Biologically active selenium nanoparticles composited with Bacillus licheniformis extracellular polymeric substances fermented from cane molasses

Organic selenium nanoparticles (SeNPs) are attracting great interest due to their unique properties and potential applications in the food industry. In this study, a novel form of SeNPs was synthesized by using Bacillus licheniformis CGMCC 2876 extracellular polymeric substances (EPS) fermented from waste cane molasses. The morphology of EPS-SeNPs was spherical with an average size of 141.8 nm and a zeta potential of −51.77 mV, and the concentration of Se reached 107.43 mg/g. Additionally, the EPS-SeNPs exhibited good stability in aqueous solution for 7 days and were resistant to the digestion of simulated gastric fluid. The zero-valent Se composition and C–O⋯Se asymmetric stretch were characterized in the EPS-SeNPs. A synthesis mechanism of EPS-SeNPs was hypothesized. Moreover, the biological activities of the EPS-SeNPs synthesized from EPS were evaluated. The EPS-SeNPs exhibit antioxidant activity in scavenging ·OH, DPPH and ·O²⁻ free radicals with abilities <90% in the range of 0.25–4 g/L and inhibit 50% of formed radicals (IC₅₀) values of 1.18, 13.71 and 1.93 g/L, respectively. EPS-SeNPs also exhibit excellent antibacterial activity, which could inhibit the growth of intestinal pathogenic gram-positive and gram-negative bacteria (>80%) in vitro with the EPS-SeNPs concentrations higher than 1000 μg/mL.