Complexation of pea albumins with anionic polysaccharides and purification of PA1a

Selective complexation with anionic polysaccharides (sulfated (SPS) and carboxylated polysaccharides (CPS)) was used to purify a target protein, pea albumin 1a (PA1a), a sulfur rich protein, from PA1a/pea albumin 2 (PA2) mixtures (PPM, two main pea albumins). The results showed that PPM-SPS system had higher critical pH c and protein recovery than that of PPM-CPS. The binding affinity of PA2 with CPS or SPS was stronger than that of PA1a, which led to the preferential complexation of PA2 and the enrichment of single PA1a in the supernatant. The high charge densities of dextran sulfate, κ-carrageenan and sodium alginate were unfavorable to the isolation of PA1a, and the highest PA1a recovery was obtained for PPM-carboxymethyl cellulose system, although it had the lowest charge density. After removal of polysaccharides by ultrafiltration in non-interacting pH conditions, a purified PA1a (>90% by SEC-HPLC) was obtained. This work provides a novel strategy for the purification of PA1a from multi-proteins system based on selective complexation.