Utilizing Biomolecule-Rich Citrus Fruit Waste as a Medium for the Eco-Friendly Preparation of Silver Nanoparticles with Antimicrobial Properties

An ample amount of fruit waste is generated as agro-industrial waste, leading to significant nutritional, economic, and environmental challenges. Fruit peels are rich in many valuable bioactive compounds with the potential for developing nanoparticles. This study examined fresh juices of two citrus fruit peel wastes (Citrus sinensis: C. sinesis and Citrus limon: C. limon) for antioxidants and total protein. Then, we investigated their ability to produce silver nanoparticles, which were further analyzed for anti-microbial activity against thirteen pathogenic microbes. Both Citrus peel juices were rich in secondary metabolites. The formation of Ag nanoparticles was initially confirmed by UV-vis spectroscopy, with peaks at 400 nm for C. sinensis peel Ag nanoparticles and 430 nm for C. limon peel Ag nanoparticles. Further characterization was conducted using zeta sizer, zeta potential, Transmission Electron Microscopy (TEM), Scanning Electron Microscope (SEM), Energy-dispersive X-ray spectroscopy (EDX) and Fourier transform infrared (FTIR) spectroscopy. The antimicrobial activity was tested using the well diffusion method against 11 bacterial strains (five Gram-positive and six Gram-negative) and two fungal strains of Candida. TEM and SEM results revealed a spherical shape, with an average diameter of about 13 nm for C. sinensis and 21 nm for C. limon Ag. EDX confirmed the presence of silver in both nanoparticles. The FTIR spectrum of the extract indicated the presence of biomolecules, which facilitated the reduction and capping of the synthesized Ag nanoparticles. The prepared nanoparticles showed remarkable antimicrobial activity, but the nanoparticles from C. sinensis exhibited stronger antibacterial properties because of their smaller size. Citrus peel waste is a suitable medium for the eco-friendly production of silver nanoparticles.