Green Synthesis of Bergamot Solid Waste-Based Silver Nanoparticles: Optimization Process for Agriculture Use

TL;DR

This study uses waste from bergamot fruit to create silver nanoparticles that can help plants grow and fight disease, offering a sustainable alternative to chemical methods.

Contribution

The study introduces bergamot pomace as a novel agri-food waste for green synthesis of silver nanoparticles with agricultural applications.

Findings

Bergamot pomace-based silver nanoparticles showed good colloidal stability and spherical morphology with 15–20 nm diameters.

The nanoparticles exhibited phytostimulatory and antimicrobial effects at low concentrations on tomato, lettuce, and bacterial pathogens.

Polyphenols and proteins in bergamot pomace were identified as key agents in nanoparticle synthesis and stabilization.

Abstract

Green-synthesized metal nanoparticles are increasingly investigated for their antioxidative, antimicrobial, and stress-protective properties as eco-friendly and cost-effective alternatives to conventional chemical synthesis. Although agri-food wastes represent biomolecule-rich and sustainable resources, they remain less explored as biological matrices for green metal nanoparticle synthesis compared with plant and microbial extracts. The aim of this study was to optimize the synthesis and evaluate the bioactivity of silver nanoparticles derived from bergamot pomace, a polyphenol-rich agri-food waste. Synthesis parameters, including extract concentration, pH, extract-to-metal ratio, temperature, and reaction time, were optimized, and the nanoparticles were characterized by UV–Vis spectroscopy, dynamic light scattering, zeta potential analysis, and electron microscopy (TEM, STEM). ATR-FTIR and proteomic analyses were employed to investigate the molecular mechanisms involved in nanoparticle reduction, capping, and stabilization. The bergamot pomace-based silver nanoparticles exhibited a surface plasmon resonance peak at 430 nm, spherical morphology, good colloidal stability, and average diameters of 15–20 nm, without irreversible aggregation. A putative synthesis mechanism was proposed, involving Ag+ bioreduction mediated by polyphenols, ascorbic acid, and oxidoreductase-associated proteins, followed by stabilization through protein corona formation. Seed nanopriming assays on tomato and lettuce, together with in vitro antimicrobial tests against Pseudomonas syringae pv. tomato and Xanthomonas campestris pv. vesicatoria, demonstrated phytostimulatory and antimicrobial effects at very low nanoparticle concentrations. Overall, this study highlights bergamot pomace as a valuable resource for green silver nanoparticle synthesis, supporting its applicability in sustainable agriculture.

Figures