Effects of Different Light Intensities on Growth and Fucoxanthin Concentration of Fistulifera solaris

Abstract

Biofuel production using algae is believed to have tremendous positive impacts on the environment, and it seems a promising solution for global warming. However, growing algae on a large scale requires many resources making mass production of biofuels not yet economically viable. In this study, an oleaginous diatom, Fistulifera solaris, was cultured in autotrophic conditions under four light intensities for 14 days to determine which conditions allowed for higher cellular growth and higher fucoxanthin concentration, a valuable photosynthetic pigment that can make the process of biofuel production affordable. As a measure of abundance, absorbance values of diatoms in 750 nm wavelength (OD 750) were obtained on days 0, 7, and 14. On day 14, fucoxanthin concentration was measured. Statistical analyses revealed a significant change in the growth of diatoms under the four treatments that may be explained by varying rates of reproduction of the diatoms grown under different light intensities. Specifically, the highest OD 750 and growth were observed in medium-high light intensity, while the highest fucoxanthin concentration was observed in low light intensity. It is suggested that diatoms grown in lower light intensities may be ideal for increased fucoxanthin concentration because the geranyl-geranyl diphosphate synthase (GGPPS) gene, which is responsible for encoding a fucoxanthin precursor, is downregulated in exposure to high light intensities. Considering this data, low light intensity leads to the highest fucoxanthin concentration, and medium-high light intensity leads to the highest OD 750 and maximum growth under autotrophic conditions.