PEG-maltodextrin aqueous two-phase system for C-phycocyanin purification from spirulina

C-phycocyanin (C-PC), a natural blue protein pigment, is increasingly sought after for use in food, healthcare, and cosmetics. Aqueous two-phase systems (ATPS) using polyethylene glycol (PEG) and salt are well-established for C-PC purification from microalgal extracts. However, PEG-C-PC complexing complicates subsequent recovery of the C-PC. This study investigates a polymer-polymer ATPS using PEG and maltodextrin (MDX) to recover and purify C-PC from a Spirulina crude extract, aiming for conditions where C-PC partitions into the MDX phase, not PEG. MDX also offers the benefits of adding thermal and oxidation protection. Phase diagrams for PEG-MDX ATPS at 25 °C showed that the MDX phase was free of PEG, and C-PC selectively partitioned into the MDX phase under all conditions tested. PEG 10000 was the best molecular weight tested, achieving a maximum C-PC purification factor of 1.33 ± 0.05 and 100% recovery to the MDX phase using 25 wt% MDX and 9 wt% PEG. PEG concentration had little effect on performance, while MDX concentration influenced the ATPS volume ratio. The ATPS alone was able to purify the crude extract to food-grade C-PC purity under the best conditions, but was short of cosmetic-grade.