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Abstract Hanem Ahmed Abd-Elalim Megahed: Utilization of Nano Chitosan as Inhibitor of Fusarium Growth in Foods. Unpublished Ph.D. Thesis, Department of Food Science, Faculty of Agriculture, Ain Shams University, 2017. Fusarium species are well-known plant pathogens and food contaminants and they appeared as one of the most important groups of medically significant fungi. Of these species of fungi, Fusarium graminearum infects corn and other cereal crops causing the reduction of yield and quality. It has the ability to produce zearalenone (ZEN) which is an estrogenic mycotoxin causes severe health hazards to human and animals. The current study was conducted to prepare and characterize chitosan nanoparticles (COS-NPs), determine its antifungal activity against different isolated fungi in particular its effect on the growth of Fusarium graminearum and ZEN production. The inhibitory effect of different concentrations of COS-NPs on fungal growth and ZEN production in talbina prepared from contaminated barley flour and on the shelf life of stored apple were also studied. Moreover, the safety of COSNPs and its protective role against ZEN toxicity was conducted in laboratory animals. Chitosan (COS) was purified and the molecular weight and the degree of deacetylation were carried out. COS-NPs were prepared and its particles size and morphology characterization were determined. The antifungal effect of different concentrations of COS-NPs was determined against fungi isolated from corn grain through the mycelium growth inhibition and agar well diffusion methods. The results of evaluation and characterization of COS revealed that the deacetylation degree (DD) was 86.9 ± 0.44 %, the average of molar mass was 171.41 ± 0.29 g/mol, molecular weight was 244 ± 7 kDa and the concentration of free amino groups was 0.05 ± 0.019 mol/L. The Scanning Electron Microscopy (SEM) showed the nanorod form of COS-NPs. The particle size of COS-NPs was around 180 nm and the zeta potential was + 70.9 ± 2.4 mV. The FT-IR spectra revealed that COS-NPs appeared at 1256/cm and the intensity of (NH2) band at 1628/ cm found in COS was decreased dramatically and a new sorption band at 1550/ cm. COS-NPs showed an excellent antifungal activity against six out of seven species of fungi isolated from corn grains included Alternaria tenuis, Aspergillus niger, A. terreus, Baeuvaria bassiana, Fusarium graminearum, F. oxysporum in a dose dependent manner however; Sclerotium rolfsii was resistant to COS-NPs at all tested doses. At a concentration of 800 mg/L, COS-NPs completely inhibited ZEN production by F. graminearum in PDA medium. Moreover, at a concentration of 200 and 400 mg/L, it succeeded to prevent the fungal spoilage of apple fruits during cooling storage period up to 3 week. On the other hand, COS-NPs at a concentration as low as 200 mg/L succeeded to induce complete inhibition of Fusarium graminearum growth and ZEN production in talbina. The biological evaluation revealed that animals treated with ZEN showed severe toxicity in the liver, kidney and testes. Addition of COS-NPs at low dose (0.5 mg/ kg b.w) or high dose (1 mg/kg b.w) did not induce any toxicity in experimental animals and succeeded to protect against ZEN toxicity in a dose dependent manner through the restoration of most of the tested parameters. An improvement of histological and histochemical pictures of the liver, kidney and testes was also occurred. Key words: Fusarium graminearum; food contaminants; chitosan nanoparticles; antifungal; antimicrobial; zearalenone; mycotoxins; oxidative stress; antioxidant; gene expression. |