Production of polysaccharide-based bioflocculant for the synthesis of silver nanoparticles by Streptomyces sp

• The marine actinobacteria are efficient candidates for bioflocculants.
• Biosynthesis of AgNPs using polysaccharide bioflocculant produced by Streptomyces sp.
• The maximum bioflocculant production was 98.96% after optimized by RSM.
• The biosynthesized AgNPs revealed strong antibacterial activity in sewage water.

Polysaccharide-based bioflocculants have attracted considerable attention in recent years due to their biodegradable, harmless and negligible secondary pollution. Bioflocculants are organic macromolecular substances secreted by microorganisms. A simple, cost-effective and green method was developed for the biosynthesis of silver nanoparticles using polysaccharides as reducing and stabilizing agents. In this paper, we report on the production and optimization of polysaccharide-based bioflocculant for the green synthesis of silver nanoparticles by Streptomyces sp. MBRC-91. Medium composition and culture conditions for polysaccharide-based bioflocculants were statistically optimized by response surface methodology (RSM). The bioflocculant production was statistically optimized with most significant factors, namely palm jaggery (18.73 g/L), yeast extract (2.07 g/L), K2HPO4 (3.74 g/L) and NaCl (0.38 g/L), respectively. The biosynthesized silver nanoparticles were characterized by UV–vis spectroscopy, XRD, FTIR, FESEM, EDXA and HRTEM. The biosynthesized silver nanoparticles revealed strong antibacterial activity in sewage water and this result could make a new avenue in the wastewater treatment. Therefore, the biosynthesized silver nanoparticles can be extended as an alternative for the development of new bactericidal bionanomaterials for wastewater treatment and biotechnological applications.

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