No abstract

This study was carried out to evaluate the antibacterial activity of ethanol, methanol, acetone, and ethyl acetate extracts of the brown seaweeds, Cystoseira myrica, Padina boergesenii and Sargassum cinereum (Phaeophyta), as well as to identify the phytochemical constituents of the most effective algal extracts. Antibacterial activities were expressed as inhibition zones and minimum inhibitory concentrations (MICs) of the algal extracts. All seaweed extracts tested exhibited a broad spectrum of antibacterial activity. The maximum inhibition activities were recorded for methanolic extracts of P. boergesenii and ethyl acetate extracts of C. myrica and S. cinereum against Shigella flexneri, Staphylococcus aureus (MRSA) and Staphylococcus aureus, respectively. The MIC values of the marine algal extracts tested for inhibiting pathogenic bacteria ranged from 3.13 to 300 mg/ml. GC-MS and FTIR analyses of algal extracts revealed the chemical components and their functional constituents in the brown seaweeds that might have potent antimicrobial activities. These components include fatty acids esters, alcohols, phenols, amines-containing compounds and others. The results indicated that brown seaweeds may be main sources of phytoconstituents which exhibited antibacterial properties and will be helpful in diminishing the adverse effects of synthetic drugs.

This study demonstrates the combination of wastewater treatment and green microalgae cultivation for the low-cost production of lipids as a feedstock for biodiesel production. Three green microalgal species were used: Chlamydomonas reinhardtii, Monoraphidium braunii, and Scenedesmus obliquus. Nutrient, heavy metals and minerals removal, biomass productivity, carbohydrate, protein, proline, lipid, and fatty acids methyl ester (FAMEs) contents besides biodiesel properties were evaluated. The results showed that all algal species were highly efficient and had the potential to reduce nitrate, ammonia, phosphate, sulfate, heavy metals (Zn2+, Cu2+, Mn2+, and Fe2+), calcium, magnesium, sodium, and potassium after 10 days of algal treatment compared to initial concentrations. The removal efficiency of these parameters ranged from 12 to 100%. The growth rates of M. braunii and S. obliquus cultivated in wastewater were significantly decreased compared to the control (synthetic medium). In contrast, C. reinhardtii showed the highest growth rate when cultivated in sewage water. Wastewater could decrease the soluble carbohydrates and protein content in all tested algae and increase the proline content in M. braunii and S. obliquus. In wastewater culture, M. braunii had the highest lipid productivity of 5.26 mg L−1 day−1. The fatty acid profiles of two studied species (C. reinhardtii and M. braunii) revealed their suitability as a feedstock for biodiesel production due to their high content of saturated fatty acids, representing 80.91% and 68.62% of the total fatty acid content, respectively, when cultivated in wastewater. This study indicated that wastewater could be used to modify biomass productivity, lipid productivity, and the quantity of individual fatty acids in some algae that affect biodiesel quality to achieve international biodiesel standards.