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

Miniaturization of aqueous two-phase extraction for biological applications: From micro-tubes to microchannels

Aqueous two-phase extraction (ATPE) is a biocompatible liquid-liquid (L-L) separation technique that has been under research for several decades towards the purification of biomolecules, ranging from small metabolites to large animal cells. More recently, with the emergence of rapid-prototyping techniques for fabrication of microfluidic structures with intricate designs, ATPE gained an expanded range of applications utilizing physical phenomena occurring exclusively at the microscale. Today, research is being carried simultaneously in two different volume ranges, mL-scale (microtubes) and nL-scale (microchannels). The objective of this review is to give insight into the state of the art at both microtube and microchannel-scale and to analyze whether miniaturization is currently a competing or divergent technology in a field of applications including bioseparation, bioanalytics, enhanced fermentation processes, catalysis, high-throughput screening and physical/chemical compartmentalization. From our perspective, both approaches are worthy of investigation and, depending on the application, it is likely that either (i) one of the approaches will eventually become obsolete in particular research areas such as purification at the preparative scale or high-throughput screening applications; or (ii) both approaches will function as complementing techniques within the bioanalytics field.

Partitioning in aqueous two-phase systems: Analysis of strengths, weaknesses, opportunities and threats

For half a century aqueous two-phase systems (ATPSs) have been applied for the extraction and purification of biomolecules. In spite of their simplicity, selectivity, and relatively low cost they have not been significantly employed for industrial scale bioprocessing. Recently their ability to be readily scaled and interface easily in single-use, flexible biomanufacturing has led to industrial re-evaluation of ATPSs. The purpose of this review is to perform a SWOT analysis that includes a discussion of: (i) strengths of ATPS partitioning as an effective and simple platform for biomolecule purification; (ii) weaknesses of ATPS partitioning in regard to intrinsic problems and possible solutions; (iii) opportunities related to biotechnological challenges that ATPS partitioning may solve; and (iv) threats related to alternative techniques that may compete with ATPS in performance, economic benefits, scale up and reliability. This approach provides insight into the current status of ATPS as a bioprocessing technique and it can be concluded that most of the perceived weakness towards industrial implementation have now been largely overcome, thus paving the way for opportunities in fermentation feed clarification, integration in multi-stage operations and in single-step purification processes.

Redefinition of working aqueous two-phase systems: a generic description for prediction of the effective phase chemical composition for process control and biorecovery

Aqueous two-phase systems (ATPS) have been widely adopted for the combined purpose of solid liquid separation, and recovery and purification of bioproducts such as proteins, viruses and organelles from biological feedstocks and fermentation broth. However, in spite of potential advantages over other techniques applied to concentrated biological feedstocks, ATPS have been applied at process scale only by a few industries and research establishments. ATPS are sensitive to loading with modest to extreme quantities of biological feedstock due to the contribution of that material to phase formation in combination with the conventional phase-forming chemicals. This causes problem associated with the definition and manipulation of loaded working systems, which may be addresses as in the present study with the aid of distribution analysis of radiolabel led analytes (DARA) in representative process samples. The present study focussed on establishing a generic description for characterising ATPS loaded with biological feedstocks and the redefinition of the biological feedstock loaded system composition in terms of phase forming chemical equivalents. This evaluation will be useful to achieve ATPS process implementation where phase recycle/reuse is adopted without compromise to process operations and consistent protein recovery performance.

Alternative bioseparation operations: life beyond packed-bed chromatography

Chromatography is undoubtedly the workhorse of downstream processes, affording high resolution for bioseparations. At the same time, it has the notoriety of being the single largest cost center in downstream processing and of being a low-throughput operation. Consequently, 'chromatography alternatives' are an attractive proposition, even if only a reduction in the extent of use of packed beds can be realized. This paper reviews the current state of unit operations posing as chromatography alternatives--including membrane filtration, aqueous two-phase extraction, three-phase partitioning, precipitation, crystallization, monoliths and membrane chromatography--and their potential to do the unthinkable.

Operational intensification by direct product sequestration from cell disruptates: application of a pellicular adsorbent in a mechanically integrated disruption-fluidised bed adsorption process

A novel prototype adsorbent, designed for intensified fluidised bed adsorption processes, was assembled by the emulsification coating of 4% (w/v) porous agarose upon a zirconia-silica solid core. The adsorbent, designated ZSA (particle density 1.75 g/ml, maximum pellicle depth 40 microm), was subjected to physical and biochemical comparison with the performance of two commercial adsorbents (Streamline and Macrosorb K4AX). Bed expansion qualities and hydrodynamic characteristics (N, D(axl) and B(o)) of ZSA demonstrated a marked robustness in the face of elevated velocities (up to 550 cm/h) and biomass loading (up to 30% (ww/v)) disrupted yeast cells. Cibracron Blue derivatives of the pellicular prototype (ZSA-CB), evaluated in the batch and fluidised bed recovery of glyceraldehyde 3-phosphate dehydrogenase (G3PDH) from unclarified yeast disruptates, exhibited superior capacities and adsorption/desorption performance to the commercial derivatives. These advanced physical and biochemical properties facilitated a demonstration of the direct, mechanical coupling of bead-milling and fluidised bed adsorption in a fully integrated process for the accelerated recovery of G3PDH from yeast. The generic application of such pellicular adsorbents and integrated processes to the recovery of labile, intracellular products is discussed.