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Christianah Adebimpe DARE, Muneerah Iyabo MUHAMMAD, Amidat Olaide EDU, Damilola Sidikat YUSUF. Influence of Solid-State Fermentation on the Green Synthesis and Properties of Silver Nanoparticles from Annona Muricata Seed Components; Proceedings of NanoBioMat 2025(2); 103-117

INFLUENCE OF SOLID-STATE FERMENTATION ON THE GREEN SYNTHESIS AND PROPERTIES OF SILVER NANOPARTICLES FROM Annona muricata SEED COMPONENTS

Christianah Adebimpe DARE^1*, Muneerah Iyabo MUHAMMAD¹, Amidat Olaide EDU¹, Damilola Sidikat YUSUF¹

¹ Department of Biochemistry, Osun State University, Oke Bale Street, Area, Osogbo 210001, Nigeria

^*Correspondence: bimpeoasis@yahoo.com; Christianah.dare@uniosun.edu.ng

ABSTRACT

Background. The green synthesis of silver nanoparticles (AgNPs) is a cornerstone of sustainable nanotechnology. The physicochemical properties of AgNPs, which dictate their functional efficacy, are highly influenced by the nature of the reducing and capping agents. This study posits that solid-state fermentation, as a bioprocessing tool, can fundamentally alter the phytochemical profile of Annona muricata seed extracts, thereby modulating the structural properties of the synthesised AgNPs, a premise supported by recent work on bio-enhancement of plant extracts.

Material and Methods. AgNPs were synthesised using aqueous extracts from fermented and unfermented seed coats and cotyledons of A. muricata by reducing a 1 mM silver nitrate solution. The formation of AgNPs was confirmed by UV-Vis spectroscopy. A comprehensive structural characterisation was performed using Scanning Electron Microscopy (SEM) for morphological analysis, Energy-Dispersive X-ray Spectroscopy (EDX) for elemental confirmation, and Fourier-Transform Infrared Spectroscopy (FTIR) to identify the functional groups involved in bioreduction and stabilisation.

Results. UV-Vis spectroscopy confirmed successful synthesis, with a sharper and more intense Surface Plasmon Resonance (SPR) peak observed for AgNPs from fermented extracts (~430 nm) compared to the broader peak of unfermented AgNPs. SEM analysis revealed a striking difference: AgNPs from fermented extracts were predominantly spherical, well-dispersed, and monodisperse with a narrow size range of 15-40 nm. In contrast, AgNPs from unfermented extracts were highly aggregated and polydisperse. EDX analysis confirmed the presence of a strong metallic silver signal in all samples. FTIR spectra indicated a marked increase in the intensity of peaks associated with O-H and C=O stretches in the fermented extracts, suggesting a higher concentration of polyphenols and carbonyl compounds acting as capping agents.

Conclusion. The structural analyses conclusively demonstrate that solid-state fermentation induces significant positive changes in the nucleation and growth of AgNPs. The enhanced phytochemical profile of fermented extracts, evidenced by FTIR, leads to superior reduction kinetics and stabilisation, resulting in monodisperse, uniform nanoparticles. This refined morphology—specifically the small size, spherical shape, and lack of aggregation—is a critical determinant of biological activity, as high surface-area-to-volume ratio and dispersion are known to enhance bio-interactions. In conclusion, fermentation is a powerful pretreatment that directly controls the structural properties of biogenic AgNPs. The superior morphology and stability of the fermented AgNPs strongly suggest a concomitant enhancement in their potential biological efficacy, positioning them as highly promising candidates for further biomedical and environmental applications.

Keywords: fermentation; green synthesis; silver nanoparticles; Annonaceae; antioxidant