Removing polychlorinated biphenyls (PCBs) from the environment is an important process for the protection of biota. This work examines three different approaches to the degradation of such contaminants. The first involves the use of iron bionanoparticles (Fe-BNPs) prepared through green synthesis from selected plant matrices. The second approach entails the use of the bacteria Stenotrophomonas maltophilia (SM) and Ochrobactrum anthropi (OA) isolated from a PCB-contaminated area, Strážsky canal, located in the Slovak republic, which receives efflux of canal from Chemko Strážske plant, a former producer of PCB mixtures. The third approach combines these two methods, employing a sequential hybrid two-step application of Fe-BNPs from the plant matrix followed by the application of bacterial strains. Fe-BNPs are intended to be an eco-friendly alternative to synthetic nanoscale zero-valent iron (nZVI), which is commonly used in many environmental applications. This work also addresses the optimization parameters for using nZVI in PCB degradation, including the pH of the reaction, oxygen requirements, and dosage of nZVI. Pure standards of polyphenols (gallic acid, GA) and flavonoids (quercetin, Q) were tested to produce Fe-BNPs using green synthesis at different concentrations (0.1, 0.3, 0.5, 0.8, and 1 g.L⁻¹) and were subsequently applied to the PCB degradation experiments. This step monitored the minimum content of bioactive substances needed for the synthesis of Fe-BNPs and their degradation effects. Experimental analysis indicated that among the selected approaches, sequential nanobiodegradation appears to be the most effective for PCB degradation, specifically the combination of Fe-BNPs from sage and bacteria SM (75% degradation of PCBs) and Fe-BNPs from GA (0.3 g.L⁻¹) with bacteria OA (92% degradation of PCBs).

This study presents an environmentally sustainable approach for synthesizing iron bionanoparticles using grape berries and grape pomace from two Vitis vinifera cultivars (Merlot and Blaufränkisch) highlighting the valorization of food industry waste within circular economy principles and the synergistic approach involving bacteria for environmental cleanup. The Merlot pomace-derived nanoparticles exhibited an amorphous structure, predominant Fe(III) species (Mössbauer spectroscopy), high specific surface area (398 m ² ·g⁻ ¹ ), and nanometric, porous morphology. Fe–O bond formation and polyphenol complexation was confirmed. Evolution of pH and redox potential values during synthesis revealed that slightly alkaline, near-physiological conditions favor nanoparticles formation and redox activity. All iron nanoparticle types were applied in removal experiments targeting polychlorinated biphenyls (from congener mixture Delor 103). The highest removal of the sum of PCBs congeners by nanoparticles alone reached 62% after 14 days using Merlot pomace-derived nanoparticles. When combined with the bacterium Ochrobactrum anthropi in a sequential synergistic approach, removal efficiency increased to 76%. Co-application with Stenotrophomonas maltophilia also resulted in high removal (70%). Ecotoxicological assessment revealed general non-toxicity of tested nanoparticles (derived from Merlot pomace) using Sinapis alba seed germination and Ochrobactrum anthropi auxanogram assays. However, higher concentrations (10 g·L ⁻¹ ) induced 46% inhibition of plant growth, likely due to restricted translocation of nutrients to the upper plant tissues. The results demonstrate the dual benefit of transforming agrowaste into effective, low-toxicity nanomaterials for remediation, supporting sustainable nanotechnology for environmental applications. Graphical abstract