Taxonomic identification and lipid production of two Chilean Chlorella-like strains isolated from a marine and an estuarine coastal environment

This paper emphasizes the value of knowing the correct identity of microalgal strains that may have biotechnological potential. Here, two Chilean small green coccoid referred as Chlorella-like strains were identified using a polyphasic approach. Only one of them corresponded to the genus Chlorella (C. vulgaris); the other belonged to the recently amended genus Chloroidium (C. saccharophilum). Lipids characterization of the biomass obtained from these strains showed that Chlorella vulgaris (Baker strain) appeared to be suitable as raw material for biodiesel production, while Chloroidium saccharophilum (Coliumo strain) would be more appropriate for animal nutrition. Abstract The genus Chlorella was the first microalga to be massively cultured as food, feed and as a source of nutraceuticals. More recently, some species have been suggested as candidates for biodiesel production. One of the most difficult tasks in studying the systematics of green coccoids is the identification of species assigned to the genus Chlorella. In the context of several projects carried out by our research group we isolated two Chlorella-like strains from a marine and an estuarine coastal environment in Chile (Coliumo strain and Baker strain, respectively). The main objectives of this research were to identify these Chilean strains—at the species level—and determine and compare their lipid production when cultured under identical conditions. Cell size and shape, autospore number and sizes, and chloroplast and pyrenoid ultrastructure were considered as taxonomic descriptors, and 18S rDNA sequences and internal transcribed spacer ITS-1 + ITS-2 sequences and secondary structure were adopted as phylogenetic tools. The combined use of these morphological, ultrastructural and molecular attributes revealed that only the Baker strain belongs to the genus Chlorella (C. vulgaris), while the Coliumo strain corresponds to the recently amended genus Chloroidium (C. saccharophilum). Lipid characterization of the biomass obtained from these strains showed that Chlorella vulgaris (Baker strain) appears to be suitable as a raw material for biodiesel production, while Chloroidium saccharophilum (Coliumo strain) would be more appropriate for animal nutrition.