Biosynthesis, characterization, and biofunctional assessment of niobium oxide nanostructures obtained using lactic acid bacteria-derived supernatants.

Nanotechnology offers innovative opportunities for developing functional materials with applications across biomedical and food-related fields. Among metallic and metal oxide nanostructures, niobium-based compounds have recently attracted attention due to their remarkable mechanical strength, corrosion resistance, thermal conductivity, and biocompatibility. In this study, niobium oxide nanostructures were synthesized through a green, cell-free approach using supernatants derived from lactic acid bacteria (LAB) Lacticaseibacillus rhamnosus and Lacticaseibacillus paracasei UFTM 2.9. The use of LAB supernatants provided an eco-friendly and sustainable route for nanoparticle production, avoiding toxic reagents while exploiting biologically active metabolites for bioreduction and stabilization. The synthesized nanostructures were characterized by scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDX), scanning-transmission electron microscopy (STEM), ultraviolet-visible spectroscopy (UV-vis), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) and zeta potential analysis. In vitro assays using Vero-CCL81 cells demonstrated that the nanostructures exhibited low cytotoxicity, confirming their potential biocompatibility. Antibacterial and antibiofilm activities were evaluated against Escherichia coli ATCC 25922, revealing significant inhibitory effects. These findings highlight a novel and sustainable route for producing niobium oxide nanostructures via LAB-mediated synthesis, with promising implications for biomedical and food safety applications.