Utilization of agro-industrial wastes and by-products by Bacillus subtilis for the biogenic synthesis and In-Depth characterization and cytotoxicity assessment of silver nanoparticles

Silver nanoparticles (AgNPs) have garnered significant attention due to their diverse applications in nanotechnology, biomedicine, and environmental science. This study explores the biogenic synthesis of AgNPs utilizing various agro-industrial wastes by Bacillus subtilis AMD2024 as a sustainable and eco-friendly alternative to conventional chemical synthesis methods. We evaluated a range of agro-industrial by-products, including blackstrap sugarcane molasses, sugar beet waste, and arish cheese whey, for their potential in AgNPs production. Comprehensive characterization techniques-such as X-ray diffraction (XRD), atomic absorption spectroscopy (AAS), dynamic light scattering (DLS), UV-visible spectroscopy, high-resolution scanning electron microscopy (HR-SEM), zeta potential analysis, and Fourier transform infrared spectroscopy (FTIR)-were employed to assess the properties of the synthesized nanoparticles. The DLS and UV-visible study findings were obtained at a particle size of 15.63 nm and a surface plasmon resonance (SPR) of 0.593 at 450 nm, respectively. The time course showed the maximum concentration of AgNPs after 48 h at 1.535 mg/L. The preliminary findings suggest that the size of the synthesized AgNPs was effectively reduced to as low as 4.849 nm when using blackstrap sugarcane molasses. The cytotoxicity assessment revealed a half-maximum inhibitory concentration (IC₅₀) of 200 mg/mL against normal kidney epithelial cell lines, indicating the potential for safe applications in infection control and water treatment. This study highlights the applicability of agro-industrial waste valorization in nanoparticle synthesis, showcasing its promise for developing effective antimicrobial agents in various sectors.