Kari Skjånes
Research Scientist
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Ralf Rautenberger Alexandre Detain Kari Skjånes Peter Simon Claus Schulze Viswanath Kiron Daniela Morales SanchezAbstract
Chlorella vulgaris is a freshwater microalga that synthesises large amounts of saturated lipids, which makes it suitable for production of bioenergy and biofuels. Since its cultivation usually requires freshwater, it competes with agriculture, economic development and ecological conservation for this limited natural resource. This study investigated the possibility of the partial replacement of freshwater by seawater (50 %) in the growth medium for a more sustainable biomass and lipid production. Chlorella vulgaris 211-11b was cultivated as shake-flask cultures in Bold's Basal Medium (BBM) formulated with 50 % freshwater and 50 % seawater under photoautotrophic, mixotrophic and heterotrophic conditions for eight days with glucose as organic carbon source in the latter two cases. The alga's best growth performance and highest lipid contents (49 % DW−1), dominated by palmitioleic and oleic acid, occurred under mixotrophic rather than photoautotrophic and heterotrophic conditions. This study demonstrates a more economic and ecologically sustainable biomass and lipid production of C. vulgaris by saving 50 % freshwater, which is available for other purposes.
Authors
Giorgia Carnovale Carmen Lama Sonia Torres Filipa Rosa Lalia Mantecon Svein Jarle Horn Kari Skjånes Carlos InfanteAbstract
Tetraselmis chui is known to accumulate starch when subjected to stress. This phenomenon is widely studied for the purpose of industrial production and process development. Yet, knowledge about the metabolic pathways involved is still immature. Hence, in this study, transcription of 27 starch-related genes was monitored under nitrogen deprivation and resupply in 25 L tubular photobioreactors. T. chui proved to be an efficient starch producer under nitrogen deprivation, accumulating starch up to 56% of relative biomass content. The prolonged absence of nitrogen led to an overall down-regulation of the tested genes, in most instances maintained even after nitrogen replenishment when starch was actively degraded. These gene expression patterns suggest post-transcriptional regulatory mechanisms play a key role in T. chui under nutrient stress. Finally, the high productivity combined with an efficient recovery after nitrogen restitution makes this species a suitable candidate for industrial production of high-starch biomass.
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