Abstract
Marine microalgae and cyanobacteria are sources of diverse bioactive compounds with potential biotechnological applications in food, feed, nutraceutical, pharmaceutical, cosmetic and biofuel industries. In this study, five microalgae, Nitzschia sp. S5, Nanofrustulum shiloi D1, Picochlorum sp. D3, Tetraselmis sp. Z3 and Tetraselmis sp. C6, and the cyanobacterium Euhalothece sp. C1 were isolated from the Adriatic Sea and characterized regarding their growth kinetics, biomass composition and specific products content (fatty acids, pigments, antioxidants, neutral and polar lipids). The strain Picochlorum sp. D3, showing the highest specific growth rate (0.009 h−1), had biomass productivity of 33.98 ± 0.02 mg L−1 day−1. Proteins were the most abundant macromolecule in the biomass (32.83–57.94%, g g−1). Nanofrustulum shiloi D1 contained significant amounts of neutral lipids (68.36%), while the biomass of Picochlorum sp. D3, Tetraselmis sp. Z3, Tetraselmis sp. C6 and Euhalothece sp. C1 was rich in glycolipids and phospholipids (75%). The lipids of all studied microalgae predominantly contained unsaturated fatty acids. Carotenoids were the most abundant pigments with the highest content of lutein and neoxanthin in representatives of Chlorophyta and fucoxanthin in strains belonging to the Bacillariophyta. All microalgal extracts showed antioxidant activity and antimicrobial activity against Gram-negative E. coli and S. typhimurium and Gram-positive S. aureus.
Highlights
Microalgae are major primary producers of organic matter in the marine environment, responsible for producing one half of global oxygen on the Earth [1,2]
The growth rate is a critical parameter for selecting the production strain since a high growth rate enables high productivity, reduces contamination risk, and decreases the cultivation time
The growth rates were calculated from the slope of semi-logarithmic plots of cell number versus time
Summary
Microalgae are major primary producers of organic matter in the marine environment, responsible for producing one half of global oxygen on the Earth [1,2]. Microalgae belonging to the division Bacillariophyceae, are an important source of eicosapentaenoic acid with 15% to 30% in total lipids [18,23]. The antimicrobial potential is affected by all these major bioactive constituents of microalgal biomass including proteins, polysaccharides, polyunsaturated fatty acids (PUFAs), especially eicosapentaenoic acid (C20:5) and docosahexaenoic acid (C22:6), amino acids, and antioxidants (polyphenols, flavonoids, carotenoids). High growth rates (0.21–0.37 d−1) with a significant content of lipids (up to 37%) rich in polyunsaturated fatty acids make these diatoms an interesting food and feed production platform [46,47,48,49,50]. Antioxidant potential and the antimicrobial activity against chosen bacterial, yeast and fungal strain were determined
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