Purification of R-phycoerythrin from a marine macroalga Gracilaria gracilis by anion-exchange chromatography

Gracilaria gracilis , a red macroalga, represents an exploited important biomass. One of the potential uses of this red seaweed is the production of valuable molecules such as R-phycoerythrin. This compound has recently found applications in food and cosmetic industries as a natural colorant, in conducting medical diagnosis and in biology. However, after R-phycoerythrin extraction the protein extract has to be concentrated and pre-purified, which is commonly expensive and requires many steps. In this paper, R-phycoerythrin from the crude extract obtained by phosphate buffer 20 mM, pH 7.1, was purified by one-step chromatographic method. Native R-phycoerythrin was achieved with a high purity index (A 565 /A 280 ratio) of 3.25 (3.2 = standard R-phycoerythrin purity) after purification on DEAE Sepharose fast flow chromatography with the obtained fraction at 200 mM NaCl. This fraction presented the absorption and emission spectra of R-phycoerythrin with major absorbance at 498, 540, and 565 nm. Native form of this molecule was presented about 260 kDa. Besides, the purified pigment R-phycoerythrin included four subunits: α subunit (18 kDa), β subunit (21 kDa), γ subunit (29 kDa), and γ’ subunit (27 kDa) by gel electrophoresis.