Effect of Nigella sativa and green synthesized zinc oxide nanoparticles on Bacillus cereus isolated from meat and milk products

Bacillus cereus (B. cereus) is Gram-positive, spore-forming bacterium not only associated with food-borne outbreaks but also responsible for spoilage of food products. Therefore, the aim of this study is to trying to control of B. cereus by safe nanoparticles and studies the antibacterial effects of Nigella sativa and green synthesized Zinc Oxide nanoparticles (NPs) on B. cereus. The isolated strains of B.cereus from meat and milk products with detection of their virulence genes (nhe, cytK, hbl and ces) by PCR were used to assess the antibacterial activity of these nanoparticles. The nanoparticles were characterized by Scanning Electron Microscope (SEM) and Dynamic Light Scattering (DLS) to investigate their properties which revealed that Nigella sativa NPs was 87.5 nm in size and cuboidal in shape, the polydispersity index, zeta potentials, viscosity and conductivity were 0.456, +15.9 mV, 0.877 cp and 58 uS/cm respectively, while Zinc Oxide NPs were 0.2484, -21.8 mV, 0.925 cp and 269 uS/cm respectively and their size was 67.8 nm and rhomboid in shape. Antibacterial activity was determined by using micro wells dilution method to determine Minimum Inhibitory Concentration (MIC). The MIC result for Nigella sativa NPs showed slight inhibition with the 30% concentration, while for Zinc Oxide NPs was 1.25 mg/ml. The morphological characters and changes of bacterial cells before and after treatment with nanoparticles were described by SEM. The Results show significant inhibitory effect of Zinc Oxide NPs than Nigella sativa NPs on B.cereus growth with distinctive destruction in its ultrastructure. SO, applications of nanoparticles in the meat and dairy industry will be a market trend to improve quality by their antibacterial effects and enhancement their shelf life.