Metabolite Regulation Of Active Substances From Rhodella Reticulata And Purification Of Phycocyanin

The unicellular red alga,Rhodella reticulata with a pyrenoid in it,can synthesize some bioactive substances such as exopolysaccharides,phycobiliprotein and pigments.In this paper,we investigated the optimization of nitrogen source,and made potassium nitrate and urea as a sole nitrogen source respectively,obtained the best nitrogen concentration,isolated and purified the phycocyanin from Rhodella reticulata,analyzed the amino acid composition and stability of the phycocyanin,as well as antioxidant activity of phycocyanin in vitro.The results were as follows:1.Potassium nitrate as a nitrogen source,Rhodella reticulata grew well when nitrogen concentration was between 1.85～296mmol/L.The production of biomass and phycocyanin had increased 5.13%and 15.94%under the best nitrogen concentration(3.7mmol/L).When the nitrogen concentration was 296mmol/L,the maximum exopolysaccharides of Rhodella reticulata increased 254.87%.Therefore, potassium nitrate was the optimum nitrogen source.2.Urea as a nitrogen source,Rhodella reticulata grew well when nitrogen concentration was between 1.85～29.6mmol/L,the production of biomass, exopolysaccharides and phycocyanin had increased 26.92%,23.58%and 35.22%at the best nitrogen concentration(14.8mmol/L).When the nitrogen concentration was above 74 mmol/L,the alga died.It indicated that high concentration of urea could inhibit the growth of Rholdella reticulata.3.The nitrate reductase(NR)was rightly related to the biomass of the alga.Potassium nitrate had higher NR activity than urea had did.The enhanced activity of superoxide dismutase was due to an increase in concentration of nitrogen.4.We used DEAE Sepharose Fast Flow ion exchange chromatography in combination of ammonium sulfate fractionation for purification of phycocyanin from Rhodella reticulata.The criterion of purity(R)was 3.92,the purified protein has two subunits with molecular mass of 18 and 22kDa each according to SDS-PAGE.The pure phycocyanin contained 17 kinds of amino acid.5.The phycocyanin was more stable under unlighted,low temperature and neutrality pH.6.For antioxidant activity assay on phycocyanin,the pure phycocyanin had higher antioxidant activity than crude phycocyanin had.Moreover,the pure phycocyanin exhibited effective antioxidant activity in a dose-dependent manner.