Sustainable biosynthesis of silver nanoparticles from vinegar bacteria fermentation waste: characterization, bioactivity and food packaging potential.

Silver nanoparticles (AgNPs) have emerged as promising agents with significant potential for biotechnological applications, particularly in active packaging systems and wound-healing dressings, owing to their broad-spectrum antimicrobial activity and ability to enhance product safety, shelf life, and infection control. In this context, AgNPs were successfully synthesized via a green synthesis method, offering an environmentally friendly, sustainable, and low-cost approach, using Acetobacter sp. (strains 1A, 1B, 2B, 2D, 3A) and Komagataeibacter sp. (strain X1) isolated from homemade vinegars in the province of Samsun. The synthesis of nanoparticles was verified by the presence of surface plasmon resonance (SPR) peaks formed at 414-432 nm in the reaction mixture. The scanning electron microscopy (SEM) analysis showed that AgNPs were spherical in shape and varied in size between 20 and 100 nm depending on the bacterial isolate used in the synthesis. DLS analysis revealed that all synthesized AgNPs exhibited hydrodynamic diameters ranging from 85.05 to 179.1 nm with PDI values between 0.274 and 0.402, indicating moderately monodisperse to heterogeneous distributions depending on the bacterial isolate. Zeta potential measurements demonstrated that AgNPs had negatively charged surfaces with moderate to high colloidal electrostatic stability (- 12.3 to - 31.8 mV). The antimicrobial activity of the obtained AgNPs was tested against Gram-negative and Gram-positive bacteria, with a low inhibition concentration (16 µg/mL) particularly observed in the ESBL-positive E. coli strain. Antioxidant tests revealed that AgNPs synthesized using Komagataeibacter sp. X1 (KX1-AgNP) exhibited the highest activity and effectively neutralized DPPH radicals by 56.01%. Cytotoxicity studies showed that AgNPs preserved fibroblast cell viability at low concentrations but exhibited toxic effects at high doses. Packaging analyses showed that X1-film effectively preserved food by significantly reducing total viable, psychrotrophic, and yeast-mold counts during storage. These results indicate that biosynthesized AgNPs possess strong antimicrobial and antioxidant properties, with vinegar bacteria serving as an efficient, eco-friendly, and cost-effective source. This strategy offers promising potential for sustainable applications in food packaging and nanotechnology.