Studies On The Low-cost Cultures Of Porphyridium Cruentum And Purification Of Phycoerythrin

The unicellular red alga,Porphyridium cruentum,belong to Rhodophyta,can synthesize some bioactive substanccs such as phycobiliprotein and exopolysaccharide, which have expansive application foreground.The cost of mass production of alga and purification of phycoerythrin will seriously constrain the wide range demands of B-phycoerythrin(B-PE)applications in biomedical and food industries.In this paper we investigated the low-cost cultures of Porphyridium cruentum,different kinds of cell disruption processes,large-scale purification of phycoerythrin.The results were as follows:The fertilizer culture media that affect the growth and metabolites production of Porphyridium cruentum were optimized.Shaken flasks experiment showed that with the fertilizer mediumⅡ,Ⅲ,the harvest dry weights of alga(1.077±0.175 g/L,0.920±0.017 g/L)were higher than that of KOCH medium(0.823±0.160 g/L).The effects of culture medium validity in the flat plate photobioreactors was investigated,the results showed that the harvest dry weights of alga as well as yield of phycoerythrin in fertilizer mediumⅡwere higher than that in KOCH culture medium.In order to establish the optimal conditions for the production of the phycoerythrin from Porphyridium cruentum,the red microalga Porphyridium cruentum was cultured by fed-batch and different renewal rate of the culture medium.The harvest biomass(dry weights)and yield of phycoerythrin in fertilizer mediumⅡ,fed-batch with NaHCO₃, were higher than that of control.The lower renewal rate(25%)increased the yield of phycoerythrin in Porphyridium cruentum mass cultivation.Four kinds of cell disruption processes(dissolving-bulging,freezing and thawing, low concentration of calcium chloride extraction and beading treated)were used to disrupt three microalge(Porphyridium cruentum,Rhodella reticulata and Nostoc punctiforme).The purity and concentration of B-PE were used in the assay.By using freezing and thawing,the highest purity of B-PE for Porphyridium cruenum and Rhodella reticulata were obtained when cell density reached 1.000 g/L.The purity and concentration of B-PE for Porphyridium cruentum were 1.250 and 29.788 mg/L,for Rhodella reticulata were 1.669 and 36.026 mg/L,respectively.Nostos punctiforme cells, which was treated with low concentration of calcium chloride extraction,reached the highest purity of B-PE(OD₅₄₅/OD₂₈₀=0.477)when cell concentration was 1.000 g/L.It was mean that by using freezing and thawing,the highest purity of B-PE and the higher extract yield for Porphyridium cruenum and Rhodella reticulata were obtained.Low concentration of calcium chloride extraction can be used for obtainning higher purity of B-PE from Nostos punctiforme.The large scale purification of phycoerythrin from Porphyridium cruentum was carried out by using ultrafiltrtation membrane,with a MWCO of 60-80 kDa.The highest purity of phycoerythrin was achievcd at the optimum conditions as follows:pressure 0.06 MPa,temperature 45℃,pH 10.Using fraction precipitation of ammonium sulphate with different concentrations,respectively,the purity of the purified B-phycoerythrin reached 4.29,the total yield was 52.09%.