Abstract

In this study, the impacts of nitrogen loading rates on microalgal communities and intracellular storage compounds in a chemostat enrichment system were investigated. The chemostat was operated at a constant dilution rate of 0.5 d-1 with different nitrogen loading rates of 10, 20, 32.5, 42 and 63 mgN.l-1.d-1. The cultures with the lowest nitrogen loading rates showed nitrogen fixation capacity. Diverse microalgal communities were observed for nitrogen loading rates of 10 and 20 mgN.l-1.d-1. Chlorella sorokiniana and Chlorella vulgaris were dominant species at nitrogen loading rates of 42 and 32.5 mgN.l-1.d-1, respectively. Different species of Arthrospira platensis, Chlorella sp., Rhopalodia coexisted under the light-limited condition at NLR of 63 mgN.l-1.d-1. Lipids accumulation overtook starch accumulation at all nitrogen loading rates. mgN.l-1.d-1. Lipids accumulation overtook starch accumulation at all nitrogen loading rates. Specifically, the concentration of lipids in the enriched species cells, Chlorella sorokiniana was 4.2 times higher than the amount of accumulated starch. The results demonstrate that the approximately balanced addition of nutrients and light in chemostat enrichment culture could be an important trait to enrich a potential lipid production organism.