Selection of the mutant of Spirulina platensis with extra-long filaments and morphology and growth of the mutant

By mechanical grinding and sedimentation, the single cells and the fragments (less than 5 cells) of Spirulina platensis strains Sp-Z were obtained. Then they were irradiated with 60Co-gamma rays with their LD50 of 1.2 kGy. After the single cells and the fragments were irradiated with 2.4 kGy γ-ray, a mutant [named Sp-Z(E.L)] with extra-long filaments was selected. The length of filaments, number of helix and length of helix of Sp-Z(E.L) were 15,10 and 1.8 times of those of Sp-Z, respectively. The growth curve of Sp-Z was almost linear, while the growth curve of Sp-Z(E.L) was S-shaped. Moreover, the yield of Sp-Z(E.L) was about 1.12 times of that of Sp-Z cultured outdoors