Isolation and characterization of microalgal strains for biomass production and wastewater reclamation in Northern Sweden

Microalgal strains adapted to the harsh Nordic climate were isolated from Swedish fresh- and wastewater sourcesand tested for their ability to grow in municipal wastewater. The 62 strains able to grow in municipal wastewaterbelonged to 12 different genera, of those Desmodesmus, Scenedesmus and Chlorella were most representative.Eight axenic strains were further characterized, all of which could efficiently remove nitrogen (> 90%) andphosphate (> 99%) from the wastewater in less than two weeks. The microalga Coelastrella sp. had the highestperformance in terms of both biomass concentration and total lipid content (1.46 g/L, 30.8%) after 13 days ofcultivation. This is the first report of a Coelastrella strain isolated in Sweden. Even Chlorella vulgaris performedvery well with a biomass concentration and total lipid content of 1.15 g/L and 34.2%, respectively. Finally, twoDesmodesmus sp. strains showed desirable traits for biofuel-feedstock, due to their fast growth rates (1.18 and1.08 d−1) together with high oil content (29.8% and 36.7% of DW).