Purification of protein from Arthrospira platensis using aqueous two-phase system associate with membrane separation process and evaluation of functional properties

Arthrospira platensis has stood out, especially due to its high protein content and its potential for food application. However, the exploration of protein concentration techniques of this microalgae still presents a great challenge. Thus, the objective of this study was to evaluate the purification of A. platensis proteins by applying two different aqueous two-phase systems (ATS) composed of potassium phosphate and ethanol, and sodium citrate and ethanol, in addition to the association with membrane separation process (MSP), and the characterization of the fractions obtained. ATS under the optimised conditions (19% potassium phosphate and 30% ethanol, and 19.5% sodium citrate and 29% ethanol) resulted in 1.27 and 1.31 purity, and 77.45% and 78% recovery, respectively. The sodium citrate and ethanol ATS showed significantly greater purity; thus, the upper phase was submitted to MSP. The association of ATS and MSP increased the recovery (~ 87%) and the purity (1.5). The top phase of ATS showed higher protein content (61%) than the bottom (5.9%), confirming the protein preference to the top. When the MSP was evaluated, the protein was increased about 8.0%, and antioxidant activity was kept (42 and 40% to top phase and ATS/MSP concentrate, respectively). Emulsions formed by ATS top phase showed a lower droplet size (33.69 µm D4.3 and 6.02 µm D3.2), and a significantly lower degree of overall destabilization (0.04 × 10–6 s−1 kh and 3.54 × 10–3 s−1 ks) than those stabilized with bottom phase and MSP/ATS concentrate. ATS associated with membrane process showed efficiency in the concentration A. platensis protein, being able to be an alternative to be used in industrial systems.