| Summary: | Microalgae are attracting considerable interest worldwide. In the present study, two native microalgae strains isolated from Tunisian cost were identified as <i>Chlamydomonas</i> sp. and <i>Navicula</i> sp. We characterized their pigment and protein contents, as well as their carbohydrate and lipid productivity. The predominant fatty acids were found to be α-linolenic acid (C18:3n-3) and palmitoleic acid (C16:1n-7) for <i>Chlamydomonas</i> sp. and <i>Navicula</i> sp. strains respectively. Microalgae methanol extracts showed important in vitro antibacterial activity against all tested gram negative bacteria. Antioxidant activities of methanol extracts were investigated by determining radical scavenging activity according to DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) methods. MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) assay showed that the newly isolated microalgae were not toxic and have potential application in the fish feeds domain as a supplement in fish meal. Also, the biosorption of cadmium from aqueous solutions by microalgae living cells was evaluated. Large removal capacities were obtained with values ranging from 89.8% to 99.38%. These results are very promising as a starting point for a potential application of these new isolates for in situ bioremediation of heavy metals contaminating aqueous systems.
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