| Aflatoxin B1(AFB1) is a secondary metabolite produced by fungi with genotoxicity, immunotoxicity and antinutritional effects which seriously polluted the food and feed worldwide. In recent years, the detoxification of AFB1 in food and feed has become a research hot spot of scholars’ in various countries’. As feed additives allowed by the country montmorillonite could effectively adsorb AFB1 in gastrointestinal tract of animals, however, it was not targeted to AFB1 and the environment would be polluted when it was excreted. Based on FS-Z1 screened from brewing soy sauce which could effectively degraded AFB1, we mutaganized and screened the new Aspergillus Niger degrading AFB1 and it was immobilized by montmorillonite, at last, evaluated its degradation efficacy and safety by animal experiments.Screen FS-UV1 with a higher detoxification rate of 34.1 % than initial strains FS-Z1 by ultraviolet irradiation and casein medium, which was sequenced and identified as Aspergillus Niger. The detoxification product of AFB1 are studied by Ames test, the results showed that the production of AFB1 showed no mutagenic activity.The spores had no effection on AFB1 and the mycelium could adsorb AFB1, the culture filtrate could also degrade it in which the protein might be the active substance. Also, the degradation production was identification by LC-MS. The changes of the enzyme produced by the new Aspergillus Niger FS-UV1 in potato glucose liquid medium(PDB) were studied. the content of protein showed the maximum of 10.07 g/L at 48 h; The crude enzyme was obtained through the dialysis and identified by SDS-PAGE electrophoresis and the three tips were found with 59, 21, 16 KD.Ore purchased from Yixing, Wuxi was characterized by XRD(X-ray diffraction), SEM(scanning electron microscope), FTIR(Infrared spectrum) the results showed that the content of montmorillonite was up to 87.6 %. The immobilized FS-UV1 were prepared at p H= 10, 40 ℃, 0.1 %(w: v). It was found that the detoxification rate of the immobilized and free cells of FS-UV1 had the same trend and the rate of immobilized FS-UV1 was higher than that of free cells. FS-UV1 immobilized cells were applied to detoxify the AFB1 in cottonseed meal of different provinces(content of 1.18, 6.5, 0.89, 0.0829 ppm). The detoxication rate of the samples was 93.46% ~ 96.82% when AFB1 was detoxified for 2 h.In vitro test of the simulative gastrointestinal, immobilized FS-UV1 could detoxicate 86.61% of AFB1 at 2 h and showed better stability of p H. In vivo evaluation of immobilized cells, we had chosen SD rats as model animal, the changes of weight, average daily feed intake, blood indicators, biochemical indicators and the photomicrographs of sections of liver and kidney were studied to evaluate the detoxification effect. Results showed that immobilized cells could alleviate the adverse effects of AFB1 when the rats were fed with AFB1 of 2.5 mg/kg. The rats which were fed with immobilized cell feed alone showed no adverse reaction. |
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