Abstract
Nannochloropsis salina was grown on a mixture of standard growth media and pre-gasified industrial process water representing effluent from a local biogas plant. The study aimed to investigate the effects of enriched growth media and cultivation time on nutritional composition of Nannochloropsis salina biomass, with a focus on eicosapentaenoic acid (EPA). Variations in fatty acid composition, lipids, protein, amino acids, tocopherols and pigments were studied and results compared to algae cultivated on F/2 media as reference. Mixed growth media and process water enhanced the nutritional quality of Nannochloropsis salina in laboratory scale when compared to algae cultivated in standard F/2 medium. Data from laboratory scale translated to the large scale using a 4000 L flat panel photo-bioreactor system. The algae growth rate in winter conditions in Denmark was slow, but results revealed that large-scale cultivation of Nannochloropsis salina at these conditions could improve the nutritional properties such as EPA, tocopherol, protein and carotenoids compared to laboratory-scale cultivated microalgae. EPA reached 44.2% ± 2.30% of total fatty acids, and α-tocopherol reached 431 ± 28 µg/g of biomass dry weight after 21 days of cultivation. Variations in chemical compositions of Nannochloropsis salina were studied during the course of cultivation. Nannochloropsis salina can be presented as a good candidate for winter time cultivation in Denmark. The resulting biomass is a rich source of EPA and also a good source of protein (amino acids), tocopherols and carotenoids for potential use in aquaculture feed industry.
Highlights
Microalgae are autotrophic microorganisms, which are able to produce biomass from solar energy, CO2 and nutrients, with higher photosynthetic activity compared to terrestrial plants [1,2]
Cultivation of N. salina in a mixture of industrial process water and F/2 standard growth media enhanced the eicosapentaenoic acid (EPA) content compared to F/2 growth media
The algae growth rate at winter condition of Denmark was slow, but results revealed that large-scale cultivation of Nannochloropsis salina in these conditions could improve the nutritional properties such as EPA, protein, α-tocopherol and carotenoids compared to culturing in lab scale
Summary
Microalgae are autotrophic microorganisms, which are able to produce biomass from solar energy, CO2 and nutrients, with higher photosynthetic activity compared to terrestrial plants [1,2]. Resulting biomass includes important metabolites such as carbohydrates, lipids, proteins and many other bioactive compounds like pigments and phenolics. Microalgal biomass may be used for different applications, such as biofuel production, wastewater treatment, production and extraction of bioactive compounds, or as a food/feed ingredient [3,4]. One of the most promising applications of microalgae biomass is as feed for aquatic animals. The importance of microalgae in aquaculture food chains is mainly due to their fatty acid, carotenoids and protein (amino acid) composition [5,6]. Use of microalgae as a rich source of fatty acids for the aquaculture has become the focus of industrial and scientific developments. Microalgae suitable for utilization in aquaculture should possess certain important characteristics such as appropriate
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