Biocidal evaluation of polyphenol-derived silver nanoparticles in a complex polymicrobial model system

Abstract

Abstract: Sustainable polyphenol-derived silver nanoparticles (PD-AgNPs), synthesized from sugarcane bagasse extracts, were evaluated for antimicrobial activity in a chemically complex, polymicrobial model system (sugarcane juice). These nanoparticles were spherical (15 nm), crystalline, and highly stable (–24.8 mV). PD-AgNPs exhibited significant (p ≤ 0.05) dose and time-dependent reductions against lactic acid-producing bacteria (LAB), mesophilic bacteria, and fungi, reaching 73%, 75%, and 85% reductions, respectively. Mesophiles were most susceptible at lower exposure levels, while fungi showed a delayed but greater reduction at higher treatment intensity. LAB were comparatively more resistant. Despite the presence of organic compounds that can inhibit nanoparticle activity, PD-AgNPs retained efficacy, attributed to the polyphenol-derived surface corona that enhances stability and enables sustained release of Ag+ ions. Microscopy confirmed membrane damage and cellular disruption, consistent with a multi-target antimicrobial mechanism. These results demonstrated that PD-AgNPs remained effective under complex conditions and highlight their potential for broader antimicrobial applications.