Public Dissemination Event

El Puerto de Santa María, 3rd October 2019

Effects of light wavelength on microalgae features: the case of Nannochloropsis

Abstract:

 

Carlos Infante1; Maria Patelou2; Lalia Mantecón1; Emmanouil Flemetakis2

1Fitoplanton Marino S.L., 11500, El Puerto de Santa María, Spain

2Agricultural University of Athens, Athens, Greece

 

ABSTRACT

Microalgae as a whole represent a huge source of many different bioactive molecules with potential applications in multiple fields. They are actually considered a sustainable source of lipids, sugars, antioxidant, enzymes, and/or nutraceuticals. However, it has to be considered that composition of microalgae, and hence the productivity of those bioactives, is strongly affected by culture conditions, in particular when dealing with outdoor cultures. Temperature, pH, nutrients and light represent major variables that can modify the biochemical features of microalgae species under culture.

 

In Nannochloropsis, existing scientific literature support such statement. For instance, it is known that this species can accumulate lipids under nitrogen starvation. By the other side, light intensity can alter lipid profile and content, as well as content of soluble metabolites. In this regard, the aim of the work presented here has been to analyze, using a multi -omics approach, the effects on Nannochloropsis when grown under different light qualities obtained through filtering with cellophane sheets of different colors: Red, Blue and Green (hereinafter referred to as R, B and G; as a Control, cultures with no filters were employed). In relation to metabolomics more than 100 compounds were found, including sugars, amino acids, organic acids, N and P containing compounds, and polyols. PCA analysis of all these metabolites clearly separated R and B/G from the Control. From all those metabolites, 54 were found to significantly change, with more than half showing the highest relative response under R, mainly including amino acids, N-compounds, polyols, and phosphates. As a whole, higher sugar and organic acid content was observed in the Control, with cellobiose, D(+)-trehalose, and 2-amino-2-deoxy-D-galactose showing a significant decline under light filtering. In relation to fatty acid composition, significant effects were found regarding levels of myristic acid (decline in G), palmitoleic acid (decline in B), oleic acid (increase in G, and decline in R), and the omega-3 EPA (increase in B). Moreover, a significant decrease in MUFAs and an increase in PUFAs was detected in B. These differences were translated in a clear differentiation of R, B, G and the Control in PLS-DA analysis. Finally, a transcriptomic approach was also employed for sample analysis. A total of 46 genes were significantly affected by light filtering, with samples being easily classified in the appropriate experimental group in PLS-DA analysis. As a whole, the highest relative expression levels were observed in R, and the lowest in G. Main pathways affected were glycolysis, TCA cycle, amino acid metabolism, and oxidative stress response. In summary, the whole results demonstrate the metabolic plasticity of Nannochloropsis under light filtering, an approach that could be optimized and used to get better productivities of selective bioactive compounds for commercial purposes.

 

Acknowledgements

This research has been funded by MSCA-RISE project 691102 (Algae4A&B). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the abstract.