Synthesis of silver nanoparticles on the basis of low and high molar mass exopolysaccharides of Bradyrhizobium japonicum 36 and its antimicrobial activity against some pathogens

Abstract

Silver nanoparticles (SNPs) were synthesized on the basis of exopolysaccharides (low and high molar mass) of diazotrophic Bradyrhizobium japonicum 36 strain. The synthesis of SNPs was carried out by direct reduction of silver nitrate with ethanol-insoluble (high molar mass, HMW) and ethanol-soluble (low molar mass, LMW) fractions of exopolysaccharides (EPS), produced by diazotrophic strain B. japonicum 36. SNPs were characterized using UV-vis spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). SNPs synthesized on the basis of LMW EPS absorbed radiation in the visible regions of 420 nm, whereas SNPs based on the HMW EPS have a wavelength maximum at 450 nm because of the strong SPR transition. Moreover, the antibacterial and antifungal activities of the SNPs were examined in vitro against Escherichia coli, Staphylococcus aureus, and Candida albicans. SNPs synthesized on the basis of LMW EPS were active than those synthesized on the basis of HMW EPS. Besides, UV-visible spectroscopic evaluation confirmed that SNPs synthesized on the basis of LMW EPS were far more stable than those obtained on the basis of HMW EPS.

Linking soil microbial community dynamics to straw-carbon distribution in soil organic carbon

“…Moreover, Bradyrhizobium can secrete extracellular polymeric substances (EPS) in response to environmental stresses, e.g., pH, temperature, carbon source shortage and toxic components 43,44 . EPS can promote the formation of soil aggregates through electrostatic action, intermolecular van der Waals force or adsorption 45 , and thus improve the distribution of straw C to POC and MaOC. This might be the main reason for the significant positive correlation we observed between the abundance of Bradyrhizobium and POC-derived from straw, and explained Figure 7.…”

Exopolysaccharide-Based Bioflocculant Matrix of Azotobacter chroococcum XU1 for Synthesis of AgCl Nanoparticles and Its Application as a Novel Biocidal Nanobiomaterial

“…Production and purification of bioflocculant by A. chroococcum XU1 was developed in our previous experiments [24,25,39] and its fractionation into protein, low- and high-molar-weight polysaccharides was used as a part of protocol for green synthesis of AgNPs [24,25]. Production of bioflocculant carried out in 2 L flasks containing 1 L of the modified medium with 150 rpm at 30 °C under intensive aeration.…”

“…C. albicans ATCC10231 was cultured in culture medium comprising of: glucose, 40 g/L and peptone, 10 g/L [25,39]. …”

“…Different concentrations of AgCl-NPs were added to these wells, and the plates were incubated at 37 °C for 24 h. Zone of inhibitions were estimated by measuring the diameter of the bacterial growth inhibition zone. The values were averaged from the three independent experiments [25,39]. …”

Green synthesis of polysaccharide-based inorganic nanoparticles and biomedical aspects

“…The majority of AgNPs reported spherical shape [15,65] varied in size, between 1.1 [62] and 65.1 nm [66]. Nevertheless, shapes such as polygonal, oval-shaped, face-centered-cubic [67], irregular shape [68], rod/oval-shaped structures [69], triangular [70], and uneven shape [71] have also been documented for AgNPs.…”