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Seasonal variation of lipids and fatty acids of the microalgae Nannochloropsis oculata grown in outdoor large-scale photobioreactors
Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences. (MPEA)
Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences. (Catherine Legrand)
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2012 (English)In: Energies, ISSN 1996-1073, Vol. 5, no 5, 1577-1592 p.Article in journal (Refereed) Published
Abstract [en]

While focus in oil-producing microalgae is normally on nutrient deficiency, we

addressed the seasonal variations of lipid content and composition in large-scale

cultivation. Lipid content, fatty acid profiles and mono- di- and triglycerides (MAGs,

DAGs, and TAGs) were analyzed during May 2007–May 2009 in Nannochloropsis oculata

grown outdoors in closed vertical flat panels photobioreactors. Total lipids (TL) ranged

from 11% of dry weight (DW) in winter to 30% of DW in autumn. 50% of the variation in

TL could be explained by light and temperature. As the highest lipid content was recorded

during autumn indicating an optimal, non-linear, response to light and temperature we

hypothesize that enhanced thylakoid stacking under reduced light conditions resulted in

more structural lipids, concomitantly with the increase in glycerides due to released

photo-oxidative stress. The relative amount of monounsaturated fatty acids (MUFA)

increased during autumn. This suggested a synthesis, either of structural fatty acids as

MUFA, or a relative increase of C16:1 incorporated into TAGs and DAGs. Our results

emphasize the significant role of environmental conditions governing lipid content and 

composition in microalgae that have to be considered for correct estimation of algal oil

yields in biodiesel production.

Place, publisher, year, edition, pages
2012. Vol. 5, no 5, 1577-1592 p.
Keyword [en]
microalgae, Nannochloropsis oculata, large-scale, seasonal variation, light, temperature, biofuels, biodiesel, lipids, fatty acids
National Category
Biological Sciences
Research subject
Environmental Science, Environmental technology; Natural Science, Biotechnology; Natural Science, Aquatic Ecology; Technology (byts ev till Engineering), Bioenergy Technology
Identifiers
URN: urn:nbn:se:lnu:diva-25900DOI: 10.3390/en5051577ISI: 000304450700017OAI: oai:DiVA.org:lnu-25900DiVA: diva2:623856
Available from: 2013-05-29 Created: 2013-05-28 Last updated: 2015-09-28Bibliographically 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
Keyword
Microalgae, algal cultivation, bioresource, bioenergy, CO2 mitigation, multi-species community approach, seasonal variation
National Category
Biological Sciences Ecology Industrial Biotechnology
Research subject
Natural Science, Aquatic Ecology; Natural Science, 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
Available from: 2015-09-28 Created: 2015-09-28 Last updated: 2015-09-28Bibliographically approved

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Citation style
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