Survival, proximate composition, and proteolytic activity of Artemia salina bioencapsulated with different algal monocultures

This study focused on testing Artemia sp. zooplankton saturation with freshwater microalgae biomass and then using this method to correct the nutritional composition of Artemia. Accordingly, the influence of three species of microalgal monocultures was analyzed (2 freshwater – Desmodesmus armatus (Chod.) Hegew. and Chlorella vulgaris Veijerinck; one halophilous – Dunaliella viridis Teodor.). The algal monocultures were applied once in a quantity of 2-3 × 106 cells × l−1 for each 200,000 Artemia individuals hatched. The control group Artemia did not receive algae. The enrichment process lasted 24 h, and control measurements were performed every 6 h. The survival of Artemia nauplii, their proteolytic activity, and the content of proteins, lipids, and carotenoids were analyzed. The choice of algae species for Artemia enrichment was guided by the size of the algal cells and their biochemical composition. Selected algae contained about 50% protein, 20% lipid, and 12 mg of carotenoids per g of dry weight. Using algae to saturate the Artemia nauplii permitted reducing their mortality during the 24 h enrichment regime. The introduction of C. vulgaris biomass halved this value. The use of algae also increased the proteolytic activity in Artemia nauplii and the content of proteins, lipids, and carotenoids in their biomass. The best results of the bioencapsulation of Artemia nauplii with algae was with the C. vulgaris biomass.

Characteristics of the response of the microalga (Dunaliella viridis) to cerium compounds in culture

Recently, nanobiotechnology has been developing intensively; therefore, various properties of nanoparticles, which depend on their origin, concentration, and size, are of interest. It is known that CeO2 nanoparticles cause a positive biological effect. These particles are able to penetrate through biomembranes. At the same time, there are assumptions about a high degree of biological risks when using nanomaterials, and it is obvious that the biosafety of nanomaterials is decisive in the development of new products, including for medicine. The cytotoxicity of samples of cerium salts and cerium dioxide nanoparticles of different sizes was assessed at different concentrations using D. viridis. The cytotoxicity level by morphological and functional disorders of D. viridis was investigated, as determined by the change in cell shape, accumulation of inclusions, loss of flagellum, change in nature and movement, the formation of micro- and macroaggregates by D. viridis cells and exometabolite release. The cytotoxicity coefficient was calculated as a quotient of total detected changes divided by their number. It was shown that cerium salts (cerium (IV) ammonium nitrate and cerium (III) chloride) had pronounced cytotoxicity, which exceeded cytotoxicity values of the control by 7 and 6 times, respectively. Cerium dioxide nanoparticles with a size of 6 nm at a concentration of 0.01 M showed intermediate cytotoxicity, which exceeded control values by 3.5 times, and after the effect of nanoparticles with a size of 2 nm at a concentration of 0.1 M, the cytotoxicity coefficient corresponded to control values. The addition of inactivated blood serum to the incubation mixture resulted in a decreased cytotoxic effect of cerium dioxide. The use of D. viridis as a test system will supplement the arsenal of biotesting tools for nanomaterials and the study of the mechanisms of their effect.