The Use of Light Spectra to Improve the Growth and Lipid Content of Chlorella vulgaris for Biofuels Production

The effects of light spectra on cell concentration, cell size, biomass production, proximate composition, pigment content, and fatty acid content in Chlorella vulgaris during two growth phases were measured. Growth rates were higher with white (0.70 division day⁻¹) and blue light (0.67 divisions day⁻¹). Cell size was greater in the exponential growth with yellow light (16.29 μm) versus blue light (14.26 μm). Higher organic dry weight (ODW) values were observed during exponential growth under green light (70.58 pg cell⁻¹) compared with white light (36.56 pg cell⁻¹). Proximate composition differed significantly by effect of light spectra and growth phases. Protein content was significantly higher in the exponential growth with white light (34.42%) and green (31.64%) light. Carbohydrate levels were significantly higher during stationary growth under yellow light (27.05%). In the exponential growth, lipid content was significantly higher with blue light (18.74%). Biomass productivity was highest in exponential growth phase with blue light (0.064 gL⁻¹ day⁻¹), meanwhile, in stationary growth phase yellow light (0.031 gL⁻¹ day⁻¹). Chlorophyll a and carotenoid levels were significantly greater during exponential growth with green and yellow lights. Fatty acid content was significantly modified by the light spectra and growth phase. The predominant saturated fatty acid was C:16:0 (palmitic acid), ranging between 10.26 (green light and exponential growth) and 20.01% (white light and stationary growth). The content of C18:1n-9 was higher (28.34 %) with the white light in the stationary growth, and C18:3n-3 content was greater with white (41.41%) and blue light (40.82%) in the exponential growth. It was concluded that blue light is the most suitable condition to induce biomass productivity and lipid content on both growth phases. Blue light during the stationary growth phase induces the production of lipids and saturated fatty acids (SFAs) which are suitable for biodiesel production.