الفهرس 
Title : Maximizing the benefits of bacterial metabolites as biocontrol agents against toxigenic fungi and mycotoxins
AbstractOnly 14 pages are availabe for public view
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Abstract
Aflatoxin contamination has become a major source of concern around the world due to the significant economic impact on crop production as well as the toxicological impacts on humans and animals. Therefore, the aim of this study was to evaluate the level of fungal contamination of various grains from different governorates and to study the ability of bacterial secondary metabolites in reducing fungal contamination and mycotoxins. Data revealed that Aspergillus was the predominant fungi followed by either Fusarium or Penicillium spp. Results also indicated that 21 of toxigenic Aspergillus isolates were positive for AFs production using HPLC. The fungal isolate showing high aflatoxin production was molecularly identified as A. flavus. A total of 36 endophytic bacteria were isolated from rice samples from Qalyubia, whereas ten bacterial strains showed variable degrees of antifungal activity. The ten bacterial isolates showing antifungal activity were identified using biochemical as well as MALDI-TOF, and were identified as B. cereus, and B. thuringiensis. Bioactive secondary metabolites were extracted from B. cereus and B. thuringiensis in comparison with L. plantarum, L. rhamnosus, and L. gasseri. Using HPLC, lactic acid bacterial secondary metabolites were found to produce different organic acids. Furthermore, using GC/MS, and LC/MS, led to the identification of several volatile organic compounds, and polyphenols in the ethyl acetate extracts. On the other hand, ethyl acetate extracts No. 5, 13, and 15 showed variable antifungal and high antiaflatoxigenic activities. Ethyl acetate extracts were observed to cause variable toxicity against brine shrimp, and therefore, cytotoxicity of the human cell line was performed, and results showed that ethyl acetate extract (No. 15) showed high toxicity against brine shrimp showed high anticancer activity against HepG2. As the ethyl acetate extract No. 5 showed high antiaflatoxigenic activity, and low toxicity against brine shrimp, this extract was tested for its safety using a mouse bioassay and was found to be safe with none of the mice had any signs of toxicity or behavioural abnormalities. Thus, different concentrations of this extract were incorporated in chitosan nanoparticles and selected for bio-preservation of corn against fungal growth, and results revealed that chitosan nanoparticles loaded with ethyl acetate extract at a concentration of 7 mg/mL prevented fungal growth for 10 days.