Study On The Bioactive Compounds Of Spirulina Platensis Mutant Strain

The optimized cultivation and bioactive compounds of Spirulina platensis have been studied in this thesis. To improve the content of bioactive compounds in the cell of Spirulina platensis mutant strain (Sp-Dz), the influence of physical and nutrient factors on the growth of Sp-Dz and the content of phycocyanins and polysaccharides were investigated in detail. Furthermore, their anticancer and antioxidant activities were also investigated. The results of the research are summarized as follows:The cultivation conditions of Sp-Dz were optimized with the method of single factor. The results show that the suitable cultivation conditions for Sp-Dz are: inoculation concentration 0.2 (OD560nm), light intensity 3500lux, temperature 25℃, pH value 10.0, and the dosage of urea 0.8g/L. Addition of organic carbon resource in Zarrouk medium may accelerate Sp-Dz growth.The physical and nutrient factors affecting the content of phycocyanin and polysaccharide in the Spirulina cells were discussed. The results show that the highest content of phycocyanin can be obtained when the cultivation conditions are: temperature 25℃, light intensity 3500lux, pH value 9.5, urea 0.8g/L, and glucose 2.0g/L. On the other hand, the highest content of polysaccharide is obtained under the conditions: temperature 30℃, light intensity 4500lux, pH value 9.5, urea 0.4g/L and glucose 2.0g/L.DEAE-Sepharose Fast Flow, SDS-PAGE, UV and FT-IR were employed to characterize phycocyanin and polysaccharide.The results indicate that the purity of phycocyanin is 3.74(OD620/OD280), which is close to the reagent grade 4.0, and its subunit molecular weight is 35.9kDa. Its maximum absorption is at wavelength 620nm, andα-helix conformation is the major element of its secondary structure. The results also show that the major component of the polysaccharide in Sp-Dz is pyranose, and the hemiacetal hydroxyl to form glycoside isα-configuration.Phycocyanin can eliminate both hydroxyl radical and DPPH radical, and its DPPH radial scavenging rate can reach at 77%. Compared to phycocyanin, polysaccharide shows weak scavenging abiliity on the above free radicals. In addition, the anticancer activity assay indicates that the phycocyanin and polysaccharide have inhibition effect on some cancer cells. When their concertratin is at 400ug/mL, the phycocyanin and polysaccharide have an inhibition rate of 31% on cancer cell BEL-7402 and 51% on cancer cell HL-60, respectively.