An antimicrobial agent is produced by the cyanobacterium Synechococcus leopoliensis which was found to be active against the Gram-positive bacterium Staphylococcus aureus. The effects of temperature, pH, incubation period, some media and different nitrogen and carbon sources on both growth and antimicrobial activity were investigated. Temperature 35 degrees C and pH 8 were the best for growth and antimicrobial agent production and 14 and 15 days of incubation were found to be the best for maximum growth and antimicrobial activity, respectively, in the medium BG-11. No antimicrobial activity could be detected by the use of G medium, moderate activity was recorded with Chu 10 medium, while high activity was reported in BG-11 medium. Leucine was the best nitrogen source for antimicrobial activity, while maximum antimicrobial activity was introduced by using the carbon sources, citrate and acetate. Very high antimicrobial activity could be detected by using the carbon source galactose in combination with the nitrogen source alanine or by using arabinose with methionine.

The roles of pendimethalin and its nano-form to induce oxidative stress, osmolytes, biochemical alterations and cytotoxic effect in algal cells of Chlorella vulgaris after exposure to sub-lethal concentrations were carried out. The data indicated that, 96-h EC 50 values were 20 and 19 ppb for pendimethalin and its nano-form, respectively. Three concentration levels (0.1EC 50 , 0.025EC 50 and EC 50 ) of the examined herbicide decreased the algal pigments (Chlorophyll a and b), but increased carotenoid contents compared with the control group. Biomolecules such as protein, carbohydrates, proline and sucrose of the algal cells significantly increased for the all treatments compared with the control groups. Similarly, malondialdehyde (MDA), some enzymes such as catalase (CAT), superoxide dismutase (SOD) and ascorbate peroxidase (APX) showed significant increases for the all treatments. On the other hand, ultrastructural investigation of the herbicide-treated algal cells showed significant changes in their organelles in comparing with the untreated cells through transmission electron microscope (TEM) images. From all findings, it was obtained that the nano-pendimethalin was more potential toxic than the traditional form to induce adverse effects on the freshwater alga. Thus, biosafety procedures must be followed on non-target species before decision for nano-herbicide practices.

A series of experiments were conducted to determine fatty acids, amino acids, protein contents and enzymes activities of the three algae (Ulva lactuca, Sargassum hornschuchii and Pterocladia capillacea), which were previously collected in the late of July 2009 from Abu Qir and subjected to UV-B radiation for 20, 40 & 60 minutes daily for five days. These parameters were estimated, when the UV-absorbing compounds contents recorded its maximum after the third day of irradiation of 60 minutes daily for the three algal species. This time was chosen as we expected a suitable response of the algal species to UV-B irradiation. Total saturated, mono unsaturated and polyunsaturated fatty acids of U. lactuca and S. hornschuchii were increased due to UV-B irradiation, the total fatty acids content in both irradiated algae increased also, while the contents of total saturated, mono and polyunsaturated fatty acids of Pterocladia capillacea decreased after exposure to UV-B radiation. The study shows that half of amino acids of Ulva lactuca increased after exposure to UV-B radiation for three days, while the other half of amino acids was decreased. S. hornschuchii showed the decreasing of all amino acids contents after exposure to UV-B radiation except the two basic amino acids histidine and lysine, and the aliphatic amino acid serine. All amino acids of P. capillacea increased after exposure to UV-B radiation for three days except the aliphatic amino acid serine and the aromatic amino acid tyrosine. The total protein content increased in U. lactuca and S. hornschuchii through out the irradiation experiment, while P. capillacea showed notable decreases of protein contents after UV-B irradiation. Exposure to UV-B radiation increased the activity of superoxide dismutase, ascorbate peroxidase and catalase of the three irradiated algal species. The findings also suggest that exposure to UV-B irradiance also affect the ultrastructure of all the irradiated algal species.

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Adsorption of hexavalent chromium using dried macro-alga Sargassum hornschuchii was studied under controlled laboratory conditions. Experimental parameters such as contact time, biomass dosage and pH were studied in a metal concentration of 25 mg L -1 . The adsorption of chromium was fast at the initial phase of study and gradually with time became slowly. The maximum removal percentage of chromium was statistically significant and it was found to be 99.36% at 36 hrs and pH 3 using 8 g L -1 algal dosage. Five consecutive adsorption / desorption cycles were operated on metal solution using 0.1 M NaOH and 0.1 M HCl. It was found that chromium adsorption decreased following each adsorption / desorption cycle. Results indicated the superiority of HCl for the recovery of chromium from algal biomass. The present investigation shows that the locally biosorbent Sargassum hornschuchii possesses high adsorption performance with regard to the removal of chromium from its aqueous solution.