Synthesis of silver nanoparticles by polysaccharide bioflocculant produced from marine Bacillus subtilis MSBN17

The polysaccharides are emerging as stabilizing and reducing agents for nanoparticles synthesis, however the commercial polysaccharides are not economically viable. Therefore, the exopolysaccharide from microbial origin such as bioflocculants are promising alternate for the synthesis and stabilization of nanoparticles. In this report, a bioflocculant (MSBF17) was produced from marine sponge-associated Bacillus subtilis MSBN17 under submerged fermentation using the economical substrates. The production was statistically optimized with most significant factors such as palm jaggery, NH4NO2, K2HPO4 and NaCl. The maximum bioflocculant production obtained with statistically optimized medium was 13.42 g/l. Based on the biochemical composition and FT-IR analysis, the flocculant compound was predicted as a polysaccharide derivative. The flocculating activity of the MSBF17 was invariably considerable at high salinity and temperature. It was found that the nano-scale silver can be synthesized in reverse micelles using the bioflocculant as stabilizer. The silver nanoparticles (AgNPs) were characterized by UV-spectroscopy, FT-IR and TEM analysis. The AgNPs were spherical shaped (60 nm) and stable for 5 months. Therefore, the bioflocculant-mediated synthesis of nanomaterials can be considered as environmental benign greener approach.

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► The marine sponge-associated endosymbionts were explored as a source of bioflocculants.
► Response surface methodology was employed to optimize the production medium for increasing bioflocculant production.
► AgNPs were synthesized using polysaccharide bioflocculant as reducing and stabilizing agent.
► The antimicrobial activity of AgNPs was checked against multi-drug resistant pathogens.
► The AgNPs were reducing the total bacterial count in sewage water.