Isolation, identification and optimization of biomass production of native Spirulina species from South of the Caspian Sea

The aim of the present study was to identify the native Spirulina species from Caspian Sea and optimize the growth conditions of this microalgae in order to reduce costs and increase the benefits of its production. In this study, water sampling was carried out from a depth of 5 meters on the coast of south Caspian Sea (Iran) in 2023-2024. After observing the Spirulina genus, its microalgae were isolated and purified using the dilution method, and finally pure single colonies were obtained. Initial identification was carried out using a light microscope and valid identification keys. Molecular identification and 16 SrRNA sequencing were used to confirm and verify it. The results showed that the studied species has the least genetic distance from the microalgae <i>Spirulina laxissima</i>. Then, the effect of three physical factors, temperature (27-29 °C), light (3000-3500 lx) and pH (9-11), on its biomass production rate was investigated using the response surface methodology. The results obtained from the design of this experiment showed that the biomass amount on the seventh day was 0.382 (g/L) with pH=10, light 3250 lx and temperature 29 °C and on the fourteenth day the biomass amount reached 0.839 (g/L) and pH=10, light 3250 lx, temperature 29 °C.•Isolation of microalgae <i>Spirulina laxissima</i> from Caspian Sea.•Molecular identification <i>Spirulina laxissima</i>.•Optimizing of <i>Spirulina laxissima</i> culture with physical changes (temperature, light, pH).