Microalgae from the Ionian Sea (Greece): Isolation, molecular identification and biochemical features of biotechnological interest

Microalgae are photosynthetic organisms of high importance for basic research and biotechnological applications. The aim of this study was the isolation of new microalgal strains from the Ionian Sea (Greece) and their taxonomic and biochemical characterization. Twelve microalgal isolates were identified using molecular techniques and were classified to the genera Picochlorum, Nannochloropsis, Tetraselmis, Chlorella and Nephroselmis. Subsequently, their ability to grow under laboratory conditions was evaluated. Tetraselmis sp. strain KAT3.M2 growing in modified artificial seawater (mASW) produced biomass in high concentrations (approaching 1600 mg L-1 of dry biomass), while P. costavermella strain VAS2.5 exhibited the highest lipid content (exceeding 19 % wt/wt of dry biomass). Most of the isolates synthesized polyunsaturated fatty acids (mainly eicosapentaenoic and a-linolenic acid) in significant quantities, while Nephroselmis pyriformis PAT2.7 produced more saturated fatty acids suitable for biodiesel manufacture. Microalgal cell mass of all strains contained considerable levels of proteins ranging from 16.5 % to 57.6 % (wt/wt). Furthermore, the strains belonging to the genera Tetraselmis, Chlorella, Nephroselmis as well as the Nannochloropsis gaditana AIT5.1 strain, synthesized polysaccharides at also considerable levels (ranging from 13.4 to 31.5 %, wt/wt). Additionally, two of the isolated Picochlorum strains, cultivated in mASW in a stirred-tank reactor, exhibited manifold production of biomass and reserve materials (i. e., polysaccharides, lipids) compared to the experiments in Erlenmeyer flasks. Lastly, the isolates were examined for their biofilm-forming capacity, a feature of interest as a cost-effective means of biomass harvesting in largescale applications and wastewater treatment. It was shown that the biofilm formation ability was strain-specific and, closely related to the medium's pH and the time of incubation. Tetraselmis sp. strain KAT.3M2 and N. gaditana strain VAT4.3 proved to be the strongest biofilm formers. The biochemical profiles of these new isolates showcased their suitability for use in aquaculture and various industrial applications.

Automated summary

This study aimed to isolate and characterize new microalgal strains from the Ionian Sea (Greece) for potential biotechnological and aquaculture applications. Molecular techniques identified 12 isolates belonging to Picochlorum, Nannochloropsis, Tetraselmis, Chlorella, and Nephroselmis genera. The isolated strains demonstrated favorable growth and biochemical characteristics, making them suitable candidates for aquaculture and various industrial applications.