الفهرس 
Review of LiteratureOnly 14 pages are availabe for public view
Abstract
English summary
• Different microbial strains were tested for their ability to reduce different metal salts to synthesize NPs including; bacteria, fungi and yeast. In this study proved that Aspergillus brasiliensis ATCC 16404 mycelial cell free filtrate (MCFF) showed good potential for the biosynthesis of silver nanoparticles (AgNPs). One-factor-at a time-optimization technique (OFAT) was applied to optimize the mycosynthesis of AgNPs, which revealed maximum production of 0.17 g AgNPs using 100 ml of the MCFF of 6 % (w:v) A. brasiliensis biomass and 2 mM silver nitrate (AgNO3) at pH 7, under fluorescent light static incubation for 72 h at 20oC. The mycosynthesized mono-dispersed spherical shaped AgNPs of average size 6-21 nm proved to be stable for about 60 days.
• Cobalt oxide nanoparticles (Co3O4-NPs) were successfully mycosynthesized for the first time by A. brasiliensis ATCC 16404 MCFF. The preliminary indication for the formation of Co3O4-NPs was the change in color from yellow to reddish color. OFAT technique was applied to determine the optimum physicochemical conditions required for the mycosynthesis of Co3O4-NPs. That were found to be; 72 h for reaction time, 11 for pH, 30ºC for temperature, 100 rpm for shaking speed in the darkness using 4 mM of CoSO4.7H2O and 5.5 g of A. brasiliensis dry weight mycelium with maximum production of 0.12g/100 ml. The prepared Co3O4-NPs proved to be stable for about 60 days.
• The mycosynthesized Co3O4-NPs were characterized using various techniques, spectroscopic including; UV/Vis spectrophotometry; DLS, zeta potential measurement, energy dispersive X-ray (EDX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and vibrating sample magnetometry and microscopic techniques including; Field emission scanning electron microscope (FESEM) and High resolution transmission electron microscope (HRTEM). The spectroscopic techniques confirmed the formation of Co3O4-NPs and the microscopic ones confirmed the shape and size of the Co3O4-NPs as quasi-spherical shaped, monodispersed nanoparticles with a nano size range of 20 to 27 nm. The XRD and EDX analyses proved the purity of the mycosynthesized Co3O4-NPs. The FTIR spectroscopy showed the involvement of biomolecules present in the MCFF of A. brasiliensis in the synthesizing, capping and stabilizing the Co3O4-NPs.
• Moreover, AgNPs were mycosynthesized using the fungus Trichoderma longibrachiatum DSMZ 16517 MCFF. The MCFF bio-reduced the silver ions (Ag+) to their metallic nanoparticle state (Ag0). That was presumptively indicated by the appearance of dark brown suspension and was confirmed by the characteristic absorbance of AgNPs at ʎ422nm. The optimization of the physicochemical factors governing the best production of AgNPs was performed by OFAT technique. The optimum conditions were 40oC, 24 h, pH 12, 3 g dry weight biomass, 4 mM AgNO3, 150 rpm, under dark condition with a maximum production of 0.3g/100 ml. The prepared AgNPs proved to be stable for 30 days.
• The mycosynthesized AgNPs were then characterized using various spectroscopic and microscopic techniques. The DLS analysis revealed average AgNPs size and zeta potential values of 17.75 nm and -26.8 mV, respectively. The XRD pattern assured the crystallinity of the mycosynthesized AgNPs, with an average size of 61 nm. The FESEM and HRTEM showed non-agglomerated spherical, triangular and cuboid AgNPs ranged from 5 to 11 nm. The FTIR analysis of the mycosynthesized AgNPs affirmed the role of MCFF as a reducing and capping agent.
• A rapid one-step green synthesis of AgNPs using the Citrus sinensis (sweet orange) peels’ hot water extract (SOPE) was introduced. A visible color change was observed from faint yellow to brown, upon the bioreduction of AgNO3 with peels’ extract and the stabilization of the synthesized AgNPs by the natural components of the extract. The UV/Vis spectrophotometric analysis proved the appearance of the characteristic absorption peak λmax 422 nm which is characteristic to AgNPs. One-factor-at-a-time-optimization technique was used to study the effect of the key factors governing the synthesis of AgNPs including; temperature, illumination, pH, different concentrations of peels’ extract and silver nitrate, mixing rates and reaction time. That revealed maximum production of 0.2 g AgNPs /100 ml using 4000 mg l-1 of SOPE and 3 mM AgNO3 at pH 9, under illumination, shaking at 100 rpm for 24 h at 40oC. The green synthesized mono-dispersed spherical shaped 3-14 nm AgNPs were stable for a long time of about 60 d. The average particle size was measured using DLS and revealed 23 nm. The zeta potential value of -20.3 mV proved the stability of the synthesized AgNPs. EDX confirmed the strong signals for elemental silver. XRD confirmed the crystalline nature of the biosynthesized AgNPs with average size of 15 nm. FTIR identified the possible functional groups involved in capping and efficient stabilization of the synthesized AgNPs. FESEM and HRTEM revealed spherical shaped AgNPs with average size of 3-12 nm.
• The waste peels of mandarin (Citrus reticulum) were used for the green synthesis of AgNPs. The hot water-MPE showed an exceptional performance as bio-reductant, bio-stabilizer and bio-capping agent for green synthesis of AgNPs. OFAT technique was applied to study and optimize the physicochemical parameters that affect the green synthesis of AgNPs using the hot water extract of mandarin peels’ waste. The physicochemical optimization revealed maximum production of 0.25 g of 10-19 nm AgNPs per 100 ml solution of 3000 mg l-1 MPE and 2 mM AgNO3 at pH 9, 30°C, within reaction time of 4 h, under fluorescent illumination of 36W/6400K and mixing speed of 100 rpm. The prepared AgNPs proved to be stable for 90 days. DLS, zeta potential, EDX, XRD, FTIR, FESEM and HRTEM were used to characterize the prepared AgNPs.
• The prepared AgNPs and Co3O4-NPs were assessed for their biocidal activity against aerobic micro-biofoulants. A water sample labeled W-2017-630 with a salinity of (15172 mg l-1) was kindly provided by the central analytical laboratory, Egyptian Petroleum Research Institute. Four microorganisms were isolated and identified as Bacillus koreensis strain BW MH569459, Micrococcus flavus strain BY MH577187, Kocuria Polaris strain BO MH577188 and Aspergillus niger isolate 1F MH518073. The prepared NPs exhibited an excellent biocidal activity against the tested aerobic micro-biofoulants. Furthermore, the obtained AgNPs proved to have an efficient biocidal effect against sulphate reducing bacteria (SRB) mixed culture obtained from a real Egyptian oil field at a concentration of 2000 mg l-1. The HRTEM analysis showed a clear evidence of alteration in cell morphology, the disruption of halotolerant planktonic SRB cell membranes, lysis in cell wall and cytoplasmic extraction after treatment with AgNPs. That confirmed the bactericidal effect of the prepared AgNPs. The recorded biocidal activity of the synthesized AgNPs against the halotolerant planktonic SRB, makes it an attractive option to control MIC in petroleum industry in a form of a coating layer within the pipelines. Further studies are still needed to understand the biocidal activity against planktonic and sessile SRB, as well as biocorrosion mitigation in petroleum industrial facilities.
• The obtained AgNPs and Co3O4-NPs exhibited good antimicrobial potency against some pathogenic microorganisms; Gram-positive Bacillus subtilis ATCC 6633 and Staphylococcus aureus ATCC 35556, Gram-negative Pseudomonas aeruginosa ATCC 10145 and Escherichia coli ATCC 23282 and yeast, Candida albicans IMRU 3669. Thus, this research provides a helpful insight into the development of new antimicrobial agents that can be applied for water disinfection from pathogenic microorganisms. However, the exact antimicrobial mechanism of action is still unclear. The observed magnetic properties of the bio-inspired Co3O4-NPs, added to its advantages as it would have successful applications in magnetic storage devices, water disinfection and wastewater treatment.
• A preliminary cost analysis for the optimized green synthesis of AgNPs was performed to estimate its feasibility and profitability. The mycosynthesis of AgNPs using A. brasiliensis and T. longibrachiatum MCFF cost was estimated as 172 US$/10 and 94 US$ per 10 g of AgNPs, respectively. According to the US Research Nanomaterials, Inc., the global cost of the chemically synthesized AgNPs is 250 US$/10 g of AgNPs. Consequently, 31% and 62% savings were achieved for the present biosynthesis process compared to the global price of AgNPs. Whilst the production cost of 10 g of Co3O4-NPs based on the produced yield was calculated as 225 US$/10 g of Co3O4-NPs. According to the US Research Nanomaterials, Inc., the global cost of the chemically synthesized Co3O4-NPs is 100 US$. Consequently, it was concluded that the present biosynthesis process of Co3O4-NPs had a higher production cost than the conventional chemical synthesis process. Meanwhile the green synthesis of AgNPs using SOPE and MPE cost approximately 81 US$ and 76 US$ with 67% and 69.6% savings were concluded compared to the global price of AgNPs.
• Moreover, the spent waste of A. brasiliensis mycelia, sweet orange and mandarin peels were upgraded to produce valuable compound e.g. activated carbon which has many different applications in order to reach zero waste. Thus, the upcycling of such waste to such valuable compounds would have positive impact on waste management and environmental pollution.