Effect of Different Light Sources on Algal Biomass and Lipid Production in Internal Leds-Illuminated Photobioreactor

Abstract

Illumination and nutrients are key factors to the biomass and biodiesel production from microalgae. In this study, the effects of various light wavelengths, light intensities and cultivation medium on the growth and lipid content of Chlorella vulgaris were investigated by using LEDs (Light Emitting Diodes) with different wavelengths in an Internal LEDs-Illuminated Photobioreactor. C. vulgaris was grown for 10 days under 18:6 h Light/Dark cycles with different light colors (cool white, blue and red) and intensities (50, 70, 90 and 110 μmol m-2 s-1). The effects of the illuminations were investigated for different light intensity at 25°C culture temperature. The maximum dry biomass of 1353.33 mg/L was observed at cool white light of 110 μmol m-2 s-1 during the 7 th culture day, with the highest overall dry biomass production (117.23 mg/ Ld-1) within cultivation time. The highest lipid content (34.06 %) was obtained with the blue color due to light efficiency and deep penetration. Moreover, the highest lipid productivity (31.86 mg/L d-1) was observed in 50 μmol m-2 s-1 with cool white lights. The lipid productivity was further optimized by increasing the light intensity of cool white light. The highest lipid productivity was observed at 110 μmol m-2 s-1 light intensity of 658.99 mg/L during the 10 th culture day. To conclude, the result of our study shows that C. vulgaris cultivated with wastewater in photobioreactors is efficient in producing algal biomass and removing nitrogen and phosphorus nutrient in wastewater sewage.

Effect of Light Intensity and Quality on Growth Rate and Composition of Chlorella vulgaris

“…In this study, biomass was collected at the same cultivation time in order to compare lipid content and productivity since the lipid content varies with cultivation time. It thus appears from this study, as well as from other relevant studies in literature that the lipid and protein content of C. vulgaris and the biomass productivity are affected both by the wavelength of light as well as by the algal biomass collection time, whether this is done before, during or past the stationary growth phase [25,47]. Also, reactor and illumination configuration may affect biomass, protein, and lipid productivities [56].…”

“…According to Wong et al [47], C. vulgaris had the highest lipid content when cultivated with blue light (LED lamp), although white light gave similar results. Lipid content increased as a function of cultivation time reaching its maximum value after 10 days at the end of the cultivation period.…”

“…In C. vulgaris, cultivation in blue monochromatic light at 475 nm resulted in higher growth rate and biomass production in comparison to cultivation at clear, red, and green light [46]. In another study, C. vulgaris grew best when cultivated under cool white light in comparison with cultivation at blue and red light [47]. It appears that the two studies differ in both the types of illumination (lamps) used as well as the configuration of illumination.…”

“…Blair et al [46] used CFL lamps which were placed outside the bioreactors at a distance of 20 cm providing light at 650 nm (red), 475 nm (blue), and clear white light but no mention of its spectral output intensity is given. On the other hand, Wong et al [47] used LED lamps of 5300 K (white light), 457 nm (blue), and 660 nm (red) placed in the interior of the bioreactor. Therefore, it appears that differences observed in the growth rates in these two studies may be due to differences in the type of lamps used, their spectral and intensity characteristics as well as the illumination configuration.…”

Cultivation of Chlorella vulgaris in Column Photobioreactor for Biomass Production and Lipid Accumulation

“…Microalgae Culture. Local freshwater microalgae, Chlorella vulgaris, isolated from Nam Sang Wai in Hong Kong were selected to use in this study based on the faster growth rate and higher biomass production found in the authors' previous studies (Wong et al, 2014;2015a). The thicker cell wall of Chlorella vulgaris is also favorable to prevent cell lysis resulting from agitated mixing in PBRs.…”