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Combined Effects of Nitrogen Concentration and Seasonal Changes on the Production of Lipids in Nannochloropsis oculata 
Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science. (Ctr Ecol & Evolut Microbial Model Syst EEMiS)
Necton SA, Olhao, Portugal.
Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science. (Ctr Ecol & Evolut Microbial Model Syst EEMiS)
IFREMER, Nantes, France.
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2014 (English)In: Marine Drugs, ISSN 1660-3397, E-ISSN 1660-3397, Vol. 12, no 4, p. 1891-1910Article in journal (Refereed) Published
Abstract [en]

Instead of sole nutrient starvation to boost algal lipid production, we addressed nutrient limitation at two different seasons (autumn and spring) during outdoor cultivation in flat panel photobioreactors. Lipid accumulation, biomass and lipid productivity and changes in fatty acid composition of Nannochloropsis oculata were investigated under nitrogen (N) limitation (nitrate:phosphate N:P 5, N:P 2.5 molar ratio). N. oculata was able to maintain a high biomass productivity under N-limitation compared to N-sufficiency (N:P 20) at both seasons, which in spring resulted in nearly double lipid productivity under N-limited conditions (0.21 g L−1 day−1) compared to N-sufficiency (0.11 g L−1 day−1). Saturated and monounsaturated fatty acids increased from 76% to nearly 90% of total fatty acids in N-limited cultures. Higher biomass and lipid productivity in spring could, partly, be explained by higher irradiance, partly by greater harvesting rate (~30%). Our results indicate the potential for the production of algal high value products (i.e., polyunsaturated fatty acids) during both N-sufficiency and N-limitation. To meet the sustainability challenges of algal biomass production, we propose a dual-system process: Closed photobioreactors producing biomass for high value products and inoculum for larger raceway ponds recycling waste/exhaust streams to produce bulk chemicals for fuel, feed and industrial material.

Place, publisher, year, edition, pages
Basel, Switzerland: MDPI AG , 2014. Vol. 12, no 4, p. 1891-1910
Keywords [en]
microalgae; outdoor; Nannochloropsis; large-scale; lipids; fatty acids; nitrogen manipulation; seasonal changes; biofuels; high value products
National Category
Microbiology Bioenergy Bioprocess Technology Biochemicals
Research subject
Ecology, Aquatic Ecology; Chemistry, Biotechnology
Identifiers
URN: urn:nbn:se:lnu:diva-33842DOI: 10.3390/md12041891ISI: 000335759500011Scopus ID: 2-s2.0-84900453929OAI: oai:DiVA.org:lnu-33842DiVA, id: diva2:711699
Projects
Algoland
Funder
Ecosystem dynamics in the Baltic Sea in a changing climate perspective - ECOCHANGEAvailable from: 2014-04-11 Created: 2014-04-11 Last updated: 2018-02-26Bibliographically approved
In thesis
1. Microalgae - future bioresource of the sea?
Open this publication in new window or tab >>Microalgae - future bioresource of the sea?
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Unicellular microalgae are a renewable bioresource that can meet the challenge forfood and energy in a growing world population. Using sunlight, CO2, nutrients,and water, algal cells produce biomass in the form of sugars, proteins and oils, allof which carry commercial value as food, feed and bioenergy. Flue gas CO2 andwastewater nutrients are inexpensive sources of carbon and fertilizers. Microalgaecan mitigate CO2 emissions and reduce nutrients from waste streams whileproducing valuable biomass.My focus was on some of the challenging aspects of cultivating microalgae ascrop: the response of biomass production and quality to seasonality, nutrients andbiological interactions. Approach spans from laboratory experiments to large-scaleoutdoor cultivation, using single microalgal strains and natural communities insouthern (Portugal) and northern (Sweden) Europe.Half of the seasonal variation in algal oil content was due to changes in light andtemperature in outdoor large-scale cultures of a commercial strain (Nannochloropsisoculata). Seasonal changes also influence algal oil composition with more neutrallipids stored in cells during high light and temperature. Nitrogen (N) stress usuallyenhances lipid storage but suppresses biomass production. Our manipulationshowed that N stress produced more lipids while retaining biomass. Thus,projecting annual biomass and oil yields requires accounting for both seasonalchanges and N stress to optimize lipid production in commercial applications.Baltic Sea microalgae proved to be a potential biological solution to reduce CO2emissions from cement flue gas with valuable biomass production. A multi-speciescultivation approach rather than single-species revealed that natural or constructedcommunities of microalgae can produce equivalent biomass quality. Diversecommunities of microalgae can offer resilience and stability due to more efficientresource utilization with less risk of contamination, less work and cost for culturemaintenance.Stable algal biomass production (annual basis) was achieved in outdoor pilot-scale(1600 L) cultivation of Baltic Sea natural communities using cement flue gas as aCO2 source. Results indicate favorable algal oil content at northern Europeanlatitudes compared to southern European latitudes.My thesis establishes the potential of cultivating microalgae as a bioresource inScandinavia, and using a community approach may be one step towardssustainable algal technology.

Place, publisher, year, edition, pages
Växjö: Linnaeus University Press, 2015
Series
Linnaeus University Dissertations ; 227/2015
Keywords
Microalgae, algal cultivation, bioresource, bioenergy, CO2 mitigation, multi-species community approach, seasonal variation
National Category
Biological Sciences Ecology Industrial Biotechnology
Research subject
Ecology, Aquatic Ecology; Chemistry, Biotechnology; Environmental Science, Environmental technology
Identifiers
urn:nbn:se:lnu:diva-46512 (URN)978-91-87925-75-7 (ISBN)
Public defence
2015-10-16, Hörsalen Fullriggaren, Landgången 4, Kalmar, 09:30 (English)
Opponent
Supervisors
Projects
AlgolandEcoChange
Available from: 2015-09-28 Created: 2015-09-28 Last updated: 2018-05-16Bibliographically approved

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Olofsson, MartinNilsson, EmmelieLegrand, Catherine

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