Authors: Panagiotis Dritsas1, Elias Asimakis2, George Tsiamis2, George Aggelis1
1Greece, University of Patras/Department of Biology 2Greece, University of Patras/Department of Sustainable Agriculture
Microalgae are phytoplankton, found in all types of aquatic systems. Due to their ability to synthesize metabolites of high-added value in significant quantities, basic research and biotechnology sectors recognize them as biological material of high importance. The goal of this study was the isolation of microalgal strains from the Gulf of Patras (Greece), their molecular identification and biochemical characterization. Emphasis was given on their ability to accumulate lipid reserves, as lipids rich in polyunsaturated fatty acids (PUFAs) are used as additives in food, pharmaceutical and chemical industries, while more saturated lipids can be utilized towards biodiesel production. The molecular identification, by PCR amplification of the 18S rRNA gene and the ITS (internal transcribed spacer) region, revealed that the 6 isolated strains belong to the genera Picochlorum, Nannochloropsis and Nephroselmis. All strains were cultured in 500cc Erlenmeyer flasks containing 0.1 L of artificial seawater and grew satisfactorily. Especially, in terms of dry biomass production, Nannochloropsis sp. from Patras city port marked the highest levels (exceeding 900 mg/L) after 450 h, while P. costavermella was placed first in lipid accumulation (i.e., 19% w/w of dry biomass). Significant quantities of PUFAs were synthesized by the Picochlorum and Nannochloropsis strains (mainly a-linolenic and eicosapentaenoic acid respectively), while the fatty acids of Nephroselmis pyriformis were suitable for biodiesel manufacture. Moreover, all strains accumulated notable amounts of proteins and carbohydrates. Furthermore, the 2 isolated Picochlorum strains were cultured in a Stirred Tank Reactor. In this setup, biomass production was much higher (2-3 times), although slight differences were observed in terms of storage material accumulation between the two types of bioreactors. In conclusion, the biochemical profiles of the isolates showcased their potential suitability in various applications, like aquaculture, which is a sector of crucial importance for the economy of many countries located in the Mediterranean Sea.