Abstract
Nannochloropsis is an industrially-promising microalga that may be cultivated for alternative sources of nutrition due to its high productivity, protein content and lipid composition. We studied the growth and biochemical profile of Nannochloropsis 211/78 (CCAP) in optimized flat-plate photobioreactors. Eighteen cultivations were performed at two nutrient concentrations. The fatty acid, protein content and calorific values were analyzed after 8, 12 and 16 days. Neutral lipids were separated and the changes in fatty acids in triglycerides (TAGs) during nutrient depletion were recorded. The maximum cell density reached 4.7 g∙L-1 and the maximum productivity was 0.51 g∙L-1∙d-1. During nutrient-replete conditions, eicosapentaneoic acid (EPA) and total protein concentrations measured 4.2–4.9% and 50–55% of the dry mass, respectively. Nutrient starvation induced the accumulation of fatty acids up to 28.3% of the cell dry weight, largely due to the incorporation of C16:0 and C16:1n-7 fatty acyl chains into neutral lipids. During nutrient starvation the total EPA content did not detectibly change, but up to 37% was transferred from polar membrane lipids to the neutral lipid fraction.
Highlights
Sustainable, healthy diets for humans and animals may benefit from incorporating larger proportions of plant-based materials [1,2]
In the low-nitrate and phosphate (NP) treatment, nitrate was eliminated from the broth by day 8, whilst in the high-NP treatment nitrate was exhausted by day 14 (Fig 2D)
Previous reports indicate that, based on percent fatty acid composition, a substantial reduction in the eicosapentaneoic acid (EPA) content can occur in Nannochloropsis during nutrient starvation [42]
Summary
Sustainable, healthy diets for humans and animals may benefit from incorporating larger proportions of plant-based materials [1,2]. Phototrophic microalgae are an especially promising source of alternative food and feed ingredients, because many species of microalgae are able to synthesize additional metabolites that are not available from natural terrestrial plant sources [3,4,5]. World aquaculture production especially is dependent on feed products from capture fisheries, and there is a need to find substitute materials that reduce the environmental costs [8,9]. Replacing feed ingredients with single-cell oils and proteins from microalgae could reduce the environmental impacts of aquaculture, improve the nutritional quality and reduce risks from pollutants that can accumulate in marine food chains [10,11,12].
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