Effects of light qualities on growth, lipid contents and fatty acids profiles of Cylindrotheca closterium

Abstract

Background Marine diatoms were considered as a promising alternative to microbial resources for the development of biofuels, food additives, medicines and chemical materials. Light of wavelength is a principal element that can easily be controlled in microalgal scale-culture and influence the growth, pigment composition, and lipids accumulation of algal cells. With the increasing implementation of light-emitting diodes (LEDs) in microalgal production systems (photobioreactors), a measure of light quality controlled by LED could be suitable to improve microalgal yields. Results In this study, Cylindrotheca Closterium, a widely used diatom, influenced by five light quality (white, red, blue, green and yellow light) was tested for its effects of growth rates, chlorophylls contents, total lipids contents and fatty acids compositions. The growth and chlorophyll experiments also showed that the green and yellow light significantly improve the growth rates and chlorophylls contents than other groups (P < 0.05). The group white light showed the greatest increases in total lipid contents of C. closterium (P < 0.05). The group blue light had the highest polyunsaturated fatty acids (PUFAs) proportion (P < 0.05), while the group white showed the lowest PUFAs and the highest saturated fatty acids (SFAs) and monounsaturated fatty acids (MUFAs) proportions (P < 0.05). The proportions of SFAs and MUFAs were negatively correlated with growth, chlorophylls, and lipids. And the proportion of PUFAs and n-3 PUFA was positively correlated with growth chlorophylls, and lipids. Principal component analysis showed that the fatty acid composition differed among light quality groups. Conclusion In summary, green light and yellow light were conductive to boosting the growth and chlorophylls accumulation of C. closterium. White light increased total lipid yields, while blue light was superior in increasing the production of unsaturated fatty acids, especially on the timnodonic acid (EPA). The application of two-step methods to increase the production of biomass and fatty acids is an effective measure for the cultivation of C. closterium; green light is used to increase the growth, followed by white light cultivation to improve total lipids or blue light to enhance the proportion of PUFAs of C. closterium.