الفهرس | Only 14 pages are availabe for public view |
Abstract The main purpose of this study is to synthesis of silver nanoparticles by eco-friendly and low-cost method using different marine bacterial and fungal isolates. The obtained results are summarized in the following points: 1. 31 bacterial and 20 fungal isolates was isolated from different marine habitatsin Egypt like Mediterranean Sea (Ras El-Bar and Alexandria), lakes (Burullus Lake and Qarun Lake) and the Red sea (Sharm El Sheikh, Ain Sokhna, Marsa Alam and Hurghada), then identified morphologically. 2. All bacterial and fungal isolates were Screened for silver nanoparticles biosynthesis. 13 bacterial isolates and 14 fungal isolates were able to synthesize silver nanoparticles. This ability was indicated visually by noticing appearance of brown color comparing with controls and confirmed with UV- vis spectra. 3. Molecular identification for the best producing AgNPs microorganism, Talaromyces stipitatus was done. 4. Fungal cell-free filtrate of Talaromyces stipitatus was used as a bio-source for the biosynthesis of silver nanoparticles (AgNPs). Its filtrate was used as reducing and capping agents. Talaromyces stipitatus was isolated from Borolls lake, as a marine habitat. 5. Optimization for the process of biosynthesis of silver nanoparticles was studied by two different methods of optimization to get best production of silver nanoparticles by using Talaromyces stipitatus, the classical method and RSM. 2 classical method is the common method of optimization by testing each factor individually, and other were constant, was done. The optimal conditions by classical method, was determined to be: modified medium containing yeast extract; peptone; potassium nitrate; and glucose, with static and lighting condition, temperature = 35 °C and pH 5 for optimization of fungal growth conditions. The optimization of mixture solution conditions for biosynthesis of Ag-NPs by Talaromyces stipitatus was resulting; AgNO3 concentration = 9: 10 mmol, time= 4 -5 days, ratio of silver nitrate solution to cell free extract was(2:1) at 50 °C. The RSM method has also been tested, this method saves efforts and time of the optimization process. Also, it takes into consideration the effects of different factors on each other. The predicted optimal conditions to get maximum SPR intensity and thus getting high amounts of AgNPs, was determined to be: AgNO3 concentration = 7mmol, temperature = 25 °C, time= 91.2 hr, pH = 8, ratio of silver nitrate solution to cell free extract is 2:1. 6. characterization of produced silver nanoparticles was done by different techniques to characterized the produced AgNPs like, Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), zeta potential, energy dispersive x-ray analysis (EDX), and transmission electron microscopy (TEM). AgNPs which appeared to be spherical, with average size of 13.95 nm and zeta potential of 9.85 mV. 7. Biosynthesized AgNPs were also studying the antibacterial, antifungal and antiviral activities of AgNPs. antimicrobial 3 properties were examined against selected bacterial and fungal pathogens including Staphylococcus aureus, Bacillus cereus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Aspergillus flavus, A. niger, Fusarium oxysporum and Alternaria alternata. Antiviral activity assay of AgNPs was done against tobacco mosaic virus (TMV). |