Effects of light and nitrogen availability on photosynthetic efficiency and fatty acid content of three original benthic diatom strains

Abstract

Microalgal biotechnology has gained considerable importance in recent decades. Applications range from simple biomass production for food and animal feed to valuable products for fuel, pharmaceuticals, health, biomolecules and materials relevant to nanotechnology. There are few reports of the exploration of wider microalgae biodiversity in the literature on high value microalgal compounds, however, because it is believed that there is little to be gained in terms of biomass productivity by examining new strains. Still, without diversity, innovation in biotechnology applications is currently limited. Using microalgal diversity is a very promising way to match species and processes for a specific biotechnological application. In this context, three benthic marine diatom strains (Entomoneis paludosa NCC18.2, Nitzschia alexandrina NCC33, and Staurosira sp NCC182) were selected for their lipid production and growth capacities. Using PAM fluorometry and FTIR spectroscopy, this study investigated the impact of nitrogen repletion and depletion as well as light intensity (30, 100, and 400 μmol.photons.m-2.s-1) on their growth, photosynthetic performance and macromolecular content, with the aim of improving the quality of their lipid composition. Results suggest that under high light and nitrogen limitation, the photosynthetic machinery is negatively impacted, leading cells to reduce their growth and accumulate lipids and/or carbohydrates. However, increasing lipid content under stressful conditions does not increase the production of lipids of interest: PUFA, ARA and EPA production decreases. Culture conditions to optimize production of such fatty acids in these three original strains led to a balance between economic and ecophysiological constraints: low light and no nitrogen limitation led to better photosynthetic capacities associated with energy savings, and hence a more profitable approach.

Influence of Nitrogen and Phosphorus on Microalgal Growth, Biomass, Lipid, and Fatty Acid Production: An Overview

“…Cointet et al [ 38 ] reported that FAME from Entomoneis paludosa, Nitzschia alexandrina and Staurosira sp. directly undergo transesterification using hydrochloric methanol and chloroform as solvent.…”

“…The studies reported that the most abundant saturated fatty acid (SFA) was palmitic acid (C16:0), ranging from 32.5 ± 4.3% to 64.6 ± 6.0% for all strains in nitrogen-limited treatment. Whereas, the highest unsaturated fatty acid was oleic acid for E. paludosa (20.1 ± 3.2%) and palmitoleic acid for N. alexandrina and Staurosira sp., with 25.2 ± 1.9% and 25.0 ± 9.0%, respectively [ 38 ].…”

“…Based on Table 2 , it is clear that nitrogen plays an important role in influencing the fatty acids profile and the trends for fatty acids production for nitrogen starvation, and nitrogen availability conditions are quite similar with the highest yield of C14:0, C16:0 and C18:0 [ 3 , 5 , 8 , 35 , 36 , 37 , 38 , 39 , 40 ]. This statement was supported by Savvidou et al [ 41 ], who reported that nitrogen limitation conditions will generate higher saturated fatty acids such as C14:0, C16:0 and C18:0.…”

Study of microalgal behaviour in continuous culture using photosynthetic rate curves: The case of chlorophyll and carotenoid production by Chlorella vulgaris

“…Culture system is another relevant aspect to take into consideration in biomolecule production and nutrient limitation studies. Although due attention is put into it in engineering, it is surprisingly overlooked in basic science research, with the great majority of it being conducted in batch cultures (Cointet et al, 2019; Ethier et al, 2011; Matos et al, 2014; Negi et al, 2016; Zhao et al, 2017). Nevertheless, the importance of continuous cultivation on nutrient limitation studies can hardly be overstated.…”

“…Although due attention is put into it in engineering, it is surprisingly overlooked in basic science research, with the great majority of it being conducted in batch cultures (Cointet et al, 2019;Ethier et al, 2011;Matos et al, 2014;Negi et al, 2016;Zhao et al, 2017).…”