Lipid production of microalgae isolated from the Ionian Sea of Greece

Abstract: Microalgae are photosynthetic organisms, considered to be a biological material of high importance for basic research and many biotechnological applications. The aim of this study was the isolation of microalgal strains from the Ionian Sea of Greece, their molecular identification and biochemical characterization with emphasis on their ability to accumulate lipid reserves. The lipids which are rich in polyunsaturated fatty acids (PUFAs) are used as additives in human and animal nutrition, in the pharmaceutical and chemical industries, while more saturated lipids towards biodiesel production. 13 strains of microalgae were isolated, belonging to the genera Picochlorum, Nannochloropsis, Tetraselmis, Chlorella and Nephroselmis as revealed by the molecular identification by PCR amplification of the 18S rRNA gene and the ITS (internal transcribed spacer) region. All strains grew satisfactorily when they were cultured in 500cc Erlenmeyer flasks containing 100 mL of artificial seawater, under continuous illumination of 387 μmol m^-2 s^-1 with initial population of 1.5 x 10⁶ cells/mL. Especially, Tetraselmis sp. reached approximately 1,600 mg L^-1 of dry biomass after 450 h. In terms of lipid accumulation, P. costavermella was placed first, exceeding 19% w/w of dry biomass. The major PUFA synthesized by Nannochloropsis strains was eicosapentaenoic acid, while the strains belonging to the genera Picochlorum, Tetraselmis and Chlorella synthesized a-linolenic acid in significant quantities. On the contrary, Nephroselmis pyriformis produced fatty acids which were more suitable for biodiesel manufacture. Additionally, microalgal cell mass of all strains contained proteins and polysaccharides in considerable levels. The biochemical profiles of these new isolates revealed their suitability for use in aquaculture and various industrial applications, highlighting the probability of a more efficient and economical production of high-added value products in large scale applications by the use of newly-isolated microalgae.