الفهرس 
Biosynthesis of nanoparticles by the microorganism
Culture media for cyanobacteria growthOnly 14 pages are availabe for public view
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Abstract
The development of the reliable and eco-friendly use of microorganisms for the synthesis of nanoparticles is an important aspect of current nanotechnology research and applications. Recently, microorganisms have been explored as potential biofactories for synthesis of silver and titanium dioxide nanoparticles. In this study, through screening of common bacteria and cyanobacteria we exploit the biosynthesis of these nanoparticles using five isolated bacteria (B. paralicheniformis, B. pumilus, B. licheniformis, R. radiobacter and S. paucimobilis) and cyanobacterial biomass of A. variabilis and S. platensis species which were all obtained from wastewater treatment plant in Tanta city, El-Gharbia Governorate, Egypt. In the present study, the synthesis of silver nanoparticles (AgNPs) by using cell free extracts (CFEs) of the bacterial strains and cyanobacterial biomass have been verified. The resulting nanoparticles have been characterization by UV-visible spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Biosynthesized AgNPs by bacteria and cyanobacteria have been characterized. UV-vis spectroscopy revealed the build –up of absorption peaks of silver plasmon resonance at ~443 nm for B. paralicheniformis, 449 nm for B. pumilus, 433 nm for B. licheniformis, 442 nm for R. radiobacter and 423 nm for S. paucimobilis. And for cyanobacteria, absorbance peaks were observed at ~ 444 nm for A. variabilis and 443 nm for S. platensis. The morphology and size of the biosynthesized AgNPs were indicated by TEM and Xray diffraction analysis as being spherical in shape and of size ranged from 4 to 20 nm for bacterial AgNPs and between from 17 to 37 nm for cyanobacterial AgNPs. FTIR measurements showed the functional groups responsible for capping and stabilizing the formed AgNPs. These groups were found to be amino group (NH), carbonyl C=O, alkyl (CH), cyanide C-N and phenyl ring implying that proteins were the main metabolites responsible for stabilizing the formed nanoparticles. The NPs were extracellularly formed outside the cells and upon agglomeration they were transported into the cells as revealed from TEM images. The formation of NPs by cyanobacterial species was also photo-catalyzed by light. On the same direction, the same five bacterial strains were found to have the ability to synthesize titanium dioxide nanoparticles (TiO2NPs) but cyanobacterial species did not have such ability. The biosynthesized TiO2NPs have been characterized by UV-visible spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The UV-VIS absorbance peaks wre observed at ~ 366 nm for B. paralicheniformis, 360 nm for B. pumilus, 366 nm B. licheniformis, 355 nm for R. radiobacter and 355 nm for S. paucimobilis which all corresponding to titanium plasmon resonance. The morphology and size of the TiO2NPs were indicated by TEM to be spherical in shape and of size ranged between 26 to 38 nm. AgNPs biosynthesized by B. paralicheniformis, B. pumilus, and S. paucimobilis, A. variabilis and S. platensis were applied for malachite green (MG) removal from wastewater as a model dye released in wastewater. The removal of MG from solution was carried out by three treatments: nanoparticles (AgNPs) produced by bacteria or cyanobacteria, bacterial suspension or cyanobacterial cultures and nanoparticles (AgNPs) added to its bacteria or cyanobacteria cultures as a mixture. The reaction was studied at 30oC and the absorbance of MG was recorded by UV-Vis spectrophotometer at λmax 617 nm. The kinetic data obtained for the removal of MG exhibited good fitting with the pseudo-first order model and the removing process was found to be dependent on both MG and NPs concentrations. The results showed that AgNPs had the highest efficiency in dye removal compared with the bacterial or cyanobacterial suspension only and/or the mixture solutions of bacterial suspension and its nanoparticles. Generally, it was observed that AgNPs of B. paralicheniformis strain KJ-16 and S. platensis had the highest efficiency in dye removal compared to the other species of bacteria and cyanobacteria with 97% and 93% MG removal efficiency, respectively depending on the MG concentration. Only TiO2NPs produced by S. paucimobilis was applied for study in MG removal from wastewater because these bacteria produced the highest concentration of TiO2NPs. The removal efficiency of MG recorded 90%. The proposed mechanism for MG removal by NPs was biosorption process of the dye molecules on the formed nanoparticles. As a safe approach for environmental recycling S. platensis biomass was used to remove the formed TiO2NPs produced by S. paucimobilis and to remove the formed TiO2–MG nanocomposite after wastewater treatment. As verified by TEM images, S. platensis cells were able to absorb the nanocomposite on their surface and eventually the formed aggregations were settled down leaving a clear wastewater effluents. The effluents produced after different AgNPs and TiO2NPs treatments were used for cultivating of Vigna radiate (L) and Triticum aestivum (Giza 171) plants. The results of germination percentage and morphological criteria of the produced seedlings proved the safety of these effluents to be used in agriculture purposed.