The present invention discloses a method for producing phycoerythrin by culturing rhodomonas. The best culturing condition for rhodomonas is achieved in an environment under white light with luminosity of 30 μmol photons per square meters per second at 24 deg C, wherein the biomass may reach 10^6 cells/ml and the concentration of sodium nitrate in the culture solution is increased to increase the concentration of phycoerythrin. The phycoerythrin of rhodomonas is extracted in with phosphate buffer solution of pH 6.8 without repeatedly freezing and thawing, and then precipitated by ammonium sulfate of 90% saturation to obtain maximum amount of phycoerythrin, wherein the desalting group is about 190 mg/g (dry weight per gram) and non-desalting group is about 805 mg/g. The phycoerythrin from rhodomonas of the present invention belongs to the PE-545 type with <；alpha>； subunit having molecular weight of about 10 kDa and <；beta>； subunit having molecular weight of about 20 kDa. Furthermore, phycoerythrin from rhodomonas is more stable under pH 5-8 and at low temperature (4 ~ 25 deg C), and, only has 20% being degraded after 24 hours of illumination. Thus, the present invention is less sensitive to light and very suitable for molecular fluorescence labeling, and also possesses the capability for removing DPPH free radicals and the reduction capability.一種紅隱藻之培養以產製藻紅蛋白之方法，其紅隱藻最佳培養條件為白光且光度在30 μmol photons m−2s−1，溫度為24°C之環境，其生物量可達106cells/ml，且增加培養液中硝酸鈉濃度可增加其藻紅蛋白濃度。紅隱藻之藻紅蛋白在不需反覆凍融之pH 6.8磷酸緩衝溶液萃取後，再以90%飽和度硫酸銨將其沉澱，即可獲得最多量之藻紅蛋白，除鹽組約為190 mg/g（每克乾重），無除鹽組約為805 mg/g。本發明之紅隱藻藻紅蛋白屬於PE-545型，其α亞基分子量約為10 kDa，而β亞基分子量約在20 kDa。另外，紅隱藻藻紅蛋白在pH 5～8及低溫（4°C～25°C）下較為穩定，經過光照24小時後僅有20%降解，屬於對光線較不敏感者，極適合應用於分子螢光標記，同時其具有清除DPPH自由基能力及還原能力。
