Abstract
Lipid production in microalgae is highly dependent on the applied light intensity. However, for the EPA producing model-diatom Phaeodactylum tricornutum, clear consensus on the impact of incident light intensity on lipid productivity is still lacking. This study quantifies the impact of different incident light intensities on the biomass, TAG and EPA yield on light in nitrogen starved batch cultures of P. tricornutum. The maximum biomass concentration and maximum TAG and EPA contents were found to be independent of the applied light intensity. The lipid yield on light was reduced at elevated light intensities (>100 μmol m-2 s-1). The highest TAG yield on light (112 mg TAG molph-1) was found at the lowest light intensity tested (60 μmol m-2 s-1), which is still relatively low to values reported in literature for other algae. Furthermore, mass balance analysis showed that the EPA fraction in TAG may originate from photosynthetic membrane lipids.
Highlights
Lipid production by phototrophic microalgae is only economically feasible today for highvalue products, such as pigments and ω-3-fatty acids [1]
The impact of five different light intensities on biomass, TAG and eicosapentaenoic acid (EPA) productivity during nitrogen starvation was assessed in batch-wise operated flat-panel photo bioreactors that were subjected to 16:8h light:dark (LD) cycles
Elevated light intensities (>100 μmol m-2 s-1) reduce the photosynthetic efficiency and the TAG yield on light during nitrogen starvation, likely caused by photo inhibition
Summary
Lipid production by phototrophic microalgae is only economically feasible today for highvalue products, such as pigments and ω-3-fatty acids [1]. One of the major hurdles for commercial bulk microalgal lipid production is the low lipid yield on light [1,2,3]. Microalgal lipid production is induced by nitrogen deficiency. When exposed to nitrogen deficient conditions, some microalgal species can accumulate triacylglycerol (TAG) up to 30–60% of dry weight [4,5,6]. Nitrogen deficiency is often accompanied with impaired or even fully inactivated photosynthesis [4,7] and results in a reduced TAG yield on light. For commercial production of TAGs, the TAG yield on light should be increased
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