Selenium nanoparticles (SeNPs) are reinforced safe forms of the essential micronutrient selenium (Se) which take a lead in countless biotechnological and biomedical applications. The phycosynthesis of SeNPs was successfully investigated using cell-free extract of the microalgae, Spirulina platensis. The phycosynthesized S. platensis-SeNPs (SpSeNPs) were characterized using several characterization techniques such as UV-Visible, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and energy dispersive X-ray. They were effectually achieved using different concentration from sodium selenite (Na2SeO3) (1, 5, and 10 mM) to give size means of 12.64, 8.61, and 5.93 nm, respectively, with spherical shapes and highly negative zeta potentialities. The infrared analyses revealed the involvement of many phycochemials in SpSeNPs production. The antibacterial properties of SpSeNPs were confirmed, qualitatively and quantitatively, against foodborne microorganisms (Staphylococcus aureus and Salmonella typhimurium); the antibacterial activity was correlated and increased with SeNPs’ size diminution. The scanning micrographs of S. typhimurium cells treated with SpSeNPs indicated the severe action of nanoparticles to destroy bacterial cells in time-dependent manners. The innovative facile phycosynthesis of SeNPs using S. platensis is recommended to generate effectual bioactive agents to control hazardous bacterial species.

Zinc oxide nanoparticles (ZnONPs) were the targets of numerous biological syntheses to attain their precious values in various biomedical fields. The phycosynthesis of ZnONPs were innovatively investigated using cell-free extract of the macroalgae, Ulva fasciata Delile. The phycosynthesized U. fasciata-zinc oxide nanoparticles (UFD-ZnONPs) had 77.81 nm mean size, with flower and sphere shapes and positive zeta potential. The UFD-ZnONPs infra-red analysis indicated their basic components’ cross-linkage. The antibacterial potentialities of UFD-ZnONPs were confirmed, qualitatively and quantitatively, against foodborne microorganisms (Escherichia coli plus Staphylococcus aureus); the bactericidal action was higher for UFD-ZnONPs than the annealed phycosynthesized ZnONPs. The scanning micrographs of S. aureus and E. coli cells treated with UFD-ZnONPs indicated the severe action of nanoparticles to destroy bacterial cells in time-dependent manners. Peeled shrimps (Fenneropenaeus indicus) were biopreservated through refrigerated storage (4 °C) with UFD-ZnONPs based solution for six days. The microbial examination of UFD-ZnONPs -treated shrimps displayed decrease in microbial loads throughout the storage days. Moreover, the UFD-ZnONPs-treated shrimps showed acceptable sensorial attributes (appearance, odor, color and texture) compared to untreated shrimps. UFD-ZnONPs nanocomposite concentration of 3% and 5% could be remarkably suggested as efficient procedure for shrimps’ biopreservation during refrigerated storage regarding sensorial quality and microbial profile of product.

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