Light Intensity And Photo Period Effect On Growth And Lipid Accumulation Of Microalgae Chlorella Vulgaris And Nannochloropsis SP For Biodiesel Production
The application of microalgal oil for energy purposes continues to present a number of challenges, including the optimization of culture conditions. In this study, the two light intensities at 2.5 Klux and 5 Klux were used in light-dark cycles of 8:16, 16:8, 0:24 and 24:0 hour to investigate the effect of light intensity and photo period on biomass production and lipid productivities in microalgae, Chlorella vulgaris and Nannochloropsis sp. in view of optimizing the illumination level for biodiesel production through algal oil. Chlorella vulgaris and Nannochloropsis sp were cultured in Guillard and Rither`s f/2 media for 21 days and 14 days growth periods respectively in a laboratory scale closed experimental set-up. The cultures were aerated with mechanical aerators. Finally, cells were harvested by flocculation and dry weight and the percentage lipid content were estimated. Significantly higher average dry matter yield was observed when the cells cultured under 5 Klux light intensity than the 2.5 Klux during all the tested photo periods in both species. In the present study, it was found that the significantly highest dry biomass of 0.63 g/L was recorded with light-dark cycle of 16:8 hour while highest percentage lipid content of 13.9 % was obtained light-dark cycle of 8:16 for C. vulgaris at 5 Klux light intensity. In Nannochloropsis sp, light-dark cycle of 16:8 hour recorded the significantly highest dry biomass of 0.62 g/L while 16:8 and 12:12 hour light-dark cycle reported the significantly highest percentage lipid content of 12.36 % and 12.96 % respectively. However, significantly higher final lipid yield of 0.07 g/L and 0.08 g/L was observed in 16:8 hour light-dark cycle for both C. vulgaris and Nannochloropsis sp respectively with 5 Klux light intensity. Therefore, it can be concluded that, the amount of light intensity affect significantly to the lipid yield of micro algae and the optimized photo period for culturing Chlorella vulgaris and Nannochloropsis sp. for lipid production, is to cultivate them with a light-dark cycle of 16:8 hour.
Index Terms- Microalgae, lipid yield, light intensity, photo period