Abstract: Purpose: To screen a mutant strain of Spirulina maxima with high photosynthetic rate. Methods: The mutagenesis and screening were conducted by a combination of spontaneous isolation, ultrasonic treatment, UV irradiation and extremely high CO2 stress. Results: Three mutants, namely KYZ1, KYZ2 and KYZ3, were obtained. The filament morphology, biomass, CO2 availability, and protein and chlorophyll contents of these three mutants were compared. Finally, KYZ2 was screened as the best strain. Conclusions: Strain KYZ2 revealed longer and larger filaments, faster growth, higher photosynthetic rate, and higher contents of protein and chlorophyll compared with the starting strain. Thus, the mutant strain could have potential for industrial culture.

Key words: Spirulina maxima, UV irradiation, mutant strain