Enhancing the light utilization efficiency of microalgae using organic dyes

• Organic dye can modify the light spectrum differently depending on its property.
• Cell growth and lipid accumulation were increased by the organic dye converter.
• Rates of growth and lipid accumulation were found to differ for each dye.
• The different light spectrum was easily combined by the simple mixing process.

Solar radiation is composed of wide light spectrum including the range which cannot be utilized for microalgae. To enhance the light utilization efficiency, organic dye solutions of rhodamine101 and 9,10-diphenylanthracene were used as wavelength converters. Each dye affected cell growth and lipid accumulation differently, based on the response of each to different light spectrum. Under a light intensity of 50 W/m2, maximum cell growth (1.5 g/L) was obtained with the red organic dye rhodamine101, whereas best lipid content (30%) with the blue type 9,10-diphenylanthracene. These two separate and complementary traits could be combined by simple mixing, and in so doing optimal growth (1.5 g/L) as well as lipid accumulation (30%) was achieved: lipid productivity was 2.3 times greater than without the organic dye. This study proved that certain organic dye solutions could convert useless wavelengths to be useful for algae cultivation, thereby increasing the productivity of biomass and lipids.