Green biosynthesis of silver nanoparticles using sodium alginate extracted from Sargassum latifolium and their antibacterial activity

Abstract Brown seaweed Sargassum latifolium produces a sufficient amount of alginate. It is derived from the cell wall of seaweed as a natural anionic polysaccharide. In the present study, alginate was extracted from S. latifolium , its physicochemical properties, the potential for silver nanoparticles formation, characterization of alginate silver nanoparticles, and its antibacterial activity was studied. Physical analysis of extracted sodium alginate as colour (pale yellow), yield (25.34%), water content (13.17%), ash content (15.5%), and pH (8.6) were investigated. In addition, UV scan analyses of extracted alginate illustrated that the bioactive compounds separated in the range of 200–400 nm. On the other hand, ultraviolet–visible spectroscopy (UV–Vis) scan analysis of synthesized alginate silver nanoparticles gave a maximum peak at 413 nm. Besides that, Fourier Transforms Infrared spectroscopy (FT-IR) analysis of alginate, and alginate silver nanoparticles revealed a variety of functional groups, such as –OH, –NH, –CH, –COOH, CO, and C–C, and thermogravimetric analysis of extracted sodium alginate demonstrated thermal degradation occurs in two steps; Dehydration followed by degradation to Na 2 CO 3 and a carbonized substance that breaks down slowly between 600 and 750 °C in N 2 . Biochemical contents, protein, and carbohydrate were receptively, respectively, and were 0.89 and 78.56 mg/g dry wt. Alginate silver nanoparticles recorded maximal antibacterial activity against Pseudomonas aeruginosa, Staphylococcus aureus, Klebsiella pneumonia, Escherichia coli, Bacillus subtilis, and Bacillus cereus more than alginate. On the other hand, alginate has no activity against E. coli .