Purification And Characterization Of Phycoerythrins From Bangia Fusco-purpurea And Porphyra Haitanensis

A convenient and fast purification procedure of phycoerythrin from the red algae Bangia fusco-purpurea was described, its spectra properties, subunit composition, stability, safety as food, and the scavenging effect of phycoerythrin on hydroxyl radical and hydrogen peroxide were investigated. For comparative study, phycoerythrin from Porphyra haitanensis was also purified and its properties were compared with that of phycoerythrin from Bangia fusco-purpurea.The purification of phycoerythrins from Bangia fusco-purpurea and Porphyra haitanensis was carried out using 35-50% ammonium sulfate fractionation and anion-exchange column chromatography on DEAE-Sepharose. New elution conditions were performed by the combination of a linear gradient of ionic strength and a linear gradient of pH. The purity (A565/A280) of the phycoerythrin from Bangia fusco-purpurea reached 4.5 and the recovery was 0.8 g/100 g algae, and the purity of the phycoerythrin from Porphyra haitanensis reached 3.6 with the recovery of 0.1 g/100 g algae. Absorption spectrum characteristic of purified phycoerythrins from Bangia fusco-purpurea and Porphyra haitanensis showed that they are both R-phycoerythrins, and their fluorescence emission maximums are 572 nm.Relative molecular weights of subunits consisting of R-phycoerythrins were estimated by SDS-PAGE followed by silver staining. The molecular weights ofα,β,γfrom Bangia fusco-purpurea are about 19,000, 21,000 and 27,000 Da, respectively, and that ofα,β,γfrom Porphyra haitanensis are about 21,000, 22,000 and 32,000 Da, respectively.The stability of R-phycoerythrins was investigated at different pHs, temperatures and light exposure. Purified R-phycoerythrins showed good stability between pH 4.0 and pH 8.0 at room temperature, and they are also stable up to 50℃at pH 7.0. However, R-phycoerythrins should keep away from light exposure for long term storage.The scavenging effect of purified phycoerythrin on hydroxyl radical and hydrogen peroxide was measured using fluorescence spectrophotometry. The result showed that the IC50 of phycoerythrin from Bangia fusco-purpurea on hydroxyl radical was 1.2μg/mL, and that of phycoerythrin on hydrogen peroxide was 4.8μg/mL. The low IC50 showed that phycoerythrin from Bangia fusco-purpurea was a good scavenger on hydroxyl radical and hydrogen peroxide. In addition, the IC50 of phycoerythrin from Porphyra haitanensis on on hydroxyl radical was 11.5μg/mL, while there was little scavenging effect of phycoerythrins from Porphyra haitanensis on hydrogen peroxide.The acute toxicity test of phycoerythrin from Bangia fusco-purpurea showed that the toxicity of phycoerythrin is very low.