Effect of light intensity on carbohydrates, lipids contents, and bioethanol production in two algal species of Coelastrella saipanensis and Oscillatoria duplisectaر

This study aimed to examine the feasibility of two algal species of Coelastrella saipanensis (Chlorophyceae) and Oscillatoria duplisecta (Cyanophyceae) to produce bioethanol production at different light intensities. In the present study, light-intensity treatments at 27, 36, and 67 μmol m-2 s-1 were used to stimulate bioethanol production from microalga. The effects of these treatments on C. saipanensis and O. duplisecta were investigated on their growth, carbohydrate and lipids contents. The results showed that the stationary phase of C. saipanensis started on the sixth day under light intensities of 27 and 36 μmol m-2 s-1 and on the eighth day under light intensity of 67 μmol m-2 s-1. The stationary stage of blue-green algae O. duplisecta started on day eight, sixth, and seventh under light intensities of 27, 36, and 67 μmol m-2 s-1, respectively. The highest amount of carbohydrate content was 0.182, and 0.310 mg/l for C. saipanensis and O. duplisecta under light intensity of 36 μmol m-2 s-1. The highest amount of lipid was 0.95 g/l for C. saipanensis under a light intensity of 36 μmol m-2 s-1, while 0.74 g/L was the highest amount of lipid for O. duplisecta under 67 μmol m-2 s-1 at a light intensity of 36 μmol m-2 s-1. The highest percentage of bioethanol in C. saipanensis and O. duplisecta were 11.35 and 10.23%, respectively. The 18S rRNA and 16S rRNA genes were used for the identification, and the sequences of algae matched those registered in the GenBank (MT375484.1 for C. saipanensis and MW405018.1 for O. duplisecta). The phylogenetic tree of the ITS area was analyzed inside the 18S rRNA and 16S rRNA and the sequences showed a strong resemblance to those species registered in the Genebank.