An Integrative Biosynthetic Approach to Silver Nanoparticles: Optimization Modeling, and Antimicrobial Assessment

Silver nanoparticles (AgNPs) are valued for their antimicrobial properties, but conventional synthesis often involves toxic chemicals. Eco-friendly biosynthesis using silver-tolerant microbes from contaminated sites offers a sustainable alternative. This study biosynthesized and characterized AgNPs using a native Bacillus sp. from contaminated soil in the Jazan region, Saudi Arabia, and developed predictive models for optimizing synthesis and antimicrobial activity. AgNPs were synthesized under optimized conditions (1.0 mM AgNO3, 4.0 mL supernatant, pH 8, 85 °C). Characterization using UV–Vis, SEM, TEM, XRD, and FTIR assessed size, shape, structure, and chemistry. Gaussian and second models evaluated yield and inhibition zones based on AgNP concentration, microorganism type, and MIC. The AgNPs were spherical with diameters of 5–10 nm. The optimal nanoparticle yield occurs when the parameters are at their optimal values; C0 = 1.0 mM, V0 = 4.0 mL, pH0 = 8, T0 = 85 °C. XRD confirmed their crystalline nature, and FTIR showed biomolecular capping agents for stabilization. The Gaussian model accurately predicted synthesis efficiency, validated by 3D plots matching experimental data. The AgNPs showed strong antimicrobial activity against Gram-positive (Bacillus subtilis) (ATCC6051), Staphylococcus aureus (ATCC12600), Gram-negative bacteria Escherichia coli (ATCC11775) and fungi Candida albicans (ATCC10231); with E. coli having the lowest MIC (1.87 μg/mL). The inhibition zone model closely matched observed data. Biosynthesized AgNPs using silver-tolerant Bacillus sp. demonstrated potent antimicrobial effects and provide a green alternative to chemical synthesis. Integrating modeling optimizes biosynthesis and predicts biological performance, supporting future nanobiotechnology and antimicrobial applications.