Evaluation and Transcriptome Analysis of the Novel Oleaginous Microalga Lobosphaera bisecta (Trebouxiophyceae, Chlorophyta) for Arachidonic Acid Production

Arachidonic acid (AA) is an omega-6 long-chain polyunsaturated fatty acid and is important for human health. The coccoid green microalga Lobosphaera bisecta has been reported to be able to accumulate high AA content under certain conditions. Nutrient management and light intensity had significant effects on the biomass and accumulation of lipids and AA in L. bisecta SAG2043. Both a high nitrogen concentration (18 mM) and high light intensity (bilateral light-300 μmol m(−2) s(−1)) were beneficial to the growth of L. bisecta, and the replacement of culture medium further enhanced the biomass, which reached 8.9 g L(−1). Low nitrogen concentration (3.6 mM) and high light significantly promoted the accumulation of lipids and AA. The highest lipid and AA content reached 54.0% and 10.8% of dry weight, respectively. Lipid compositions analysis showed that 88.2% of AA was distributed within the neutral lipids. We then reconstructed the lipid metabolic pathways of L. bisecta for the first time, and demonstrated that the upregulation of a key desaturase and elongase in the Δ6 pathway was conducive to the accumulation of fatty acids toward AA synthesis. L. bisecta SAG2043 exhibits high biomass, lipid and AA production. It may be a potential candidate for AA production.