiolabeled amino acids, selected on the basis of their relative hydrophobicity A unique linear relation was established between the tie-line length (TLL: commonly determined by graphical methods) and the hydrophobic factor (HF) for ATPS comprising potassium phosphate and PEG alone, and validated for polymer molecular weights from 300 to 8000 Da in systems operated at an apparent pH value of 7.5. Radiolabeled amino acids were subsequently applied to the characterization of ATPS loaded with whole bovine blood by the determination of effective tie-line lengths (TLL(e)). The addition of biomass to ATPS increased TLL(e) relative to that of blank ATPS of equivalent original composition of PEG and phosphate. In addition, an increase of biomass loading (variously sourced from blood, yeast, and E. coli) contributed to phase formation and stabilization of loaded ATPS in respect of system sensitivity toward operational conditions. The controlled application of sensitive ATPS (adjacent to the binodal curve) could thus be reconsidered for further application of aqueous two-phase partitioning as a primary purification process. The application of effective tie-line determinations by distribution analysis of radiolabeled analytes (DARA) as a process-aid in the design and operation of ATPS in biorecovery is discussed.

Poly(ethylene glycol)-based aqueous biphasic systems: effect of temperature on phase equilibria and on partitioning of 1,10-phenanthroline-copper(II) sulphate complex

Solvent extraction is a proven technology for the selective removal and recovery of metal ions from aqueous solutions: the use of aqueous biphase systems can be attractive for many separation processes. These systems have usually been used previously at temperatures around 25 degrees C; however it is possible that better separations may be achieved at other temperatures: phase diagrams have been determined for a polyethylene glycol (AMW 3350)-ammonium sulphate-water system over the temperature range 269-343 K and the effect of temperature on partitioning has been determined for 1,10-phenanthroline-copper(II) sulphate complex.

Partitioning behavior of amino acids in aqueous two-phase systems with recyclable volatile salts

As part of an ongoing research effort on aqueous two-phase systems (ATPSs) with volatile salts, this work describes the partitioning behavior of a series of amino acids, namely L-serine, glycine, L-alanine, L-valine, L-methionine, L-isoleucine, and L-phenylalanine, in these systems. The results show that amino acids partition in a similar way in polymer-volatile salt ATPSs and in traditional polymer-salt ATPSs. Increasing amino acid hydrophobicities lead to increasing partition coefficients. Moreover, the common linear relationship between the logarithm of the partition coefficient and the tie line length is observed here as well. Furthermore, the relation between relative partition coefficients and relative hydrophobicities of amino acids in the extraction systems investigated in this work is comparable to that in other extraction systems.

Centrifugal partition chromatographic reaction for the production of chiral amino acids

The use of a centrifugal partition chromatographic reactor is investigated for the production of chiral amino acids from racemic mixtures. Chirally selective enzymatic hydrolysis of N-acetyl-L-methionine into acetic acid and L-methionine was carried out in the chromatographic reactor to demonstrate the concept of integrated reaction and separation in centrifugal partition chromatography (CPC). The products L-methionine and acetic acid, as well as the unconverted substrate, N-acetyl-D-methionine are obtained separately. An aqueous two-phase system, consisting of PEG 600, potassium phosphate and water was successfully applied as liquid-liquid two-phase system in CPC. A model is presented, which describes the reaction chromatograms on the basis of the independently measured partition and mass transfer coefficients of the individual (reacting) components. The model appears to be a valuable tool for optimizing the reaction-separation process.