Screening and phylogenetic analysis of lipid-rich microalgae

Microalgae are considered to be a potential alternative source for the production of biofuels, and isolation of microalgae capable of high lipid concentration and high biomass production is the foundation for microalgal biofuel development. To date, over 1200 microalgal clones have been isolated in our laboratory. Among them, 37 strains were identified and further compared based on total lipid content, growth rate and biomass production. From the ITS1-5.8S-ITS2 sequences and morphological characteristics, these strains were identified as belonging to the genera Scenedesmus, Chlorella, Stichococcus, Nannochloropsis, Tetraselmis, Isochrysis, Phaeodactylum and Cylindrotheca. The lipid content of these strains varied from 6% dry weight (dw) to 42% dw. All three Isochrysis galbana strains could accumulate lipid at more than 35% dw, and their average was the highest among the tested genera (P < 0.05), followed by genera Nannochloropsis and Chlorella. Based on the phylogenetic data, a taxonomic pattern of lipid accumulation was found in microalgae, which suggested that a genera strategy should be considered in screening for lipid-rich microalgal strains. A comprehensive consideration of growth rate, biomass production and lipid content indicated that marine species Nannochloropsis maritima strain IOAC710S, and I. galbana strains IOAC683S and IOAC724S could be promising candidates for biodiesel feedstock.