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

M A Gonzalez,P I Gomez,I Inostroza,Y Palacios,P Aguayo,T Proschold

doi:10.1093/aobpla/plt020

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.

Highlights

Green algae represent one of the main taxonomic groups from which oleaginous strains have been identified
The aims of this research were (i) to identify taxonomically, at the species level, the Coliumo and Baker strains by means of ultrastructure and molecular attributes and (ii) to determine and compare the growth parameters and lipid production of both strains, grown under identical culture conditions
The strains have been maintained at a photon flux density (PFD) of 15– 20 mmol m22 s21, a temperature of + 2 8C and a photoperiod of : 8 h

Summary

Introduction

Green algae represent one of the main taxonomic groups from which oleaginous strains have been identified. Two main applications of lipid-rich strains have been proposed: as raw material for biodiesel production (Hu et al 2008; Converti et al 2009; Rodolfi et al 2009; Lu et al 2010) and as essential fatty acid sources for animal and human nutrition (Spolaore et al 2006). Gonzalez et al — Taxonomic identification and lipid production of two Chilean Chlorella-like strains. The genus Chlorella encompasses spherical or ellipsoidal non-motile green cells that produce autospores, and inhabit freshwater, soil and marine habitats (Komarek and Fott 1983). It has been suggested that they are good candidates for fuel production (Li et al 2007; Converti et al 2009; Mata et al 2010)

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