Using microalgal communities for high CO2-tolerant strain selection

Abstract

Certain species of microalgae are capable of growing under high concentrations of carbon dioxide (CO2). These microalgae have potential to be used for sequestering CO2 released as industrial pollutants using a phototrophic carbon fixation system. While some CO2-tolerant algal species have been identified from existing algal culture collections, this study explored a community-based approach to enrich and isolate CO2-tolerant microalgae. Meanwhile, we monitored the change of bacterial and microalgal communities during the CO2 enrichment period based on the 16S and 18S rRNA gene sequences. Four different treatments were set up in the laboratory to test the effect of nutrient and CO2 on the natural planktonic community. At the end of the enrichment experiment (17 days), green algae (Chlorophyta), especially Scenedesmus species, dominated the microalgal community when the water samples were enriched with high CO2 (10%) and nutrient. The dominance of species in the CO2-enriched samples was also evident in the clonal isolation of microalgae at the end of the experiment. This study clearly demonstrates that the supplementation of high levels of CO2 to a natural phytoplankton community is an efficient way to enrich and isolate CO2-tolerant microalgae. The community-based approach described here poses several advantages over the traditional culture-based screening method for isolating microalgae with specific characteristics.