Hydrodynamics and mass transfer in aqueous two-phase protein extraction using a continuous perforated rotating disc contactor

Abstract

A continuous perforated rotating disc contactor was used to extract bovine serum albumin (BSA) with aqueous two-phase systems based on polyethylene glycol (PEG) and phosphate salts. The dispersed phase holdup and mass transfer coef®cient were determined. It was found that the dispersed phase holdup increased with increasing PEG phase velocity. The overall mass transfer coef®cient for BSA was independent of the PEG phase velocity.List of symbols C concentration of BSA in phosphate-rich phase (mg/ml) C u concentration of BSA in PEG-rich phase (mg/ml) C ui concentration of BSA in PEG-rich phase at the column inlet (mg/ml) C uo concentration of BSA in PEG-rich phase at the column outlet (mg/ml) H dispersed phase holdup K da mass transfer coef®cient (min )1 ) K partition coef®cient VD dispersed phase¯ow rate (ml/min) IntroductionAqueous two-phase (biphasic) systems have been extensively used for separation and analytical studies of biomaterials since Albertsson [1] developed the technique in the 1950s. Although similar in principle to conventional liquid-liquid extraction, aqueous two-phase extraction has uncommonly wide ranges of physical properties. For instance, the density difference between the two phases varies over the range 10±100 kg/m 3 , the interfacial tension over the range 10 )3 ±10 )2 mN/m, and the viscosities over the range 10±1000 mPa. Conventional liquid-liquid extraction has no property ranges of this magnitude [2]. It has been shown that conventional extraction techniques can be adequately applied to aqueous two-phase systems such as polymer-salt or polymer-polymer systems [1].Aqueous two-phase systems have an important potential in downstream processing such as continuous operation for the large-scale separation of biomolecules. A number of different conventional contactors, e.g. spray columns and packed columns, can be used for aqueous two-phase extraction [3]. Extraction columns with rotatory motion, namely a rotating disc contactor (RDC) and a perforated rotating disc contactor (PRDC), with free areā ow [4] have been used in industry as alternative apparatus to conventional separations equipment. With this type of extractor, high mass transfer rates between the phases were obtained to recover a recombinant cutinase from an aqueous solution to a reversed micellar phase of AOT in isooctane [5].For the design of commercial scale columns, data on the following parameters are needed: protein mass transfer coef®cients, dispersed phase holdup and the extent of mixing in both the phases. Usually, these parameters depend on the velocities of the two phases, their physical properties, the column diameter and the sparger design. In this work it is analyzed bovine serum albumin (BSA) mass transfer data from a laboratory perforated rotating disc contactor (PRDC) using the PEG-phosphates system. The BSA transfer took place from the PEG phase to the salt phase. Speci®cally, the dispersed phase holdup (H) is measured and the mass transfer coef®cients determined as well as the correlations for different disperse...

Multi‐Stage Aqueous Two‐Phase Extraction for the Purification of Monoclonal Antibodies

“…These results are within the range reported for the operation of columns with PEG/salt [29][30][31]. As previously observed for such systems, a fast hold-up increase with rising flow rate was also observed [32,33].…”

Recovery of ascorbic oxidoreductase from crude extract with an aqueous two-phase system in a perforated rotating disc contactor

“…Investigations with York-Sheibel columns (Raghav Rao et al, 1991) using ATPS of PEG 4000 and potassium phosphate salts and sodium sulfate salts showed mass transfer coefficients three times higher than the ones obtained with spray columns (Jafarabad et al, 1992a and b), while the mass transfer coefficients for the PRDC using PEG-phosphate systems (Porto et al, 1997;2000) were 20 times higher than the ones for Spray and York-Sheibel columns. This proportion was also observed in values obtained in this investigation.…”

“…In this extraction column, which has a rotating element, a better contact between the two phases can be achieved (Vermijs and Kramers, 1954). Porto et al (1997Porto et al ( , 2000 have reported the extraction of cytochrome b5 in a PRDC using PEG-phosphate aqueous two-phase systems. More recently, Sarubbo et al (2003) have shown the characterization of Bovine Serum Albumin mass transfer in a PRDC using a polymer-polymer aqueous two-phase system.…”

Extraction of Ascorbate Oxidase from Cucurbita maxima by Continuous Process in Perforated Rotating Disc Contactor Using Aqueous Two-Phase Systems

“…Liquid-liquid extraction equipments are widely used in biotechnology process for extraction of proteins [8,9], enzymes [8,[10][11][12], toxin [7], etc. The rotating disc contactor, consisting of a vertical shell equipped with a series of rotor discs and stators, can be used for this process [13].…”