Polymer and alcohol‐based three‐phase partitioning systems for separation of polysaccharide and protein

Natural polymers are macromolecules produced by living organisms, and they have a wide range of applications and relevance for the development of a circular economy. However, large-scale production continues to be hindered by several factors, such as downstream processing. In this work, three-phase partitioning (TPP) systems were investigated for separation of model polysaccharide (dextran, alginate, and gum arabic) from protein [Bovine serum albumin (BSA) and lysozyme]. The recyclability of the phase-forming compounds used to form the extractive platform was assessed by ultrafiltration (UF). This study contributes to the development of production processes for biopolymers from fermented waste by proposing an effective separation technique for fractionation of biopolymers. Such biopolymers are often collected as mixtures, but with the studied approaches, fractionation of polysaccharides from proteins may also be employed. With the chosen systems, the scope of TPP systems is expanded by using another class of phase-forming compound (polymers); in addition, UF was studied as a versatile regeneration approach.
Within the TPP approach, the best separation of dextran from BSA was achieved using TPP systems composed of 25 wt% polyethylene glycol (PEG) + 25 wt% K3C6H5O7 and 36 wt% EtOH + 10 wt% K3PO4, in which more than 95% of dextran and BSA were found as precipitate and partitioned to top phase (PEG or EtOH-rich), respectively. By using other model compounds, it was found that the molecular weight and charge of the biopolymer play a key role in the yield and selectivity of TPP systems. Finally, by using ultrafiltration/diafiltration, about 99% of the ethanol and phosphate salt used to form the extractive platform could be retrieved in the permeate stream.
The high extraction yields, good selectivity, and recyclability of phase-forming compounds confirm the potential of polymer-based and alcohol-based TPP systems to fractionate biopolymer mixtures