الفهرس 
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Abstract
In the present investigation, phycosynthesis and characterization of selenium nanoparticles (SeNPs) and Zinc oxide nanoparticles (ZnONPs), and their application on pathogenic bacteria were investigated. SeNPs were phycosynthesized using cell-free extract of the microalgae, Spirulina platensis (S. platensis) and ZnONPs were prepared using cell-free extract of the macroalgae, Ulva fasciata Delile (UFD). The detail characterization of the NPs was carried out using UV-Vis spectroscopy, Transmission Electron Microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR) analysis, Zeta potential (ζ), Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD) analysis and Energy Dispersive X-Ray (EDX) analysis. The average particle size was found to be 5.93-12.64 nm and 77.81 nm, for SeNPs and ZnONPs, respectively. from the analysis of XRD pattern, UV-VIS spectroscopy and FTIR, the formation of nanoparticles was confirmed. Antibacterial assay of phycosynthesized SeNPs was carried out, qualitatively and quantitatively, against Staphylococcus aureus and Salmonella typhimurium. In the same manner, ZnONPs were tested on Escherichia coli and Staphylococcus aureus. The scanning micrographs of bacterial cells treated with SeNPs and ZnONPs indicated severe action of NPs to destroy bacterial cells in time-dependent manners. Peeled Shrimp (Fenneropenaeus indicus) were biopreservated through refrigerated storage (4 °C) with UFD-ZnONPs based solution for six days. The microbial examination of UFD-ZnONPs -treated Shrimp displayed decrease in microbial loads throughout the storage days. Thus, phycosynthesized NPs could be remarkably suggested as efficient procedure for Shrimp’ biopreservation during refrigerated storage regarding sensorial quality and microbial profile of product.