Separation of polysaccharides from Spirulina platensis by HSCCC with ethanol-ammonium sulfate ATPS and their antioxidant activities

Three separation methods for water-soluble polysaccharides from Spirulina platensis (PSP) were compared, including sevage deproteinization and column chromatography, ethanol-ammonium sulfate aqueous two-phase system (ATPS) and column chromatography, and one-step high speed counter-current chromatography (HSCCC) with ethanol-ammonium sulfate ATPS. ATPS was confirmed as an efficient alternative method of protein removal for PSP purification. For the HSCCC with ethanol-ammonium sulfate ATPS, the stationary retention reached to 50.8% at the optimized rotation speed and flow rate. Moreover, the yield of PSP purified by one-step HSCCC rose nearly five times to 12.45 mg/g(dry algae powder), it was higher than PSP yield by two-step column chromatography separation methods. PSP purified by HSCCC has the same purity as PSP obtained by traditional methods, which was proved by a single symmetrical peak of purified PSP with molecular weight of 12.33 kDa through gel chromatography. Purified PSP was an α-acidic polysaccharide, composed of major glucose, slight rhamnose and mannose, which were detected within GC and FT-IR spectra. The antioxidation activity experiment showed that HSCCC-purified PSP had strong scavenging effects on hydroxyl free radical and DPPH free radical.